METHOD FOR CONTROLLING A MOBILE WORK MACHINE

Description

TECHNICAL AREA

[0001] The invention relates to a method for controlling a mobile work machine, wherein the work machine comprises at least one drive motor (e.g. an electric motor or an internal combustion engine) as a power source and at least two power devices, each of which is configured to receive energy from the internal combustion engine and to convert it into a work task and / or a driving task of the work machine. STATE OF THE ART

[0002] Work machines are known from the prior art in which the energy generated by a drive motor is distributed among multiple power devices. Examples of such power devices can be a working hydraulic system, a traction drive (electric or hydraulic), or an electrical device comprising an electric machine that, if necessary, converts the mechanical energy from the combustion engine into electrical energy so that various work functions of the work machine (such as air conditioning, cooling of various components, etc.) can be performed.

[0003] A basic way to distribute power in a mobile work machine, for example, is a control element known as an "inch pedal." The pedal setting selected by the operator divides the drive power available to the work machine between the drive and work functions (different power users).

[0004] In order to avoid overloading the motor, various types of energy management strategies are known from the state of the art, which focus on optimizing the power participants.

[0005] To limit power, known energy management strategies intervene reactively. When overloading begins, the power consumption of an affected power device is individually limited by intervening in its functional control system. In the case of hydrostatic drive systems, this limitation of power consumption occurs indirectly, by limiting the displacement volume of the hydraulic machine(s). One such solution is known from the applicant's company as LLC Load Limit Control for a drive system with working hydraulics. However, this limit load control strategy generally only has a one-sided effect on a consumer, meaning that adjustable power distribution is not possible.

[0006] On the drive engine side, solutions are known in which a speed specification for the drive engine follows a fixed interpretation of a driver's request, whereby a subsequent speed reduction is possible, for example, in a selected "eco mode". No power management takes place in this case.

[0007] In contrast, the applicant's publication DE 10 2013 214 732 A1 shows proactive energy and power management of the drive system and the working hydraulics of a mobile work machine. For this purpose, a higher-level overall energy coordinator (GEK) and subordinate consumer energy coordinators (VEK) connected to it via signals are provided. The latter are each assigned to one or more consumers, which may be hydrostatic, mechanical, or electrical in nature, for example, and which fulfill the driving function, work functions, and other auxiliary functions. The GEK communicates with the VEKs and with a control system of the drive machine and determines the total power requirement of the consumers and the total available power of the drive machine. The GEK intervenes, in particular, in the event of a power shortage to the consumers and limits their power consumption so that no more power is consumed than is available.

[0008] All of the energy management strategies described above have the disadvantage that the calculations are very complex and the system is very difficult to adapt if small changes occur in the power components of the mobile machine. Furthermore, such strategies initially require a significant amount of analysis and modeling effort.

[0009] In contrast, the invention is based on the object of creating a method for controlling a working machine which enables a very simple power limitation of the power participants, in particular a simple but scalable power distribution without modeling and analysis effort. SHORT DESCRIPTION OF THE CHARACTERS

[0010] The present invention is described with reference to the accompanying figures, wherein like reference numerals refer to like parts and / or similar parts and / or corresponding parts of the system. Regarding the figures: Figure 1shows a schematic overview of the control structure for a mobile work machine, components of the control structure and possible signal flows between the components according to an embodiment of the present invention, Figure 2 shows a method for limiting the power of the Figure 1 illustrated service participants according to an embodiment of the present invention. DETAILED DESCRIPTION

[0011] The present invention will now be described with reference to specific embodiments as shown in the accompanying figures. Nevertheless, the present invention is not limited to the specific embodiments described in the following detailed description and shown in the figures; rather, the described embodiments merely illustrate some aspects of the present invention, the scope of which is defined by the claims.

[0012] Further modifications and variations of the present invention will be apparent to those skilled in the art. Thus, the present description encompasses all modifications and / or variations of the present invention, the scope of which is defined by the claims.

[0013] According to Fig. 1 The work machine comprises three different power devices 4, 6, 8, each configured to receive energy from a drive motor 2 (hereinafter referred to as the motor for the sake of simplicity) and to convert this energy into a work task and / or a driving task of the work machine. As will become clearer in the course of the description, this invention can be applied both with an internal combustion engine (e.g., a diesel engine) and with an electric motor.

[0014] A first power device 4 is a power consumer equipped with a hydraulic pump 41 for supplying pressure medium to at least one actuator 43. The pressure generated by the hydraulic pump 41 enables the movement of a working kinematics of the mobile work machine by means of the actuator 43. The actuator can be used, for example, to move a boom or an arm of the work machine. The movement of the actuator is controlled by the proportional valve 42.

[0015] A second power device 6 is a hydraulic traction consumer equipped with a hydraulic pump 61 for supplying pressure medium to a hydraulic motor 62 that can be coupled to an output 63. The pressure generated by the hydraulic pump 61 enables movement along a direction of travel of the mobile work machine by means of the hydraulic motor 62. Alternatively, the traction consumer can be an electric traction consumer.

[0016] A third power device 8 is a power consumer comprising an electric motor 81. The electric motor is optionally configured to convert the mechanical energy of the internal combustion engine 2 into electrical energy so that various work functions 83 of the work machine (such as air conditioning, cooling of the various components, etc.) can be performed or energy can be stored in a battery 82.

[0017] It will be clear to those skilled in the art that the number of power users can be greater or less than three (but at least equal to two). Several of the described power users can also be used. For example, according to one embodiment of the present invention, at least two of the power consumers 4 can be used to move two different elements of the work kinematics independently of one another.

[0018] The three power devices are signal-connected to a controller 16. The controller 16 is configured to receive information 161 from at least one input unit. The input unit can, for example, comprise a plurality of joysticks configured to allow a driver to input requests for the various power devices so that the work machine can perform a desired movement. For example, target power requests for the power devices can be entered via the input unit.

[0019] Furthermore, the controller is signal-connected to the motor 2. In particular, the controller 16 will detect a current speed of the motor and specify a target speed to the motor so that the motor 2 can deliver the target power requirements determined from the information 161.

[0020] Figure 2 shows a method for limiting the power of the Figure 1described service participants according to an embodiment of the present invention.

[0021] In a first step, a load on engine 2 is determined in the form of a load factor I make LLC determined.

[0022] The load can be determined based on a difference between a current speed n ist and a target speed n Soll of the engine 2. In particular, if the current speed n ist is smaller than the target speed n Soll, a load factor I make LLC greater than zero, since this condition corresponds to an overload (known in the field as "squeezing") of the combustion engine 2. This means that the load factor I make LLC is configured to provide information about the overload of the combustion engine. In the event that an overload is not detected (ie, if the current speed ni is greater than the target speed n target), the load factor I make LLCbe equal to zero.

[0023] It will be clear to those skilled in the art that some tolerances are acceptable. According to one embodiment of the present invention, a certain tolerance (e.g., 200 rpm) for the difference between the actual speed n actual and the target speed n target may be acceptable. Only when the calculated difference exceeds the specified tolerance is an overload detected and a value for the load factor I make LLC greater than zero.

[0024] Alternatively, if the engine 2 is an internal combustion engine, the load can be determined based on an injection quantity (i.e., how much fuel is injected into the internal combustion engine). Conversely, if the engine 2 is an electric motor, the load can be determined based on a current flowing to the electric motor.

[0025] It is therefore clear to the person skilled in the art that this invention is not limited to a particular method for determining the load on the engine.

[0026] In a further step, a power factor facV_x for each power participant 4, 6, 8, where the power factor facV_x is calculated by means of a prioritization function assigned to the respective power subscriber 4, 6, 8, whereby the respective prioritization function provides a value for the power factor I do x depending on the determined load factor I make LLC and a prioritization factor Pr_x assigned to the service participant.

[0027] In the last paragraph, x meant any participant. It is therefore clear to the expert that for the first participant a first performance factor facV_2 depending on the determined load factor I make LLCand the prioritization factor Pr_2 assigned to the first service participant. The same applies to the other service participants.

[0028] The sum of the prioritization factors Pr_x assigned to each benefit participant corresponds to a full unit. This means that, for example, if the factors are calculated as a percentage, the sum of the prioritization factors will be 100.

[0029] In the event that consumers of different power levels are connected to the system—e.g., a broom or a snow blower—it is particularly important that the prioritization factors are adjustable. For this reason, the prioritization factors Pr_x can be adjusted during runtime by the driver or higher-level functions.

[0030] The respective prioritization function calculates the performance factor facV_xwith any function. In case a linear function is selected, the power factor facV_x for each benefit participant using the following formula: facV _ x = 1 − fac LLC ∗ 1 − Pr _ x where I do _x der respective power factor, I make LLC the load factor, Pr_x the respective prioritization factor.

[0031] In a further step, the target performance for each service participant 4, 6, 8 is determined based on the respective performance factor facV_x and a respective requested power. The calculation of the target power for each power participant can be done by simply multiplying the respective power factor facV_xand the respective requested power (which, as already described, is known as the target power requirement of the controller 16 through the input unit). The determined target power is then communicated to the power users so that power limitation can take place.

[0032] While the present invention has been described with reference to the embodiments described above, it will be apparent to those skilled in the art that it is possible to make various modifications, variations and improvements to the present invention in light of the above teachings and within the scope of the appended claims without departing from the scope of the invention.

[0033] Furthermore, the areas in which those skilled in the art would be familiar have not been described here in order not to unnecessarily obscure the invention described.

[0034] Accordingly, the invention is not to be limited by the specific illustrative embodiments, but only by the scope of the appended claims.

Claims

1. Method for controlling a mobile working machine, wherein the working machine is provided with at least two power participants (4, 6, 8) that are each configured to receive energy from a motor (2) and convert it into a work task and / or into a driving task of the working machine, characterized in that the method comprises the following steps: a. ascertaining a load on the motor (2) in the form of a load factor (facLLC); b. calculating a power factor (facV_x) for each power participant (4, 6, 8), wherein the power factor (facV_x) is calculated by means of a prioritization function assigned to the respective power participant (4, 6, 8), wherein the respective prioritization function can ascertain a value for the power factor (facV_x) based on the ascertained load factor (facLLC) and a prioritization factor (Pr_x) assigned to the respective power participant; c. calculating a target power for each power participant (4, 6, 8) on the basis of the respective power factor (facV_x) and a respective requested power.

2. Method according to Claim 1, wherein the load is ascertained on the basis of a difference between a current speed (nist) and a target speed (nSoll) of the motor (2).

3. Method according to either of Claims 1 and 2, wherein the motor (2) is an electric motor.

4. Method according to either of Claims 1 and 2, wherein the motor (2) is an internal combustion engine.

5. Method according to one of Claims 1 to 4, wherein at least one of the at least two power participants (4, 6, 8) is a driving load (6) that is provided with a hydraulic pump (61) for supplying pressure medium to a hydraulic motor (62) that is able to be coupled to an output (63), wherein the pressure generated by the hydraulic pump (61) allows movement along a direction of travel of the mobile working machine by means of the hydraulic motor (62).

6. Method according to one of Claims 1 to 5, wherein at least one of the at least two power participants (4, 6, 8) is a working load (8) that comprises an electric motor (81).

7. Method according to one of Claims 1 to 6, wherein at least one of the at least two power participants (4, 6, 8) is a working load (4) that is provided with a hydraulic pump (41) for supplying pressure medium to an actuator (43), wherein the pressure generated by the hydraulic pump (41) allows a working kinematics system of the mobile working machine to move by means of the actuator (43).

8. Method according to one of Claims 1 to 7, wherein, in step c., the calculation of the target power for each power participant is ascertained by multiplying the respective power factor (facV_x) and the respective requested power.

9. Method according to one of Claims 1 to 8, wherein the sum of the prioritization factors (Pr _x) assigned to the respective power participant corresponds to a full unit.

10. Method according to one of Claims 1 to 9, wherein the respective prioritization function calculates the power factor (facV_x) for the respective power participant using the following formula: facV _ x = 1 − fac LLC * 1 − Pr _ x where facV_x is the respective power factor, facLLC is the load factor, and Pr_x is the respective prioritization factor.

11. Method according to one of Claims 1 to 10, wherein the load factor (facLLC) is equal to zero if the target speed of the internal combustion engine is less than a current speed, and therefore the target power for each power participant (4, 6, 8) corresponds to the respective requested power.

12. Method according to one of Claims 1 to 11, wherein the method furthermore comprises the following step: d. defining the prioritization factor (Pr_x) assigned to the respective power participant.

13. Computing unit (16) that is configured to carry out a method according to one of the preceding claims.

14. Computer program that causes a computing unit to carry out a method according to one of Claims 1 to 11 when it is executed on the computing unit.

15. Machine-readable storage medium with a computer program according to Claim 14 stored thereon.