Method for operating a drive of a mobile work machine

Abstract

The invention relates to a method for operating a drive of a mobile work machine, wherein the drive comprises an engine which drives at least one wheel of the work machine, and the mobile work machine comprises an input device which has one or more operating elements by means of which the driver of the mobile work machine can control the drive. The method is characterized by the following steps: a) detecting a rotational speed which corresponds to the engine rotational speed or a variable which is based on the engine rotational speed; b) determining a rotational speed setpoint value from the input device, the rotational speed setpoint value describing a setpoint value for the engine rotational speed or a setpoint value for a variable which is based on the engine rotational speed; c) determining an upper and / or a lower engine torque limit, each of which represents a limit for the torque generated by the engine, from the input device, from the rotational speed detected in step a), and from the rotational speed setpoint value determined in step b) such that the input device has both a direct influence on the rotational speed setpoint value determined in step b) and a direct influence on the upper and / or lower engine torque limits determined in step c); and d) controlling the rotational speed while taking into account the upper and / or lower engine torque limits determined in step c).

Description

[0001] R. 415123

[0002] Robert Bosch GmbH

[0003] 415123 - Mumcu

[0004] Method for operating a drive system of a mobile working machine

[0005] TECHNICAL AREA

[0006] The invention relates to a method for operating a drive system of a mobile working machine.

[0007] STATE OF THE ART

[0008] Mobile working machines, such as wheel loaders, excavators or telescopic handlers, usually have a drive system that powers wheels or tracks, and controls for the driver, such as a foot pedal and a direction selector lever, with which the driver can control the drive system.

[0009] From DE 10 2022 204 376 A1, a method for operating a mobile working machine is known in which the torque or force for the drive system is specified using a characteristic map as a function of the machine's speed and driver input. In this method, the torque or force is the primary parameter because the drive system is given a target value for this parameter. This type of control allows the driver good control of the thrust, which is advantageous, for example, when driving a wheel loader into a pile of material to fill its bucket. This good control of the thrust enables the driver to avoid a loss of traction due to wheel spin. However, there are also driving situations in which this type of control may be less suitable, such as when driving uphill or downhill.In these driving situations, a nearly constant speed is often desirable. With torque- or force-based control, the driver must continuously adjust the torque generated by the drive system, for example via the accelerator pedal, depending on the current gradient, in order to maintain a nearly constant speed.

[0010] There are also drive systems known that regulate the driving speed depending on a predetermined speed setpoint. Such speed-based controls allow the driver good control in driving situations where a predetermined speed must be maintained, for example, when transporting payload. For the driving situation described above, in which a wheel loader is used to load the R. 415123

[0011] However, when the shovel enters a pile of material, such speed control is often not practical, as the known speed control systems can cause the wheels to spin in this driving situation, which can lead to a loss of traction.

[0012] The invention is based on the objective of creating a method for operating the drive system of a mobile work machine that provides the operator of the work machine with improved control over the driving behavior compared to known torque- and speed-based methods, taking into account both driving situations in which good control over thrust is advantageous and driving situations in which good control over speed is advantageous. The invention is also based on the objective of finding a corresponding method that is equally applicable to both hydrostatic and electric drives, so that it is possible to achieve uniform driving behavior for work machines with different drive types using this method.

[0013] SUMMARY

[0014] According to one embodiment of the present invention, a method for operating a drive system of a mobile working machine, for example a wheel loader, a telescopic handler, a municipal vehicle, or an excavator, is provided, wherein the drive system comprises a motor, for example an electric motor or hydraulic motor, which drives at least one wheel of the working machine, for example the two wheels of the rear axle via a cardan shaft and a differential gear, wherein the mobile working machine comprises an input device having one or more control elements, for example an accelerator pedal, a brake pedal, an inching pedal, a direction selector lever, a joystick, a selector switch for choosing a driving mode, a touchscreen, and various rotary controls with which the operator of the mobile working machine can control the drive system, characterized in that the method comprises the following steps: a) detecting a rotational speed,which corresponds to the engine speed of the aforementioned engine or to a quantity dependent on the engine speed, for example, the travel speed of the machine; b) Determination of a speed setpoint from the input device, for example, from the accelerator pedal, the inching pedal, and the direction selector lever, wherein the speed setpoint directly describes a setpoint for the engine speed of the aforementioned engine or a setpoint for a quantity dependent on the engine speed, for example, the travel speed of the machine; R. 415123 c) ​​Determination of an upper and / or a lower engine torque limit, each representing a limit for the torque produced by the aforementioned engine, from the input device, for example, from the accelerator pedal, the inching pedal, the direction selector lever, and a rotary control, from the speed detected in step a), and from the speed setpoint determined in step b),so that the input device has both a direct influence on the speed setpoint determined in step b) and a direct influence on the upper and / or lower motor torque limit determined in step c); d) control of the speed taking into account the upper and / or lower motor torque limits determined in step c).

[0015] The method described above is based on the idea of ​​operating a drive system of a working machine with a speed control system, in which the driver of the working machine not only specifies the target speed value by means of an input device, but also a permissible range for the torque generated by the engine, so that the driver has the opportunity to control the behavior of the speed control system so precisely that optimal driving behavior is enabled in every driving situation.

[0016] According to one embodiment of the present invention, a method is provided wherein the motor is an electric motor and the drive system comprises an inverter that performs the speed control of the electric motor as described in step d). For example, the electric motor can be designed as a permanent magnet synchronous machine and the inverter can have a digital communication interface via which an electronic control unit can provide the inverter with the speed setpoint and the upper and lower motor torque limits for speed control.

[0017] According to one embodiment of the present invention, a method is provided wherein the motor is a hydraulic motor which is adjustable in its displacement volume, for example an axial piston motor in swashplate design with electroproportional control of the swivel angle, and the drive comprises a hydraulic pump which is adjustable in its delivery volume, for example an axial piston pump in swashplate design.

[0018] According to one embodiment of the present invention, a method is provided wherein at least one control element of the input device, for example the accelerator pedal, has an influence on the speed setpoint in step b), and the same control element also has a direct influence on the upper and / or lower torque limit in step c), so that the operator of the working machine is enabled to simultaneously specify the speed setpoint and influence the control options on the speed in step d) with a single control element.

[0019] According to one embodiment of the present invention, a method is provided wherein at least one control element of the input device, for example a rotary control, has no influence on the speed setpoint in step b), but the same control element has a direct influence on the upper and / or lower torque limit in step c), thus enabling the operator of the machine to influence the control's effects on the speed in step d) with a single control element without changing the speed setpoint. An advantage of such a control element is that the operator can precisely adapt the speed control's effects to the current driving situation without affecting the speed setting, which is determined by other controls.For example, in such an embodiment, the operator of a wheel loader can use a rotary control to limit the torque range permitted by the engine torque limits before driving into a pile of material. This restricts the speed control's influence, reliably preventing wheel spin. For transport operations, the operator can expand the permissible torque range for speed control, ensuring that the set speed is maintained precisely even on hilly terrain.

[0020] According to one embodiment of the present invention, a method is provided wherein, in step c), the upper and / or lower determined motor torque limit depends on a control error such that the control system can influence the motor's generated torque more effectively the greater the control error, wherein the control error is the difference between the speed setpoint determined in step b) and the speed detected in step a). The dependence of a motor torque limit on the control error is advantageous because it ensures that the speed control is limited according to the instantaneous control error, since the greater the control error, the greater the intervention required by the control system for optimal effect.

[0021] According to one embodiment of the present invention, a method is provided wherein the upper and / or lower determined motor torque limit depends on the control error such that the control error is incorporated linearly. An advantage of a linear dependence of a motor torque limit on the control error compared to a non-linear dependence is that the meaningful adjustment of associated parameters is usually simpler. R. 415123

[0022] According to one embodiment of the present invention, a method is provided wherein the dependence of the upper and / or lower determined motor torque limit on the control error can be influenced by a parameter that is acquired in an additional step e), and wherein this parameter can be influenced by the input device so that the operator of the machine can influence the behavior of the control system. For example, the parameter can depend on a selected driving mode, which the operator can select via a selector switch, so that the parameter influences the dependence of the motor torque limits on the control error appropriately to the selected driving mode, wherein a work mode and a transport mode are typical examples of a driving mode.

[0023] According to one embodiment of the present invention, a method is provided wherein increasing the parameter weakens the dependence of the upper and / or lower determined engine torque limit on the control error, and decreasing the parameter strengthens this dependence, so that the operator of the machine is able to allow the control system to achieve greater compliance with the target speed by decreasing the parameter, and to restrict the control system's ability to achieve compliance with the target speed by increasing the parameter. An advantage of such a dependency is, for example, that it allows the operator to continuously fine-tune the driving behavior depending on the current application, for example by means of a rotary control that influences the parameter.

[0024] According to one embodiment of the present invention, a method for operating the drive system of a mobile work machine is provided, wherein, in determining the upper and / or lower motor torque limit in step c), the dependence on the control error is combined with a direct dependence on the input device in such a way that the dependencies interact multiplicatively, enabling the operator of the work machine to limit and expand the control system's influence on the rotational speed. The combination described above is advantageous because, on the one hand, the operator always retains control over the control system's influence, while on the other hand, the control system's influence also automatically and appropriately adapts to the control error.

[0025] According to one embodiment of the present invention, a method for operating a drive system of a mobile working machine is provided, wherein the upper and / or lower determined motor torque limit in step c) depends on a limit value for the power consumed by the drive system, such that the power consumed by the drive system R. 415123

[0026] The power output can be dynamically limited by a higher-level power control system of the working machine.

[0027] According to one embodiment of the present invention, a method for operating a drive system of a mobile working machine is provided, wherein in step b) a target value for the driving speed of the working machine is determined.

[0028] According to one embodiment of the present invention, a method is provided in which the motor is coupled to at least one wheel of the working machine via a switchable two-gear transmission. The combination of the method with a switchable transmission has the advantage that, depending on the driving situation, either a greater maximum tractive force or a greater maximum speed of the working machine can be selected by choosing the transmission gear.

[0029] According to one embodiment of the present invention, a computing unit is provided which is configured to carry out a method according to the invention.

[0030] According to one embodiment of the present invention, a mobile working machine is provided which has a drive system and a computing unit which is configured to carry out a method according to the invention, wherein the drive system comprises a motor which drives at least one wheel of the working machine, and wherein the mobile working machine comprises an input device which has one or more control elements with which the driver of the mobile working machine can control the drive system.

[0031] According to one embodiment of the present invention, a computer program is provided which causes a computing unit to perform a method according to the invention when it is executed on the computing unit.

[0032] BRIEF DESCRIPTION OF THE FIGURES

[0033] The present invention is described with reference to the accompanying figures, where identical reference numerals refer to identical parts and / or to similar parts and / or to corresponding parts of the system. Regarding the figures:

[0034] Figure 1 schematically describes the inventive method by means of a cycle of the main process steps according to an embodiment of the invention.

[0035] Figure 2 schematically describes the determination of a target speed value in the electronic control unit according to an embodiment of the invention. R. 415123

[0036] Figure 3 schematically describes the determination of an upper and lower motor torque limit in the electronic control unit according to an embodiment of the invention.

[0037] Figure 4 schematically describes the determination of a power limit, which is used as the basis for determining the upper and lower motor torque limits according to an embodiment of the invention.

[0038] DETAILED DESCRIPTION

[0039] The present invention is described below with reference to certain embodiments as shown in the accompanying figures. However, 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.

[0040] Further modifications and variations of the present invention are obvious to a person skilled in the art. The present description therefore encompasses all modifications and / or variations of the present invention whose scope of protection is defined by the claims.

[0041] In a first embodiment, the mobile working machine comprises an electric motor, an inverter that controls the electric motor, a battery that serves as an energy source for the mobile working machine, an electronic control unit that is connected to the inverter via a communication interface, and the following additional components that are connected to the electronic control unit in which they are evaluated: an accelerator pedal, a brake pedal, a direction selector lever, a first rotary control for setting a maximum speed, and a second rotary control for setting a control parameter with which the driver can influence the behavior of the speed control.The brake pedal is designed as a combination of a brake pedal and an inching pedal, which, although it influences the control of the drive system throughout its entire range of operation as described below, only activates an additional mechanical brake above a certain minimum actuation, for example, above an actuation of more than 50% of the maximum deflection.

[0042] Fig. 1 schematically shows the main steps that are repeatedly performed during the operation of the electric drive of the mobile work machine. R. 415123

[0043] In step 1, the inverter determines the current speed of the electric motor, for example by means of a resolver, and provides this information to the electronic control unit via the communication interface so that, as will become clearer in the course of the description, this information is available there for determining the target speed and the motor torque limits.

[0044] In step 2, the target speed for the electric motor is determined in the electronic control unit and provided to the inverter via the communication interface. The determination of the target speed is described in detail in Fig. 2.

[0045] In step s, an upper and a lower motor torque limit are determined in the electronic control unit and provided to the inverter via the communication interface. The determination of the motor torque limits is described in more detail with reference to Figures 3 and 4.

[0046] In step 4, the inverter regulates the speed of the electric motor, taking into account the speed setpoint, upper motor torque limit, and lower motor torque limit provided by the electronic control unit. This ensures that the torque generated by the electric motor does not exceed the upper motor torque limit or fall below the lower motor torque limit. The torque generated by the electric motor is adjusted using current control, which is subordinate to the speed control. Such current control methods are well-known from the literature, for example, from the following standard textbook: Schröder D, Böcker J (2020), Elektrische Antriebe - Regelung von Antriebssystemen, 5th edition, Springer Vieweg, Berlin.

[0047] Figure 2 illustrates the steps performed sequentially in the electronic control unit to determine a target speed. These steps can be carried out for both electric and hydrostatic drive systems. In step 200, a maximum speed for the machine is determined, depending on the setting of the first rotary control. Step 201 also records the position of the accelerator pedal, step 202 the position of the brake pedal, and step 203 the position of the direction selector lever. The direction selector lever allows the operator of the machine to choose between forward, reverse, and neutral.In step 204, the accelerator pedal position is converted into a dimensionless accelerator pedal velocity factor between zero and one using a monotonically increasing accelerator pedal velocity characteristic curve, so that a stronger application of the accelerator pedal results in a larger accelerator pedal velocity factor. The brake pedal position is converted in step 205 using a monotonically decreasing brake pedal characteristic curve. R. 415123.

[0048] The speed characteristic curve is converted into a dimensionless brake pedal velocity factor between zero and one, so that a stronger application of the brake pedal results in a smaller brake pedal velocity factor. The exact shape of these characteristic curves defines the driving behavior of the mobile work machine and can be selected by the manufacturer to suit the machine's intended use. It is also possible to store several characteristic curves for a work machine in the electronic control unit and to switch between them depending on the situation, for example, depending on a selected driving mode such as work mode or transport mode. In step 206, the position of the direction selector lever is converted into a direction-speed factor, where the forward position of the direction selector lever corresponds to a factor of one, the reverse position to a factor of minus one, and the neutral position to a factor of zero.

[0049] The maximum speed determined in step 200 is multiplied in step 207 by the accelerator pedal speed factor, the brake pedal speed factor, and the direction-of-travel speed factor to obtain a target speed for the machine. The value of the target speed lies between zero and the maximum speed determined in step 200. The forward position of the direction selector lever results in a positive target speed, and the reverse position in a negative target speed. In step 208, the target speed is filtered by limiting its rate of change, ensuring that the target speed can only change as quickly as necessary to prevent unstable machine behavior.This limitation of the rate of change is also influenced by the current speed of the machine, which is calculated in step 210 from the rotational speed of the motor used (electric motor in the case of an electric drive, hydraulic motor in the case of a hydrostatic drive), the gear ratio, and the wheel circumference. It is also influenced by the position of the brake pedal and the direction selector lever, particularly to ensure that the operator can reduce the target speed quickly enough to stop safely at any time. For example, applying the brake pedal or moving the direction selector lever to neutral may result in a faster reduction of the target speed than releasing the accelerator pedal. In step 209, the filtered target speed for the machine is converted into a target speed for the motor used, depending on the gear ratio and wheel circumference.

[0050] Figure 3 illustrates the steps performed sequentially to determine upper and lower motor torque limits. These steps can be carried out for both electric and hydrostatic drive systems. R. 415123

[0051] In step 300, the power limit 420, the determination of which is described in Fig. 4, is converted into a torque limit using the engine speed and taking into account the position of the direction selector lever. The accelerator pedal position determined in step 201 is converted in step 303 into a first dimensionless accelerator pedal torque factor using a first accelerator pedal torque characteristic curve. The brake pedal position determined in step 202 is converted in step 304 into a first dimensionless brake pedal torque factor using a first brake pedal torque characteristic curve. In step 305, the upper engine torque limit is determined by multiplying the torque limit determined in step 300 by the first accelerator pedal torque factor and the first brake pedal torque factor.

[0052] The lower engine torque limit is determined analogously, using different characteristic curves than those for the upper engine torque limit. However, it has been shown that the torque limit determined in step 300 can also be used to determine the lower engine torque limit. The accelerator pedal position determined in step 201 is converted into a second dimensionless accelerator pedal torque factor in step 306 using a second accelerator pedal torque characteristic curve. The brake pedal position determined in step 202 is converted into a second dimensionless brake pedal torque factor in step 307 using a second brake pedal torque characteristic curve. In step 308, the lower engine torque limit is determined by multiplying the torque limit determined in step 300 by the second accelerator pedal torque factor and the second brake pedal torque factor.

[0053] Just like the accelerator pedal speed curve and brake pedal speed curve described above, the accelerator pedal torque curves and brake pedal torque curves described here also have a significant influence on the driving behavior of the mobile work machine and can be selected by the manufacturer to suit the intended application. It is also possible to store several curves for a single work machine in the electronic control unit and to switch between them depending on the situation, for example, depending on the selected driving mode such as work mode or transport mode. Optionally, to simplify parameterization, only a single accelerator pedal torque curve can be used.The first accelerator pedal torque factor can then be determined by evaluating this single accelerator pedal torque characteristic curve, and the second accelerator pedal torque factor can be determined, for example, by calculating the multiplicative inverse of the first accelerator pedal torque factor. Optionally, the determination of the second brake pedal torque factor can also be simplified in this way (see R. 415123).

[0054] Figure 4 illustrates the determination of a power limit, which forms the basis for determining the upper and lower motor torque limits. The steps described in Figure 4 can be performed for both electric and hydrostatic drive systems.

[0055] The determination of the power limit is based on a power value 410 specified by a higher-level function in the electronic control unit, which determines how much power is available to the drive system. In step 412, the difference between the specified power value 410 and the power loss 411 is calculated. The power loss 411 is a constant that approximates the power that the drive system must supply to overcome the driving resistance. The power determined in step 412 is referred to here as excess power, since it is effectively available for accelerating the machine. In step 415, the control error is determined, which is the difference between the target speed 413 and the actual engine speed 414.In step 416, a parameter is determined from the setting of the second rotary control. This parameter is subsequently referred to as impedance because it influences the torque with which the motor can respond to a deviation of the motor speed from the target speed. In step 417, the control error is divided by the impedance, and in step 418, it is multiplied by the excess power. In step 419, a power limit 420 is determined by adding the power value determined in step 418 to the power loss 411. The steps described above for determining the power limit result in a higher power limit the greater the control error. The operator of the machine can influence this relationship between the power limit and the control error via the impedance using the rotary control.If the driver reduces the impedance, the dependency is strengthened, allowing the control system to exert greater influence over maintaining the target engine speed. Conversely, if the driver increases the impedance, the dependency is weakened, limiting the control system's ability to maintain the target engine speed.

[0056] In a second embodiment, the mobile working machine comprises an internal combustion engine driving a hydraulic pump with adjustable delivery volume, an adjustable hydraulic motor with electro-proportional control of the swivel angle, which is connected to the pump via a closed hydraulic circuit, and a two-speed gearbox between the output shaft of the hydraulic motor and the driven wheel axle, which can be operated by the driver when stationary by means of a lever. R. 415123

[0057] The system consists of a gear selector switch, an electronic control unit that controls the combustion engine, the hydraulic pump, and the hydraulic motor, and the following additional components connected to and evaluated by the electronic control unit: a sensor for detecting the hydraulic motor speed, an accelerator pedal, a brake pedal, a direction selector lever, a first rotary control for setting a maximum speed, and a second rotary control for setting a control parameter that allows the driver to influence the behavior of the speed control. The brake pedal is a combination of a brake pedal and an inching pedal, which, while influencing the control of the drive system across its entire range of operation as described below, only engages a mechanical brake above a certain minimum actuation, for example, above 50% of its maximum deflection.

[0058] The main steps of the procedure for the hydrostatic drive are similar to those illustrated in Fig. 1 for the electric drive, so a separate illustration is omitted. In a first step, the current speed of the hydraulic motor is determined in the electronic control unit using the speed sensor. In a second step, the target speed for the hydraulic motor is determined in the electronic control unit as described in Fig. 2. In a third step, upper and lower motor torque limits are determined in the electronic control unit as described in Figs. 3 and 4.In a fourth step, the electronic control unit regulates the speed of the hydraulic motor, taking into account the setpoint speed, upper motor torque limit, and lower motor torque limit, so that the torque generated by the hydraulic motor does not exceed the upper motor torque limit and does not fall below the lower motor torque limit. Known methods can be used for this control of the hydrostatic drive, for example, the method described in DE 10 2020 210 196 A1.

[0059] While the present invention has been described with reference to the embodiments described above, it is clear to the person skilled in the art that it is possible to implement various modifications, variations and improvements of the present invention in light of the teaching described above and within the scope of the attached claims without deviating from the scope of protection of the invention.

[0060] Furthermore, the areas in which experts would likely be knowledgeable have not been described here in order to avoid unnecessarily obscuring the described invention. R. 415123

[0061] Accordingly, the invention should not be limited by the specific illustrative embodiments, but only by the scope of protection of the attached claims.

Claims

R. 415123 Patent claims 1. A method for operating a drive system of a mobile working machine, wherein the drive system comprises a motor that drives at least one wheel of the working machine, and wherein the mobile working machine comprises an input device having one or more operating elements with which the operator of the mobile working machine can control the drive system, characterized in that the method comprises the following steps: a) detecting a rotational speed corresponding to the motor speed or a quantity dependent on the motor speed; b) determining a target speed value from the input device, wherein the target speed value describes a target value for the motor speed or a target value for a quantity dependent on the motor speed;c) Determination of an upper and / or a lower motor torque limit, each representing a limit to the torque generated by the motor, from the input device, from the speed detected in step a), and from the speed setpoint determined in step b), such that the input device has direct influence on both the speed setpoint determined in step b) and the upper and / or lower motor torque limit determined in step c); d) Control of the speed taking into account the upper and / or lower motor torque limits determined in step c).

2. Method according to claim 1, wherein the motor is an electric motor and the drive system comprises an inverter which performs the speed control of the electric motor as described in step d).

3. Method according to claim 1, wherein the motor is a hydraulic motor which is adjustable in its displacement volume, and the drive system comprises a hydraulic pump which is adjustable in its delivery volume.

4. Method according to one of the preceding claims, wherein at least one control element of the input device has an influence on the speed setpoint in step b), and the same control element also has a direct influence on the upper and / or lower torque limit in step c), so that the operator of the working machine is enabled to simultaneously specify the speed setpoint and influence the control options on the speed in step d) with a single control element.

5. Method according to one of the preceding claims, wherein for at least one control element of the input device it is the case that in step b) it has no influence on R. 415123 has the speed setpoint, but the same control element in step c) has a direct influence on the upper and / or lower torque limit, so that the operator of the working machine is enabled to influence the control possibilities on the speed in step d) with a single control element without changing the speed setpoint.

6. Method according to one of the preceding claims, wherein in step c) the upper and / or lower determined motor torque limit depends on a control error such that the control can influence the motor in its generated torque more the greater the control error, wherein the control error is the difference between the speed setpoint determined in step b) and the speed detected in step a).

7. Method according to claim 6, wherein the upper and / or lower determined motor torque limit depends on the control error in such a way that the control error is linearly incorporated.

8. Method according to claim 6 or 7, wherein the dependence of the upper and / or lower determined motor torque limit on the control deviation can be influenced by a parameter which is detected in an additional step e), and wherein this parameter can be influenced by the input device so that the driver of the working machine can influence the behavior of the control.

9. Method according to claim 8, wherein an increase in the parameter weakens the dependence of the upper and / or lower determined engine torque limit on the control deviation, and a decrease in the parameter increases this dependence, so that the operator of the working machine is able to allow the control to a greater extent to ensure compliance with the speed setpoint by decreasing the parameter, and to restrict the control to a greater extent in ensuring compliance with the speed setpoint by increasing the parameter.

10. Method according to one of claims 6 to 9, wherein, in determining the upper and / or lower motor torque limit in step c), the dependence on the control error is combined with a direct dependence on the input device in such a way that the dependencies interact multiplicatively, enabling the operator of the machine to limit and extend the control's influence on the speed.

11. Method according to one of the preceding claims, wherein the upper and / or lower determined motor torque limit in step c) depends on a limit value for the power consumed by the drive system, such that the power consumed by the drive system R. 415123 The power recorded can be dynamically limited by a higher-level power control of the working machine.

12. A method according to any one of the preceding claims, wherein in step b) a target value for the travel speed of the working machine is determined.

13. A method according to any one of the preceding claims, wherein the motor is coupled to at least one wheel of the working machine via a switchable transmission with two gears.

14. A computing unit configured to perform a method according to any one of the preceding claims.

15. A mobile working machine comprising a computing unit according to claim 14 and a drive system, wherein the drive system comprises a motor that drives at least one wheel of the working machine, and wherein the mobile working machine comprises an input device having one or more controls with which the operator of the mobile working machine can control the drive system.

16. A computer program that causes a computing unit to perform a method according to any one of the Claims 1 to 13 can be carried out when it is executed on the computing unit.

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