Method for operating a drive motor of a vehicle and motor control device

Abstract

The present invention relates to a method for operating a drive motor (104) coupled to at least one wheel (108) of a vehicle (100) via a powertrain (106). [Solution] The drive motor (104) is controlled using a dynamic model (130) of the powertrain (106), the model (130) representing the relationship between the drive torque (114) transmitted through the powertrain (106) and deformations (116) of the powertrain (106).

Description

[Technical field]

[0001] The present invention relates to a method for operating a drive motor coupled to at least one wheel of a vehicle via a powertrain, and to a corresponding motor control device. [Background technology]

[0002] The vehicle can have a drive slip control. If at least one wheel of the vehicle has too much drive slip, the drive slip control can reduce or limit the drive torque of the wheel. The slip is detected by a speed sensor coupled to the wheel and can be recognized in the speed signal of the speed sensor. In response to this recognition, a drive motor of the vehicle coupled to the wheel can be controlled to reduce its torque. Alternatively or additionally, the brake of the wheel can be controlled to brake the wheel by a brake torque acting opposite to the drive torque. For shorter response times and improved control, a controller based on the drive motion of the drive motor can be installed in the motor control device. This can be called a distributed traction control. Summary of the Invention

[0003] Against this background, a method for operating a drive motor coupled to at least one wheel of a vehicle via a power train using the technique presented herein, and a corresponding motor control device as well as a corresponding computer program product and a machine-readable storage medium are presented in the independent claims. Advantageous developments and improvements of the technique presented herein become apparent from the following description and are set forth in the dependent claims.

[0004] An embodiment of the invention can advantageously make it possible to compensate for the influence of the rotational motion of the wheels by a powertrain arranged between the drive motor and the wheels by varying the control of the drive motor. In particular, such a drive slip control can be realized with short signal propagation times. The drive motion of the drive motor can be detected. The influence of the powertrain on the rotational motion of the wheels can be read out from a pre-stored model. To influence the drive motion, the drive torque of the drive motor can be directly compensated for and controlled by the influence of the powertrain.

[0005] A method is presented for operating a drive motor coupled to at least one wheel of a vehicle via a powertrain, the drive motor being controlled using a dynamic model of the powertrain stored in a motor controller of the drive motor, the model representing a relationship between a drive torque transmitted through the powertrain and deformations of the powertrain.

[0006] The ideas relating to the embodiments of the present invention may be considered to be based, inter alia, on the ideas and realizations described below.

[0007] The drive motor can be an internal combustion engine or an electric motor. The drive motor can in particular be an electric motor, the rotor position of which can be substantially always known. This rotor position can be used to control the drive torque of the drive motor. The rotor position can be detected, for example, using a rotor position sensor. In the control, the drive torque of the drive motor can be controlled so that the drive motor rotates at a desired drive speed.

[0008] The powertrain of the vehicle may comprise one or more shafts and a transmission. The powertrain is configured to transmit the rotational motion of the drive motor to at least one wheel of the vehicle. The powertrain may also comprise at least one differential gear to transmit the rotational motion to at least two wheels of the vehicle. The elements of the powertrain may be slightly flexible and may deform slightly due to the transmission of the drive torque through the powertrain. There may also be, for example, a small amount of play between the elements, which allows relative movement of the elements.

[0009] The model of the powertrain can represent the deformations or play of the powertrain depending on the drive torque. The model can be based on support points detected under controlled conditions and can represent the deformations over the operating range of the drive motor. Interpolation can be performed between the support points. Alternatively or supplementarily, the deformations can also be stored in the model as expressions. The model can be calculated based on tests and / or simulations. Furthermore, the model can be calculated using analytical and / or numerical calculations. The model can then represent the deformations when the drive torque is increasing and when the drive torque is decreasing.

[0010] The model can represent the torsion of the powertrain as a function of the drive torque as a deformation. The deformation or torsion can vary linearly or nonlinearly depending on the drive torque. The drive motor can be controlled taking the torsion into account. The torsion can represent the difference between the input angular position of the powertrain at the drive motor and the output angular position of the powertrain at the wheels. The torsion can also be called a twist. Due to the torsion, with an acceleration drive torque, the drive motor can slightly lead the wheels. With a braking drive torque, the drive motor can slightly lag the wheels. The braking drive torque can be called a drag torque. The acceleration drive torque and the braking drive torque can have opposite signs.

[0011] The drive speed of the drive motor can be controlled using a speed setpoint and a twist. The speed setpoint can be provided by the vehicle's ESP (electronic stability program) control unit. The twist can cause the drive speed to be slightly higher than the speed setpoint when accelerating. When braking, the drive speed can be slightly lower than the speed setpoint.

[0012] The model can represent the gear backlash of the powertrain as a deformation depending on the drive torque. The drive motor can be controlled taking into account the gear backlash at the zero crossing of the drive torque. The gear backlash can be caused by fits and manufacturing tolerances. The gear backlash can be an angular amount of rotational motion that cannot practically transmit the drive torque. Without the gear backlash the transmission can be damaged. The zero crossing can be a sign change of the drive torque. The drive torque can change from an accelerating drive torque to a braking drive torque and vice versa at the zero crossing. The gear backlash allows the drive motor to work against no resistance or only against a small resistance due to the angular amount.

[0013] At the zero crossing, the drive speed can be controlled using the speed setpoint and the gear backlash. At the zero crossing, the drive speed can be controlled by deviating from the speed setpoint by the gear backlash. The gear backlash can be taken into account in the drive speed.

[0014] The model can furthermore represent at least one control condition for the drive motor as a function of the drive torque. If the drive torque changes, the control condition read from the model can be used to control the drive motor. The control condition can be, for example, a maximum increase rate of the drive torque. If the speed setpoint requires a large increase in the drive torque, the increase rate of the drive torque can be limited to the control condition in order to protect the powertrain and / or the drive motor.

[0015] To avoid erroneous control, a waiting time depending on the change in drive torque can be read from the model as a control condition. The drive motor can be controlled with a delay by the waiting time. For example, a waiting time can be waited for at the zero crossing of the drive torque. After the waiting time, there may be torsions and / or gear backlash in the powertrain. After the waiting time, the drive torque can be transmitted directly to at least one wheel.

[0016] The method may be implemented, for example, in software or hardware, or a mixture of software and hardware, for example in a motor controller.

[0017] The techniques presented herein further provide a motor controller configured to perform, control or effectuate the steps of the method variations presented herein in a corresponding device.

[0018] The motor controller may be an electric device comprising at least one computing unit for processing signals or data, at least one storage unit for storing signals or data, and at least one interface and / or communication interface for reading or outputting data embedded in a communication protocol. The computing unit may be for example a signal processor, a so-called system ASIC, or a microcontroller for processing sensor signals and outputting data signals in dependence on the sensor signals. The storage unit may be for example a flash memory, an EPROM or a magnetic storage unit. In the storage unit a dynamic model of the powertrain may be stored. The interface may be formed as a sensor interface for reading sensor signals from sensors and / or as an actuator interface for outputting data and / or control signals to actuators. The communication interface may be formed to read or output data wirelessly and / or wired. The interface may be a soft module present for example in the microcontroller besides other software modules.

[0019] A computer program product or computer program having a program code is also advantageous, which program code may be stored on a machine-readable carrier or storage medium, such as a semiconductor memory, a hard disk memory or an optical memory, and is used for executing, realizing and / or controlling the steps of the method according to one of the above embodiments, in particular when the program product or program is run on a computer or device.

[0020] It should be noted that some of the possible features and advantages of the present invention are described herein in conjunction with different embodiments, and those skilled in the art will recognize that the features of the motor controller and method can be appropriately mixed, matched, or exchanged to arrive at further embodiments of the present invention. [Brief description of the drawings]

[0021] [Figure 1] 1 is a diagram of a vehicle equipped with a motor control device according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Embodiments of the present invention will now be described with reference to the accompanying drawings, but neither the drawings nor the description should be construed as limiting the present invention.

[0023] The drawings are only schematic and not to scale. Same reference numbers indicate same or functionally similar features.

[0024] FIG. 1 shows a diagram of a vehicle 100 with a motor controller 102 according to an embodiment. The vehicle 100 has a drive motor 104. The drive motor 104 is coupled to at least one wheel 108 of the vehicle 100 via a powertrain 106. The powertrain 106 may have a fixed transmission ratio of a drive speed 110 of the drive motor 104 to an output speed 112 of the powertrain 106. The powertrain 106 may also have a variable transmission ratio. The powertrain 106 is at least partially elastically deformed by a drive torque 114 of the drive motor 104. Due to a deformation 116 of the powertrain 106, the drive speed 110 slightly leads the output speed 112. The deformation 116 may be, for example, a torsion 118 of the powertrain 106. The deformation 116 may also be a gear backlash 120 of the powertrain 106.

[0025] If the drive motor 104 is directly coupled to the individual wheels 108 via the powertrain 106, the output speed 112 corresponds fixedly to the wheel speeds 122 of the wheels 108. If the powertrain 106 comprises an axle 124 of the vehicle 100 having a differential 126, the output speed 112 corresponds fixedly to the shaft speed 128 of the axle 124. The shaft speed 128 corresponds fixedly to the average value of the wheel speeds 122 of the wheels 108 of the axle 124.

[0026] The motor controller 102 controls the drive motor 104 using a dynamic model 130 of the powertrain 106. The model 130 represents the relationship between the drive torque 114 of the drive motor 104 and the deformation 116 of the powertrain 106.

[0027] The motor controller 102 reads the speed setpoint 132 from the ESP controller 134 of the vehicle 100. In the motor controller 102, the drive torque 114 is controlled so that the drive speed 110 follows the speed setpoint 132. However, as the drive torque 114 increases, the torsion 118 also increases. In one embodiment, to achieve the output speed 112 corresponding to the speed setpoint 132, the target value 136 of the drive speed 110 is increased by the amount of the torsion 118, taking into account the transmission ratio of the powertrain 106.

[0028] When the drive torque 114 has a zero crossing, i.e., changing from, for example, a positive drive torque 114 to a negative drive torque 114, the twist 118 becomes smaller. However, at the zero crossing, gear backlash 120 occurs. In one embodiment, the target value 136 of the drive speed 110 is corrected by the gear backlash 120 at the zero crossing.

[0029] In one embodiment, the model 130 includes a control condition 138 for the drive motor 104 that depends on the drive torque 114. The control condition 138 is, for example, a wait time 140 at a zero crossing of the drive torque 114. The drive speed 110 is increased after the zero crossing with a time delay of the wait time 140. The wait time 140 gives the powertrain 106 time to adapt to the changed conditions. After the wait time 140 has elapsed, the drive motor 104 can be robustly controlled and the drive speed 110 can be made to follow the speed setpoint 132 directly.

[0030] In other words, a robust control in distributed traction control is presented.

[0031] In drive slip control using decentralized control, a fast controller is used that is located in the motor controller of the electric drive or the internal combustion engine in order to be able to control without elapsed time losses due to communication times between different control devices. The ESP then sets the desired value of the controller, which is optimized for the situation.

[0032] In conventional drive slip control, the wheel speed is used to determine the drive slip, whereas in distributed traction control, the actual motor speed is used instead of the wheel speed and is compared to the target motor speed in the motor control device. If the target speed is exceeded, the controller reduces the drive torque, which allows for higher quality and faster control by eliminating communication times between different control devices.

[0033] The motor is usually connected to the wheels via a differential and a shaft. Alternatively, one motor per wheel can be connected to the wheels via a shaft. In that case, the connecting elements have unfavorable properties such as gear backlash or torsion, which makes it difficult to convert the motor speed to the wheel speed using a proportionality factor. Even if the driving wheels do not have excessively high drive slip, the properties of the connecting elements can increase the motor speed so much that a disruptive or overly sensitive drive torque reduction occurs.

[0034] The approach presented here avoids a sensitive reduction in the drive torque and the resulting traction losses by taking into account the properties of the mechanical connection between the motor and the wheels.

[0035] For example, the torsional stiffness of the shaft increases the torsion angle when the drive torque increases, resulting in a higher motor speed compared to a constant drive torque. Furthermore, gear backlash occurs, especially at the zero crossings of the drive torque. This causes the motor speed to rise for a short time without the wheel speed having a similar rise in wheel slip. These properties of the mechanical connection between the motor and the wheels are represented by a situation-dependent model implemented in the motor controller in order to be insensitive to communication latency times (Latenzzeit).

[0036] Torsion can be compensated for, for example, by increasing the target motor speed. Alternatively or additionally, gear backlash can be compensated for by robust control conditions.

[0037] The overly sensitive control of conventional distributed traction control systems, caused by gear backlash and torsion, can be avoided, and the advantages of distributed control are still preserved, thereby achieving a higher quality of control.

[0038] In the approach presented herein, the dynamic ramp up of the motor torque, or the zero crossing of the motor torque, is controlled slower compared to a constant motor torque.

[0039] Finally, it is to be mentioned that the terms "comprise", "include", etc. do not exclude other elements or steps, and the singular terms "a", "an", and "an" do not exclude a plurality. Reference signs in the claims are not to be construed as limiting. [Explanation of symbols]

[0040] 100 vehicles 102 Motor control device 104 Drive motor 106 Powertrain 108 wheels 110 Drive RPM 114 Driving Torque 116 Transformation 118 Twist 120 Gear Backlash 130 Model 132 Rotation speed setting value 138 Control Conditions 140 Waiting Time

Claims

1. A method of operating a drive motor (104) coupled to at least one wheel (108) of a vehicle (100) via a powertrain (106) for drive slip control, the drive motor (104) being controlled using a dynamic model (130) of the powertrain (106), the model (130) representing a relationship between a drive torque (114) transmitted through the powertrain (106) and a deformation (116) of the powertrain (106); The method, wherein the model (130) represents a gear backlash (120) of the powertrain (106) depending on the drive torque (114) as the deformation (116), and the drive motor (104) is controlled taking into account the gear backlash (120) at zero crossings of the drive torque (114).

2. 2. The method of claim 1, wherein the model (130) represents as the deformation (116) a torsion (118) dependent on the drive torque (114) of the powertrain (106), and the drive motor (104) is controlled taking into account the torsion (118).

3. The method of claim 2, wherein a drive speed (110) of the drive motor (104) is controlled using a speed setpoint (132) and the torsion (118).

4. 4. The method according to claim 1, wherein the drive speed (110) of the drive motor (104) is controlled at the zero crossing using a speed setpoint (132) and the gear backlash (120).

5. 5. The method according to claim 1, wherein the model (130) further represents at least one control condition (138) for the drive motor (104) depending on the drive torque (114), and the drive motor (104) is controlled using the control condition (138) read from the model (130) when the drive torque (114) changes.

6. A method for operating a drive motor (104) coupled to at least one wheel (108) of a vehicle (100) via a powertrain (106) for drive slip control, the drive motor (104) being controlled using a dynamic model (130) of the powertrain (106), the model (130) representing a relationship between a drive torque (114) transmitted via the powertrain (106) and a deformation (116) of the powertrain (106); The method of claim 1, wherein the model (130) further represents at least one control condition (138) for the drive motor (104) depending on the drive torque (114), and the drive motor (104) is controlled using the control condition (138) read from the model (130) when the drive torque (114) changes.

7. 7. The method according to claim 5 or 6, wherein a waiting time (140) dependent on a change in the drive torque (114) is read as a control condition (138) from the model (130), and the drive motor (104) is controlled with a delay of the waiting time (140).

8. A motor controller (102) for a drive motor (104), wherein a dynamic model (130) of a powertrain (106) coupled to said drive motor (104) is stored in said motor controller (102), said motor controller (102) being configured to execute, realize and / or control a method according to any one of claims 1 to 7 in a corresponding device.

9. 8. A computer program product configured to instruct a processor to perform, implement and / or control a method according to any one of claims 1 to 7, when said computer program product is executed.

10. A machine-readable storage medium having stored thereon the computer program product according to claim 9.

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