Method for designing a control system of a drive motor of a motor vehicle and method for controlling a drive motor of a motor vehicle

Abstract

The invention relates to a method for designing a control system of a drive motor of a motor vehicle, the motor vehicle having a drive train which comprises: the drive motor; at least one wheel driven by the drive motor; and at least one shaft for transmitting to the at least one wheel the torque provided by the drive motor, and the control system being designed to control a torque provided by the drive motor in such a way that torsional vibrations in the drive train are reduced, wherein: to design the control system, a rotational speed of the drive motor and a transmission ratio of the drive train are detected and at the same time a rotational speed of the at least one wheel is detected; a vibration signal of the drive train is derived from the rotational speed averaged over the wheels and the rotational speed of the motor; a modeled vibration signal is determined from a transfer function; the transfer function is optimized by suitable selection of their zero points and poles in such a way that deviations between the frequency response of the vibration signal determined from the measured values and the frequency response of the modeled vibration signal are minimized.

Description

[0001] 202401107

[0002] 1

[0003] Methods for designing a control system for a drive motor of a motor vehicle and methods for controlling a drive motor of a motor vehicle

[0004] Description

[0005] The present invention relates to a method for designing a control system for a drive motor of a motor vehicle. It further relates to a method for controlling a drive motor of a motor vehicle, as well as a control device for a motor vehicle and a motor vehicle itself.

[0006] The powertrain of a motor vehicle comprises several components, in particular the drive motor, the wheels driven by the drive motor, and at least one mechanical component for transmitting the torque provided by the drive motor to the driven wheels. The moments of inertia of the components, their stiffness, and damping within the powertrain determine the dynamic behavior of the system. This can lead to vibrations in the powertrain, especially torsional vibrations of a shaft, which are perceived as a disturbing judder. One option is to implement judder damping, which uses relatively complex and expensive low-pass and high-pass filters that require calibration.

[0007] It is therefore an object of the present invention to provide a method for designing a control system for a drive motor of a motor vehicle and a method for controlling a drive motor of a motor vehicle which achieves damping of torsional vibrations in the drive train in a simple manner.

[0008] This problem is solved by the subject matter of the independent patent claim. Advantageous embodiments and further developments are the subject matter of the dependent claims. 202401107

[0009] 2

[0010] According to one aspect of the invention, a method for designing a control system for a drive motor of a motor vehicle is provided, wherein the motor vehicle has a drive train comprising the drive motor, at least one wheel driven by the drive motor and at least one shaft for transmitting the torque provided by the drive motor to the at least one wheel.

[0011] The control system is designed to regulate the torque provided by the drive motor in such a way as to reduce, and in particular minimize, torsional vibrations in the drivetrain. To design the control system, test drives are conducted with a suitable test vehicle, during which the rotational speed of the drive motor and the gear ratio of the drivetrain are recorded, along with the rotational speed of at least one wheel. Sensors already installed in the vehicle can be used for this purpose.

[0012] A vibration signal of the drivetrain is derived from the rotational speed averaged across the wheels and the rotational speed of the motor.

[0013] Furthermore, a modeled vibration signal is determined from a transfer function, whereby the transfer function is optimized by appropriately choosing its zeros and poles in such a way that deviations between the frequency behavior of the vibration signal determined from the measured values ​​and the frequency behavior of the modeled vibration signal are minimized.

[0014] Thus, the optimized transfer function reproduces the vibration behavior of the drivetrain as a function of motor speed as accurately as possible. The modeled vibration signal determined in this way can then be used to control the drive motor in such a way as to generate a counter-torque that dampens the jerking. 202401107

[0015] 3

[0016] According to one embodiment, the vibration signal of the drive train is determined by multiplying the average rotational speed of the wheels by the gear ratio and subtracting the result from the rotational speed of the drive motor, which is then compared with the modeled vibration signal.

[0017] The plan is to model the vibration signal of the drivetrain using the transfer function, whereby the zeros and poles of the transfer function are optimally defined to reproduce the vibration behavior in the drivetrain as accurately as possible. In particular, the frequency response should be reproduced as accurately as possible.

[0018] This method has the advantage that torsional vibrations in the drive train can be damped in a technically very simple way by providing a counter-torque that is matched to the vibration signal. Once implemented, the control system requires only the rotational speed of the drive motor as an input.

[0019] According to one embodiment, an optimized algorithm is used to determine the zeros and poles of the transfer function. This ensures that the modeled vibration signal, represented by the transfer function, accurately reflects the vibration signal of the powertrain. As it turns out, short test drives during which the juddering occurs are sufficient to model the vibration signal.

[0020] To determine the transfer function, the z-transformation of the system is formed in particular, since the measured values ​​from the vehicle are available as time-discrete values ​​when designing the control system.

[0021] According to one aspect of the invention, a method for controlling a drive motor of a motor vehicle is specified, wherein the motor vehicle has a 202401107

[0022] 4

[0023] The drivetrain comprises the drive motor, at least one wheel driven by the drive motor, and at least one shaft for transmitting the torque provided by the drive motor to the at least one wheel. The control system is designed to regulate the torque provided by the drive motor in such a way as to reduce, and in particular minimize, torsional vibrations in the drivetrain, whereby the transfer function determined as described is used as the basis for generating a counter-torque from the drive motor to dampen the torsional vibrations.

[0024] The control system receives the rotational speed of the drive motor as its input variable.

[0025] According to one embodiment, a signal corresponding to the inverted transfer function multiplied by a scaling factor is defined to generate the counter-torque. The scaling factor, which influences the amplitude of the signal, is determined, for example, by means of an optimization algorithm and / or empirically such that a desired vibration behavior is achieved in the drivetrain.

[0026] While the frequency response determines the timing of an intervention by means of the counter-torque, the scaling factor determines the strength of this intervention.

[0027] The method makes it possible to dampen torsional vibrations in the drive train in a simple way or to avoid them altogether.

[0028] According to one embodiment, a counter-torque is only provided if the amount of the determined counter-torque exceeds a defined threshold.

[0029] According to this embodiment, it is intended to generate a counter-torque only in the case of relevant vibrations and to reduce vibrations to noise levels.

[0030] 5

[0031] Ignore. An activation logic can be provided for this purpose, which only allows the generation of a counter-torque above the defined threshold.

[0032] Alternatively, the activation logic can be placed in the process flow before the counter-torque is determined. Since the vibrations in the drivetrain are caused by the engine speed, the activation logic can, for example, refer to a signal derived directly from the engine speed and only provide a counter-torque if this signal exceeds a defined threshold.

[0033] When the engine speed changes, for example during vehicle acceleration, torsional vibrations can occur under certain circumstances. For instance, strong or uneven acceleration can promote the occurrence of torsional vibrations. The engine speed over time can therefore be used to derive a measure of the torsional vibrations that occur.

[0034] According to one aspect of the invention, a computer program product is provided comprising instructions which, when the program is executed by a computing unit, cause it to carry out the described method for controlling the drive motor.

[0035] The processing unit can be, in particular, a control unit, for example, the engine control unit of a motor vehicle. It is also possible to execute parts of the process on different processing units, either on board the vehicle or externally.

[0036] According to a further aspect of the invention, a control device is specified, comprising at least one control unit, wherein the control unit is configured to carry out the described method. Furthermore, a motor vehicle is specified, comprising a drive motor, a drive train, and the described control device. 202401107

[0037] 6

[0038] Embodiments of the invention will now be described in more detail with reference to schematic figures. These show

[0039] Figure 1 shows a block diagram of the design of a control system according to an embodiment of the invention and

[0040] Figure 2 shows a block diagram of the control system according to one embodiment of the invention.

[0041] Figure 1 shows a block diagram of a method for designing a control system according to an embodiment of the invention. The control system is intended to dampen torsional vibrations in the drivetrain of a motor vehicle. The drivetrain typically comprises a drive motor that provides torque which is transmitted to the driven wheels of the motor vehicle via a drive shaft. Furthermore, the drivetrain typically includes a transmission and a differential, on whose output shafts the wheels are arranged.

[0042] During operation of a motor vehicle, torsional vibrations, particularly of the drive shaft in the drivetrain, can occur, which are perceived as jerking. To dampen these vibrations, the torque provided by the drive motor is regulated by a control device.

[0043] The block diagram shown in Figure 1 illustrates the procedure for designing the control system of the drive motor. During test runs, the rotational speed 1 of the drive motor is determined together with the rotational speed 2 of the wheels and the gear ratio 3. From the rotational speeds 2 measured at the individual wheels, an average rotational speed of the wheels is calculated and multiplied by the gear ratio 3.

[0044] The difference between this quantity and the rotational speed 1 of the motor is the vibration signal in the drivetrain. To reproduce this vibration signal, the z-transform 4 of the system is considered and its poles 202401107

[0045] 7

[0046] and zeros are chosen using an optimization procedure such that at least the resulting frequency response corresponds as closely as possible to that of the oscillation signal. Here and in the following, this means that the signals should match as closely as possible, except for any scaling factors affecting the amplitude.

[0047] Thus, the z-transform 4 of the system, or its poles and zeros, is selected in such a way that the vibration signal produced thereby matches the vibration signal determined from the measured values ​​during the test drives as well as possible in comparison 5, and especially in its frequency behavior.

[0048] The function of the z-transformed 4 found in this way is then made available to the procedure for controlling the drive motor.

[0049] Figure 2 shows a block diagram of a method for controlling a drive motor of a motor vehicle, wherein the control is designed as explained with reference to Figure 1 to dampen torsional vibrations in the drive train which cause jerking.

[0050] As shown in Figure 2, the control system receives the motor rotational speed as input E.

[0051] The R module calculates a counter-torque to counteract any jerking. For this purpose, the torsional vibration signal, reproduced using the optimized z-transform, is multiplied by a scaling factor s. The scaling factor s has a negative sign, so the resulting counter-torque signal is already inverted and therefore has a different sign than the torsional vibration signal itself.

[0052] An activation logic L determines whether a jerk exceeds a defined threshold. Torsional vibrations that are within the noise range can be ignored, while stronger vibrations are passed through the 202401107

[0053] 8

[0054] The activation logic L is recognized as relevant. The control system only intervenes in the operation of the drive motor by providing a counter-torque if the activation logic has detected a relevant jerking motion.

[0055] The two components R and L can alternatively be used in reverse order, so that the activation logic L precedes the determination of the counter-torque. In this case, the activation logic checks whether, for example, a signal derived directly from the motor speed exceeds a defined threshold, so that a counter-torque is only determined if the signal derived from the motor speed exceeds the defined threshold.

[0056] Subsequently, a limiter B ensures that the applied counter-torque does not exceed specified values. Limiter B serves to ensure the safety of the control procedure, as it prevents, for example, excessively high counter-torques from being applied due to faulty or inaccurate measurements.

[0057] The resulting signal 6 is passed as output A to the motor control, which provides the determined and, if necessary, limited counter-torque. 202401107

[0058] 9

[0059] Reference symbol list

[0060] 1 Motor rotation speed 2 Wheel rotation speed 3 Gear ratio

[0061] 4 z-transformed

[0062] 5 Comparison

[0063] 6 Signal

[0064] E Input size

[0065] A Initial variable

[0066] R building block

[0067] L Activation logic

[0068] B limiter

Claims

202401107 10 Patent claims 1. Method for designing a control system for a drive motor of a motor vehicle, wherein the motor vehicle has a drive train comprising the drive motor, at least one wheel driven by the drive motor and at least one shaft for transmitting the torque provided by the drive motor to the at least one wheel, the control system is designed to regulate the torque provided by the drive motor in such a way as torsional vibrations in the drive train are reduced, wherein, for the design of the control system, a rotational speed of the drive motor and a gear ratio of the drive train are detected, and simultaneously a rotational speed of at least one wheel is detected, wherein a vibration signal of the drive train is derived from the rotational speed averaged over the wheels and the rotational speed of the motor, wherein a modeled vibration signal is determined from a transfer function, wherein the transfer function is optimized by appropriate choice of its zeros and poles such that deviations between the frequency response of the vibration signal determined from the measured values ​​and the frequency response of the modeled vibration signal are minimized.

2. Method according to claim 1 , the vibration signal of the drive train is determined by multiplying the rotational speed averaged over the wheels by the gear ratio and subtracting the result from the rotational speed of the motor.

3. Method according to claim 1 or 2, where an optimization algorithm is used to determine the zeros and poles of the transfer function.

4. Method according to one of claims 1 to 3, 202401107 11 where the z-transformation of the system is formed to determine the transfer function.

5. Method for controlling a drive motor of a motor vehicle, wherein the motor vehicle has a drive train comprising the drive motor, at least one wheel driven by the drive motor and at least one shaft for transmitting the torque provided by the drive motor to the at least one wheel, the control system is designed to regulate the torque provided by the drive motor in such a way as torsional vibrations in the drive train are reduced, wherein the transfer function determined according to one of claims 1 to 4 is used as a basis for generating a counter-torque of the drive motor to dampen the torsional vibrations.

6. Method according to claim 5, where the control system receives the rotational speed of the drive motor as an input variable.

7. Method according to claim 5 or 6, where a signal is defined to generate the counter-torque, which corresponds to the inverted transfer function multiplied by a scaling factor.

8. Method according to any one of claims 5 to 7, where a counter-torque is only provided if the amount of the determined counter-torque and / or a signal derived from the engine speed exceeds a defined threshold.

9. Computer program product comprising instructions which, when the program is executed by a computing unit, cause the unit to perform the method according to any one of claims 5 to 8. 202401107 12 10. Control device comprising at least one control unit, wherein the control unit is configured to carry out a method according to one of claims 5 to 8.

11. Motor vehicle comprising a drive motor, a drive train and a control device according to claim 10.

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