METHOD AND SYSTEM FOR A MARINE POWER STEERING SYSTEM

Field of the invention

The present invention relates to a marine power steering system comprising an electronic control unit and a rudder device.

The electronic control unit is arranged for receiving steering signals from two or more steering devices, where the control unit is further arranged for computing and transmitting a rudder control signal that is a function of said steering signals. The rudder device is arranged for receiving said rudder control signal and, based on said rudder control signal, steering a positioning device such as a rudder or a thruster, so as for changing or maintaining the heading of said boat.

Background of the invention

Marine power steering systems are well known in the prior art. Most systems comprise hydraulic parts or electro-hydraulic parts in combination with different types of backup systems, control systems, autopilot systems, safety systems, etc. as known to a person skilled in the art.

Marine vessels may comprise two or more steering devices, such steering devices being arranged for example on a flybridge in addition to a steering device arranged on an ordinary bridge as often found on yachts etc. Oil tankers often require a plurality of steering devices to enable visual contact with surrounding obstacles to provide safe voyage, for example when entering or leaving ports.

In prior art there exist many solutions to the problem of transferring command of the ship from one steering device to another steering device on board a ship. Usually there is an interlock system between the steering devices which enables only one active steering device at a time, thereby avoiding a problem of "competing helmsmen", where each of the helmsmen are trying to control the ship at the same time. Another problem related to a marine vessel with a plurality of steering devices, is to sense the rudder position and report the rudder position

to each steering device such that when the steering device is enabled by the interlock system, the movement of the steering wheel starts from the position the rudder is actually located in when the activation of the steering device takes place. In prior art there exist many complex solutions to these demands.

In small vessels or boats the heading and position of the rudder may be inferred by the helmsman or helmsmen by observing the behaviour of the boat. Thus there should be no need for synchronising the steering device with the actual position of the rudder. Likewise, in small vessels or boats the problem regarding competing helmsmen is much smaller. Either one helmsman operates the different steering devices at different times, or several helmsmen operate the different steering devices at the same time and are able to communicate since the steering devices may be close to each other. In small vessels or boats where the helmsmen may often have only a minimum of skills for manoeuvring the boat, the interlock system may lead to confusion in critical situations, such as for an evasion manoeuvre where the steering device accessible for the person discovering the critical situation may be in a disabled state because of the position of the interlock handle.

Thus, a demand exists for a marine power steering system that is easy to operate and at the same time constitutes a simple technical design. A simple design without the need for synchronising the steering device with the actual position of the rudder and without an interlock system between the steering devices could simplify production time, production cost, installation time and maintenance costs. A power steering system without an interlock system and without a synchronisation of the steering devices and the rudder would simplify operation of a small vessel or boat. In addition it would be more intuitive to operate for a person with little technical background or little marine experience.

Background art

Boats that may be operated from either of two steering devices where an interlock system activates only one steering device at the time are known. A

disadvantage with such solutions is that the boat can only be operated from one steering device at the time. On small vessels without a command hierarchy this may be a serious disadvantage.

US Patent 3,958,524 and US patent 5,253,604 both describe solutions for transferring command from one steering device to another steering device on board a ship. However they both suffer from the problems described above, since only one of the steering devices can be active at the time.

Short summary of the invention According to an aspect of the present invention, such problems in prior art may be solved in a simpler manner by introducing a scheme for steering marine vessels comprising a power steering system with at least two steering devices, by detecting and sensing the shift of each steering device, and providing a driving signal to the rudder that is a combination of signals from each of the steering devices.

Specifically the invention is a power steering system (2) for a boat (1) where the power steering system (2) comprises an electronic control unit (10) arranged for receiving steering signals (Sa, Sb) from two or more steering devices (5a, 5b), where the control unit (10) is further arranged for computing and transmitting a rudder control signal (Sr) that is a function of the steering signals (Sa, Sb) and

- a rudder device (19) arranged for receiving the rudder control signal (Sr) and, based on the rudder control signal (Sr), steering a positioning device (20), such as a rudder or a thruster, so as for changing or maintaining the heading of the boat (1 ).

In another aspect, the invention is a method for steering a boat (1 ) characterised by the following steps;

- the control unit (10) receives steering signals (Sa, Sb) from steering devices (5a, 5b), and computes and transmits a rudder control signal (Sr) that is a function of the steering signals (Sa, Sb), and

- the rudder device (19) receives the rudder control signal (Sr) and, based on the

signal (Sr), steers a positioning device (20), such as a rudder or a thruster, so as for changing or maintaining the heading of the boat (1 ).

Further advantages and features of the marine power steering system according to the invention are disclosed in the accompanying dependent claims.

Short description of the drawings

Figure 1 shows schematically an example of an embodiment of the present invention.

Figure 2 depicts an example of an embodiment of the present invention, including hydraulic, electrical and mechanical components.

Figure 3 illustrates an example of sensors located on a steering wheel according to the present invention.

Figure 4 illustrates components of a power steering system according to the present invention.

Embodiments of the invention

The invention will in the following be described referring to the attached figures, and a number of embodiments according to the invention will be described. It should be noted that the invention should not be limited to the embodiments described in this disclosure, and that any embodiments lying within the spirit of this invention should also be considered part of the disclosure.

Figure 1 shows an example of an embodiment of the present invention where the power steering system (2) comprises an electronic control unit (10) and a rudder device (19). The electronic control unit (10) is arranged for receiving steering signals (Sa, Sb) from two or more steering devices (5a, 5b), where the control unit (10) is further arranged for computing and transmitting a rudder control signal (Sr) that is a

function of said steering signals (Sa, Sb).

The rudder device (19) is arranged for receiving said rudder control signal (Sr) and, based on said rudder control signal (Sr), steering a positioning device (20), such as a rudder or a thruster, so as for changing or maintaining the heading of the boat (1 ).

Further, in another example of an embodiment of the present invention, Figure 1 shows that the steering control unit (10), in addition to sensing the steering signals (Sa, Sb) also may sense a steering signal (Sp) from an autopilot system (30).

Figure 2 illustrates an example of embodiment of the present invention comprising an upper helm pump connected to the upper steering wheel and a lower helm pump connected to the lower steering wheel. The upper steering wheel and lower steering wheel comprise sensors (6a, 6b) for sensing the position of the steering wheels. The hydraulic steering system may be provided as a backup system and may be bypassed during normal electrical steering operation.

Figure 3 depicts an example of such a detector comprising two inductive detector elements detecting movements of a wheel with indentations. As known to a person skilled in the art, this information may be used to detect the rotational direction, and the speed of rotation (rotational frequency of the wheel). In an example of embodiment of the present invention, the central control unit (system unit in figure 1 ) comprises a programmable device receiving sensor signals from two or more steering devices. In figure 3 the steering device illustrated is part of a steering wheel, but as known to a person skilled in the art, a steering device may be a joystick or similar device.

Figure 4 depicts some of the components used to implement a system as depicted in figure 1. Whenever a steering wheel is turned, the helm pump provides a hydraulic pressure transferred to the system unit. The hydraulic

system in this embodiment of the invention is a backup system. The system unit (or central controlling unit) receives electrical signals generated by sensors located in the steering wheels.

A program running in the programmable device in the central control unit may control a rudder device as known to a person skilled in the art. In figure 2, the control unit controls the rudder cylinder by providing hydraulic pressure from a servo pump in a desired direction and flow rate, as known to a person skilled in the art.

In another example of embodiment of the present invention, the program running in the central processor performs steps according to a method of controlling a marine vessel. For example, the method and system according to the present invention may provide any type of algorithmic control through implemented programs in the programmable device controlling the rudder position by reading or receiving sensor signals form steering devices, autopilot systems, backup systems, alarm systems etc. as known to a person skilled in the art. It is also possible to store in the central control unit parameters controlling the rudder position according to predefined reaction patterns. These reaction patterns may be feedback signals from sensors or components in the power steering system thereby realizing an autonomous regulated power steering system as known to a person skilled in the art. As readily understood by a person in the art, any form of alarm condition, (signals from an anti-collision system, a radar system etc.) may trigger a certain reaction pattern to be taken by the power steering system to avoid collision and grounding, etc. Any such application of the method and power steering system according to the present invention is regarded as being within the scope of the attached claims.

The present invention discloses a power steering system (2) for a boat (1 ). The boat may be a small water craft, a sailing boat, a yacht, a small ship or any kind of marine vessel for leisure or professional activities. The power steering system (2) comprises an electronic control unit (10) and a rudder device (19).

The electronic control unit (10) is arranged for receiving steering signals (Sa, Sb,...) from two or more steering devices (5a, 5b,...), the control unit (10) being further arranged for computing and transmitting a rudder control signal (Sr) being a function of the steering signals (Sa, Sb,...). The rudder device (19) is arranged for receiving said rudder control signal (Sr) and, based on said rudder control signal (Sr), steering a positioning device (20), such as a rudder or a thruster, so as for changing or maintaining the heading of the boat (1 ).

In small vessels or boats the heading and position of the rudder may be inferred by the helmsman or helmsmen by sensing or observing the behaviour of the boat. Thus there should be no need for synchronising the steering device with the actual position of the rudder. Likewise, in small vessels or boats the problem regarding competing helmsmen is much smaller. Either one helmsman operates the different steering devices at different times, or several helmsmen operate the different steering devices at the same time and are able to communicate since the steering devices may be close to each other. In small vessels or boats where the helmsmen may often have only a minimum of skills for manoeuvring the boat, the interlock system may lead to confusion in critical situations, such as for an evasion manoeuvre where the steering device accessible for the person discovering the critical situation may be in a disabled state because of the position of the interlock handle.

A power steering system according to the invention is easier to operate than comparable power steering systems from prior art and constitutes a simple technical design is proposed. The simple design without the need for synchronising or aligning the steering device with the actual position of the rudder and without an interlock system between the steering devices could also simplify production time, production cost, installation time and maintenance costs. Further, there is no need to synchronise the position of the steering devices.

According to an embodiment of the present invention, the control unit (10) is arranged for receiving steering signals (Sa, Sb), and further arranged for computing and transmitting a rudder control signal (Sr) that is a function of the sum of the steering signals (Sa, Sb). In this embodiment of the invention the steering signals from the steering devices are summarised in the control unit. Based upon the summarised signals the control unit issues a control signal to the rudder device. As described above the advantage is that no interlock system is needed. Thus, the system is easy to operate even without previous training.

According to another example of embodiment of the present invention, a mean value of two or more steering signal values are used to generate the driving signal for the rudder device.

According to an embodiment of the present invention, the control unit (10) is arranged for receiving steering signals (Sa, Sb) and further arranged for computing and transmitting a rudder control signal (Sr) being a function of the steering signal (Sa, Sb) from the steering device (5a, 5b) with the highest rate of change of desired heading. In this embodiment of the invention one of the steering signals from the steering devices is selected in the control unit, and furnished as a control signal to the rudder device. The selection is based on the rate of change for a steering device. In this embodiment all steering devices are treated equally and if only one of the steering devices is operated the steering signals from said operated steering device is used by the control unit to generate a rudder control signal (Sr). If more than one steering device is operated simultaneously, the control unit will select the steering signal from the steering device with the highest rate of change of desired heading and suppress steering signals from other steering devices temporarily. One advantage of a power steering system according to the invention is that one or more helmsmen can steer the boat from any of the steering devices and easily move to another steering device at any time without operating any interlock switches. A further advantage of the invention is that any

person onboard the boat can make an evasion manoeuvre from any of the steering devices if the person catches sight of an obstacle or a danger.

According to an example of embodiment of the present invention, the speed of shift of each steering device from a first position to a second position is measured, and the steering signal from the steering device with highest speed of shift is used as the driving signal for the rudder device.

According to an embodiment of the present invention the steering device (5a, 5b), comprises at least one sensor (6a, 6b) arranged for sensing a desired change in position (δPa, δPb) in the respective steering device (5a, 5b).

According to an embodiment of the present invention one or more of the steering devices (5a, 5b) are steering wheels, and the sensors (6a, 6b) senses the rotational direction (di, d ₂ ) and rotational speed (oi, ω ₂ ) of the steering wheels, respectively.

According to an embodiment of the present invention one or more of the steering devices (5a, 5b) are joysticks, and the sensors (6a, 6b) senses the position of the joysticks. The position of the joystick may be measured as the angular deviation from a neutral position.

According to an embodiment of the present invention the positioning device (20) is a rudder, a transverse thruster or a rotatable thruster.

According to an embodiment of the present invention the rudder device (19) comprises an hydraulic cylinder, an hydraulic motor or an electromotor.

According to an embodiment of the present invention the control unit (10) comprises a programmable microcontroller.

According to an embodiment of the present invention one of said steering

devices (5a, 5b) is an autopilot system (30) furnishing directional control signals to the control unit (10). Alternatively the control unit (10) is, in addition to receiving said steering signals (Sa, Sb) from said steering devices (5a, 5b), further provided with an additional input line arranged for receiving directional control signals (Sp) from an autopilot system (30). The control unit (10) may be arranged to suppress the steering signal (Sa, Sb, Sp) from the auto pilot system (30) if and when the position of at least one of the manual input steering devices (5a, 5b) changes. The steering signal (Sa, Sb, Sp) from the auto pilot (30) is resumed when the position of manual input steering devices (5a, 5b) becomes static.

According to an embodiment of the present invention the power steering system (2) comprises a backup steering system (2b) and a supervisory unit (10b) arranged for supervising components of the power steering system (2) and further arranged for handing over control to the backup steering system (2b) when a failure is detected in one or more components in the power steering system (2).

According to yet another example of embodiment of the present invention, a backup system may gain control of the power steering system according to the present invention when an alarm condition appears. Such alarm conditions may be power failure, loss of hydraulic pressure, etc.

According to an embodiment of the present invention the rudder control signal (Sr) is compared with one or more predefined threshold values (Vt), and if the rudder control signal (Sr) exceeds said threshold values (Vt) an alarm signal (A) is issued.

According to yet another example of embodiment of the present invention, the generated driving signal for the rudder device is compared with a threshold value which may be a predefined value, or a value of a signal issued from an attached autopilot system. According to an aspect of the present invention, when the

generated driving signal for the rudder device is exceeded an alarm signal is issued, or alternatively or in combination with the alarm signal, a central control unit according to the present invention may hand over control of the ship to the autopilot system. The predefined threshold value (Vt) may be produced by the auto pilot system (30), and may be frequently updated by the auto pilot system (30).

According to an embodiment of the present invention the control unit (10) comprises a set of pre-defined values (Vp), related to states (50) of the boat (1 ) or external to the boat (1), that leads to a pre-defined change in the heading of the boat (1 ) if one or more of the states (50) in the boat (1 ) or external to the boat (1 ) occurs. A predefined set of driving signals controlling the position of the rudder may reflect certain reaction patterns that should be taken if certain conditions occur on the marine vessel or in the surroundings of the marine vessel. According to this example of embodiment the issued steering signal to the rudder is compared witch such pre-stored rudder signals, and whenever a situation defined by the conditions occur, the driving signal is selected to be one of the pre defined driving signals for the rudder positions.

According to an embodiment of the present invention the control unit (10) is programmable in order to be able to normalize the steering signals (Sa, Sb) and adjust the rudder control signal (Sr) to the characteristics of the positioning device (20).

According to an embodiment of the present invention the sensor or sensors (6a, 6b) are magnetic inductive or mechanical sensors and the steering signals (Sa, Sb) are electrical signals.

According to an embodiment of the present invention the sensor or sensors (6a, 6b) are optical sensors and the steering signals (Sa, Sb) are optical signals.

According to an example of embodiment of a power steering system according to

the present invention, a sensor is provided at the steering wheel mechanism providing an output signal representing direction of rotation and a frequency measure of the rotational speed. In a preferred embodiment of this example, a sensor similar to rotational sensors used for car brakes may be applied.

According to an embodiment of the present invention the power steering system is arranged for halting the relative displacement of the positioning device (20) as soon as the steering signals (6a, 6b) represents a static position of the steering devices (5a, 5b) even when the positioning device (20) has not yet reached the previously commanded position corresponding to the integrated steering signals (6a, 6b) from the steering devices (5a, 5b), due to the potential latency of the power steering system (2). This may facilitate the steering of the boat if one or more of the helmsmen have commanded a too fast and too large rotation of the steering wheel, and decides to stop the rudder.

According to an embodiment of the present invention the power steering system is arranged for changing the direction of the relative displacement of the positioning device (20) as soon as the calculated output value resulting from the function of the steering signals (6a, 6b) represents a change in direction of the steering devices (5a, 5b) even when the positioning device (20) has not yet reached the previously commanded position corresponding to the integrated steering signals (6a, 6b) from the steering devices (5a, 5b), due to the potential latency of the power steering system (2). This may facilitate the steering of the boat if one or more of the helmsmen decides to override the present rudder angle, and decides to reverse the change of direction of the rudder by changing the direction of the steering wheel.

According to the present invention the method for steering a boat (1 ) is characterised by the following steps; - a control unit (10) receives steering signals (Sa, Sb) from the steering devices (5a, 5b), and computes and transmits a rudder control signal (Sr) being a function of the steering signals (Sa, Sb), and

- the rudder device (19) receives the rudder control signal (Sr) and, based on the signal (Sr), steers a positioning device (20), so as for changing or maintaining the heading of the boat (1 ).

One fundamental aspect of the present invention, is that the driving signals sent to the rudder device only affects a relative displacement of the rudder from the present position of the rudder to a next position, and wherein the swing of the rudder from the present position to the next position is proportional to the signal value of the generated driving signal to the rudder device. This is contrary to prior art systems that provide an initial wheel position related to a neutral rudder position (rudder position for straight movement of the ship, for example), and any displacement of the wheel is derived as an absolute value relative to this initial wheel position and a second commanded wheel position signalled by turning a steering wheel, for example.

The combination of the heading of the boat and the inferred position of the rudder as perceived by the helmsman or helmsmen and the relative change of displacement of the steering wheel at any instant is considered to be the most relevant inputs for the control unit when used in a boat.

As readily understood by a person skilled in the art, the relative displacement of the steering wheel according to the present invention makes it possible to avoid costly and complex rudder driving components providing signals representing the initial position of the rudder and further does not require any information about the position of the other steering devices when the command is transferred from one steering wheel to another. Further, a microcontroller or computer device may be used to generate the driving signal to the rudder device. The computer device may then control hydraulic and/or electro hydraulic components as known to a person skilled in the art to achieve the controlling of the rudder device. According to an aspect of the present invention, the principles of the present invention provides a possibility to realize a "fly by wire" concept for marine power steering systems by using only electronic components and software in a programmable

device controlling an electro motor driving the rudder from side to side dependent on control signals connected to the electro motor, and which are generated by software running in the programmable device, wherein the programmable device receives signals from a plurality of steering devices and systems (autopilot systems, backup systems, etc.) that indicate intended swing of the rudder at any time.

A further aspect of the invention, is that it is possible to provide a method for steering a boat from one or more of two or more steering devices without the need to provide sensor signals or report all the different steering wheel angular positions etc. amongst the steering devices, and without any form of interlock functions between the steering devices.