EP2342108A1

EP2342108A1 - Method for producing a vehicle differential torque

Info

Publication number: EP2342108A1
Application number: EP09781104A
Authority: EP
Inventors: Andreas Erban; Markus Henzler
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-09-25
Filing date: 2009-07-27
Publication date: 2011-07-13
Also published as: WO2010034543A1; DE102008042363B4; CN102164790A; DE102008042363A1

Abstract

The invention relates to a method for producing a differential torque acting on a vehicle, wherein a differential torque between two vehicle wheels is adjusted by actuating a wheel brake unit and a differential torque is generated through an additional actuator separately from the wheel brake unit. The desired differential torque is adjusted primarily through the additional actuator, wherein the wheel brake unit is used supplementarily in the event the differential torque cannot be adjusted through the additional actuator.

Description

description

title

Method for generating a vehicle differential torque

The invention relates to a method for generating a difference moment acting on a vehicle according to the preamble of claim 1.

State of the art

From DE 10 2006 031 511 Al a method for stabilizing a vehicle in a driving-dynamic limit situation is known, in which a vehicle controller engages by automatically actuating at least one wheel brake in the driving operation. In order to perform the stabilization process faster, an additional drive torque is generated on at least one wheel, which causes an additional yaw moment, which supports the stabilizing effect of the braking intervention. In addition to the stabilization effect, the braking deceleration, which is due to the situation, can also depend on the situation

Brake intervention occurs, are partially or completely compensated by the additional drive torque.

The control of the wheel brakes via a vehicle control system such as an ESP system

(electronic stability program) or an ABS (anti-lock system). In the interaction of brakes of the wheels on the one hand and applying a drive torque on the other hand, it should be ensured that the opposing influences of the wheel brake and the drive torque in principle do not lead to comfort restrictions. At the same time, the stabilizing effects should complement each other in the best possible way. In addition, it should be ensured that the distribution of drive torques on the vehicle wheels and the braking of individual wheels is usually carried out with different vehicle control systems that are to be matched or integrated in the vehicle.

Disclosure of the invention

The invention is based on the object, the function of a vehicle control device, which is a wheel brake for

Application of a difference torque applied to combine in the most efficient manner with an actuator which is formed separately from the wheel brake and also generates a differential torque on the vehicle.

This object is achieved with the features of claim 1. The dependent claims indicate expedient developments.

The inventive method is based on a

Vehicle control system in a vehicle, comprising a vehicle control device, which comprises at least one wheel brake, and a further actuator via which a differential torque acting on the vehicle is to be generated separately from the wheel brake. This makes it possible to provide a difference torque in the vehicle via the vehicle control device and the control of the wheel brake units as well as via the further actuator.

On the one hand, the differential torque is used to generate a stabilizing yawing moment on at least one axis, for example for stabilizing an over / understeering vehicle. On the other hand, the differential torque is used for traction assistance by generating a blocking effect by a differential braking torque (active braking of the spinning wheel) or a differential drive torque to a driven Axis for maintaining traction on one-sided smooth surfaces (μ _Sp i _lt ) is applied. As a rule, significantly larger differential moments are required in the traction region than in the stabilization case of the vehicle in the traction region. A differential torque on at least one driven

Axis exerts an intended blocking effect in the case of μ _sp i _lt ; the resulting yaw moment is accepted with approval.

According to the method of the invention, it is provided that the desired difference moment occurs primarily via the further actuator which functions independently of the actuation of the wheel brake unit. The wheel brake unit is used only in the event that the desired differential torque is set only partially or not at all via the further actuator.

In this way, a hierarchy is set when setting the desired differential torque. The differential torque is preferably provided via the further actuator, the vehicle control device, which comprises a control unit and the wheel brake, is used only in addition. This hierarchical structure has various advantages with regard to the integration of different systems and also with regard to comfort. On the one hand, different and separately formed vehicle control devices and actuators in the manner of a modular system can be combined with one another or integrated in the vehicle. These vehicle control devices or actuators can thus be manufactured as individual modules independently of each other and combined in the vehicle to form an overall system. The vehicle control device, which acts on the wheel brake unit, here comes to a so-called watchdog or monitoring function, since the difference moment is generated primarily via the further actuator and not on the wheel brake and the wheel brake are activated only in the event that Generation of the differential torque alone on the other actuator is not ensured in a sufficient manner. This means for the rule that the differential torque is generated exclusively on the other actuator, which contributes to a comfort improvement, since the other actuator usually distributes a drive torque selectively on one or more vehicle wheels and thus do not act in principle opposing moments on the vehicle wheels.

The integration of the various systems can also be accomplished in a simple manner, since both systems are torque-based and based on the moments common control strategies are feasible. For example, a manipulated variable of one system is supplied to the other system as an input variable.

In principle, various types of further actuators can be integrated together with the vehicle control device acting on the wheel brakes into a vehicle control overall system. The only prerequisite is that the other actuator is able to produce a differential torque in the vehicle, including in particular active to be set actuators with an asymmetric distribution of drive torque. These include so-called torque vectoring systems, which include an active coupling member for driving torque distribution between the driven wheels of an axle or between driven wheels of different axes. In addition, there are also electromotive drives, for example wheel hub motors, via which different levels of drive torque can be applied to different vehicle wheels.

Such electric motors are preferably part of a hybrid drive, which includes not only the electric motors but also an internal combustion engine. Optionally, the drive of the vehicle but also takes place exclusively by electric motor. Another way to set an additional differential torque via an active actuator, for example, represents a rear-wheel steering. The additional actuator can either be provided with its own control unit or be integrated into the control structure of the wheel brakes acting on the vehicle control device. In the first case, that is, with its own control unit, the further actuator is part of a separate vehicle control system, which is brought together with the wheel brake acting on the vehicle control device. In the second case, ie in another actuator without its own control unit, can be relatively simple

Actuator systems are used, wherein the control is performed to adjust the desired differential torque in the further actuator via the controller structure of the wheel brakes acting on the vehicle control device.

The said structure with modular structure

Vehicle control device and further actuator, in which the differential torque is preferably used via the further actuator, has the advantage that in case of failure of the other actuator, the desired differential torque at least partially, but preferably can be provided by the wheel brakes acting on the vehicle control device due to their monitoring function occurs immediately when the desired differential torque can not or not completely generated by the other actuator. This gives additional security with regard to a system failure.

According to a preferred embodiment it is provided that the actually realized control variable of the further actuator is provided as an operating point for the control unit, which is assigned to the wheel brake. This procedure is particularly suitable in the embodiment of the further actuator as part of an independent vehicle control device, which is equipped with its own control unit. The the

Wheel brakes acting on vehicle control device uses the actual realized manipulated variable as the operating point, so that the Control in which the wheel brakes acting on vehicle control device put on a better output value and thus can react faster or more spontaneously in the event that the desired differential torque can not be provided completely by the other actuator. However, if the other actuator adjusts the differential torque completely, the operating point at which the control unit of the wheel brakes acting vehicle control device, so dimensioned that no deviation arises and thus the wheel brakes also do not have to complement function to set the desired differential torque.

According to a further expedient embodiment, it is provided that a desired torque supplied by the control unit of the vehicle brake device acting on the wheel brakes is fed to the further actuator as an input variable. This embodiment is particularly suitable for further actuators without their own control unit, so that the control of the further actuator is taken over by the control unit of the wheel brakes acting on the vehicle control device. The further actuator is thus embedded in the controller structure of the vehicle control device.

The actual realized manipulated variable of the further actuator will act on the wheel brakes

Vehicle control device supplied in each case, so both in the execution of the actuator without its own control unit as well as in the version with its own control unit. In this case, however, it may be expedient to limit to a manipulated variable maximum before entry into the vehicle control device, which may be a fixed quantity, but possibly also a variable, of current state variables of the vehicle and / or the other Actuator dependent size, for example, depends on the temperature of the actuator. This ensures that, in particular when the further actuator is embedded in the controller structure, the wheel brakes act on it Vehicle control device in the further actuator under consideration of boundary conditions and safety regulations only a maximum possible differential torque is generated. If this is not sufficient to set the desired differential torque in the vehicle, in addition occurs the wheel brakes acting on vehicle control device in place.

Further limitations may be provided in the vehicle control device, preferably following the control unit provided there. The target torque delivered by the control unit is hereby limited to a desired torque maximum, which preferably also depends on the current driving state of the vehicle, for example, the vehicle speed, the lateral acceleration or the coefficient of friction between the wheels and the road. In this way, the differential torque can be adapted to the current driving condition, for safety reasons, for example, at a very low coefficient of friction, a limitation can be performed.

The vehicle control device for acting on the wheel brake is, in particular, an ESP control system (electronic stability program), via whose control signals the wheel brakes can be applied to vehicle wheels on opposite sides. In principle, however, is also another vehicle controller into consideration, such as a traction control or anti-lock braking system.

Further advantages and expedient embodiments can be taken from the further claims, the description of the figures and the drawings. Show it:

1 is a schematic representation of a motor vehicle with a vehicle control device for applying wheel brakes to the vehicle wheels and with a torque vectoring system for the active distribution of

Drive torque is equipped to different vehicle wheels, Fig. 2 is a block diagram showing the overall structure of the vehicle control device for applying the wheel brakes and the torque vectoring system.

The motor vehicle 1 shown in FIG. 1 has front wheels 2 and 3 on a front axle 16 and rear wheels 4 and 5 on a rear axle 17, wherein each wheel is assigned a wheel brake unit 6, 7, 8, 9. The wheel brake units 6 to 9 are adjusted by actuating signals of a control or control unit 10, which is an example of part of an ESP control system. The Regelbzw. Control unit 10 sensor signals of a sensor 11 are supplied, which may include both an environment sensor for detecting the vehicle environment and a state sensor for detecting the current vehicle condition. The environmental sensor system includes, for example, radar sensors or optical sensors, with the state sensors can be determined vehicle state variables of longitudinal and / or lateral dynamics such as vehicle speed, vehicle deceleration, lateral acceleration or wheel slip.

The motor vehicle 1 is also equipped with a front and a rear torque vectoring system 12 and 13, respectively, which is an actively adjustable clutch actuator for distributing drive torque between a left and a right driven wheel of an axle. Each torque vectoring system 12 or 13 is assigned a control unit 14 or 15, wherein the control units 14 and 15 communicate with the central control or control unit 10. However, the torque vectoring systems 12 and 13 acting on different axes can also be set by a common control unit.

In the exemplary embodiment, each axis 16, 17 of the motor vehicle 1 is associated with a torque vectoring system 12 or 13, so it is a vehicle with two driven Axes. In principle, however, it is also sufficient within the scope of the invention to provide a torque vectoring system only on a driven axle.

Moreover, it is also sufficient or possible for the invention not to provide a torque vectoring system, but wheel hub motors in the vehicle wheels, the wheel hub motors of opposite vehicle wheels are separately controlled, so that in this way different drive torques can be applied to opposite vehicle wheels ,

Both via the vehicle control device for acting on the wheel brake, which includes the control unit or control unit 10 and the wheel brake units 6 to 9, as well as via the torque vectoring system 12 and 13 respectively acting on the vehicle differential torque can be generated.

FIG. 2 shows the overall structure with the vehicle control device 20 for acting on the wheel brake units 6 to 9 and the torque vectoring system 12, 13. The vehicle control _device 20 includes the control unit 10, which _supplies at the output as a control variable a control deviation Δv _{Dlf of} the wheel difference speed v _Dlf , which indicates the speed difference between the wheels of an axle, and / or a control deviation Δv _{yaw of} the yaw rate v _yaw . The controlled variable v _Dlf or v _yaw enters into a control unit 21 of the vehicle control _device 20, which supplies a differential _torque M _Dlf as a manipulated variable. The differential _torque M _Dlf represents a desired torque, which is initially limited in a subsequent limiting unit 22 to a desired torque maximum M _{Dlf; Lim} , which expediently depends on the current state variables of the motor vehicle, for example on the vehicle _speed , the lateral acceleration or the coefficient of friction between them Wheels of the vehicle and the road. The current actually realized differential torque M _Dlf, _Act subtracted as a manipulated variable limited _Lim setpoint torque M _Dlf for determining a control deviation .DELTA.M _{_Dlf;} Following the limiting unit 22 is in a differential point from the optionally on the Sollmoment- maximum M _Dlf. The

Control deviation .DELTA.M _Dlf then enters a dynamic model of the torque vectoring system 12, 13 containing unit 23, which has the task of a possible phase difference between the pressure control in the wheel brake of the vehicle control device 20 and in the actuator of the torque vectoring Systems 12, 13 compensate. Such phase differences can occur due to the faster response of the wheel brakes compared to the actuator of the torque vectoring system. By means of the dynamic model in the unit 23, such phase differences are compensated.

Subsequent to the unit 23, the dynamized control deviation flows into a further limiting unit 24, in which, analogously to the limiting unit 22, a limitation is preferably carried out as a function of the current state variables of the vehicle, for example the vehicle speed. The limitation unit 24 takes into account the particularly sensitive response of the dynamic vehicle behavior to an intervention via the wheel brakes.

The control deviation finally enters the last block of the vehicle control device, which contains the wheel brake units 6 to 9, via which the desired pressure p _L or p _R in the wheel brake units on the vehicle wheels is different

Vehicle pages is set. In this way, it is possible to generate a desired differential torque in the vehicle via the vehicle control device 20 and the application of the wheel brake units. The overall system shown in FIG. 2 contains, in addition to the vehicle control device 20, also the torque vectoring system 12, 13, via which likewise a differential torque in the vehicle can be adjusted to different vehicle wheels by a different drive torque distribution. in the

Cooperation with the vehicle control device 20 are various, explained below modes of operation into consideration.

The various operating modes in the interaction of vehicle control device 20 and torque vectoring system 12, 13 are symbolized by switches S1 and S2. The switch Sl is located between the output of a limiting unit 26, which is associated with the torque vectoring system 12, 13, and the controller unit 22, which is part of the vehicle control device 20. The switch S2 is located in a feedback path between the output of the control unit 21 downstream limiting unit 22 and the input of the torque vectoring system 12, 13, and in front of another limiting unit 25 which is arranged in this feedback branch. The switches S1 and S2 are symbolic of the presence (closed switch) or absence (open switch) of a corresponding connection between said units of the overall system.

In a first mode of operation, the switch S1 is closed and the switch S2 is opened. This operating mode is preferably used in the event that the further actuator for generating a differential torque - in the exemplary embodiment, the torque vectoring system - is provided with its own control unit, via which the desired differential torque on the

Torque vectoring system is set. In this case, the feedback loop between the output of the controller unit 21 of the vehicle controller 20 and the input of the torque vectoring system 12, 13 is not mandatory.

In the first mode with closed switch Sl is actually realized in the torque vectoring system 12, 13 _Actuating variable M _{Dlf; Act} , which is optionally limited to a manipulated variable maximum M _{Dlf; Pot} in a limiting unit 26, is supplied to the vehicle control device 20 as input variable of the control unit 21. The actually realized manipulated variable M _{Dlf; Act} , serves as an operating point in the control unit 21 for determining the manipulated variable _torque M _Dlf . In a regulator unit 21 with an I component, for example a PI regulator, the realized manipulated variable M _{Dlf; Act represents} the operating point of the control circuit the I component. Building on this operating point is a better response of the controller or a faster setting of the desired moment feasible.

In addition, the realized manipulated variable M _{Dlf; Act is} supplied to the point of difference as an input variable, specifically on the output side of the limiting unit 22, which adjoins the regulator unit 21. As already described above, in the point of difference the realized manipulated variable M _{Dlf; Act is} subtracted from the calculated manipulated variable M _Dlf , whereby the control deviation ΔM _Dlf is obtained.

In a second mode of operation, the switch S1 is open and the switch S2 is closed. This mode is preferably used for actuators 12, 13 without its own control unit. When the switch S2 is closed, a return branch for returning the setpoint torque M _Dlf as an input variable for the further actuator 12, 13 is closed. In the return branch, the limiting unit 25 for limiting is contained to a maximum, the manipulated variable to be supplied to the further actuator 12, 13 is referred to as the set input variable with M _{Dlf; Tar} .

In the limiting units 25 and 26, which are located in the return branch or in the branch of the further control element, there is a limitation to a maximum value M _{Dlf; Pot} , which is the maximum torque that can be set via the further control element 12, 13. M _{Dlf; Pot} can be a fixed Be size, but optionally also variable, for example, depending on the current temperature in the other actuator.

In both cases, so both closed switch Sl and S2 open switch and with open switch Sl and S2 closed switch, the vehicle control device 20 is used as a backup function in the event that the desired differential torque is not adjustable via the further actuator 12, 13 in the vehicle is. Only in these cases does one get one

Control deviation ΔM _Dlf not equal to 0, which leads to an application of the wheel brake 6 to 9. If, on the other hand, the desired differential _torque can be set completely by the further actuator 12, 13, then the manipulated variable M _Dlf delivered in the control unit 21 is identical to the actual realized one

_Actuating variable M _{Dlf; Act} from the further actuator 12, 13, so that the control deviation ΔM _Dlf is zero and the wheel brake 6 to 9 are not operated.

The supplementary function of the vehicle control device 20 also comes into play in the event that the further actuator 12, 13 completely fails. In this case, the differential torque is set completely via the application of the wheel brake.

Claims

claims

1. A method for generating a differential torque acting on a vehicle, wherein a differential torque between two vehicle wheels (2, 3, 4, 5) is adjustable by actuating a wheel brake unit (6, 7, 8, 9) and via a further actuator (12, 13) a differential torque can be generated separately from the wheel brake unit (6, 7, 8, 9), characterized in that the setting of a desired differential torque primarily via the further actuator (12, 13) and independently of the operation of the wheel brake (6, 7 , 8, 9) takes place, the wheel brake unit (6, 7, 8, 9) is additionally used for the case that the desired differential torque is not or only partially via the further actuator (12, 13) is set.

2. The method according to claim 1, characterized in that the realized manipulated variable (M _{Dlf; Act} ) of the further actuator (12, 13) represents the operating point of the wheel brake unit (6, 7, 8, 9) associated control unit (21).

3. The method according to claim 1 or 2, characterized in that one of the regulator unit (21) supplied target torque (M _Dlf ) to the further actuator (12, 13) as a target input quantity (M _{Dlf; Tar} ) is supplied.

4. The method according to claim 3, characterized in that the target input quantity (M _{Dlf; Tar} ) is limited to an input variable maximum (M _{Dlf; Pot} ).

5. The method according to any one of claims 1 to 4, characterized in that in case of failure of the further actuator (12, 13) the desired differential torque completely about a deceleration of the vehicle wheels (2, 3, 4, 5) is set.

6. The method according to any one of claims 1 to 5, characterized in that the realized manipulated variable (M _{Dlf; Act} ) of the further actuator (12, 13) to a manipulated variable maximum (M _Dl f, p _ot ) is limited.

7. The method according to claim 4 or 6, characterized in that the manipulated variable or the

Input variable maximum (M _{Dlf; Pot} ) of current state variables of the vehicle and / or the other actuator (12, 13) depends, for example, on the temperature of the actuator.

8. The method according to any one of claims 1 to 7, characterized in that the of the control unit (21) supplied target torque (M _Dlf ) is limited to a desired torque maximum (M _{Dlf; Lim} ).

9. The method according to claim 8, characterized in that the desired torque maximum (M _{Dlf; Lim} ) depends on current state variables of the vehicle, for example, from the vehicle _speed , the lateral acceleration or the coefficient of friction.

10. The method according to any one of claims 1 to 9, characterized in that the torque difference (ΔM _Dlf ) from the of the control unit (21) supplied target torque (M _Dlf ) and the realized manipulated variable (M _{Dlf; Act} ) of the further actuator (12 , 13) of the wheel brake unit (6, 7, 8, 9) is supplied as a manipulated variable.

11. The method according to claim 10, characterized in that the torque difference (.DELTA.M _Dlf ) in a dynamic model (23) of the further actuator (12, 13) before the application of the wheel brake (6, 7, 8, 9) with the Adjustment movement of the further actuator (12, 13) is synchronized.

12. A vehicle control system in a vehicle for carrying out the method according to one of claims 1 to 11, with a

Vehicle control device (20) comprising a control unit (21) and a wheel brake (6, 7, 8, 9), wherein via the wheel brake (6, 7, 8, 9), a torque difference between two vehicle wheels is adjustable, and at least one another actuator (12, 13) via which separate from the

Wheel brake unit (6, 7, 8, 9) a differential torque is generated.

13. Vehicle control system according to claim 12, characterized in that the further actuator (12, 13) an axle differential with integrated clutch system for

Drive torque distribution between two vehicle wheels (2, 3, 4, 5).

14. Vehicle control system according to claim 12 or 13, characterized in that the further actuator (12, 13) comprises at least one electric motor for driving at least one vehicle wheel (2, 3, 4, 5).

15. Vehicle control system according to claim 14, characterized in that at least two vehicle wheels (2, 3, 4, 5) are each equipped with an electric hub motor.

16. Vehicle control system according to one of claims 12 to 15, characterized in that the vehicle control device (20) for actuating the wheel brake unit (6, 7, 8, 9) is an ESP control system (electronic stability program).

17. Vehicle control system according to one of claims 12 to 16, characterized in that the further actuator (12, 13)

Part of another vehicle control device is equipped with a control unit.

18. Vehicle control system according to one of claims 12 to 16, characterized in that the further actuator (12, 13) is embedded in the controller structure of the first vehicle control device (20), such that one of the controller unit (21) of the vehicle control device (20). supplied target torque (M _{Dlf; Tar} ) to the further actuator (12, 13) can be fed as an input variable.

19. Control unit containing means for carrying out the

Method according to one of claims 1 to 11 are configured.