Method for controlling a drive motor of a motor vehicle

Abstract

A method for controlling a drive motor (2) of a motor vehicle, wherein the motor vehicle has a drive train (1) comprising the drive motor (2), at least one wheel (6) which is driven by the drive motor (2), and at least one mechanical component for transmitting the torque provided by the drive motor (2) to the at least one wheel (6), wherein the torque provided by the drive motor (2) is controlled in order to minimize torsional vibrations in the drive train (1), wherein the torque provided by the drive motor (2) is controlled using a state-space model, which represents the drive train (1) of the motor vehicle, and state variables of a controller determined therefrom, wherein the controller is designed by pole placement in the state space.

Description

[0001] 202301112

[0002] 1

[0003] Method for controlling a drive motor of a motor vehicle

[0004] Description

[0005] The present invention relates to a method for controlling a drive motor of a motor vehicle. It further relates to a control device for a motor vehicle and to a motor vehicle.

[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 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.

[0009] 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 drive train with the drive motor, at least one wheel driven by the drive motor and at least one mechanical component for transmitting the torque provided by the drive motor to the 202301112

[0010] 2

[0011] The vehicle must have at least one wheel. The mechanical component for transmitting the torque can be, in particular, one or more shafts. The torque provided by the drive motor is controlled to minimize torsional vibrations in the drivetrain. This control of the torque provided by the drive motor is achieved using a state-space model representing the vehicle's drivetrain and state variables derived from this model for a controller, whereby the controller is designed by pole specification in state space.

[0012] The state-space model represents the relationships between all input variables, output variables, and state variables in the form of vectors and matrices. State variables of the state model can include, in particular, the wheel speed, the engine speed, the torque supplied by the drive motor, and the torsion angle of a drivetrain shaft. An input variable can be, in particular, the torque requested by the driver of the vehicle, and an output variable the torque actually supplied.

[0013] The method has the advantage of not requiring a multitude of parameters that necessitate complex calibration. Furthermore, it is easy to implement for providing vibration damping in a motor vehicle.

[0014] The pole setting makes it possible to adjust the control so that torsional vibrations are strongly dampened, while still providing a realistic torque through the drive motor.

[0015] The state-space model is described by two systems of differential equations. The first system describes, in particular, the dynamic behavior of the drivetrain as a function of the drive motor's torque, and the second system describes the drivetrain's vibration behavior as a function of changes in the drive motor's torque. The dynamic behavior of the 202301112

[0016] 3

[0017] The drive train can be described depending on the torque of the drive motor by

[0018] cp •• ± = -- d * (p.1+- d * (p.2-- c * (Pi +- c * (p2+^ iG*—VG * MH JT ( / A1\)

[0019] •• dd cc / o\

[0020]

[0021] < P 2 — Y * < Pi ~ Y * + Y2* — Y2* (2)

[0022] The constants c and d characterize the vibration or...

[0023] Damping behavior in the drive train, where c is the stiffness, the quantities Ji, < P1<< P1<< P1 d as moment of inertia or the angle of rotation of the shaft, while the quantities J2, < P2<< P2<< P2 denote the moment of inertia or the angle of rotation and its derivatives of the driven wheel.

[0024] The quantities iG and ηG denote the gear ratio and efficiency of a gearbox in the drive train, and M the torque provided by the drive motor.

[0025] According to one embodiment, the pole setting is used to minimize torsional vibrations in the drivetrain. This can be achieved by setting the imaginary part of the eigenvalues ​​to zero. However, it has been found that it is advantageous to set the poles in such a way that vibrations do occur, but are strongly damped, since complete suppression of vibrations typically leads to unrealistic target torques. Thus, the pole setting can be achieved, for example, by ensuring that the vibrations lie within a predefined vibration range and that the manipulated variable lies within a predefined manipulated variable range. The vibration range is defined in such a way that no disruptive vibrations result in the vehicle.

[0026] The two systems of differential equations can be used in a simulation to determine suitable pole positions and a target torque for the drive motor. 202301112

[0027] 4

[0028] Based on the state space model, state variables can be determined in particular as a wheel speed, a torsion angle, a drive shaft of the drive train and / or a speed of the drive motor.

[0029] According to a further aspect of the invention, a control device is provided, comprising at least one control unit, wherein the control unit is configured to carry out the described method. The control unit can, in particular, be the control unit of a drive motor of a motor vehicle.

[0030] According to a further aspect of the invention, a motor vehicle is specified comprising a drive motor, a drive train and the described control device.

[0031] The vehicle has the advantage of having a shock absorption system that is easy to implement.

[0032] According to another aspect of the invention, a computer program is provided which includes instructions that, when the computer program is executed by a computer, cause it to carry out the described method.

[0033] According to another aspect of the invention, a storage medium with a computer program is provided, wherein the computer program includes instructions which, when the computer program is executed by a computer, cause it to carry out the described method.

[0034] Embodiments of the invention will now be described in more detail with reference to schematic figures. These show

[0035] Figure 1 shows a drive train of a motor vehicle according to an embodiment of the earth finding device,

[0036] Figure 2 shows a model of the drive train according to Figure 1 and 202301112

[0037] 5

[0038] Figure 3 shows a model of a control loop for controlling the drive train according to Figure 1 according to an embodiment of the invention.

[0039] Figure 1 shows a drive train 1 of a motor vehicle. The drive train 1 comprises a drive motor 2, which provides torque that is transmitted to the driven wheels 6 of the motor vehicle via a drive shaft 3. The drive train 1 also comprises a transmission 5 and a differential 8, on whose output shafts 7 the wheels 6 are arranged.

[0040] During operation of the motor vehicle, torsional vibrations can occur, particularly of the drive shaft 3 in the drive train 1. To dampen these vibrations, the torque provided by the drive motor 2 is regulated. For this purpose, the control device 9, shown only schematically, is provided. It receives as inputs the motor speed and the measured wheel speed of the right and left wheels. The average value is calculated from the wheel speeds and used as... <p2verwendet.

[0041] Figure 2 shows a model of the drive train 1 with the drive motor 2, which provides the torque M. The quantities iG and ηG denote the gear ratio and efficiency of the gearbox 5. The behavior of the wheels 6 is described by the quantities J2, < P2<< P2<< P2, which denote the moment of inertia and the angle of rotation, respectively, and their derivatives.

[0042] Furthermore, the constants c and d characterize the vibration or...

[0043] Damping behavior in the drive train, where c is the stiffness of shaft 3, and the quantities J1, < Pi, < Pi, < Pi are the moment of inertia or the angle of rotation of shaft 3 and its derivatives.

[0044] The differential equation systems of the state-space model describe the dynamics and vibration behavior of the drivetrain as a function of torque changes of the drive motor: 202301112

[0045] 6

[0046] •• dd cc iG*VG

[0047] CP ± = --* (p1+-* (p2--* (Pi +-* (p2+^—* M (1).. dd CC / o\

[0048]

[0049] <?2 — / 2 ( ^ 1 ~ / 2 / 2 ( ^ 1 ~ / 2

[0050] The constants c and d characterize the vibration or...

[0051] Damping behavior in the drive train, the parameters J1,

[0052]

[0053] the moment of inertia or the angle of rotation of the shaft and its derivatives of rotating masses in the drive train, while the quantities J2, < P2<< P2<< P2 d as denote the moment of inertia or the angle of rotation and its derivatives of the driven wheel.

[0054] The quantities iG and ηG denote the gear ratio and efficiency of a gearbox in the drive train, and M the torque provided by the drive motor.

[0055] If the quantity r = φ̇₂ − φ̇₁ is introduced as a measure of the torsion of the shaft supporting the driven wheel, then (1) and (2) yield:

[0056] d c f iG * T]G

[0057] ml = — * rd - * I rd - * M

[0058] JI JI J J1

[0059] d c f

[0060] <p2 = - * r - * I r

[0061]

[0062] and from integration

[0063] d c f ( d cf iG * T]G J2 ]2 J Vl / IJ J1 dr dr d c f ( d c f iG * T]G dt dC J2 J2 J VI / IJ

[0064] dc / dc iG * r / G. \r = - * f - * r — I — * rd - * rd - * MI

[0065]

[0066] J2 J2 \J1 J1 J1 )

[0067] and thus

[0068] ddc

[0069] Ji J2 Tl 202301112

[0070] 7

[0071] Figure 3 shows a model of the control loop for the method for controlling the drive motor according to an embodiment of the invention.

[0072] With the state space representation

[0073] ẋ(t) = A(t)x(t) + B(t)u(t)

[0074] y(t) = C(t)x(t) + £)(t)u(t),

[0075] where x(t) is the state vector, u(t) is the input vector, A(t) is the system matrix, B(t) is the input matrix, C(t) is the output matrix, and D(t) is the pass matrix, it follows from equations (1) and (2)

[0076] - 0 0 1 0 - '< P1 0 0 0 1 Vi

[0077] ccdd

[0078] <p2 = <p2

[0079] ep M

[0080] < P1 Ji Ji Ji Ji i

[0081] <p2- c c d d <p2.

[0082] - J2 J2 J2 J2-

[0083] (Pl

[0084] 1 <p2 y(O = < P1

[0085]

[0086] .(p2.

[0087] and thus from the equation of motion

[0088] ddcc ■ r = (— - — — ) * r + (— - — — ) * r - - - * M

[0089] Jl J2 Jl J2 Ji

[0090]

[0091] 202301112

[0092] 8

[0093] The system is in state space as described above by

[0094] ẋ(t) = A(t)x(t) + B(t)u(t)

[0095] described. A regression is now planned.

[0096] u(t) = — K * x(t)

[0097] The matrix K is also known as the observation matrix; it links the state vector of a system with the output vector. This defines the closed control loop.

[0098] x = (A - BK) * x(t)

[0099] described. The eigenvalues ​​of the closed control loop are the solutions s of the equation.

[0100] det [s * I - (A - BK)] = 0

[0101] with the identity matrix I, i.e.

[0102] 0

[0103] − iG*ηG / J1 [k1 k2].

[0104]

[0105] JI -

[0106] The pole selection is now carried out by determining the elements of K such that

[0107] n

[0108] det [s * I — ( / I — BK)] = J” — sj

[0109]

[0110] i-1

[0111] This applies. The Si are the target poles of the closed control loop. The pole specification allows the poles of the system to be positioned precisely so that the 202301112

[0112] 9

[0113] The system exhibits a desired behavior, in this case, damping of torsional vibrations.

[0114] The determined torque, which is based on the determination of the elements of K, is taken into account in the current torque specification in order to achieve the damping of torsional vibrations.

[0115] In particular, a two-stage approach can be chosen, in which, in the first step, the control system of a drive motor is pre-designed using a simulation, in which the poles are appropriately defined. Then, further adjustments are made in the vehicle, similar to fine-tuning, for example, based on specifications from test drives, in which the K-vector is changed to adapt the behavior of the control system as desired. 202301112

[0116] Reference symbol list

[0117] 1 Powertrain

[0118] 2 Drive motor

[0119] 3 Drive shaft

[0120] 5 gearboxes

[0121] 6 wheels

[0122] 7 Output shaft

[0123] 8 Differential

[0124] 9 Control device

Claims

202301112 11 Patent claims 1. Method for controlling a drive motor (2) of a motor vehicle, wherein the motor vehicle has a drive train (1) with the drive motor (2), at least one wheel (6) driven by the drive motor (2) and at least one mechanical component for transmitting the torque provided by the drive motor (2) to the at least one wheel (6), wherein the torque provided by the drive motor (2) is controlled in order to minimize torsional vibrations in the drive train (1), wherein the control of the torque provided by the drive motor (2) is carried out using a state space model representing the drive train (1) of the motor vehicle and state variables of a controller determined therefrom, wherein the controller is designed by pole specification in the state space.

2. Method according to claim 1, wherein the state space model is described by two systems of differential equations, where a first system of differential equations describes the dynamic behavior of the drive train (1) depending on the torque of the drive motor (2) and a second system of differential equations describes a vibration behavior of the drive train (1) depending on torque changes of the drive motor (2).

3. Method according to claim 1 or 2, where the pole selection is carried out to minimize torsional vibrations in the drive train (1), and the two differential equation systems are used in a closed control loop to determine a target torque of the drive motor (2).

4. Method according to any one of claims 1 to 3, where, based on the state-space model, a wheel speed, a torsional angle of a drive shaft (3) of the drive train (1), a torque requested by a driver, a rotational speed of the 202301112 12 The drive motor (2) and the actual torque of the drive motor (2) are determined.

5. Control device (9) comprising at least one control unit, wherein the control unit is configured to carry out a method according to any one of claims 1 to 4.

6. Motor vehicle comprising a drive motor (2), a drive train (1) and a control device (9) according to claim 5.

7. Computer program comprising instructions which, when executed by a computer, cause the computer to perform a method according to any one of claims 1 to 4.

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