TECHNICAL FIELD

The present invention relates to a method for controlling operation of a hydraulic system of a mining machine. The invention also relates to a computer program product comprising program code for a computer for implementing a method according to the invention. The invention also relates to a system for controlling operation of a hydraulic system of a mining machine and a mining machine being equipped with such a system.

BACKGROUND

Heavy duty vehicles, such as mining machines, are often provided with hydraulic systems for operating various functions/systems of the vehicle. Such

functions/systems may relate to loading/tipping or operating certain devices, such as drilling devices, on-board the vehicle. The hydraulic systems may be powered by a diesel engine. Alternatively, the hydraulic systems may be powered by an electrical motor.

In case a diesel engine is used for powering the hydraulic system exhaust gas emissions may be problematic, in particular if the vehicle is operated in a closed space, such as in a mine.

One way of controlling operation of a hydraulic system by means of an electrical motor involves to estimate a power demand of hydraulic consumer units of the hydraulic system, determine a required motor speed for operating a hydraulic pump unit and provide and operate said motor at a motor speed higher than the determined required motor speed for avoiding malfunctioning/stalling. Hereby efficiency losses are at hand. Naturally this solution is not cost-effective due to said operation at relatively high motor speeds of said electrical motor. SUMMARY OF THE INVENTION

One object of the present invention is to provide a new and advantageous method for controlling operation of a hydraulic system of a mining machine.

Another object of the invention is to provide a novel and advantageous system for controlling operation of a hydraulic system of a mining machine and a new and advantageous computer program for controlling operation of a hydraulic system of a mining machine.

Yet another object of the invention is to provide an alternative method, an alternative system and an alternative computer program for controlling operation of a hydraulic system of a mining machine.

Yet another object of the invention is to provide a robust, cost-effective and reliable method for controlling operation of a hydraulic system of a mining machine.

Yet another object of the invention is to provide a method, a system and a computer program for improving performance of a hydraulic system of a mining machine.

Yet another object of the invention is to provide an energy effective method for controlling operation of a hydraulic system of a mining machine.

Some of said objects are achieved by a method for controlling operation of a hydraulic system of a mining machine according to claim 1. Other objects are achieved by a system for controlling operation of a hydraulic system of a mining machine according to claim 6. Advantageous embodiments are depicted in the dependent claims.

According to an embodiment there is provided a method for controlling operation of a hydraulic system of a mining machine, said hydraulic system comprises an electric motor configuration, a variable displacement pump configuration configured to power at least one hydraulic consumer unit, comprising the steps of: - obtaining a desired operational displacement value relating to said variable displacement pump configuration;

- determining a prevailing operational displacement value of said variable

displacement pump configuration;

- comparing said desired operational displacement value and said prevailing operational displacement value; and

- controlling operation of said electric motor configuration on the basis of a result of said comparison, wherein controlling operation comprises controlling a motor speed of said electric motor configuration so that said motor speed is minimized while meeting a current power demand of said at least one hydraulic consumer unit.

Hereby a robust and reliable method is provided. This solution is cost-effective since the operational motor speed is continuously kept at a desired/required level. This solution is thus also energy-efficient.

Hereby efficiency losses during idle/low operation of the variable displacement pump configuration is reduced. Production performance of the mining machine is

advantageously increased. Due to the reduced efficiency losses longer work cycles of the mining machine may be achieved.

The inventive method is applicable to various setups of hydraulic systems. The method is hereby versatile.

Advantageously an increased comfort for an operator of the mining machine is achieved because of an overall lower operational motor speed. Advantageously wear of e.g. the electric motor and the variable displacement pump configuration is reduced. Hereby total operational time of these components may be increased.

Advantageously flow/friction losses in said variable displacement pump configuration is minimized.

The hydraulic system may comprise a sensor arrangement arranged at said variable displacement pump configuration. The electric motor configuration may be arranged to power the variable displacement pump configuration. The electric motor

configuration may comprise an electric motor, an inverter, and a power source, wherein the electric motor is arranged to power the variable displacement pump configuration.

The method may comprise the step of determining the prevailing operational displacement value of said variable displacement pump configuration by means of said sensor arrangement. Hereby reliable and accurate values of the prevailing operational displacement value of said variable displacement pump configuration may be determined in a cost-effective manner.

The electric motor configuration may comprise a motor, inverter, and a power source, such as a battery pack. In this case the method may comprise the step of controlling the inverter to reduce or increase electrical power supply from the power source to the electric motor. Hereby a reliable and robust method is provided. The power supply to the electric motor is hereby controlled in a highly accurate manner.

The method may comprise the step of controlling operation of said electric motor configuration such that a difference between said desired operational displacement value and said prevailing operational displacement value is minimized. Hereby efficiency of the variable displacement pump configuration may be optimized.

The method may comprise the steps of:

- determining at least one parameter value of the hydraulic system; and

- controlling operation of said electric motor configuration on the basis of said at least one parameter value. Said parameter value may relate to a temperature of a hydraulic fluid of the hydraulic system. Hereby an improved operation of said hydraulic system is provided taking various parameters into consideration when controlling motor speed of the electric motor.

The method may comprise the step of controlling operation of said electric motor configuration on the basis of operational parameters of a fixed displacement pump configuration further comprised in said hydraulic system. Advantageously the provided method is applicable to various configurations of the hydraulic system.

Hereby a versatile method is provided. According to an example embodiment there is provided hydraulic system of a mining machine, said hydraulic system comprises an electric motor configuration, a variable displacement pump configuration and at least one hydraulic consumer unit, said hydraulic system further comprises control circuitry configured to:

- obtain a desired operational displacement value relating to said variable

displacement pump configuration;

- determine a prevailing operational displacement value of said variable displacement pump configuration;

- compare said desired operational displacement value and said prevailing

operational displacement value; and

- control operation of said electric motor configuration on the basis of a result of said comparison, wherein controlling operation comprises controlling a motor speed of said electric motor configuration so that said motor speed is minimized while meeting a current power demand of said at least one hydraulic consumer unit.

The hydraulic system may comprise a sensor arrangement being arranged at said variable displacement pump configuration. The sensor arrangement may be arranged to determine the prevailing operational displacement value of said variable displacement pump configuration.

According to an embodiment the electric motor configuration comprises an electrical motor, an inverter and a power source, wherein the power source may comprise a battery pack. Hereby there is provided means being arranged to control the motor speed by controlling the inverter to reduce or increase electrical power supply from the power source to the electric motor.

According to an embodiment the system comprises means being arranged for controlling operation of said electric motor configuration such that a difference between said desired operational displacement value and said prevailing operational displacement value is minimized.

According to an embodiment said hydraulic system comprises a first control unit configured to: - obtain a desired operational displacement value relating to said variable displacement pump configuration;

- determine a prevailing operational displacement value of said variable displacement pump configuration;

- compare said desired operational displacement value and said prevailing

operational displacement value; and

- control operation of said electric motor configuration on the basis of a result of said comparison, wherein controlling operation comprises controlling a motor speed of said electric motor configuration so that said motor speed is minimized while meeting a current power demand of said at least one hydraulic consumer unit. Said first control unit may hereby comprise said control circuitry.

According to an embodiment the system comprises:

- means being arranged for determining at least one parameter value of the hydraulic system; and

- means being arranged for controlling operation of said electric motor configuration on the basis of said at least one parameter value.

According to an embodiment the system comprises:

- means being arranged for controlling operation of said electric motor configuration on the basis of operational parameters of a fixed displacement pump configuration further comprised in said hydraulic system.

Hereby it is provided a cost effective system for achieving a reliable and robust operation of the hydraulic system. Advantageously operator comfort may be increased due to comparably lower operational motor speed thus also providing reduced wear of components of the hydraulic system, e.g. components of the variable displacement pump configuration.

According to an embodiment there is provided a mining machine comprising a system for controlling operation of a hydraulic system of the mining machine.

According to an embodiment there is provided a mining machine being equipped with a hydraulic system according to the teachings herein. Said mining machine may be intended for earth surface use. A mining machine is a machine adapted for various mining operations.

According to an aspect of the present invention there is provided an autonomous mining machine comprising a hydraulic system. According to an embodiment there is provided an autonomous mining machine comprising a system according to claim 6. According to an embodiment there is provided an autonomous mining machine comprising a hydraulic system according to the teachings herein. Said autonomous drilling rig may be intended for earth surface use.

According to an embodiment there is provided a vehicle equipped with a hydraulic system. Said vehicle may be an arbitrarily suitable vehicle. Said vehicle may be a, tractor, dumper, wheel loader, platform comprising an industrial robot, forest machine, earth mover, asphalt construction machine, road planner or a tracked vehicle.

According to an embodiment there is provided an autonomous vehicle equipped with a hydraulic system according to the teachings herein. Said autonomous vehicle may be any suitable vehicle.

According to an embodiment there is provided a computer program for controlling operation of a hydraulic system of a mining machine, where said computer program comprises program code for causing an electronic control unit or a computer connected to the electronic control unit to perform the steps according to anyone of the claims 1 -5.

According to an embodiment there is provided a computer program product comprising a program code stored on a, by a computer readable medium, for performing the method steps according to anyone of claims 1 -5, when said program code is run on an electronic control unit or a computer connected to the electronic control unit.

According to an embodiment there is provided a computer program for controlling operation of a hydraulic system of a mining machine, where said computer program comprises program code for causing an electronic control unit or a computer connected to the electronic control unit to perform the steps according to anyone of the claims 1 -5, when said program code is run on said electronic control unit or said other computer.

According to an embodiment there is provided a computer program for controlling operation of a hydraulic system of a mining machine, where said computer program comprises program code stored on a, by a computer readable, medium for causing an electronic control unit or a computer connected to the electronic control unit to perform the steps according to anyone of the claims 1 -5.

According to an embodiment there is provided a computer program product comprising a program product comprising a program code stored on a, by a computer readable, medium for performing the method steps according to anyone of the claim 1 -5, when said program code is run on an electronic control unit or a computer connected to the electronic control unit.

According to an embodiment there is provided a computer program product comprising a program code non-volatile stored on a, by a computer readable, medium for performing the steps according to anyone of claims 1 -5, when said program code is run on an electronic control unit or a computer connected to the electronic control unit.

Further objects, advantages and novel features of the present invention will become apparent to the one skilled in the art from the following details, and also by applying the invention. Although the invention is described below, it should be noted that it is not limited to the specific details described. One skilled in the art who has access to the teachings herein will recognize further applications, modifications and

incorporations within other fields, which are within the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For fuller understanding of the present invention and its further objects and advantages, the detailed description set out below should be read in conjunction with the accompanying drawings, in which the same reference notations denote similar items in the various diagrams, and in which:

Figure 1 schematically illustrates a mining machine;

Figure 2 schematically illustrates a hydraulic system of the mining machine;

Figure 3a schematically illustrates a flowchart of a method, according to an embodiment of the invention;

Figure 3b schematically illustrates a flowchart of a method in greater detail, according to an embodiment of the invention; and

Figure 4 schematically illustrates a computer, according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to Figure 1 there is illustrated a side view of a mining machine 100. According to this example the mining machine is a drilling rig which may be used for various kinds of ground works and/or construction works and for which the present invention may be used. The mining machine 100 may be adapted for mining operation. The mining machine 100 may be adapted for surface mining. Hereby the mining machine 100 may be adapted for performing so called percussion drilling.

The mining machine 100 is according to an embodiment arranged for operation in open quarries. The mining machine 100 is according to an example adapted for use at infrastructure works. The mining machine 100 may be of any suitable size and may present a mass within an interval of for example 3 to 30 tons (3.000 to 30.000 kilograms). According to one example the mining machine 100 may present a mass within an interval of for example 30 to 70 tons (30.000 to 70.000 kilograms).

Said mining machine 100 comprises, among other elements, an elongated, movable arm having a drilling device arranged at one end thereof, tracks for propulsion of the mining machine 100, a cabin for an operator and a motor body. Said movable arm may also be denoted articulated arm. Various components are located in said motor body as well as systems for providing satisfactory function of said mining machine 100 such as for example an engine which is arranged to provide necessary power to said drilling rig 100. Said engine may be used for propulsion of said drilling rig 100.

Said motor body is comprising a system 299 comprising a hydraulic system. The system 299 is depicted in greater detail with reference to Figure 2.

Herein the term“link” refers to a communications link which may be a physical wire, such as an opto-electronic communication wire, or a non-physical wire, such as a wireless connection, for example a radio link or microwave link.

Herein the term“passage” and“passage configuration” relate to a passage for holding and transporting a hydraulic fluid, such as for example hydraulic oil. The passage may be a pipe of suitable dimensions. The passage may consist of an arbitrary, suitable material, such as plastics, rubber or metal.

It should be noted that the invention is suitable for application at an arbitrary suitable vehicle or other platform having a hydraulic system and is not limited to systems of a mining machine. The inventive method and the inventive system may also be used for other platforms than mining machine, such as mining vehicles, tractors, dumpers, vehicle/platforms for industrial robots, forest machines, tracked vehicles,

constructions vehicles, utility vehicles, terrain vehicles or military vehicles.

Herein the term“suitable” among other things may be interpreted as“arbitrary suitable” or“according to a relevant embodiment of the invention”.

Figure 2 schematically illustrates a system 299 of said mining machine 100, according to an embodiment of the present invention. The system 299 comprises a hydraulic system.

A first control unit 210 is arranged for communication with an inverter 231 via a link L231. The inverter 231 is arranged to communicate information regarding a prevailing motor speed RPM (revolutions per minute) of said electric motor 230. The prevailing motor speed RPM may be determined in any suitable way, e.g. by means of said inverter 231. According to one example there is a motor speed sensor (not shown) arranged at the electric motor 230. According to this example the motor speed sensor may be arranged for communication directly with the first control unit 210 via a suitable link (not shown). According to one example said inverter 231 is arranged to determine a prevailing motor speed by means of said motor speed sensor. According to one example said inverter 231 is arranged to determine a prevailing motor speed by evaluating prevailing phase currents. This is advantageous in case said motor speed sensor is malfunctioning.

The first control unit 210 is arranged to control operation of an electric motor 230 by means of said inverter 231. Said inverter 231 is electrically connected to a power source 232. The power source 232 is an electrical power source. The power source 232 is according to one example comprising a battery. Said inverter 231 is electrically connected to the electric motor 230. This electrical connection may comprise a 3- phase current arrangement, e.g. at 700V. According to one example there is provided a 3-phase system, 400 Volt Alternating Current, VAC) being motor speed dependent and wherein a DC aspect is arranged for 700VAC being SoC-dependent (State of Charge). The first control unit 210 is arranged to power/operate said electric motor 230 by means of said power source 232 and said inverter 231. Controlling of operation of said electric motor 230 may for an example comprise to control said motor speed RPM. Controlling of operation of said electric motor 230 may for an example comprise to control said motor speed RPM and/or an output torque and/or an electrical power.

Herein the term“electrical motor configuration” refers to an arrangement comprising the electrical motor 230, the inverter 231 and said power source 232.

The first control unit 210 is arranged for communication with a first actuator means 201 via a link L201. Said first actuator means 201 is arranged for controlling operation of at least one hydraulic consumer unit CU1 -CU6 of the mining

machinel OO. According to this example there is provided six hydraulic consumer units CU1 -CU6. The number of hydraulic consumer units may be any number depending on the specific configuration of the mining machine 100. The first control unit 210 is arranged for communication with a second actuator means 202 via a link L202. Said second actuator means 202 is arranged for controlling operation of at least one hydraulic consumer unit CU1 -CU6 of the mining machinel OO.

According to this example there is provided two actuator means, however any suitable number of actuator means may be provided depending on the configuration of the mining machine 100 comprising the hydraulic system depicted herein.

According to a first example said first actuator means 201 and said second actuator means 202 are manually controlled by one or more operators of the mining machine 100. According to a second example the hydraulic consumer units CU1-CU6 may be remotely controlled by one or more operators located at a distance from said mining machine 100. Hereby suitable arrangements are provided for allowing to remotely control operation of the mining machine 100, including the hydraulic consumer units CU1 -CU6.

According to one example embodiment said first actuator means 201 and said second actuator means 202 may comprise a steering wheel, touch screen, pedal, paddle, joystick or any other suitable device for controlling operation of said mining machine 100, including said hydraulic consumer units CU1-CU6.

According to one example feedforwarding may be applied regarding operation of said first actuator means 201 and said second actuator means 202. The first control unit 210 may hereby comprise a high pass filter for processing signals received from said first actuator means 201 and said second actuator means 202. In response to operation of said first actuator means 201 and said second actuator means 202 a certain value DELTA is added to a desired/preferred/most suitable/optimal operational displacement value D1. Said certain value DELTA may be a

predetermined value. Said certain value DELTA may be determined continuously or intermittently on the basis of operation of said first actuator means 201 and said second actuator means 202. Hereby improved response of operation of the hydraulic system is achieved. Hereby hydraulic response time advantageously may be compensated for to a certain extent.

According to another example feedforwarding may be applied regarding operation of said first actuator means 201 and said second actuator means 202 by providing the first control unit 210 with a suitable band pass filter for processing signals received from said first actuator means 201 and said second actuator means 202. In response to operation of said first actuator means 201 and said second actuator means 202 a certain value BETA is added to a desired/preferred/most suitable/optimal operational displacement value D1. Said certain value BETA may be a predetermined value.

Said certain value BETA may be determined continuously or intermittently on the basis of operation of said first actuator means 201 and said second actuator means 202. Hereby improved response of operation of the hydraulic system is achieved. Hereby hydraulic response time advantageously may be compensated for to a certain extent.

Said hydraulic consumer units CU1-CU6 may be any suitable hydraulically operated unit, such as a cylinder arrangement, loading/tipping arrangement for a loading platform or bucket, continuous load conveying arrangement, drill positioning arrangement, brake system, suspension arrangement, hoist motor configuration, fan motor configuration, AC compressor arrangement, air compressor arrangement, steering arrangement, etc.

Said electrical motor 230 is arranged to operate/power a variable displacement pump configuration 240. Said variable displacement pump configuration 240 may be denoted main pump of the hydraulic system. Said first control unit 210 is arranged for communication with said variable displacement pump configuration 240 via a link L241. A sensor arrangement 241 is arranged at said variable displacement pump configuration 240. Said sensor arrangement 241 is arranged to detect a prevailing operational displacement value Dcont. Said sensor arrangement 241 is arranged to communicate said detected prevailing operational displacement value Dcont to said first control unit 210 via said link L241. Said detected prevailing operational displacement value Dcont refers to a swash plate angle of said variable displacement pump configuration 240. Said prevailing operational displacement value Dcont may be a normalized value and is expressed as a number within the interval of 0-1.

Herein the desired operational displacement value D1 is referred to a

desired/preferred/most suitable/optimal operational displacement value. The desired operational displacement value D1 may be denoted“target value”, which is sought to be achieved. Said desired operational displacement value D1 may be a normalized value and is expressed as a number within the interval of 0.0-1.0. D1 is a

predetermined value relating to the specific variable displacement pump

configuration 240. D1 is according to one example 0.8. D1 is according to one example 0.9. D1 is according to one example a value within the interval 0.6-0.9. According to one example D1 is a value within the interval 0.9-0.95.

The proposed method is also applicable to various variable displacement pump configuration, such as bent axis pumps/motors and digital displacement pumps (DDP).

According to an example embodiment said system 299 comprises at least one variable displacement pump configuration. Said electrical motor 230 is hereby arranged to operate/power said at least one variable displacement pump

configuration 240. In a case where at least two variable displacement pump configurations are hydraulically connected in parallel a mean value of determined prevailing operational displacement values Dcont may be used for controlling the variable displacement pump configurations according to the method depicted herein. Hereby the variable displacement pump configurations are considered as one single pump configuration.

According to one example said system 299 comprises at least two variable displacement pump configurations which are not hydraulically connected in parallel. Hereby said at least two variable displacement pump configurations operate separate hydraulic sub-systems of said system 299. In such a case said first control unit 210 is arranged to control operation of the system 299 on the basis of a highest requested motor speed value.

The method and system depicted herein are applicable to various variable

displacement pump configurations. According to one example said prevailing operational displacement value Dcont may be a normalized value and is expressed as a number within another interval than 0.0-1.0, e.g. -1.0 to 1.0. Hereby a

correspondingly suitable desired operational displacement value D1 is used.

A sensor arrangement 205 is arranged for communication with the first control unit 210 via a link L205. Said sensor arrangement 205 is arranged to detect at least one parameter value of the hydraulic system and communicate said at least one parameter value to said first control unit via said link L205. Said parameter value may refer to any suitable parameter of the hydraulic system, such as a temperature Temp of a hydraulic fluid of the hydraulic system. The first control unit 210 is arranged to control operation of said variable displacement pump configuration 240 on the basis of said at least one detected parameter value of the hydraulic system.

Said variable displacement pump configuration 240 is arranged with a hydraulic passage configuration 289. Said hydraulic passage configuration 289 is holding a hydraulic fluid by means of which a number of hydraulic consumer units CU1-CU3 is powered by said variable displacement pump configuration 240.

According to one embodiment a fixed displacement pump configuration 250 is provided. Said fixed displacement pump configuration 250 is arranged with said hydraulic passage configuration 289. Said hydraulic passage configuration 289 is holding said hydraulic fluid by means of which a number of hydraulic consumer units CU1 -CU3 is powered by said fixed displacement pump configuration 250. Said fixed displacement pump configuration 250 may be denoted auxiliary pump of the hydraulic system. The fixed displacement pump configuration 250 may be powered by any suitable means (not shown). According to one example the fixed

displacement pump configuration 250 is powered by a separate electric motor configuration, comprising an electrical motor, an inverter and a power source, such as a battery pack.

According to an embodiment of the invention more than one auxiliary pump (fixed displacement pump configuration) may be provided. The inventive method is applicable to different configurations of the hydraulic system. The inventive method is applicable to a hydraulic system comprising at least one variable displacement pump configuration and any number of fixed displacement pump configurations and any number of hydraulic consumer units. According to one example the inventive method is applicable to a hydraulic system comprising at least one variable displacement pump configuration and no additional fixed displacement pump configurations. The first control unit 210 is according to one example arranged to control operation of said variable displacement pump configuration 240 considering a total power demand of the hydraulic consumer units. The first control unit 210 is according to one example arranged to control operation of said variable displacement pump

configuration 240 on the basis of said desired operational displacement value D1 , said prevailing operational displacement value Dcont and a total power demand of the hydraulic consumer units of the hydraulic system.

Said first control unit 210 may be arranged for communication with presentation means 260 via a link L260. Said presentation means 260 may be provided in a cabin of said mining machine 100. Said presentation means 260 may comprise a presentation screen, for example a touch screen. Hereby said first control unit 210 may be arranged to present alphanumerical signs and/or symbols regarding operational status parameters of said mining machine 100. According to one example said first control unit 210 may be arranged to present information regarding a prevailing motor speed RPM of said electric motor 230. According to one example said first control unit 210 may be arranged to present information regarding a current efficiency of said variable displacement pump 240. According to one example said first control unit 210 may be arranged to present information regarding a current efficiency of said fixed displacement pump 250. According to one example said first control unit 210 may be arranged to present information regarding a load level of said power source 232.

Said presentation means 260 may comprise means for audio and/or tactile and/or visual presentation of information/instructions/recommendations regarding operation of said hydraulic system of the mining machine 100.

Said first control unit 210 may be arranged to, where applicable, present information comprising instructions for operating said hydraulic consumer units CU1-CU6. Said information may thus be presented in a suitable way by means of said presentation means 260.

According to an example there is provided a hydraulic system of a mining machine 100, said hydraulic system comprises an electric motor configuration, a variable displacement pump configuration 240 and at least one hydraulic consumer unit CU1 - CU6, and a sensor arrangement 241 arranged at said variable displacement pump configuration 240, the electric motor configuration is arranged to power the variable displacement pump configuration 240. The hydraulic system further comprises a first control unit 210, being arranged for obtaining a desired operational displacement value D1 relating to said variable displacement pump configuration 240. The sensor arrangement 241 is arranged for detecting a prevailing operational displacement value Dcont of said variable displacement pump configuration 240. The first control unit 210 is arranged for determining the prevailing operational displacement value Dcont of said variable displacement pump configuration 240. The first control unit 210 is arranged for comparing said desired operational displacement value D1 and said prevailing operational displacement value Dcont. The first control unit 210 is arranged for controlling operation of said electric motor configuration on the basis of a result of said comparison, wherein controlling operation comprises controlling a motor speed RPM of said electric motor configuration so that said motor speed RPM is minimized while meeting a current power demand of said at least one hydraulic consumer unit CU1 -CU6.

A second control unit 220 is arranged for communication with the first control unit 210 via a first link L210. The second control unit 220 may be detachably connected to the first control unit 210. The second control unit 220 may be an external control unit of the mining machine 100. The second control unit 220 may be arranged to perform the method steps depicted herein. The second control unit 220 may be used for transferring program code to the first control unit 210, in particular program code for performing the inventive method. The second control unit 220 may alternatively be arranged for communication with the first control unit 210 via an internal network of the mining machine 100. The second control unit 220 may be arranged to perform substantially similar functions as the first control unit 210. According to an aspect of the present invention said mining machine 100 is an autonomous mining machine. It should hereby be noted that the mining machine 100 in such a case is equipped with suitable sensor configurations and navigation means so as to in an autonomous way be used for any suitable application, such as for example drilling works.

According to an example embodiment the hydraulic system and the mining machine 100 are arranged to be remotely controlled. Hereby an operator may be located at any suitable distance from the mining machine 100. The inventive method is hereby applicable by means of use of stored control routines of said first control unit 210 and/or second control unit 220.

Figure 3a schematically illustrates a flowchart of a method for controlling operation of a hydraulic system of a mining machine 100, said hydraulic system comprises an electric motor configuration, a variable displacement pump configuration 240 configured to power at least one hydraulic consumer unit. The method comprises a first method step s401. The step s401 comprises the steps of:

- obtaining a desired operational displacement value D1 relating to said variable displacement pump configuration;

- determining a prevailing operational displacement value Dcont of said variable displacement pump configuration;

- comparing said desired operational displacement value D1 and said prevailing operational displacement value Dcont; and

- controlling operation of said electric motor configuration by the basis of a result of said comparison, wherein controlling operation comprises controlling a motor speed RPM of said electric motor configuration so that said motor speed RPM is minimized while meeting a current power demand of said at least one hydraulic consumer unit. After the method step s401 the method ends or is returned.

Figure 3b schematically illustrates a flowchart of a method for controlling operation of a hydraulic system of a mining machine 100, said hydraulic system comprises an electric motor configuration, a variable displacement pump configuration 240 configured to power at least one hydraulic consumer unit. The method comprises a first method step s410. The step s410 comprises the step of obtaining a desired operational displacement value D1 relating to said variable displacement pump configuration 240. The step s410 may be performed by the first control unit 210. Said desired operational displacement value D1 may be a predetermined value. Said desired operational displacement value D1 may have been empirically determined. Said desired operational displacement value D1 may be uniquely determined for said variable displacement pump configuration 240.

After the method step s410 there is performed a subsequent method step s420.

The step s420 comprises the step of determining a prevailing operational displacement value Dcont of said variable displacement pump configuration 240. This may be performed by means of the first control unit 210. Said prevailing operational displacement value Dcont may be determined in any suitable way, e.g. by means of the sensor configuration 241. After the method step s420 there is performed a subsequent method step s430.

The step s430 comprises the step of comparing said desired operational

displacement value D1 and said prevailing operational displacement value Dcont. This may be performed by means of the first control unit 210.

After the method step s430 there is performed a subsequent method step s440.

The step s440 comprises the step of controlling operation of said electric motor configuration by the basis of a result of said comparison, wherein controlling operation comprises controlling a motor speed RPM of said electric motor configuration so that said motor speed is minimized while meeting a current power demand of said at least one hydraulic consumer unit.

This may be performed by means of the first control unit 210.

After the method step s440 a subsequent method step s450 is performed.

The step s450 comprises the step of, wherein the electric motor configuration comprises an electric motor 230, an inverter 231 , and a power source 232, wherein controlling the motor speed RPM comprises controlling the inverter 231 to reduce or increase electrical power supply from the power source 232 to the electric motor 230 This step is performed by the first control unit 210. Hereby an optimal efficiency of the variable displacement pump configuration 240 may be achieved.

After the method step s450 a subsequent method step s460 is performed.

The step s460 comprises the step of controlling operation of said electric motor configuration such that a difference between said desired operational displacement value D1 and said prevailing operational displacement value Dcont is minimized. Hereby an optimal efficiency of the variable displacement configuration 240 may be achieved. This is performed by means of said first control unit 210.

After the method step s460 a subsequent method step s470 is performed.

The step s470 comprises the steps of:

- determining at least one parameter value of the hydraulic system; and

- controlling operation of said electric motor configuration on the basis of said at least one parameter value.

The step s470 is an optional step. According to one embodiment of the hydraulic system comprises a sensor configuration 205 being arranged for detecting at least one parameter value of the hydraulic system. Said sensor configuration 205 is arranged to transmit said detected at least one parameter value to the first control unit 210. Alternatively, said at least one parameter value may be

determined/modelled/calculated/estimated by means of said first control unit 210. Said at least one parameter value may relate to various temperatures, component settings, hydraulic fluid pressures, or other, of the hydraulic system.

According to an example controlling operation of said electric motor configuration on the basis of said at least one parameter value comprises the step of determining a modified desired operational displacement value D2, which may be higher than said desired operational displacement value D1 , and comparing said modified desired operational displacement value D2 and said prevailing operational displacement value Dcont. The step of controlling operation of said electric motor configuration is hereby performed on the basis of said comparison.

After the method step s470 a subsequent method step s480 is performed. The step s480 comprises the step of controlling operation of said electric motor configuration on the basis of operational parameters of a fixed displacement pump configuration 250 further comprised in said hydraulic system.

The step s480 is an optional step. The step s480 may be performed by means of said first control unit 210. Said operational parameters of the fixed displacement pump configuration 250 may be determined in any suitable way. According to one example said operational parameters may be detected by a suitable sensor configuration (not shown). According to another example said operational parameters may be determined/modelled/calculated/estimated by means of said first control unit 210. Hereby the operation of the electric motor configuration may be controlled on the basis of a fixed displacement pump configuration, in addition to the previously mentioned parameter. In a case where the hydraulic system comprises a fixed displacement pump configuration, controlling operation of the electric motor configuration is also taking into account the operational parameters of the fixed displacement pump configuration.

According to one example said operational parameter is a temperature Temp of said hydraulic fluid of said hydraulic system. Hereby a flow rate of a cooling fluid of said hydraulic system may be controlled. Cooling may be initiated at a certain temperature of the hydraulic fluid and may be maximized at a certain, higher, temperature of the hydraulic fluid. According to this example the motor speed RPM of the electrical motor 230 is controlled to a value higher than what is determined in the step s440.

According to one example the motor speed RPM of the electrical motor 230 is controlled to a value higher than what is determined in the step s440 for the purpose of affecting a transmission clutch unit pressure of the mining machine 100. Hereby a transmission arrangement of the mining machine may be properly lubricated. Said operational parameter may according to this example relate to a motor speed value request of said transmission arrangement.

According to one example said operational parameter is a temperature of said electrical motor 230. In case said temperature is exceeding a predetermined temperature value the motor speed RPM of the electrical motor 230 is controlled to a value higher than what is determined in the step s440 for the purpose of reducing currents of the electrical motor 230 and thus reducing generation of heat.

According to an example controlling operation of said electric motor configuration on the basis of said operational parameters comprises the step of determining a modified desired operational displacement value D3, which may be higher than said desired operational displacement value D1 or modified desired operational displacement value D2, and comparing said modified desired operational

displacement value D3 and said prevailing operational displacement value Dcont.

The step of controlling operation of said electric motor configuration is hereby performed on the basis of said comparison.

After the method step s480 the method ends. Alternatively, the method step s410 is performed again.

It should be noted that even though a particular sequence of the method steps is given, any suitable sequence of the method steps s410-s480 may be provided.

Where applicable, at least two method steps may be performed simultaneously.

With reference to Figure 4 there is illustrated a diagram of an embodiment of a device 500. The control units 210 and 220 depicted with reference to Figure 2 may in one version comprise the device 500. The device 500 comprises a non-volatile memory 520, a data processing unit 510 and a read/write memory 550. The non volatile memory 520 has a first memory portion 530 wherein a computer program, such as an operative system, is stored for controlling the function of the device 500. The device 500 further comprises a bus-controller, a serial communication port, I/O means, A/D converter, a time and date input and transfer unit, an event counter and an interruption controller (not shown). The non-volatile memory 520 also has a second memory portion 540.

There is provided a computer program P comprising routines for controlling operation of a hydraulic system of a mining machine 100, said hydraulic system comprises an electric motor configuration, a variable displacement pump configuration configured to power at least one hydraulic consumer unit. The computer program P may comprise routines for obtaining a desired operational displacement value D1 relating to said variable displacement pump configuration. The computer program P may comprise routines for determining a prevailing operational displacement value Dcont of said variable displacement pump

configuration.

The computer program P may comprise routines for comparing said desired operational displacement value D1 and said prevailing operational displacement value Dcont.

The computer program P may comprise routines for controlling operation of said electric motor configuration by the basis of a result of said comparison, wherein controlling operation comprises controlling a motor speed RPM of said electric motor configuration so that said motor speed is minimized while meeting a current power demand of said at least one hydraulic consumer unit.

The computer program P may comprise routines for, wherein the electric motor configuration comprises a motor, an inverter, and a power source, controlling the motor speed by controlling the inverter to reduce or increase electrical power supply from the power source to the electric motor.

The computer program P may comprise routines for controlling operation of said electric motor configuration such that a difference between said desired operational displacement value D1 and said prevailing operational displacement value Dcont is minimized.

The computer program P may comprise routines for determining at least one parameter value of the hydraulic system. The computer program P may comprise routines for controlling operation of said electric motor configuration on the basis of said at least one parameter value.

The computer program P may comprise routines for controlling operation of said electric motor configuration on the basis of operational parameters of a fixed displacement pump configuration further comprised in said hydraulic system. The computer program P may be stored in an executable form or in compressed form in a memory 560 and/or in a read/write memory 550.

Where it is stated that the data processing unit 510 performs a certain function, it means that the data processing unit 510 affects a certain part of the program stored in the memory 560 or a certain part of the program stored in the read/write memory 550.

The data processing device 510 can communicate with a data port 599 via a fourth data bus 515. The non-volatile memory 520 is intended for communication with the data processing unit 510 via a second data bus 512. The separate memory 560 is intended to communicate with the data processing unit 510 via a first data bus 51 1 . The read/write memory 550 is intended to communicate with the data processing unit 510 via a third data bus 514. The data port 599 may for example be connected to the link L201 , link L202, link L205, link L210, link L231 and link L240 (see Figure 2).

When data are received on the data port 599, they are stored temporarily in the second memory element 540. When input data received have been temporarily stored, the data processing unit 510 will be ready to effect code execution in a manner described above. In one version, signals received on the data port 599 comprise information about a prevailing operational displacement value Dcont of said variable displacement pump configuration. In one version, signals received on the data port 599 comprise information about a current motor speed RPM. The desired operational displacement value D1 may be stored in any suitable memory of the device 500.

Parts of the methods herein described may be applied by the device 500 by means of the data processing unit 510 which runs the program stored in the memory 560 or the read/write memory 550. When the device 500 runs the program, methods herein described are executed.

The foregoing description of the preferred embodiments of the present invention is provided for illustrative and descriptive purposes. It is not intended to be exhaustive, nor to limit the invention to the variants described. Many modifications and variations will obviously suggest themselves to one skilled in the art. The embodiments have been chosen and described in order best to explain the principles of the invention and its practical applications and hence to make it possible for one skilled in the art to understand the invention for various embodiments and with the various modifications appropriate to the intended use.