The disclosure relates to a control system for controlling a pressurised fluid supply system on a mobile machine. The control system is particularly applicable for use with a pressurised fluid supply system on a mobile agricultural machine, such as a tractor, which is capable of supplying pressurised fluid to consumers on the machine and to consumers on an agricultural implement attached to the machine. The disclosure also relates to a mobile machine, or to a combination of a mobile machine and attached implement, having such a control system, and to a method of controlling a pressurised fluid supply system on a mobile machine or on a mobile machine and attached implement combination.

BACKGROUND

Pressurised fluid (hydraulic) supply systems are widely used to drive consumers on agricultural or construction mobile machines, e.g. a tractor or a self-propelled harvester, or on implements attached thereto. Such mobile machines will be referred to hereinafter simply as machines and are sometimes referred to as vehicles. These hydraulic systems are mostly provided with a pump supply, consumers, control means (respectively control valves) and a tank to provide a fluid reservoir. The term “consumer” is used in the further description to encompass hydraulic drives such as rotary motors or linear rams but also for the respective control valves assigned to these drives. The term “control” in relation to supply systems hereby includes any adjustment of the supply system regarding direction, supply time or pressure of the fluid flow or the delivery of the pump used to supply the system. The term “pump supply” includes the pump and all valve means which are needed to adjust the fluid flow and/or fluid pressure supplied by the pump to a pump supply line. The pressure of the fluid provided by the pump supply being referred to herein as the pump supply pressure PSP.

In a hydrostatic hydraulic system, a pressure differential is needed to provide hydrostatic work (an output). This pressure differential between the pump supply (source) and consumer results in a fluid flow which is sufficient to undertake work, such as to lift a tractor three-point hitch or a operate a rotary drive on an implement or in a hydrostatic drive for example. Furthermore, a stand-by or static pressure differential AP _s t is also needed when the system is otherwise in idle mode to keep control valves (assigned to consumers) responsive so that the spool of the valve can be moved on demand.

Hydraulic losses are present whenever oil circulates within a hydraulic system even when no consumer is operated. To mitigate this problem, it is known to provide means to forward a demand of a consumer to the pump supply. These systems are generally called load sensing systems (the term load sensing is abbreviated to LS). In such systems, a load induced pressure demand of the consumers, hereafter referred to as a “load sensing pressure” LSP, is hydraulically fed back to the pump supply via pipes or hoses so that pump supply oil flow/pressure can be adjusted according to the needs of the consumers. This load sensing pressure LSP feedback signal is typically generated by the control valve assigned to a consumer and the highest load sensing pressure LSP of all the consumers supplied by the pump is used to adjust the pump supply.

In general there are two different types of hydraulic supply systems with LS demand feedback available on the market - closed-centre load sensing systems (CC-LS systems) and open-centre load sensing systems (OC-LS systems).

CC-LS systems are equipped with variable displacement pumps whereby the demand of the consumers is hydraulically fed back to the pump supply including an adjustment means for the pump so that the displacement of the pump is adjusted according to the needs of the consumers.

To ensure that a stand-by pressure differential AP _s t is maintained in the supply to support fast system response, the pump is kept on low displacement to compensate for losses/leakage resulting in a stand-by pressure even if there is no demand by consumers. As a result of the reduction of the hydraulic fluid circulation, losses and power input required by the pump are reduced.

Figure 1 illustrates part of a simplified known CC-LS hydraulic circuit. A pump supply 10 includes a variable displacement pump 12 which draws fluid from a tank 14 and forwards pressurised fluid to consumers (not shown) via a pump supply line P. Fluid is returned to the tank from the consumers via a return or tank line T. The pump 12 can be any suitable variable displacement pump and could, for example, be a swash plate axial piston pump in which the displacement of the pump is changed by pivoting the swash plate by means of a pump actuator 16 to vary the piston stoke. In the arrangement illustrated, actuator 16 is biased by a spring to pivot the swash plate in a direction to increase pump displacement and hence the output of the pump. Pressurised fluid introduced into a chamber 20 of the actuator opposes the force of the spring and if the force of the fluid is greater than that of the spring the swash plate is pivoted to reduce the delivery of the pump.

Operation of the actuator 16 is controlled by a flow control valve 22 and a pressure limiting valve 24, which together with the actuator 16 form a pump controller and form part of the pump supply 10. Each of the valves is biased by a respective spring 26, 28 to the position shown in which the actuator chamber 20 is connected to the tank 14. Each of the valves has a pump pressure port 30, 32 connected to the pressure line P of pump so that the fluid pressure acting on the valve spool through the pump pressure port 30, 32 opposes the force of the respective spring 26, 28. The flow control valve 22 also has a LS pressure port 34 to which a load sensing pressure signal line LS is connected. The highest consumer load sensing pressure LSP of the various consumers in the hydraulic LS system is fed into the LS pressure signal line so that the load sensing pressure LSP is added to the force of the spring to move the valve spool towards the position shown. The spring 26 in the flow control valve sets the stand-by pressure differential AP _s t which is typically in the region of 10 to 30 bar for tractor applications. The spring force may be adjustable to enable the stand-by pressure differential APstto be adjusted. The spring 28 of the pressure limiting valve sets the maximum operating pressure of the system, which could be in the region 250 bar in the present example. Again, the spring force may be adjustable to enable the maximum operating pressure to be adjusted.

In normal operation when the system is at idle with no demand from the consumers, the pump supply pressure PSP acting through the pump pressure port 30 of the flow control valve 22 moves the spool against the force of the spring 26 to introduce pressurised fluid in to the chamber 20 of the actuator. This causes the actuator to pivot the swash plate and reduce the output of the pump until the pump supply pressure PSP balances the force of the spring 26 so that the output of the pump is held at the stand-by pressure APst.

When a load sensing pressure signal LSP (or an increasing load sensing pressure signal) is reported to the LS pressure port 34 via the LS sensing line, this is added to the force of the spring 26 moving the valve spool so that the fluid pressure in the chamber 20 of the actuator is reduced. In response, the actuator 16 moves the swash plate to increase the output of the pump until the pump supply pressure PSP balances the force of the spring 26 and the load sensing pressure signal LSP. The pump therefore delivers a pump supply pressure PSP that is higher than the load sensing pressure LSP by the stand-by pressure differential AP _s t.

The pressure limiting valve 24 is usually held in the position shown by the spring 28 so that fluid passes into and out of the actuator chamber 20 under the control of the flow control valve 22. However, should the pump supply pressure PSP exceed the maximum permitted system pressure, as defined by the spring 28, the spool of the pressure limiting valve 24 is moved against the spring force to admit pressurised fluid into the chamber 20 of the actuator. This reduces the output of the pump until the pump supply pressure PSP it is brought back below the maximum permitted system pressure.

Generally, CC-LS systems are more expensive and complex than OC-LS systems but they have the advantage that the pump is only delivering above the stand-by pressure AP _s t on demand. This has a positive effect on the overall system efficiency. These systems are mainly used in high performance and high specification tractors (e.g. >100kW) used to supply complex and powerful implements.

In contrast to CC-LS systems, OC-LS systems are provided with a fixed displacement pump. Figure 2 illustrates part of a simplified OC-LS hydraulic circuit. A constant displacement pump 12’ draws hydraulic fluid from a tank 14 and delivers it to various consumers (not shown) via a pump supply or pressure line P. Fluid is returned to the tank 14 from the consumers via a return or tank line T. A proportional pressure compensator valve 40 forms part of the pump supply and is operative to selectively connect the pump supply line P to the tank 14. The spool of the valve 40 is biased by a spring 44 towards a closed position, as shown, in which pump supply line P is not connected to the tank. This spring sets a static or stand-by pressure differential APstand the spring force may be adjustable to enable the stand-by pressure differential APstto be adjusted. The pump supply pressure PSP is applied to the opposite end of the spool via a pressure port 46 to oppose the force of the spring. The valve also has an LS pressure port 48 through which a consumer load sensing pressure signal LSP is applied to the valve spool to act in addition to the spring force. In an idle mode where there is no consumer demand, the pump supply pressure PSP opposes the spring force to open the valve and connect the pump supply line P to the tank. The pump supply pressure PSP in the pump supply line falls until it balances the spring force and is then held at the stand-by pressure differential AP _s t. If a consumer load sensing pressure signal LSP is forwarded to the valve 40 via the LS pressure port 48, this adds to the spring force tending to close the valve so that the pump supply pressure PSP increases until it balances the combination of the spring force and the load sensing pressure LSP. The pump supply pressure PSP is thereby held a level which is higher than the load sensing pressure LSP by the stand-by pressure differential AP _s t defined by the spring 44.

A further trend can be seen related to the supply and control means used on implements attached to an agricultural machine, such as a tractor. Due to increasing automation in agricultural work, implements are provided with more and more control functions which require complex control strategies. While in the past implements were equipped with only a few controllable drives (e.g. hydraulic cylinders or motors) which were controlled by valves on the tractor, today implements are provided with numerous controllable drives which cannot be controlled by the valves installed on the tractor. To address this, tractors are often equipped with power beyond systems. As the name suggests, these systems supply an uncontrolled (at the tractor) fluid flow from the pump supply to the implement via a respective interface, such as quick couplers. The implement itself is then equipped with control means in form of valves to adjust the parameters of the fluid supply. Similar to internal consumers on the tractor, these power beyond systems also include a LS function so that the load sensing pressure of consumers on the implement can be fed back to the pump supply on the tractor via a hydraulic LS line.

A typical power beyond interface 50 is illustrated in Figure 1 and includes quick release hydraulic couplings 50a, 50b, 50c for releasably connecting a pump supply line P, a return or tank line T, and an LS signal line on the tractor to equivalent hydraulic lines Pi, Ti, LSi on the implement. As illustrated, the LS line (LSpb) from the power beyond interface which reports a LS signal from the consumers on the implement and an LS line (LSt) which reports a LS signal from the consumers on the tractor are connected to the LS pressure port 34 on the flow control valve 22 though a shuttle valve 52 or another other functionally similar arrangement. This ensures that the highest LS load sensing pressure signal from the implement or the tractor is used to control the output of the pump. Where there are a number of consumers on the implement, shuttle valves are used to ensure the highest LS load sensing pressure signal LSP of the implement consumers is fed through to the power beyond LS connection 50c. Similarly, where there are a number of consumers on the tractor, shuttle valves or other functionally similar arrangements are used to feed the highest LS load sensing pressure signal LSP of the tractor consumers to the LSt line and hence to the shuttle valve 52.

A major advantage of the power beyond system is that the costs involved with fluid supply control are moved from the tractor to the implement so that a wider range of applications can be handled by tractors with reduced hydraulic control capability. These power beyond systems have mainly been the reserve of tractors with higher performance (>100kW) and CC-LS systems. However, a demand has been recognized for smaller tractors with OC-LS systems to provide power beyond, for example vineyard tractors with about 70 kW have to provide a supply to complex implements such as fruit harvesters equipped with many hydraulic drives to be controlled.

A drawback with purely hydraulic LS arrangements is that the hydraulic load sensing pressure signal LSP has to be forwarded to the pump supply by hydraulic lines. Where the load sensing pressure signal LSP comes from a consumer on an implement, a coupling is required to releasably connect the implement hydraulic LS signal line with a hydraulic LS signal line on the tractor. Furthermore, the various hydraulic LS signal lines from different consumers must be connected via shuttle valves to ensure that the highest consumer load sensing pressure LSP is forwarded to the pump supply. This all involves considerable additional expense and takes up valuable installation space. To overcome these drawbacks, electrohydraulic load sensing (E-LS) arrangements have been developed.

US 20070151238 A1 discloses a hydrostatic drive system in which a variable displacement pump controller is actuated electronically by an electronic control device. A pressure sensor is used to detect a hydraulic consumer load sensing pressure LSP and provides an input to the electronic control system. The electronic control system generates an electronic control signal for actuating the displacement pump controller via a LS control valve to set the pump supply pressure PSP so that it is higher than the sensed load sensing pressure LSP by a set amount AP _s t. The system avoids the need for lengthy hydraulic LS load sensing pressure signal lines. DE 10 2014 103 932 B3 discloses an E-LS system for an implement towed by a tractor. The towed implement has an electronic control device which determines the difference between the pump supply pressure PSP and the highest load sensing pressure LSP of the consumers on the towed implement. An electronic signal indicative of the pressure difference is forwarded to a hydraulic control module coupled to a LS connection of a variable displacement pump on the tractor. The hydraulic control module converts the electronic signal to a hydraulic control signal for controlling the pump displacement.

LIS2019345694 A1 discloses a further E-LS system for a tractor and towed implement which does not necessarily require an electronic controller on the implement. In the arrangement disclosed, a pressure sensor is provided on the tractor to detect a hydraulic LS load sensing pressure signal LSP provided by the implement via a power beyond LS coupling. The pressure sensor forwards an electronic load sensing pressure signal ELSPS representative of the hydraulic load sensing pressure LSP to an electronic control unit on the tractor which controls a transducer (e.g. a solenoid actuated pressure limiting valve) to provide a hydraulic pump supply control signal HPSCS having a pressure P _se t for forwarding to a variable displacement pump controller. A further pressure sensor may be provided to forward an electronic load sensing pressure signal ELSPS representative of the highest load sensing pressure LSP of a number of consumers on the tractor. In this case, the electronic control unit selects the highest of the electronic load sensing pressure signals to use as a basis to control the transducer. The hydraulic pump supply control signal HPSCS output from the transducer may be connected with the pump controller via a shuttle valve, with a hydraulic load sensing pressure signal LSP from a steering system providing a further input to the shuttle valve. In this case, the highest pressure of the hydraulic pump supply control signal HPSCS from the transducer or the load sensing pressure LSP from the steering system is forwarded to the pump controller. This illustrates how E-LS and traditional hydraulic LS can be combined.

Arrangements for adjusting the pump supply pressure PSP in an E-LS system can be similar to those illustrated in either of Figures 1 and 2, except that a hydraulic pump supply control signal HPSCS for application to the LS pressure port 34, 48 of a flow control valve 22 or pressure compensator valve 40 is produced using a suitable transducer in dependence on an electronic pump supply control signal EPSCS from the controller. The transducer may be a solenoid controlled pressure limiting valve, for example. The solenoid valve is actuated by the controller as a function of the hydraulic load sensing pressure demand LSP detected by a pressure sensor.

Figure 3 illustrates how a pump supply 10 including a variable displacement pump 12 similar to that described above in relation to Figure 1 can be adapted to incorporate a solenoid controlled pressure limiting valve for use with an E-LS system. The pump supply 10 includes a flow control valve 22’ to control the flow of fluid between the pump supply line P, the chamber 20 of the pump control actuator 16 and the tank 14. As in the hydraulic LS system of Figure 1 , a spring 26 sets the stand-by or static pressure differential and is opposed by the pressure in the pump supply line P connected to the pressure port 30 of the flow control valve 22’. However, for use in an E-LS system, the fluid pressure P _se t supplied to the LS pressure port 34 is set by a solenoid controlled pressure limiting valve 54. When no current is provided to the solenoid 56 of the pressure limiting valve 54, the LS pressure port 34 is fully connected to the tank 14 and the pump supply pressure PSP at port 30 is opposed only by the force of the spring 26 in the flow control valve 22’ so that the pump output is maintained at the stand-by pressure AP _s t. When a consumer load sensing pressure LSP is detected by a pressure sensor and forwarded to a controller, the controller generates an electronic pump supply control signal EPSCS which is forward to the solenoid of the pressure limiting valve 54. The electronic pump supply control signal EPSCS actuates the pressure limiting valve 54 so that a hydraulic pump supply control signal HPSCS at a pressure P _se t is applied at the LS port 34 of the flow control valve 22’ in addition to the spring force. This causes the pump displacement to be increased until the pump supply pressure PSP balances the combination of the spring force and the pressure P _se t of the hydraulic supply control signal HPSCS.

As illustrated in US2019345694 A1 , the hydraulic pump supply control signal HPSCS generated by the pressure limiting valve 54 may be forwarded to the LS port 34 via a shuttle valve with a conventionally generated hydraulic load sensing pressure signal LSP provided as second input to the shuttle valve. This arrangement enables an E- LS system to be integrated with a conventional hydraulic LS system.

For use with a fixed displacement pump arrangement such as that illustrated in Figure 2, a solenoid actuated pressure limiting valve 54 can be used to generate a hydraulic pump supply control signal HPSCS for application to the LS pressure port 48 of the pressure compensator valve 40. Other electronically controlled transducer arrangements can be used to convert an electronic pump supply control signal EPSCS into a hydraulic pump supply control signal HPSCS.

Whilst the known E-LS systems and methods work well and alleviate some of the problems of a purely hydraulic LS system, they have their own drawbacks. One issue the applicant has found is that E-LS increases the overall reaction time to adjust the pump supply pressure PSP in response to an increase in consumer load sensing pressure LSP. This can be explained by the fact that in a hydraulic LS system, the load sensing pressure signal LSP is forward by a generally static fluid column in the LS lines which immediately forwards a load sensing pressure demand. In electrohydraulic E-LS systems, the pressure sensors must communicate with the controller and the controller must communicate with the solenoid pressure limiting valve or other actuator for adjusting the pump supply pressure. This communication typically takes place over CAN or ETHERNET-BUS Networks. As a consequence, the electronic LS signal transfer depends on cycle times and these depend on the performance levels of the components. With the numerous electronic control systems used in agricultural machines today, the overall response time may be considerably higher compared to purely hydraulic LS systems.

There is a need then for alternative methods of controlling a hydraulic supply system which overcome, or at least mitigate, some or all of the drawbacks of the known methods and a need to provide hydraulic supply systems configured to carry out such alternative methods.

SUMMARY OF THE INVENTION

Aspects of the invention relate to a control system for controlling a hydraulic supply system of a mobile machine and/or of a mobile machine and attached implement combination, to a mobile machine and/or a mobile machine and attached implement combination, and to a method of controlling a hydraulic system of a mobile machine and/or of a mobile machine and attached implement combination.

In a first aspect of the invention, there is provided a control system for controlling a hydraulic supply system on a mobile machine, wherein the hydraulic supply system includes a pump supply for supplying pressurised fluid to a plurality of consumers on the mobile machine and/or an implement attached to the mobile machine; the control system comprising one or more controllers configured to: receive, from a pressure sensor of a load sensing LS system associated with at least one of the consumers, a pressure signal indicative of a sensed load sensing pressure LSP associated with the at least one of the consumers; be operative in a load sensing mode of control to compute and generate a control signal for regulating a pump supply pressure PSP provided by the pump supply in dependence on the sensed load sensing pressure LSP; wherein the one or more controllers configured to receive and/or monitor data indicative of an actuation state of the at least one of the consumers and to determine, from the received/monitored data, when the at least one of the consumers is actuated; and following a determination that the at least one of the consumers is actuated be selectively operative to enter a predictive mode of control in which the one or more controllers compute and generate a control signal to increase the pump supply pressure not based on the sensed load sensing pressure LSP; wherein, the one or more controllers configured when operating in the predictive mode of control to monitor the pressure signal indicative of a load sensing pressure LSP of the at least one of the consumers and to switch to a load sensing mode of control of the pump supply in dependence on the sensed load sensing pressure LSP.

Predictively increasing the pump supply pressure when actuation of a consumer is initially detected enables the hydraulic supply system to respond dynamically, whilst reverting to a load sensing based control in dependence on the load sensing pressure helps to maintain overall efficiency of the hydraulic supply system.

In an embodiment, the one or more controllers configured to switch from the predictive mode of control to the load sensing mode of control if the load sensing pressure LSP is at or above a threshold value.

In an embodiment, the one or more controllers configured to monitor or determine the pump supply pressure PSP and to switch from the predictive mode of control to the load sensing mode of control if the pump supply pressure PSP is determined to be at least within a predetermined percentage of the load sensing pressure LSP. The predetermined percentage may be 80%, or 90%, or 95%, or 100%.

In an embodiment, the one or more controllers are configured to determine, from the received pressure signal, a rate of change of load sensing pressure LSP and to switch from the predictive mode of control to the load sensing mode of control if the rate of change of the load sensing pressure is at or falls below a threshold value or where the rate of change of the detected load sensing pressure LSP shows a general decrease indicative that the hydraulic demand of the at least one of the consumers will be met within a given time limit.

The control system may be configured when operating in the load sensing mode of control to compute and generate a control signal for regulating a pump supply pressure PSP provided by the pump supply in dependence on the value and rate of change of the sensed load sensing pressure LSP

In an embodiment, the one or more controllers configured to determine, from the received pressure signal, a rate of change of the load sensing pressure LSP, and to receive, from a pressure sensor associated with the pump supply, a second pressure signal indicative the pump supply pressure PSP, the one or more controllers further configured to determine from a comparison of the second pressure signal and the first mentioned pressure signal whether the pump supply pressure PSP is higher than the sensed load sensing pressure LSP, the one or more controllers configured to switch from the predictive mode of control to the load sensing mode of control following a determination that the pump supply pressure PSP is higher than the sensed load sensing pressure LSP and that the determined rate of change of the load sensing pressure LSP is at or below a threshold value.

In an embodiment, the one or more controllers configured to determine, from the received pressure signal, a rate of change of the load sensing pressure LSP, and to switch from the predictive mode of control to the load sensing mode of control if the rate of change of the load sensing pressure LSP is decreasing indicative that the hydraulic demand of the at least one of the consumers will be met within a set time limit.

In an embodiment, the one or more controllers configured to switch from the predictive mode of control to the load sensing mode of control after a set time limit in the event that a switch has not been otherwise triggered prior to the end of the time limit.

In an embodiment, the one or controllers configured to receive/monitor data indicative of an actuation state of the at least one of the consumers in the form of a control signal from a user interface for controlling actuation of the at least one of the consumers. The one or more controllers may be configured to determine a value and/or rate of change of the pressure signal and, when operative in the predictive mode of control, to compute and generate a control signal for increasing the pump supply pressure in dependence on the value and/or rate of change of the control signal.

In an embodiment, the one or more controllers configured when operative in the predictive mode of control to determine an operational response of the at least one of the consumers with reference to an operational target associated with the at least one of the consumers. The one or more controllers may be configured to: store (in a memory accessible by the one or more controllers) predetermined value(s) for the pump supply pressure PSP in dependence on the determined operational response “meeting” the operational target; and retrieve/apply stored predetermined value(s) for the pump supply pressure PSP during subsequent implementation of a predictive mode of control for the at least one of the consumers.

Thus the control system may be self-learning and adjust the amount and timing of the increase in pump supply pressure when operative in the predictive mode to meet the hydraulic demand of a particular consumer dynamically whilst also maintaining overall efficiency. The balance between dynamic response and efficiency may be pre-set or the control system may enable an operator to adjust the balance by requesting higher dynamic response or greater efficiency. The system may enable the operator to select between different modes of operation, which may include a dynamic mode where dynamic response is prioritised over efficiency or an efficient mode where the economy is priorities over efficiency. There may also be a balanced mode between these two.

The one or more controllers may collectively comprise an input (e.g. an electronic input) for receiving one or more input signal(s) (e.g. the pressure signal) indicative of a sensed load sensing pressure LSP and one or more input signal(s) (e.g. signals from sensors, operator input devices, and or cameras etc.) indicative of an actuation state of the at least one of the consumers. The one or more controllers may collectively comprise one or more processors (e.g. electronic processors) operable to execute computer readable instructions for controlling operation of the control system, for example to determine the load sensing pressure LSP from a pressure signal received from a pressure sensor and to determine when the at least one of the consumers has been or is being actuated from the signal(s)/data indicative of an actuation state of the at least one of the consumers. The one or more processors may be operable to generate one or more control signals for controlling the pump supply pressure PSP. The one or more controllers may collectively comprise an output (e.g. an electronic output) for outputting the one or more control signals, such as a pump supply control signal.

In an embodiment, the one or more controllers configured to enter a predictive mode of control of the pump supply in respect of only one or some of the consumers and/or in response to a particular operational parameter being met.

The one or more controllers may be configured to generate an electronic pump supply control signal, the control system comprising a transducer for converting the electronic pump supply control signal to a hydraulic pump supply control signal P _se t for forwarding to a hydraulic pump supply adjustment system.

The hydraulic system may include more than one consumer and more than one pressure sensor, each pressure sensor for sensing a load sensing pressure LSP associated with one or more of the consumers, in which case, the one or more controllers may be configured to receive pressure signals indicative of sensed load sensing pressure LSP from each of the pressure sensors and to adjust the pump supply pressure in dependence on the pressure signal indicative of the highest load sensing pressure LSP at any given time when operating in a load sensing mode for controlling the pump supply.

The hydraulic system may comprise at least one consumer on an implement attached to the mobile machine which is supplied with pressurised fluid from the pump supply on the mobile machine, in which case, the one or more controllers may be configured to receive, from a pressure sensor of a load sensing LS system associated with the at least one consumer on the implement, a pressure signal indicative of a sensed load sensing pressure LSP associated with the at least one consumer on the implement. In an embodiment, the one or more controllers comprise at least a first controller on the mobile machine and a second controller on an implement attached to the mobile machine; the first and second controllers being in communication with one another.

In an embodiment, the pump supply includes a variable displacement pump having a pump controller including a flow control valve for regulating movement of an actuator to adjust the pump displacement. In this embodiment, the one or more controllers may be configured to generate an electronic pump supply control signal, the control system comprising a transducer for converting the electronic pump supply control signal to a hydraulic pump supply control signal HPSCS having a pressure P _se t for forwarding to an LS pressure port of the flow control valve. The transducer may be a solenoid controlled pressure limiting valve.

In an alternative embodiment, the pump supply includes a fixed displacement pump, the pump supply comprising a pressure compensator valve for selectively connecting a pump supply line to a reservoir (tank) to vary the pump supply pressure PSP. In this embodiment, the one or more controllers may be configured to generate an electronic pump supply control signal, the control system comprising a transducer for converting the electronic pump supply control signal to a hydraulic pump supply control signal HPSCS having a pressure P _se t for forwarding to an LS pressure port of the pressure compensator valve. The transducer may be a solenoid controlled pressure limiting valve.

In accordance with a further aspect of the invention, there is provided a mobile machine comprising a hydraulic supply system including a pump supply for supplying pressurised fluid to a plurality of consumers on the mobile machine and/or an implement attached to the mobile machine and a control system for controlling the hydraulic supply system according to the above aspect of the invention. The mobile machine may be part of a combination comprising the mobile machine and an attached implement, wherein the implement has one or more consumers supplied with pressurised fluid from the pump supply. The mobile machine may be a mobile agricultural machine, such as a tractor. The attached implement may be an agricultural implement.

In accordance with a still further aspect of the invention, there is provided a method of controlling a hydraulic supply system on a mobile machine, wherein the hydraulic supply system includes a pump supply for supplying a pressurised fluid to a plurality of consumers on the mobile machine and/or an implement attached to the mobile machine, the hydraulic supply system comprising an electronic load sensing (E-LS) system operative to adjust a pump supply pressure provided by the pump supply in dependence a sensed load sensing pressure LSP associated with at least one of the consumers in a load sensing mode of control of the pump supply; the method comprising selectively controlling the pump supply in a predictive mode to increase the pump supply pressure independently of the sensed load sensing pressure LSP in response to a determination that the at least one of the consumers has been actuated and monitoring the sensed load sensing pressure LSP whilst controlling the pump supply in the predictive mode and switching to a load sensing mode of control of the pump supply in dependence on the sensed load sensing pressure LSP.

Predictively adjusting the pump supply following a determination that a consumer is actuated improves dynamic performance whilst continuing to monitor the load sensing pressure and reverting to a load sensing mode of controlling the pump supply in dependence on the sensed load sensing pressure LSP helps to maintain the overall efficiency of the hydraulic supply system.

In an embodiment, the method comprises switching from the predictive mode of control to the load sensing mode of control if the load sensing pressure LSP is at or above a threshold value.

In an embodiment, the method comprises monitoring or determining the pump supply pressure PSP and switching from the predictive mode of control to the load sensing mode of control if the pump supply pressure PSP is at least within a predetermined percentage of the load sensing pressure LSP. The predetermined percentage may be 80%, or 90%, or 95%, or 100%.

In an embodiment, method comprises determining a rate of change of load sensing pressure LSP and switching from the predictive mode of control to the load sensing mode of control if the rate of change of the load sensing pressure is at or below a threshold value or where the rate of change of the detected load sensing pressure LSP shows a general decrease indicative that the hydraulic demand of the at least one of the consumers will be met within a given time limit. The method may comprise switching from the predictive mode of control to the load sensing mode of control if the rate of change of the load sensing pressure LSP is decreasing indicative that the hydraulic demand of the at least one of the consumers will be met within a given time limit.

The method may comprise switching from the predictive mode of control to the load sensing mode of control after a set time limit if a switch to the load sensing mode has not been triggered otherwise beforehand.

The method may comprise adjusting the pump supply pressure provided by the pump supply in dependence on both the value and rate of change of the sensed load sensing pressure LSP when operating in a load sensing mode of control of the pump supply, especially for an increasing load sensing pressure LSP.

In an embodiment, the method comprises monitoring a control signal generated by a user interface for controlling operation of the at least one consumer to determine when the at least one consumer is actuated. The method may comprise selecting a set point to which the pump supply pressure PSP is raised in the predictive mode of control in dependence on the value and/or the rate of change of the control signal.

The method may comprise determining an operational response of the at least one consumer with reference to an operational target associated with the at least one consumer following adjustment of the pump supply in a predictive mode of control. The method may comprise storing predetermined target value(s) for the pump supply pressure PSP in dependence on the determined operational response “meeting” the operational target; and retrieve/apply stored predetermined target value(s) for the pump supply pressure PSP during subsequent implementation a predictive mode of control for the at least one of the consumers.

Accordingly, the method may comprise automatically adjusting various parameters for controlling the pump supply, such as the amount and timing of the increase in pump supply pressure, whilst also maintaining overall efficiency. The method may comprise setting a preferred balance between dynamic response and efficiency

The control system may comprise one or more controllers configured to: receive, from a pressure sensor of a load sensing LS system associated with the at least one of the consumers, a pressure signal indicative of a sensed load sensing pressure LSP associated with the at least one of the consumers; determine a rate of change of the sensed load sensing pressure from the pressure signal; and when operating in a load sensing mode of control of the pump supply, compute and generate a control signal for regulating a pump supply pressure provided by the pump supply in dependence on the rate of change of the sensed load sensing pressure LSP; wherein the one or more controllers are configured to receive and/or monitor data indicative of an actuation state of the at least one of the consumers and to determine, from the received/monitored data, when the at least one of the consumers is actuated; the method comprising using the one or more controllers to: determine from the data indicative of an actuation state of the at least one of the consumers when the at least one of the consumers is actuated; following a determination that the at least one of the consumers has been actuated, selectively enter a predictive mode of control of the pump supply in which the one or more controllers compute and generate a control signal to pre-emptively raise the pump supply pressure independently of the sensed load sensing pressure; and to monitor the sensed load sensing pressure whilst operative in the predictive mode of control and to revert to a load sensing mode of control in dependence on the value and/or the rate of change of the load sensing pressure.

The method may comprise generating an electronic pump supply control signal for adjusting the pump supply and using a transducer for converting the electronic pump supply control signal to a hydraulic pump supply control signal HPSCS having a pressure P _se t for forwarding to a hydraulic pump supply adjustment system. In a further aspect of the invention, there is provided computer software comprising computer readable instructions which, when executed by one or more processors, causes performance of the method of the previous aspect of the invention.

A further aspect of the invention provides a computer readable storage medium comprising the computer software of the preceding aspect of the invention. Optionally, the storage medium comprises a non-transitory computer readable storage medium.

Within the scope of this application it should be understood that the various aspects, embodiments, examples and alternatives set out herein, and individual features thereof may be taken independently or in any possible and compatible combination. Where features are described with reference to a single aspect or embodiment, it should be understood that such features are applicable to all aspects and embodiments unless otherwise stated or where such features are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the further accompanying drawings, in which:

Figure 4 is a schematic side view of an agricultural machine and implement combination embodying aspects of the invention;

Figure 5 is a schematic representation of an embodiment of a hydraulic system in accordance with the invention which is embodied in the combination of Figure 4.

Figure 4 illustrates a combination comprising a mobile agricultural machine 60 and an implement 62 attached to the rear of the machine, which combination embodies aspects of the present invention. The implement 62 can be any suitable agricultural implement attachable to an agricultural machine having hydraulic consumers supplied with pressurised hydraulic fluid from a hydraulic supply system on the machine 60. The implement 62 will be referred to as a rear implement 62 and a further implement having hydraulic consumers fed by the supply on the machine, not shown in Figure 4 but see Figure 5, may be attached to the front of the tractor and will be referred to as a front implement 63. The agricultural machine in the embodiment shown in the drawings and described below is specifically an agricultural tractor 60 and the rear implement 62 is a baler. Other types of agricultural implement commonly used with tractors, and which fall within the scope of the invention, include without limitation: a loading wagon, a towed sprayer, a plough, a row unit planter, and a towed potato harvester. Furthermore, the invention is not limited to application on tractors or other mobile agricultural machines but can be adapted for use with other mobile machines having a hydraulic supply system whether connected with an implement or not.

Figure 5 is a simplified representation of a hydraulic supply system 64 suitable for use on the tractor 60 and implement 62, 63 combination. The hydraulic supply system 64 incorporates an E-LS system and is configured in accordance with one or more aspects of the invention.

Hydraulic Network

The hydraulic supply system 64 has pump supply 66 including main pump MP which is of variable displacement type and a pump output controller 68 for adjusting the displacement of the pump. In an embodiment, the pump output controller 68 is configured in a manner similar to that illustrated in Figure 3. However, in other embodiments, alternative pump output controller arrangements can be adopted including any of those currently used with E-LS systems which enable an electronic controller to regulate and adjust the flow and/or pressure output of the pump supply 66.

The pump MP draws fluid from a tank 69 and supplies pressurised hydraulic fluid at a pump supply pressure PSP to consumers on the tractor and the implement via a pump supply line P. The tank 69 provides a reservoir for the hydraulic supply system in which the fluid is held generally at ambient pressure. The tank 69 is illustrated schematically in Figure 5. In practice in any given hydraulic supply system 64 there may a single tank 69 or multiple tanks 69.

The consumers on the tractor 60 include a hydraulic steering system SS, a central valve manifold CVM, and a rear valve manifold RVM. The steering system SS may include a hydraulic cylinder and control valve designated tractor consumer TC1 for moving the steered wheels. The control valve is connected to the pump supply line via a pressure port P and to the tank via a tank port T.

The central valve manifold CVM is generally installed in the middle of the tractor and includes a number of functional valves for controlling a corresponding number of hydraulic consumers located usually in or towards the middle and front area of the tractor. In the example illustrated, the central valve manifold CVM includes three functional valves CM 1 , CM 2, CM 3 assembled together and connected to the pump supply line via a common pressure port P and to a return line to the tank at a common return port T. Each valve is assigned to a specific consumer and the valves CMV1 , CMV2, CMV3 may have different configurations (e.g., ON/OFF, proportional valves, 3/2 valves, 4/2 valves) according the functional needs of their respective consumer. The valves CM 1 , CM 2, CMV3 are solenoid valves and each has a valve controller VC for controlling the solenoid. The number and configuration of the valves in the CVM may be varied to meet the requirements of the tractor manufacturer and/or the end customer. There may, for example, be more or fewer than three functional valves in the CVM.

The CVM has a common load sensing port LS1 and each of the valves CMV1 , CMV2, CM V3 have LS ducts connected to the common LS port LS1 by means of shuttle valves so that the highest load sensing pressure LSP generated by the various valves CMV1 , CMV2, CMV3 at any given point in time is forwarded to the LS port.

The CVM can be used to supply hydraulic fluid to various consumers such as, without limitation, a front linkage actuator FLC and an axle suspension system indicated as tractor consumer TC2. Valves in the CVM can also be used to supply consumers on a front implement 63 attached to the tractor indicated as FIC1. Each consumer on the front implement 63 being hydraulically connected to a respective valve CMV2 via front valve couplings FVC.

The RVM is installed in the rear of the tractor and is provided to supply consumers which are mainly in the rear area of the tractor and/or on a rear implement 62. The RVM is similar to the CVM in terms of design and variability and contains a number of functional valves indicated as RMV1 to RMV5 assembled together and connected to the pump supply line via a common pressure port P and to a return line to the tank at a common return port T. At least some of the valves in the RVM may be used to supply consumers on a rear implement 62 and/or on the tractor 60. In the exemplary embodiment illustrated, three of the valves, RMV3, RMV4, and RVM5, are connected with respective consumers RIC1 , RIC2, RIC3 on the rear implement 62 via rear valve couplings RVC. The RVC may be directly flanged to the RVM as described in EP2886926. As it is common to attach complex implements to the rear of a tractor, there may be more than three valves in the RVM for connection to consumers on a rear implement 62. There may, for example, be as many as six, seven, eight or more valves in the RVM assigned for connection to consumers on rear implements. At least some of the valves in the RVM may be assigned to consumers located at or towards the rear of the tractor such as actuators on a rear linkage system. In the exemplary embodiment shown, valve RMV1 is assigned to a pair of lower link hydraulic cylinders LLC being supplied in parallel and valve RMV2 is assigned to a hydraulically driven top link actuator cylinder TLC. In an alternative embodiment, the top link actuator may be a mechanical actuator and the valve RMV2 used for other purposes.

Each valve RMV1 to RMV5 in the RVM is a solenoid actuated valve and is provided with a valve controller VC which moves the solenoid and provides a pilot pressure. Each valve is configured according to the requirements of its respective consumer (e.g., ON/OFF, proportional valves, 3/2 valves, 4/2 valves).

The RVM has a common load sensing port LS2 and LS ducts of the valves RMV1 , RMV2, RMV3, RMV4, RMV5 are all connected to the common LS port LS2 by means of shuttle valves so that the highest load sensing pressure LSP generated by the various valves at any given point in time is forwarded to the common LS port LS2.

As with the CMV, the RVM can be configured to have any required number and configuration of valves depending on the number and requirements of the hydraulic consumers on the tractor and any implements that are expected to be attached to the tractor. It should be understood, therefore, that the configuration of the CVM and RVM shown in Figure 5 is for illustrative purposes only and can be varied.

The hydraulic supply system 64 includes a power beyond interface 70 to provide an “uncontrolled” supply of pressurised fluid to a rear implement 62 which requires more hydraulic functions than can be controlled using the available valves on the tractor. Such a complex implement 62 may be a baler, for example. The power beyond interface 70 includes quick release couplings 70a, 70b to connect the pump supply line P and a return tank line T on the tractor to a pump pressure supply line PI and a return line Tl respectively on the implement 62. The power beyond interface provides a pressurised fluid supply to an implement which is at the pump supply pressure PSP but which is otherwise uncontrolled on the tractor.

In a typical arrangement, the rear implement 62 has an implement valve manifold IVM similar to the CVM and RVM as described above. The IVM has a number of functional control valves IMV1 to IMV3 which are each connected to the implement pump supply pressure line PI through a common pressure port P and to the implement return line Tl via a common return port T. The IVM also has a common LS pressure signal port LS3 to which LS ducts of each of the valves IMV1 to IMV3 are connected via a series of shuttle valves or the like, arranged so that the highest consumer load sensing pressure LSP from the various valves in the IVM at any given point in time is reported to the common LS port LS3. Each valve IMV1 to IMV3 is connected to a respective consumer (e.g. a hydraulic cylinder or hydraulic motor) which are schematically designated RIC4 to RIC6. Each valve is configured according to the requirements of its respective consumer (e.g., ON/OFF, proportional valves, 3/2 valves, 4/2 valves). The valves are all solenoid controlled valves and each is provided with an electronic valve controller VC which moves the solenoid and provides a pilot pressure (supplied via pump connection to support the valve slider movement).

The number of valves in the IVM is selected depending on the number of consumers on the implement that are to be supplied via the power beyond interface and can be varied as required. Furthermore, there may be more than one valve manifold on the implement and/or one or more separate valves not incorporated into a manifold can be connected to the power beyond interface via suitable hydraulic lines.

In the embodiment shown, the tractor has a further hydraulic consumer in the form of a hydraulic motor 72 for driving a cooling fan CF. The hydraulic motor 72 is controlled by a cooling fan valve CFV which regulates the cooling fan motor to vary the speed of the fan. The CFV is a solenoid controlled valve having an electronic valve controller VC which is operably connected with an electronic controller 102 on the tractor. The controller is configured to actuate the CFV in order to adapt the motor speed to the cooling demand.

As illustrated in Figure 3, the hydraulic supply system may also be provided with a main pressure limiting valve MLV which opens to vent the pump supply P to the tank 69 if the pressure exceeds a predetermined pressure. The MLV is set to open at a pressure above the maximum permitted operating pressure of the system. This provides an additional level of safety in case the limitation of the pump supply pressure PSP through the pump controller should fail. For use with current tractor hydraulic supply systems, the MLV may be set to open a pressure value of around 250 bar for example. However, the pressure at which the MLV opens can be selected as appropriate for any given system.

The hydraulic supply system 64 illustrated in Figure 5 is exemplary only and the invention can be modified for use with hydraulic supply systems which have alternative layouts, including an alternative number and type of consumers and control valves. For example, the tractor 60 may have more than one pump and may have a fixed displacement pump in addition to the main pump MP for supplying other consumers such as a lubrication system for the driveline, a transmission (of hydrostaticmechanical split type) or a hydraulic brake system, for example. These are not shown in Figure 5 as they are not included in the E-LS control arrangements which are the subject of the present invention.

Electronic Network

Figure 5 also illustrates an electronic control system network 100 for the hydraulic supply system 64. As shown, the control network 100 includes a controller 102 on the tractor having an electronic processor 104. The processor 104 is operable to access a memory 106, which may be part of the controller 102, and execute instructions stored therein to perform the steps and functionality according to aspects of the present invention. The memory 106 may include any one or a combination of volatile memory elements (e.g., random-access memory RAM, such as DRAM, and SRAM, etc.) and non-volatile memory elements (e.g., ROM, hard drive, tape, CDROM, etc.). The memory 106 may store a native operating system, one or more native applications, emulation systems, or emulated applications for any of a variety of operating systems and/or emulated hardware platforms, emulated operating systems, etc. The memory 106 may furthermore store parameters or settings needed to operate the control systems and/or perform the methods as described below.

It should be appreciated by one having ordinary skill in the art that in some embodiments, additional or fewer software modules (e.g., combined functionality) may be stored in the memory 106 or in additional memory. In some embodiments, a separate storage device may be coupled to the data bus, such as a persistent memory (e.g., optical, magnetic, and/or semiconductor memory and associated drives). In a further embodiment, the memory 106 may be connectable with an off-board network architecture (via mobile communication or WLAN) to provide parameters or settings.

The processor 104 may be embodied as a custom-made or commercially available processor, a central processing unit (CPU) or an auxiliary processor among several processors, a semiconductor based microprocessor (in the form of a microchip), a macro processor, one or more application specific integrated circuits (ASICs), a plurality of suitably configured digital logic gates, and/or other well-known electrical configurations comprising discrete elements both individually and in various combinations to coordinate the overall operation of the controller 102.

Electronic communications among the various components of the control network 100, as indicated by the dashed lines, may be achieved over a controller area network (CAN) bus or via a communications medium using other standard or proprietary communication protocols (e.g., RS 232, Ethernet, etc.). Communication may be achieved over a wired medium, wireless medium, or a combination of wired and wireless media.

The controller 102 is in communication with each of the electronic solenoid valve controllers VC of the various valves on the tractor, with the pump output controller 68, and with various user interfaces such as a steering wheel SW, valve rockers represented as UI1 and UI2, a linkage control represented as UI3, and a touch screen TS. The touch screen is typically located within a cab of the tractor to provide information to the driver and receive input (e.g. to select, adjust and/or save settings). The touch screen TS may alternatively be replaced or enhanced by a keyboard to receive input. Indeed, any input or presentation of information whether by manual, speech or gestures may be included herein. Each user interface Ul may be permanently assigned to one consumer of the tractor or the implement. Alternatively, one or more of the user interfaces may be variably assignable to any one of two or more consumers by the operator. Such an assignment might be effected via the touch screen, for example.

The controller 102 may also receive further data, such as from a GPS receiver to determine the current vehicle position, and/or may be operative to control further devices. The rear implement 62 may also be connected to the tractor controller 102, say via a standardized agricultural ISOBUS for example, to exchange data and control between the implement and tractor as described later on. For this purpose, the implement 62 may be provided with an implement controller 110 which communicates with the tractor controller 102. Where present, an implement controller 110 may have an electronic processor 114 which is operable to access a memory 112, which may be part of the implement controller 110, and execute instructions stored therein to perform the steps and functionality according to aspects of the present invention.

The memory 112 may include any one or a combination of volatile memory elements (e.g., random-access memory RAM, such as DRAM, and SRAM, etc.) and non-volatile memory elements (e.g., ROM, hard drive, tape, CDROM, etc.). The memory 112 may store a native operating system, one or more native applications, emulation systems, or emulated applications for any of a variety of operating systems and/or emulated hardware platforms, emulated operating systems, etc. The memory 112 may furthermore store parameters or settings needed to operate the control systems as described below.

It should be appreciated by one having ordinary skill in the art that in some embodiments, additional or fewer software modules (e.g., combined functionality) may be stored in the memory 112 or additional memory. In some embodiments, a separate storage device may be coupled to the data bus, such as a persistent memory (e.g., optical, magnetic, and/or semiconductor memory and associated drives). In a further embodiment, the memory 112 may be connectable with an off-board network architecture (via mobile communication or WL N) to provide parameters or settings.

The processor 114 may be embodied as a custom-made or commercially available processor, a central processing unit (CPU) or an auxiliary processor among several processors, a semiconductor based microprocessor (in the form of a microchip), a macro processor, one or more application specific integrated circuits (ASICs), a plurality of suitably configured digital logic gates, and/or other well-known electrical configurations comprising discrete elements both individually and in various combinations to coordinate the overall operation of the controller 102.

Load Sensing Returning to the hydraulic supply system, at any given time, a highest of the load sensing pressure demands LSP from the consumers on the tractor 60 and any attached implements 62 is used to regulate the pump output controller 68 by means of a load sensing LS system. The load sensing system includes an electronic (electrohydraulic) load sensing (E-LS) system including a number of pressure sensors for sensing load sensing pressure demand signals LSP from consumers which are part of the E-LS system. Each of the pressure sensors is in communication with a controller 102 or 110 and forwards to the controller an electronic load sensing pressure signal ELSPS (a pressure signal) representative of the sensed consumer load sensing pressure LSP.

The electronic load sensing pressure signal ELSPS may be an analogue signal in which a characteristic of the signal is modulated in dependence on the pressure of the hydraulic load sensing pressure signal LSP. In an embodiment, the current of the ELSPS is modulated in dependence on the pressure of the hydraulic load sensing pressure signal LSP but in another embodiment it is the voltage. In an embodiment where the ELSPS is an analogue signal, the controller 102, 110 converts the ELSPS into a pressure value by reference to data stored in the controller (or to which the controller has access) which provides a correlation between the modulated characteristic and pressure for the sensed load sensing pressure LSP. This data may be provided in the form of a characteristic map or a look up table assigned to the sensor. In another embodiment, the pressure sensor has a CPU and communicates with the controller through a CAN interface. In this case, conversion of the analogue signal to a pressure value is made at the sensor and the pressure value forwarded to the controller 102, 110.

In the embodiment illustrated, a first pressure sensor 122 is connected with the LS port LS1 on the CVM where it is subject to the highest consumer load sensing pressure signal LSP of the valves in the CVM. A second pressure sensor 124 is connected with an LS port LS2 on the RVM where it is subject to the highest consumer load sensing pressure signal LSP of the valves in the RVM. A third pressure sensor 125 is connected with an LS port LS4 on the cooling fan valve CFV to sense the load sensing pressure of the cooling fan motor.

A fourth pressure sensor 126 on the tractor is connected with a LS coupling 70c of the power beyond interface. On the implement, the LS power beyond coupling may be hydraulically connected with the common LS port LS3 of the IVM so that the highest load sensing pressure demand LSP from the various valves in the IVM is forwarded to the fourth pressure sensor 126 when the implement is coupled to the tractor. However, for implements which have a controller 112, an implement pressure sensor 128 can be connected with the common LS port LS3 of the IVM. In this case, the implement pressure sensor 128 communicates with the implement controller 112 and forwards to the implement controller 112 an electronic load sensing pressure signal ELSPS representative of the sensed consumer load sensing pressure LSP at the IVM common LS port LS3. The implement controller 112 forwards data relating to the sensed load demand pressure LSP to the tractor controller 102. The implement controller 110 may process the load sensing pressure demand data and forward to the tractor controller 102 data which is modified or a signal which is a function of the sensed load sensing pressure signal LSP.

The load sensing pressure demand LSP of the steering system is also sensed electronically to form part of the E-LS system. Figure 5 illustrates two alternative arrangements. In one embodiment, an LS port LS5 of the steering system actuator/control valve TC1 is hydraulically connected by a LS signal line to an LS input port LS6 on the CVM. The LS input port LS6 is connected together with the LS ducts of each of the valves in the CVM to the common LS port LS1 by a suitable cascade of shuttle valves so that the highest load sensing pressure demand LSP from the steering system and the various valves CMV1 To CMV3 is reported to the common LS port LS1 to be sensed by the first pressure sensor 122. In an alternative embodiment, a dedicated pressure sensor 130 is provided to sense the load demand pressure LSP of the steering system. The steering system pressure sensor 130 may be hydraulically connected to the LS port of the steering system and electronically connected to the tractor controller 102 to forward to the controller an electronic load sensing pressure signal ELSPS representative of a sensed consumer load sensing pressure LSP of the steering system.

The tractor controller 102 is configured to select an electronic load sensing pressure signal ELSPS representative of the highest consumer load sensing pressure LSP forwarded to it, either directly from a pressure sensor or from the implement controller 112. The controller processes the selected signal and forwards an electronic pump supply control signal EPSCS to the output controller 68 of the main pump MP to vary the output of the pump MP in dependence on the highest sensed load sensing pressure LSP. Where the pump output controller 68 comprises a solenoid controlled pressure limiting valve 54 as illustrated in Figure 3, the tractor controller 102 forwards an electronic pump supply control signal EPSCS to actuate the solenoid of the pressure limiting valve 54 in order to vary the output of the main pump. Typically, the current of the electronic pump supply control signal EPSCS will determine the extent of movement of the solenoid and so will determine the pressure P _se t of the resulting hydraulic pump supply control signal HPSCS applied to the LS port 34 of the flow control valve 22’ and hence the supply pressure PSP of the main pump. The resulting pump supply pressure PSP can be calculated by equation 1 :

PSP = APst + Pset Equation 1

Where

APst is the static or stand-by pressure differential defined by the spring 26 in the flow control valve 22’, and

Pset is the pressure of the hydraulic pump supply control signal HPSCS provided at the LS pressure port of the flow control valve.

Where the implement has an electronical controller 110, communication between the tractor controller 102 and electronic components of the LS pressure control system on the implement, such as valve controllers VC and pressure sensors 128 of the IVM, is typically made via the implement controller 110, with data and instructions being transmitted between the implement controller 110 and the tractor controller 102 via a standardized ISOBUS connection.

In an embodiment, the controller 102 converts a target pressure value for P _se t to a current value for forwarding to the solenoid controlled pressure limiting valve 54 (or other transducer) as an analogue electronic pump supply control signal EPSCS. In another embodiment, the pump output controller 68 has a CPU and communicates with the controller 102 through a CAN interface. In this case, the controller 102 forwards the target set point pressure value P _se t to pump controller 66 in an electronic pump supply control signal EPSCS through a CAN interface and the pump CPU converts the pressure value to an analogue signal for controlling the pressure limiting valve 54 or other transducer.

Conversion of the target pressure value for P _se t to a current value may be made by reference to data which provides a correlation between a current value and the resulting pressure P _se t generated by the solenoid controlled pressure limiting valve 54 or other transducer. This data may be stored in, or is otherwise accessible to, the controller 102 or pump controller CPU and may be provided in a characteristic map or a look up table assigned to the valve 54 and/or the pump MP for example. In other embodiments it may be a voltage of the analogue which is modulated to control the output of the solenoid controlled pressure limiting valve 54.

The pressure sensors, the one or more controllers 102, 110, and the pump output controller 68 can all be considered as part of a control system for the hydraulic supply system.

Pressure Differential Set in Dependence on the Rate of Increase of Load Pressure Demand LSP

In accordance with an embodiment, the tractor controller 102 is programmed and configured to control adjustment of the output of the main pump MP in dependence not only on the value of the sensed load sensing pressure LSP but also in dependence on the rate of change of an increasing load sensing pressure demand LSP (referred to as the LSP pressure gradient).

In accordance with a suitable algorithm, the tractor controller 102 determines the LSP pressure gradient of a highest of the load sensing pressure signals LSP forwarded to it by the various pressure sensors in the E-LS network. Where the LSP pressure gradient is below a threshold value Tr, the controller 102 regulates the main pump output so that the supply pressure PSP is maintained above the load sensing pressure LSP by a first differential. In an embodiment, the first differential is the stand-by or static pressure differential AP _s t defined by the spring 26 in the flow control valve 22’ and the tractor controller 102 forwards an electronic pump supply control signal EPSCS to the pressure limiting valve 54 calibrated to generate a hydraulic pump supply control signal HPSCS having a pressure P _se t that is the same as (or equivalent to) the load demand pressure LSP. The resulting pump supply pressure PSP under these circumstance can be derived from equation 1 where P _se t = LSP so that equation 1 can be re-written as:

PSP = APst + LSP Equation 2

Accordingly, when the rate of change of an increasing consumer load sensing pressure LSP is below the threshold value Tr, the E-LS system operates broadly in the same manner as a conventional E-LS system. However, when the rate of increase of a consumer load sensing pressure LSP is at or above the threshold value Tr, the controller 102 is programmed and configured to regulate the main pump output so that the supply pressure PSP is maintained above the load sensing pressure LSP by a second differential larger than the first pressure differential AP _s t. The second pressure differential can be considered to be made up of the static or stand-by pressure differential AP _s t regulated by the spring 26 in the flow control valve 22’ plus an additional dynamic pressure differential APd _yn which is applied by the controller 102 through the hydraulic pump supply control signal HPSCS generated by the pressure limiting valve 54. In this case, the tractor controller 102 forwards to the pressure limiting valve 54 an electronic pump supply control signal EPSCS calibrated to generate a hydraulic pump supply control signal HPSCS having a pressure P _se t thatis higher than the load demand pressure LSP by the amount of the dynamic pressure differential APd _yn , such that P _se t is equal to the load demand pressure LSP plus the dynamic pressure differential APd _yn (P _S et= LSP + APd _yn ). Equation 1 in this case can be re-written as:

PSP = Pst + LSP + APd _yn Equation 3

By providing an increased pressure differential when the rate of increase of the load sensing pressure LSP is at or above a certain threshold Tr, the dynamic response of the system is increased. The dynamic pressure differential APd _yn may be applied for a set time period once it is triggered as discussed below

In a first example, AP _s t is set at 20 bar, the threshold value Tr of the LSP pressure gradient is set at 5 bar/50 ms (a pressure increase of 5 bar in 50 ms), and the dynamic pressure differential APd _yn is set at 20 bar.

The following tables compare the dynamic performance of a conventional E-LS system and an E-LS system in accordance with the embodiment described above when a consumer valve is opened to produce a consumer load sensing pressure LSP rapidly increasing to 140 bar. Table 1 below illustrates a typical dynamic response of a conventional E-LS control system in these circumstances.

Table 1 - pressure differential increased by LSP in accordance with prior art

As illustrated in table 1 , at each cycle the pressure P _se t of hydraulic pump supply control signal HPSCS forwarded to the pump controller is equal to the consumer load sensing pressure signal LSP at that time. In the arrangement illustrated, it takes seven cycles for the system to increase the pump supply pressure PSP to 160 bar as required to maintain the pump supply pressure higher than the final consumer load sensing pressure LSP of 140 bar by the static pressure differential AP _s t Table 2 below shows the effect of increasing the pressure P _se t of the hydraulic pump supply control HPSCS to include a dynamic pressure differential APd _yn of 20 bar when the rate of increase of LSP reaches the threshold value Tr of 5 bar/50 ms.

Table 2 - Pressure differential increased depending on rate of change of LSP in accordance with an aspect of the invention

It can be seen from table 2 that increasing P _se t to include an additional dynamic pressure differential APd _yn when the rate of increase of the load sensing pressure LSP reaches the threshold Tr, fewer cycles (four in this case) are required to increase the pump supply pressure PSP to 160 bar using the method according to the invention. This considerably increases the speed of response of the system in adapting the pump supply pressure PSP to meet a rapidly rising consumer load.

In the above example, once application of a dynamic pressure differential APd _yn has been triggered by the rate of increase of the load sensing pressure reaching the threshold Tr, the dynamic pressure differential APd _yn is applied continuously until the consumer demand is met, that is to say when the pump supply pressure PSP equals the sum of the load sensing pressure LSP, the static pressure differential AP _s t , and the dynamic pressure differential APd _yn . However, in an alternative embodiment, the dynamic pressure differential APd _yn is only applied for a limited time period after its application is triggered by the rate of increase of the load sensing pressure LSP reaching the threshold Tr and is then ramped down. The time period over which the dynamic pressure differential APd _yn is applied will be referred to as an application period (AP). Applying a dynamic pressure differential APd _yn for a time limited application period AP has been found to provide a dynamic response to a rapidly increasing load sensing pressure LSP but in a more efficient way than applying a dynamic pressure differential APd _yn continuously. The relatively brief application of a dynamic pressure differential APd _yn gives the pump output supply an initial boost to meet the hydraulic load demand but without over supplying the hydraulic system. The application period AP can be selected to meet system requirements but the applicant has found an application period AP in the range of 50 to 300 ms, or in the range of 80 to 200 ms, or in the range of 90 to 150 ms, or in the region of 100 ms to be effective. The system may be configured to apply a dynamic pressure differential APd _yn for different application periods AP depending on operational requirements, say for different consumers.

In embodiments where the dynamic pressure differential APd _yn is applied for a time limited application period AP, the system may also be configured to set a delay period DP following one application of a dynamic pressure differential APd _yn before a subsequent application of a dynamic pressure differential APd _yn is permitted. The application of a delay period DP between applications of dynamic pressure differential APd _yn helps to maintain system stability, reducing the risk that oscillations in a load sensing pressure LSP signal are unduly amplified by the addition of a dynamic pressure differential APd _yn . The delay period DP is timed from the point at which a dynamic pressure differential APd _yn is first applied. In other embodiments, the delay period DP is timed from the point at which application of a dynamic pressure differential APd _yn is stopped. Indeed, the delay period DP can be timed from any suitable point in relation to an application of a dynamic pressure differential APd _yn . Once the delay period DP has expired, a dynamic pressure differential APd _yn can be applied again for the set application period AP if the operating conditions meet the criteria for application of a dynamic pressure differential APd _yn . For example, if at the end of the delay period DP following a one application of a dynamic pressure differential APd _yn the rate of increase of the load sensing pressure LSP is at or above the threshold T r, the controller 102 will again apply a dynamic pressure differential APd _yn for a further application period AP and a further delay period DP begins. The delay period DP can be selected to meet system requirements but the applicant has found that where the delay period DP is timed from the start of a dynamic pressure differential APd _yn being applied, a delay period DP in the range of 600 to 1400 ms, or in the range of 800 to 1200 ms, or in the region of 1000 ms to be effective. The delay period DP is longer than the application period AP and once a dynamic pressure differential APd _yn has been ramped down, no dynamic pressure differential APd _yn is applied for at least the remainder of the delay period DP. Thus the delay period DP defines a minimum interval between applications of a dynamic pressure differential APd _yn .

In other embodiments, once application of a dynamic pressure differential APd _yn is triggered by the rate of increase of the load sensing pressure LSP reaching the threshold Tr, the dynamic pressure differential APd _yn is applied continuously until the rate of rate of increase of the load sensing pressure LSP falls below a threshold value Tr*. This threshold value Tr* may be the same as the threshold value Tr which triggers the application of a dynamic pressure differential APd _yn or it may be a different value. Again the system may apply a delay period DP following one application of a dynamic pressure differential APd _yn before another application is permitted.

A delay period DP between applications of dynamic pressure differential APd _yn can be adopted in any of the embodiments disclosed herein.

The performance of the hydraulic supply system will be influenced by the choice of dynamic pressure differential APd _yn and threshold value Tr broadly as follows:

1. A higher value for the dynamic pressure differential APd _yn will increase the system dynamics as it leads to a faster reaction time to change the pump supply pressure PSP once the rate of increase of the consumer load sensing pressure LSP has reached the threshold value. A lower APd _yn value would tend to lead to a slower response but perhaps a smoother and less abrupt change in pump supply pressure PSP.

2. Lowering the threshold value T r will increase system dynamics as it causes the dynamic pressure differential APd _yn to be applied sooner when an increase in load sensing pressure LSP occurs, whilst a higher threshold will delay application of the dynamic pressure differential APd _yn leading to a less dynamic system response. Increasing the dynamic pressure differential APd _yn and/or lowering the threshold value Tr of the rate of increase of the load sensing pressure LSP can both be used to provide higher system dynamics. However, use of a lower threshold value Tr is dependent on the ability of the system to sense the load sensing pressure to the tolerances required for reliable control with a smaller threshold value Tr. In view of this it is generally preferred to increase the dynamic pressure differential APd _yn in order to increase the dynamic performance of a hydraulic system. However, a lower threshold value Tr can be used to increase system dynamics where the value selected and the system permits reliable operation.

As both the dynamic pressure differential APd _yn and the threshold value Tr of the rate of increase of consumer load sensing pressure LSP influence the dynamic behaviour of the pump adjustment based on consumer load sensing pressure LSP, they are collectively referred to as “LS dynamic parameters”.

The actual values for the threshold Tr and the dynamic pressure differential APd _yn are selected as appropriate to any given hydraulic system and the person skilled in the art will be able to establish suitable values by, for example, trial and error. However, in trials with a typical hydraulic supply system on a tractor having a pump MP with a maximum delivery rate of about 229.5 l/min at an engine speed of 2700 RPM and a maximum pump supply pressure of about 230 bar, the applicant has found that a dynamic pressure differential APd _yn in the range of 10 bar to 40 bar and a threshold value Tr in the range of 4 to 10 bar/50ms are generally suitable. Values outside of these ranges though might also be applicable in some hydraulic systems.

Values for the LS dynamic parameters may be stored in the memory 106 of the tractor controller 102 or be otherwise accessible to the electronic processor 104. LS dynamic parameters may be provided as a default setting permanently saved to the memory 106 or the system may be configured so the values of the LS dynamic parameters can be set or modified via a user interface, such as the touch screen. This would enable the parameters to be input or adjusted by a driver or other user. Where the LS dynamic parameters can be input or modified, this would enable a driver to set the LS dynamic parameters to provide a suitable dynamic performance for a particular job or task and/or enable different values for the parameters to be used for different implements. For example, use of a particular implement may be improved by a more dynamic response whilst a different type of implement may be better suited to a less dynamic response. The ability to vary the value of one or more of the LS dynamic parameters enables the driver to adapt the hydraulic supply system accordingly. In a further alternative, instead of entering respective values for the threshold Tr and/or the dynamic pressure differential APd _yn , the system may be configured to operate in different LS modes which may be optionally selected by a user. The system could, for example, be configured to be operable in a “dynamic mode” or an “efficiency mode”, with the values of the LS dynamic parameters being set to provide a faster response to increases in consumer load sensing pressure LSP in the dynamic mode and to provide a slower response time in efficiency mode to reduce power consumption. The system may be further configured to enable selection of a “balanced mode” with the values of the LS dynamic parameters set in-between the dynamic and efficiency modes. The use of predefined, selectable modes require less skill and experience by the driver whilst still providing an ability to customize the hydraulic supply system settings.

In a further optional refinement, the method may utilise more than one threshold value Tr for the rate of increase of load sensing pressure LSP and more than one dynamic pressure differential APd _yn so as to enable a stepped ramp up of the dynamic pressure differential APd _yn depending on the rate of increase of the load sensing pressure LSP. Accordingly, in an embodiment the system may configured to apply a first dynamic pressure differential Ap1d _yn , for example 20 bar, when the rate of increase of the load sensing pressure LSP is at or above a first threshold value Tr1 but below a second threshold value Tr2, and to apply a higher, second dynamic pressure differential AP2d _yn , for example 40 bar, when the rate of increase of the load sensing pressure LSP is at or above the second threshold value T r2. For example, a first threshold value Tr1 could be set at 5bar/50ms and a second threshold value Tr2 set at 10bar/50ms. It will be appreciated that the values for Tr1 , Tr2, AP1d _yn , and AP2d _yn mentioned above are illustrative only and that the values used can be selected as desired to suit any particular hydraulic supply system and performance requirements. It should also be appreciated that more than two different dynamic pressure differentials can be utilized and implemented at suitable threshold values for the rate of increase of the load sensing pressure.

In a yet still further optional refinement, different settings for the LS dynamic parameters are adopted depending on the value of the load sensing pressure LSP. For example, a first dynamic pressure differential AP1d _yn and/or threshold value T r1 for the LSP pressure gradient is/are applied when the load sensing pressure LSP is below a first threshold pressure TP1 and a second dynamic pressure differential AP2d _yn and/or threshold value Tr2 for the LSP pressure gradient is/are applied if the load sensing pressure LSP is equal to or above the first threshold pressure TP1. In an embodiment, the LS dynamic parameters may be selected to provide a less dynamic response at higher load sensing pressures. Thus the LS dynamic parameters can be set to provide a fast reaction initially (e.g. to overcome internal inertia in the pump controller when starting to pivot the pump) but then provide a smoother control of the pump supply pressure as the dynamic behaviour of the pump increases. This also provides a tiered dynamic response and it will be appreciated that more than two ranges of load sensing pressure LSP in which different LS dynamic parameters are adopted can be defined. In one example, different LS dynamic parameters are applied in two ranges:

Range 1 : a first dynamic pressure differential AP1d _yn , say in the region of 10-20 bar, is applied when the rate of increase of the load sensing pressure is at or above a threshold value Tr1 of 7 bar/50ms and the load sensing pressure LSP is below a first pressure threshold TP1 , say in the region of 40-45 bar.

Range 2: a second dynamic pressure differential AP2d _yn , say in the region of 5-10 bar, is applied when the rate of increase of the load sensing pressure is at or above a second threshold value Tr2 of 5 bar/50ms and the load sensing pressure LSP at or above the first pressure threshold TP1 , say in the region of 40-45 bar.

It will be noted that the threshold value Tr1 of the rate of increase of the load sensing pressure is slightly higher in the first range than the second range. The means that the system will wait for a higher increase per time of the load sensing pressure LSP before applying the first dynamic pressure differential AP1d _yn . Nevertheless, since the dynamic pressure differential AP1d _yn applied in the first range is significantly higher than that applied in the second range, the dynamic response is higher overall in the first range than the second. In tests it has been found that the control system is less prone to oscillation by applying a slightly higher threshold value Tr initially. However, there may be circumstances where the threshold Tr for the load sensing pressure LSP gradient is the same in all LSP pressure ranges or where a lower threshold Tr is used for a range where the LSP pressure is lower than in a later range where the LSP pressure is higher.

Additional ranges could be added with a second, a third or more threshold pressures TP2, TP3,...TPn with a different dynamic pressure differentials AP23d _yn , AP4d _yn , ... APridyn and/or threshold value(s) Tr for the LSP pressure gradient being applied in each range.

In one embodiment, no dynamic pressure differential APd _yn is applied once the LSP reaches a threshold pressure TP. Thus in the above example, in a third range where the LSP pressure is at or above a threshold value TP2 of 70 bar, no dynamic pressure differential APd _yn is applied regardless of the rate of increase of the load sensing pressure LSP.

The actual values for the dynamic pressure differential(s) AP1d _yn , AP2d _yn , the threshold value(s) Tr for the LSP pressure gradient, and threshold pressure(s) TP can be selected to meet system requirements and are not limited to the above examples.

In an embodiment, the controller 102 is configured to require that the conditions for a particular range are met for a set period of time, referred to as a range delay period RDP, before a dynamic pressure differential APd _yn for that range is applied. The range delay period RDP may be in the region of 150 to 450 ms, or in the range of 200 to 400 ms, or in the range of 250 to 350 ms, for example. Thus if the system is operating in range 1 and the load sensing pressure LSP increases to or above the threshold value TP1 indicating a change to range 2, the controller 102 waits for the range delay period RDP to expire before the dynamic pressure differential AP2d _yn for range 2 can be applied. During this time delay, no dynamic pressure differential APd _yn is applied to control the output of the pump. If after expiry of the range delay period RDP the conditions for range 2 are still met, the dynamic pressure differential AP2d _yn for range 2 is adopted and can be applied if the appropriate threshold Tr2 for the load sensing pressure LSP gradient in that range is met. However, if during the range delay period RDP the load sensing pressure LSP indicates a further change of range, say back to range 1 , a further range delay period RDP is applied from the moment the new range is triggered before the dynamic pressure differential AP1d _yn for the new range can be applied.

Where the system is configured to apply a dynamic pressure differential APd _yn for a limited application period AP when triggered and to apply a minimum delay period DP between applications of a dynamic pressure differential APd _yn , the system can be configured to apply the both a minimum delay period DP and a range delay period RDP. In this case, the controller 102 may be configured to apply the delay period DP and the range delay period RDP concurrently should a change of range occur whilst a delay period DP is still running following an earlier application of dynamic pressure differential APd _yn in the previous range. Typically, the delay period DP will be longer than the range delay period RDP.

To further clarify concurrent running of the delay period DP the range delay period RDP, two examples are considered where the delay period DP is set to 1000 ms and the range delay period RDP is set to 300 ms. In the examples, a change from range 2 to range 1 takes place after the dynamic pressure differential AP2d _yn for range 2 has been applied but before the end of the delay period DP triggered by that application.

In a first example, the change of range takes place 600 ms after the delay period DP began. In this case, the range delay period RDP ends 900 ms after the delay period DP had begun. Accordingly, when the delay period DP expires after 1000 ms, the LS dynamic parameters for range 1 are adopted and the dynamic pressure differential AP1d _yn for range 1 can be applied, provided the conditions for range 1 are still met and the rate of increase of the load sensing pressure is at or above the threshold value Tr1 for range 1 at the time. If the dynamic pressure differential AP1d _yn is subsequently applied, this will be applied for the application period AP and a further delay period DP is commenced.

In a second example the change in range takes place 800 ms after the delay period DP has begun. In this case, the delay period DP expires 100 ms before the end of the range delay period RDP. Accordingly, application of the LS dynamic parameters for range 1 is delayed for a further 100 ms after the end of the delay period DP. After the range delay period RDP has expired (1100 ms after the previous application of dynamic pressure differential AP2d _yn when the system was operating in range 2) the dynamic pressure differential AP1d _yn for range 1 can be applied, provided the conditions for range 1 are still met and the rate of increase of the load sensing pressure is at or above the threshold value Tr1 for range 1 at the time. If the dynamic pressure differential AP1d _yn is applied, this will be applied for the application period AP and a further delay period DP is commenced.

Should a change of range occur during the application period AP, the controller continues to apply the dynamic pressure differential APd _yn until the end of the application period AP. The controller will also concurrently apply the delay period DP and the range delay period RDP before any further dynamic pressure differential APd _yn is applied. Use of the delay periods in this way helps to maintain system stability when changing between ranges and smooths reaction when a range is maintained.

It is expected that varying the LS dynamic parameters in discreet ranges of load sensing pressure LSP will offer smoother control with less risk of oscillation. However, in some systems, the LS dynamic parameters may be varied in proportion (e.g. a linear or other mathematical relationship) to the value of pressure of the load sensing pressure LSP, at least over a certain range of pressures.

Automatic Adaptation of LS Dynamic Parameters

In an embodiment, the controller 102 is programmed to use one or more algorithms to adapt the LS dynamic parameter settings automatically. In such an arrangement, target values may be defined for at least one operational target or parameter. Examples of operational targets might include a desired time limit by which a certain pump supply pressure PSP is achieved depending on the sensed load sensing pressure demand LSP. The controller may be enabled to permanently adapt the LS dynamic parameter settings for a given consumer. For example, if for a particular consumer the ideal value is to adjust the pump supply pressure PSP to match a load sensing pressure of say 100 bar within 200ms, the system measures the change in pump supply pressure PSP values against time and adapts the LS dynamic parameter settings (e.g. increases the dynamic pressure differential APd _yn ) to enable the target to be met. The adapted settings may be stored, say in a lookup table, in a memory accessible to the controller from which they can be subsequent recalled and/or applied in respect of that consumer and/or under certain operating conditions.

Thus in a self-learning system, the controller may compare the set value of the pump supply pressure PSP and the response of the LS system to adjust LS dynamic parameter settings. The controller may be programmed to apply a time limit for meeting the set pump supply pressure PSP. If the time limit is exceeded the controller changes the LS dynamic parameters to a more dynamic setting (e.g. by increasing the dynamic pressure differential APd _yn ). This may be an iterative process. The settings derived can be stored in memory, say for a particular combination of tractor and implement for subsequent use when that particular tractor/implement combination is detected or input by a user. The controller may be configured to update a model used to control the pump supply pressure with LS dynamic parameter settings derived during runtime. In an embodiment, the system is additionally or alternatively configured to take into consideration actuation of a consumer III to adapt the LS dynamic parameter settings for the consumer assigned to that III. Where the III is operated in a manner that indicates a demand or a faster or greater actuation of the consumer, then the controller may apply a more dynamic setting for the LS dynamic parameters (e.g. a higher dynamic pressure differential APd _yn ) than if a slower or smaller actuation is requested. Where the III is a rocker switch for example, the degree and/or speed of movement of the rocker may be monitored. In this case, a quicker movement of the rocker switch may be indicative that a fast response is required whilst a larger or longer movement of the rocker switch may be indicative that a greater actuation is required. Alternatively, the output signal from the III may be analyzed to determine the size and speed of the requested actuation. By recording a III input (in terms of deviation or actuating speed), the system can be enabled to recognize a similar III input and apply suitable LS dynamic parameters as previously determined.

Additional Electronic Stand-By Pressure Differential

In the embodiments described above, the stand-by pressure differential AP _s t is wholly set hydro-mechanically by the spring 26 in the flow control valve 22’ and can be designated as a mechanical stand-by pressure differential M-Ap _s t. This mechanical stand-by pressure differential M-AP _s t is applied at all times when the pump is being driven, including whilst the engine is being started.

In a further embodiment, the E-LS system is configured to apply an additional hydro- electronically defined stand-by pressure differential E-AP _s t to increase the overall stand-by pressure differential Ap _s t. This can be designated as an electronic stand-by pressure differential E-AP _s t. In order to produce the electronic stand-by pressure differential E-Ap _s t, the controller 102 sends an electronic pump supply control signal to the pressure limiting valve 54 to generate a hydraulic pump supply control signal HPSCS having a pressure P _se tat the LS port 34 of the flow control valve 22’ which causes the pump supply pressure to be raised at least by the amount of the E-AP _s t.

The controller 102 may be configured to apply the electronic stand-by pressure differential E-AP _s t at all times even when there is no load sensing pressure LSP. Thus, when the pump is running but there is no load sensing pressure, P _se t will be equal to the electronic stand-by pressure differential E-AP _s t. The resulting pump supply pressure PSP can be calculated by equation 4:

PSP - M-Apst + E-APst Equation 4 Where

M-APstis the mechanically defined stand-by pressure differential defined by the spring 26 in the flow control valve 22’, and

E-APst is the electronically defined stand-by pressure differential.

When a load sensing pressure LSP arises and is forwarded to the controller 102, the controller will increase P _se t to include the electronically defined stand-by pressure differential E-Ap _s t, the load sensing pressure LSP, and any dynamic pressure differential Apd _yn as appropriate depending on the rate of increase of the load sensing pressure LSP as described above. The resulting pump supply pressure PSP can be calculated by equation 5:

PSP = M-Apst + E-APst + LSP + APdyn Equation 5

Where

M-APstis the mechanically defined stand-by pressure differential defined by the spring 26 in the flow control valve 22’,

E-Apst is the electronically defined pressure differential, LSP is the load sensing pressure forwarded from a consumer, and APdyn is the dynamic pressure differential applicable depending on the rate of increase of the LSP.

The electronic stand-by pressure differential E-AP _s t is applied to raise the overall stand-by pressure differential and could be applied whenever the engine is running or in response to an LSP from one or more consumers. In an embodiment, an electronic stand-by pressure differential E-AP _s t is applied when a load sensing pressure LSP from a consumer on an attached implement is detected to compensate for losses in the system due to the long hydraulic lines but is not dependent on the rate of change of the LSP.

In an embodiment, the controller 102 is configured to apply the electronic stand-by pressure differential E-AP _s tonly once the engine of the tractor is determined to be running normally but not during engine start up. In an embodiment, the controller 102 is configured to apply the electronically defined stand-by pressure differential E- APst once a condition, or a set of conditions, is/are met which indicate that the engine has started and is running properly. In an embodiment, the controller 102 is configured to apply the electronic stand-by pressure differential E-AP _s tonce the engine RPM exceeds a set speed for a set period of time, such as 400 R/min for more than 4 seconds for example. The controller may receive or be configured to monitor data relating to engine speed from one or more sensors, e.g., an engine speed sensor, (indicated schematically at 103 in Fig. 5) to determine when the engine has started and is running sufficiently for the electronic stand-by pressure differential E-AP _s tto be applied.

Predictive Pump Adjustment

In hydraulic supply systems on agricultural machines such as tractors, it is known to increase pump delivery automatically when a consumer demand is initially detected without considering the load sensing pressure LSP. This results in a fast response but may decrease efficiency.

In accordance with an aspect of the invention, the hydraulic supply control system is configured to initially increase the pump supply pressure irrespective of the load sensing pressure LSP in a predictive mode when a consumer is first actuated and to subsequently revert to a load sensing mode of adjusting the pump supply pressure PSP in dependence on the load sensing pressure LSP.

The control system may be configured to subsequently revert to adjusting the pump supply pressure PSP in dependence on the load sensing pressure LSP in a load sensing mode of pump supply control if: a) a rate of change of the detected load sensing pressure LSP is at or below a threshold value; b) a rate of change of the detected load sensing pressure LSP shows a general decrease indicative that the hydraulic demand of the at least one of the consumers will be met within a given time limit; c) the pump supply pressure PSP is determined to be at least within a predetermined percentage of the detected load sensing pressure LSP; or d) if the detected load sensing pressure LSP as at or above a threshold value.

The predetermined percentage in option c) may be 80%, or 90%, or 95%, or 100%. Thus the control system may switch to load sensing control of the pump supply when the pump supply pressure is at or above the load sensing pressure or when it is approaching the load sensing pressure. In an embodiment, the control system is configured to change to a load sensing based adjustment after a set time limit if such a change has not been triggered prior to the end to the time limit. This provides a fallback position to ensure a switch to load sensing based control in the event the pump supply is unable to meet the load sensing demand rather than maintaining a high pump output.

In an exemplary embodiment, the controller 102 is configured to set the pump supply to a high delivery rate immediately when activation of a consumer is first determined, e.g. when a consumer III is activated, and, if the rate of change (increase) of load sensing pressure LSP from that consumer falls below a threshold value T, say 2 bar /50 ms, indicating that that the pump supply is reaching a level to meet the demand of the consumer(s), the controller proceeds to regulate the output of the pump supply in dependence on the load sensing pressure LSP. Instead of considering the shortfall of a threshold value T, the controller may alternatively proceed to regulate the output of the pump supply in dependence on load sensing pressure LSP when rate of change of the load sensing pressure LSP shows a general decrease indicating that the pump supply will soon meet the consumer demand, i.e. within a given time limit.

In an alternative approach, the pump is initially controlled in a predictive mode to raise the pump supply pressure PSP irrespective of the reported load sensing pressure LSP at the time when activation of a consumer is first determined and in parallel the controller 102 monitors the load sensing pressure LSP signal from the consumer. If the load sensing pressure LSP does not change (e.g. the rate of change of the load sensing pressure LSP is at or close to zero) and the pump supply pressure PSP is at a higher value (indicating that the pump is more than capable to meet the demand), this system may return to a LS based pump adjustment.

Alternatively, the controller may be configured to return to a LS based pump adjustment if the load sensing pressure LS is at or above a predetermined threshold value.

In respect of any of the above embodiments, the controller may be arranged to revert to a load sensing based control of the pump supply after a set time if a change to load sensing mode of a control is not triggered before the end of the time limit.

When operative in the load sensing mode of control, the control system may be configured to regulate the output of the pump supply in dependence on both the value and the rate of increase of the load sensing pressure LSP and apply a dynamic pressure differential APd _yn as described above. However, this aspect of the invention could also be adopted in hydraulic supply control systems which are configured to regulate the output of the pump supply in dependence on the value the load sensing pressure LSP, without taking the rate of change of the load sensing pressure LSP into account when adjusting the pump supply pressure PSP, provided such systems are capable of determining the rate of change of load sensing pressure LSP for use in determining when the predictive mode of control is to be terminated.

These type of predictive pump adjustment protocols can be applied for all consumers or only selectively applied for one or more specific consumers. For example, the controller 102 may be configured to enter a predictive mode of pump supply control only when a particular consumer (or consumers) requiring a fast response, such as the steering system, is/are activated but not when a consumer, such as the cooling fan motor, which does not generally require a fast response is activated.

The controller 102 can be configured to monitor various operational parameters to determine when a particular consumer has been actuated and that an increased hydraulic load demand can be expected. In an embodiment, the controller 102 is configured to receive and/or monitor data/signals from the III and/or valve controllers VC for at least some of the hydraulic consumers. Such data/signals are indicative of an actuation state of the consumers and the controller 102 is programmed to determine from the received/monitored data/signals when a consumer has been or is being actuated. In a further refinement, the controller may be configured to enter a predictive mode of control for a particular consumer in dependence on parameters of a control signal/data from a user interface III for that consumer. Thus the controller 102 may be configured to enter a predictive mode of pump supply control if the control signal/data from the III reaches a predetermine threshold value (indicative of the amount of deviation of the III) or if the rate of change of the control signal (indicative of the speed of actuation of the III) reaches a predetermined threshold value. For example, in respect of the steering system, the controller 102 could be programmed to enter a predictive mode of control of the pump supply if the steering wheel is turned through a given angle and/or at or above a given rotational speed.

Predictive pump supply adjustment as described above can be combined with selflearning techniques such as those described in the section headed Automatic Adaptation of LS Dynamic Parameters so that the system is configured to “learn” an appropriate predictive pump supply adjustment based on a III input by optimizing the setup values to meet an operational target. By recording a III input (in terms of deviation or actuating speed), the system can be enabled to recognize a similar III input and apply a particular set point for the pump supply pressure which meets the operational target efficiently. This may, for example, be a lower set point pump supply pressure than is used initially when entering the predictive mode of control for the particular consumer. For example, in response to a first III input for a particular consumer, the controller 102 may adjust the pump supply pressure to a first set point which is relatively high and monitor the pump supply pressure PSP against the actual load sensing pressure demand of the consumer arising as a consequence of the III input. If the controller determines that the pump supply pressure PSP exceeds the highest actual consumer load sensing pressure LSP reported by an amount outside of preset tolerances, the controller may set the highest actual reported load sensing pressure as a predicted load sensing pressure for that III actuation and apply this setting to determine a revised set point for the pump supply pressure when a predictive adjustment of the pump supply is subsequently trigged for the same or a similar III input.

Alternatively, the operational target may be a set time limit for response of the particular consumer. Thus the target may be a set time limit for the consumer to respond to its actuation. Data from one or more sensors arranged to determine response of the consumer is provided to the controller and the controller 102 configured to automatically adjust the set point for the pump supply pressure so as to meet the set time limit using the lowest possible pump supply pressure PSP. In the case where a consumer is an actuator which moves a component, a sensor or sensors may be arranged to detect movement of the component as indicative of the response of the consumer.

The system may also be configured to be self-learning by comparing the set values of the pump supply pressure PSP and the response of the LS load sensing pressure signal LSP to adjust setting of the LS dynamic parameters.

The controller may be configured to update a model used to control the pump supply pressure with set points for the pump supply pressure and/or LS dynamic parameter settings derived during runtime. The settings learned may be stored for a combination of tractor/implement for subsequent use when that tractor/implement combination is detected or input.

Various modifications to the systems and methods according to the invention will be apparent to those skilled in the art, without departing from the scope of the invention. For example, the main pump MP may be a fixed displacement pump and the pump supply may be configured generally as illustrated in Figure 2. In this case, the pump supply pressure PSP may be regulated by directing a hydraulic LS pump supply control signal P _se t from a solenoid controlled pressure limiting valve similar to the pressure limiting valve indicated with 54 in Figure 3 to the load sensing port 48 of the proportional pressure compensator valve 40. The solenoid controlled pressure limiting valve 54 being controlled by the electronic pump supply control signal EPCS from the tractor controller 102.