DE102009056674A1 - Device for influencing transverse dynamics of motor vehicle, comprises one or multiple actuators for individual wheel adjustment of drive and brake torques, and driving dynamics observer - Google Patents

Abstract

The device comprises one or multiple actuators (4) for individual wheel adjustment of drive and brake torques, and a driving dynamics observer (2), which provides a yaw rate and yaw acceleration corresponding to the reference model of the vehicle. A servo control unit is provided for production of an adjusting signal component for the actuator corresponding to the signal. An independent claim is also included for a method for influencing the transverse dynamics of a motor vehicle.

Description

The invention relates to the field of vehicle lateral dynamics and in particular to an active influencing of the yaw angle of motor vehicles. The latter is sometimes referred to as Active Yaw or Torque Vectoring.

Conventional open differentials make it possible to turn a motor vehicle by permitting different speeds to be used on the vehicle wheels of an axle. The drive torque is transmitted equally to both wheels. However, the driving dynamics characteristics are limited to the extent that the traction of the wheel is limited with the better adhesion by the wheel with the lower liability. This is particularly noticeable on slippery roads or fast cornering.

By means of a limited slip differential, the drive wheels z. B. coupled by friction at least partially with each other, traction and driving dynamics can be improved. However, the locking makes it difficult to turn, so that the vehicle tends to understeer. Adjustable differential locks combine the cornering ability of an open differential with the improved traction of a limited slip differential. By an intelligent logic, which takes into account the respective driving condition, the differential is closed only to the extent required by the respective driving situation. However, even a regulated limited slip differential is only in exceptional situations able to make a vehicle curving. The advantageous properties of a transverse barrier principle can be experienced predominantly only in the limit driving range. Due to the principle, a limited slip differential can not increase existing speed differences or transmit a larger torque to a faster rotating wheel.

Furthermore, it is generally known to influence by automatic braking interventions the yaw angle of a motor vehicle to improve vehicle dynamics and driving safety. However, during brake intervention drive energy is converted into friction losses, which is contrary to a dynamic driving style.

Torque Vectoring Differentials, such as those from DE 103 17 316 A1 . DE 10 2004 001 019 A1 . DE 10 2005 040 253 B3 . DE 10 2007 020 356 A1 or US 7,267,628 B2 are known, make it possible to selectively apply a faster or slower wheel with higher drive torque. In this case, a drive torque, which in principle can be predefined arbitrarily, is subtracted at one wheel and added to the opposite wheel. The sum of the drive torques of the wheels of an axle remains the same, whereby the driving speed is not affected. Torque vectoring, ie activation of the torque vectoring differential in order to distribute the drive torque to the vehicle wheels in a targeted manner, can improve the stability of the vehicle during dynamic driving, so that an intervention of an electronic stability program (ESP) is delayed. However, as soon as the ESP detects a critical driving condition, it takes control and deactivates the torque vectoring system.

Furthermore, it is possible for four-wheel drive vehicles to distribute the drive torque provided by the vehicle engine variably to the vehicle axles, for example via a torque vectoring differential.

A central problem with torque vectoring systems is the determination of the required wheel torques, i. H. the drive and braking torques on the vehicle wheels.

From the DE 10 2008 032 763 A1 In this context, it is known to determine a target yaw rate for the vehicle by means of a vehicle dynamics observer and then to determine the deviation to a measured actual yaw rate. The yaw rate difference is applied to a vehicle dynamics controller, with which among other things a control signal is generated, which enables a torque vectoring differential and the vehicle brake system to set wheel-specific drive and braking torques.

Based on this, the present invention seeks to provide a robust adjustment of the wheel torques of a motor vehicle, which is characterized by a highly dynamic and harmonious response.

This object is achieved by a device for influencing the transverse dynamics of a motor vehicle according to claim 1. The device according to the invention comprises one or more actuators for wheel-individual adjustment of drive and braking torques, a vehicle dynamics observer, which provides a yaw rate and / or yaw acceleration based on a reference model of the vehicle, a pre-control for generating a first actuating signal component for the actuator (s) the basis of a first signal representing a driver's request with respect to the direction of travel and a second signal representing a driver's request with respect to the vehicle speed, and a controller to which a yaw rate and / or yaw acceleration difference is applied as an input variable consisting of a setpoint and an actual value is formed, wherein the setpoint determined by the vehicle dynamics observer and the actual value measured or off measured vehicle parameters is determined, and the output signal provides a second actuating signal component for the actuator (s).

The actuating signal formed from the actuating signal components causes a yawing moment through torque vectoring via the actuator (s) on the vehicle. The structure of the additional yaw moment can be realized by a division of drive torque, a braking intervention or the combination of both.

The pilot component, ie the first actuating signal component, is based on variables which are noise-free, reliable and instantaneous. This allows a highly dynamic, yet harmonious intervention possible.

The second actuating signal component, which is generated parallel to the first actuating signal component, can be used to compensate for modeling inaccuracies and environmental influences.

Due to the pre-control, the control difference applied to the controller in most cases remains much lower than in a device without feedforward control.

As a result, a higher control stability can be achieved and higher controller gains possible.

The low control interventions also contribute to a greater harmony of the control of the wheel torques.

Advantageous embodiments of the invention are specified in further claims.

The vehicle dynamics observer is preferably configured to determine a desired yaw rate and / or a desired yaw acceleration by means of the first signal representing the driver's intention with respect to the direction of travel and with the aid of the second signal representing the driver's intention regarding the vehicle speed. Corresponding signals are used in the feedforward control to generate the first actuating signal component. Signals required by the pilot control and the controller are thus only calculated once.

The reference model of the vehicle underlying the vehicle dynamics observer is preferably a single-track model. It has been shown that such a system is able to supply suitable reference variables for driving vehicle dynamics control systems. Compared to multi-track models, the required computational effort is considerably lower. In an advantageous embodiment, variables are fed back in the vehicle dynamics observer, which represent a slip angle at the front and rear axles.

To improve the quality of the control, the controller can be switched as a further input variable representing a vehicle speed signal, so that a control intervention by the controller is dependent on driving speed.

As already explained above, the regulation of the wheel torques can be achieved by torque vectoring both via a targeted distribution of the drive torque to different vehicle wheels and / or vehicle axles and / or by a braking intervention. In the former case, at least one actuator in the form of a torque vectoring differential is provided on the vehicle, which may be designed in a conventional manner, for example as in the above-mentioned publications. A braking intervention can be realized via the wheel brakes known to the person skilled in the art.

The above-described device allows a method according to claim 8. The inventive method for influencing the transverse dynamics of a motor vehicle by wheel individual adjustment of drive and / or braking torque includes, inter alia, the following steps. On the basis of a reference model of the vehicle, set values for the yaw rate and / or the yaw acceleration of the vehicle are determined from specific input variables, namely a direction of travel desired by the driver and a driving speed desired by the driver. A first actuating signal component is generated from the aforementioned input variables and / or setpoint values obtained by means of the reference model. In addition, a yaw rate and / or yaw acceleration difference is formed from the setpoint values provided by the reference model as well as from corresponding actual measured values measured or measured from measured vehicle parameters. Parallel to the generation of the first control signal component, a second control signal component is generated from the yaw rate and / or yaw acceleration difference and added to the first control signal component in order to carry out a wheel-individual adjustment of drive and / or braking torques and thus to generate an additional yaw moment on the vehicle.

The invention will be explained in more detail with reference to an embodiment shown in the drawing. The drawing shows in:

1 a schematic representation of the structure of a device according to the invention for influencing the transverse dynamics of a motor vehicle,

2 a schematic representation of the structure of the vehicle dynamics controller with pilot control and controller,

3 a detailed view of the vehicle dynamics observer, and in

4 a detailed view of the feedforward control and the controller in the vehicle dynamics controller.

In the 1 schematically illustrated device for influencing the transverse dynamics of a motor vehicle comprises the following basic components, namely input elements 1 , with which the driver's request in terms of driving direction and driving speed is detected, a driving dynamics observer 2 which provides specific yaw response setpoints based on a reference model of the vehicle, a vehicle dynamics controller 3 , as well as one or more actuators 4 for influencing the wheel torques or the longitudinal forces on the vehicle wheels.

With the actuator (s) 4 It is possible to make a wheel-individual adjustment of drive and braking torques to produce a yaw moment regardless of the steering. In particular, despite straight ahead position of the vehicle wheels, a yawing of the vehicle, ie, a rotation about its vertical axis can be achieved. Furthermore, an additional yaw moment can be superimposed on a yaw moment caused by the steering angle of the vehicle wheels. This is preferably done by means of one or more torque vectoring differentials, which allow to selectively apply a faster or slower wheel of an axle with higher drive torque and / or to influence the distribution of the drive torque on the front and rear axle. A reduced drive torque or braking torque can also be displayed on existing wheel brakes on the vehicle.

The determination of the required drive and braking torques or corresponding control signals for influencing the lateral dynamic driving behavior will be explained in more detail below. In this case, a combined precontrol-controller approach based on an inverted single-track model is used.

The driver's request regarding the direction of travel can be detected by means of a steering wheel angle sensor. This is due to the mechanical characteristics of the vehicle ultimately also the steering angle δ _{va known} at the front axle.

The driver's request regarding the driving speed can be determined, for example, by evaluating the signals of an accelerator pedal sensor, which detects the accelerator pedal position. Alternatively or additionally, other sensors, for example wheel speed sensors on the vehicle wheels, can also be evaluated to determine the driving speed. Corresponding signals are usually available on vehicles that are equipped with an antilock braking system or an electronic stability program.

From steering wheel angle and accelerator pedal position, the desired movement of the vehicle is determined.

As 3 shows are the driving dynamics observer 2 a first signal, which represents a steering wheel angle and thus a steering angle δ _va on the front axle, and a second signal xap, which represents the accelerator pedal position and thus the desired driving speed by the driver, as input variables. Based on these input variables are in the vehicle dynamics observer 2 On the basis of a reference model of the vehicle, among other things, continuously a yaw rate Ψ. _ref and / or yaw acceleration Ψ .. _ref calculated and provided as outputs.

The vehicle dynamics observer 2 includes a tire model 21 with which from the _{slip angles} α _v and α _{h of} the vehicle _wheels on the front and rear axles the side forces F _yv and F _yh acting on the axles are determined as follows. F _yv = c _av · α _v F _yh = c _ah · α _h where c _av and c _{ah represent} skew stiffnesses on the front and rear axles. The slip angles α _v and α _h at the respective wheels of an axle are assumed to be the same size.

By means of the lateral forces of the front and rear axles F _yv and F _yh can be in another module 22 calculate the forces and moments acting in the vehicle center of gravity, in particular the lateral force F _y and the yaw moment M _Z. In particular: M _Z = F _yv · l _v + F _yh · l _h where l _{v represents} the distance between the front axle and vehicle center of gravity and l _{h represents} the distance between the rear axle and the center of gravity of the vehicle.

In conjunction with the signal xap representing the driver's intention with regard to the driving speed, the transverse force F _y and the yaw moment M _{Z can be} determined by integration taking into account the geometrical conditions of the vehicle in a further module 23 the yaw rate Ψ. _ref and the yaw acceleration Ψ .. _ref be calculated. Furthermore, the speed in the vehicle longitudinal direction v _x and the speed in the vehicle transverse _direction v _y can be calculated. For the latter applies:

With the help of the thus determined sizes can be in another module 24 calculate the slip angles β _v and β _h at front and rear axle as follows:

The signals representing the slip angles β _v and β _h at the front and rear axles are in the vehicle dynamics observer 2 are fed back and used to calculate the above slip angle α _v and α _h as follows: α _v = β _v - δ _va α _h = β _h

The output variables of the vehicle dynamics observer 2 namely the yaw rate Ψ. _ref and the yaw acceleration Ψ .. _ref serve in addition to the first, the driver's request regarding the direction of travel representative signal and the second, the driver's request in terms of driving speed signal representing as input to the vehicle dynamics controller 3 like this in 4 is shown.

Furthermore, measured parameters available on the vehicle become the current yaw rate Ψ. _is and optionally continue the current yaw acceleration Ψ .. _ref determined. Corresponding signals can, for example via a bus system the vehicle dynamics controller 3 to be provided.

2 shows the controller structure of the vehicle dynamics controller 3 , This includes on the one hand a feedforward control 31 in which a first actuating signal component s ₁ for the actuator (s ₎ 4 is generated for wheel-individual adjustment of drive and braking torques. Furthermore, the driving dynamics controller includes 3 additionally a regulator 32 , which is parallel to the feedforward 31 is arranged and a second actuating signal component s ₂ for the actuator (s ₎ 4 generated. The combined control signal from the components s ₁ and s ₂ represents the additional yaw moment required for realizing the desired vehicle movement by torque vectoring M _{Z, TV} .

Both the pilot control 31 as well as the regulator 32 are with the vehicle dynamics observer 2 connected. This gives the feedforward control 31 as reference variables the desired yaw rate Ψ. _ref , the target yaw acceleration Ψ .. _ref , the steering wheel angle and the driving speed, while on the controller 32 the target yaw rate Ψ. _ref and / or the desired yaw acceleration Ψ .. _ref be used on the input side. As 2 shows is due to the controller 32 a difference signal from the target yaw rate Ψ. _ref and actual yaw rate Ψ. _is and / or desired yaw acceleration Ψ .. _ref and actual yaw acceleration Ψ .. _is at. The control intervention in the controller 32 In particular, it is also possible to make travel speed-dependent, for which purpose the signal xap can also be applied to the controller 32 is transmitted.

The combination of feedforward control 31 and regulators 32 in conjunction with a vehicle dynamics observer 2 allows a highly dynamic influence on Fahrzeuggierrate. In the feedforward control 31 In this case, the basic setting of the actuating signal for the actuator (s) takes place 4 , Since only the driving speed and the steering wheel angle or corresponding parameters for calculating the reference values and the torque to be controlled are used as input variables, and these input variables are noise-free, reliable and instantaneous, torque vectoring interventions can be performed highly dynamically. In addition, the feedforward control 31 the controller 32 effectively relieve, resulting in a harmonious driving behavior. The at the entrance of the regulator 32 applied control difference is much lower than in a vehicle dynamics controller without feedforward control 31 , About the regulator 32 In particular, modeling inaccuracies and environmental influences are compensated. This results in a stable system, which also allows high controller gains.

Of the structure described above, in particular with regard to the configuration of the vehicle dynamics observer 2 and the input elements 1 be deviated as long as it is ensured that the driving dynamics controller 3 Signals are transmitted that represent a driver's request in terms of direction and speed as noise-free and instantaneous.

To influence the transverse dynamics of a motor vehicle by wheel-individual adjustment of drive and / or braking torques, it is preferable to proceed as follows.

By means of the driver's request in terms of direction of travel and driving speed representing signals, for example, a predetermined steering angle by the driver and a predetermined driving speed, are based on a reference model of the vehicle on the basis of a one-track model setpoints for the yaw rate and / or the yaw acceleration of the vehicle is determined.

From the aforementioned driver-side input variables and / or setpoint values obtained by means of the reference model, a first actuating signal component s ₁ for the actuator (s ₎ is generated 4 generated. In this case, the first actuating signal component s ₁ usually represents the main part of an additional yaw moment M _{Z, TV} by torque vectoring.

Furthermore, a yaw rate and / or yaw acceleration difference is formed from the setpoint values of the reference model and from corresponding actual measured values determined from measured vehicle parameters.

Parallel to the generation of the first actuating signal component s ₁ , the yaw rate and / or yaw acceleration difference becomes a second actuating signal component s ₂ for the actuator (s ₎ 4 generated. This is added to the first control signal component s _{1 in} order to generate the desired additional yaw moment on the vehicle.

The invention has been explained above with reference to an embodiment. However, it is not limited thereto, but includes all the embodiments defined by the claims.

LIST OF REFERENCE NUMBERS

1

input elements

2

driving dynamics observers

3

driving dynamics controller

4

Actuator (s)

21

tire model

22

module

23

module

24

module

31

feedforward

32

regulator

F _yv

Lateral force on the front axle

F _yh

Side force on the rear axle

F _y

lateral force

M _z

yaw moment

M _{Z, TV}

Additional yaw torque through torque vectoring

s ₁

Actuating signal component

s ₂

Actuating signal component

xap

Road speed signal

α _v

Slip angle of the front axle

α _h

Slip angle of the rear axle

β _v

Swim angle at the front axle

β _h

Float angle at the rear axle

δ _va

steering angle

Ψ. _is

Actual yaw rate

Ψ .. _is

Actual yaw acceleration

Ψ. _ref

Target yaw rate

Ψ .. _ref

Target yaw acceleration

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10317316 A1 [0005]
• DE 102004001019 A1 [0005]
• DE 102005040253 B3 [0005]
• DE 102007020356 A1 [0005]
• US 7267628 B2 [0005]
• DE 102008032763 A1 [0008]

Claims (9)

Device for influencing the lateral dynamics of a motor vehicle, comprising: - one or more actuators ( 4 ) for wheel-individual adjustment of drive and braking torques, - a vehicle dynamics observer ( 2 ) providing a yaw rate and / or yaw acceleration based on a reference model of the vehicle, 31 ) for generating a first actuating signal component for the actuator (s) ( 4 ) on the basis of a first signal, which represents a driver's request with respect to the direction of travel and a second signal, which represents a driver's request with regard to the driving speed, - a controller ( 32 ), to which a yaw rate and / or yaw acceleration difference, which is formed from a desired value and an actual value, is applied as the input variable, the nominal value being determined by the vehicle dynamics observer ( 2 ) and the actual value is measured or determined from measured vehicle parameters, and the output signal is a second actuating signal component for the actuator or actuators ( 4 ). Device according to claim 1, characterized in that the vehicle dynamics observer ( 2 ) is determined by means of the first signal representing the driver's request with respect to the direction of travel and the second signal representing the driver's request in terms of driving speed, a target yaw rate and / or a desired yaw acceleration and corresponding signals of the feedforward control are connected as input variables. Apparatus according to claim 1 or 2, characterized in that the driving dynamics observer ( 2 ) underlying reference model of the vehicle is a one-track model. Device according to one of claims 1 to 3, characterized in that in the vehicle dynamics observer ( 3 ) the float angle representing quantities are fed back. Device according to one of claims 1 to 4, characterized in that the controller ( 32 ) as a further input variable representing a vehicle speed signal is switched on and the controller ( 32 ) is configured such that a control intervention occurs depending on the driving speed. Device according to one of claims 1 to 5, characterized in that one or the actuator ( 4 ) is a torque vectoring differential for the variable distribution of a drive torque to different vehicle wheels and / or vehicle axles. Device according to one of claims 1 to 6, characterized in that an actuator ( 4 ) is a wheel brake. Method for influencing the transverse dynamics of a motor vehicle by wheel-individual adjustment of drive and / or braking torques, in which Determining set values for the yaw rate and / or yaw acceleration of the vehicle based on a reference model of the vehicle from detected input variables in relation to a driver direction of travel and vehicle speed, A first actuating signal component is generated from the input variables and / or nominal values obtained by means of the reference model, A yaw rate and / or yaw acceleration difference is formed from the setpoint values provided by the reference model and from corresponding actual values determined from measured vehicle parameters, and - Generated parallel to the generation of the first actuating signal from the yaw rate and / or yaw acceleration difference, a second control signal component is added to the first control signal component, wherein the control signal formed from the components is used to by Radindividual adjustment of drive and / or braking torques on Vehicle to generate a Zusatzgiermoment. A method according to claim 8, characterized in that as input variables, a predetermined by the driver steering wheel angle and an accelerator pedal position predetermined by the driver are detected.

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