DE102005035882A1 - Method for controlling travelling stability of motor vehicle entails regulating slip of driven wheels directly by control of torque transmitted by clutch between engine and wheels of vehicle - Google Patents

Abstract

The method for controlling the travelling stability of a motor vehicle entails regulating slip of the driven wheels directly by control of the torque transmitted by the clutch (10) between the engine (6) and wheels of the vehicle. Locking of the wheels in the overrun is prevented by the reduction of the torque from the clutch. The RPM difference between a non-driven and driven wheel is determined and clutch torque controlled in such a way that a predetermined RPM difference is not exceeded. An independent claim is included for system for the controlling of the travelling stability of a motor vehicle in which sensors (28,30,32,34) determine the slip of at least one driven wheel, sensors determine clutch slip, and an electronic control unit (26) controls the clutch actuator (20) in order to carry out the aforesaid method.

Description

The The invention relates to a method and a device for regulating the driving stability of a motor vehicle.

electronic Driving stability systems, in which blocking or spinning of vehicle wheels prevented is and / or on individual wheels acting drive or braking torque is controlled such that A skidding of the vehicle altogether is avoided in modern motor vehicles to increase driving safety increasingly used.

From the DE 198 50 978 A1 For example, it is known to operate an automatic clutch on a signal indicative of the activation of an electronic stabilization system in a predetermined manner. For example, the clutch may be slowed down from a current engagement position to its fully engaged position so that no unwanted reactions are initiated to counteract the electronic stabilization control. Alternatively, the clutch may be left in its current engagement position so as not to initiate unwanted reactions that oppose the control of the electronic stabilization system. In a further embodiment, in the presence of the signal indicative of electronic stabilization activation, the clutch may be slowed from the current engagement position to a further disengaged position such that a closed clutch is at least partially slipping, which is beneficial to the operation of the electronic stabilization system ,

From the DE 101 57 506 A1 a control device for controlling the vehicle stability is known in which, when the vehicle stabilization system is activated, the torque which can be transmitted by the clutch is lowered.

Of the Invention is based on the object, a method and an apparatus for controlling the driving stability to create a motor vehicle, with or the driving safety is further improved.

The Part of the invention task is concerned with the features of claim 1.

According to the invention Clutch control directly active part of the electronic Driving stabilization by the slip of the driven wheels immediately by controlling the transmissible by the clutch torque at least is influenced. In this way, for example, a release of the clutch not only to the operation of an electronic vehicle stabilization system, such as ABS system, ASR system or ESP system to facilitate by disturbing influences on the contrary, in certain operating situations immediate active component of such slip control systems the driven wheels.

The under claims 2 to 5 are advantageous embodiments of the method according to the invention directed, as it is used in particular in overrun operation.

For example is a blocking of the driven wheels in overrun by reducing of the transferable from the coupling Moments prevented.

there Advantageously, the speed difference between a not driven and a driven wheel is determined and will that transferable from the coupling Moment controlled such that a predetermined speed difference not exceeded becomes.

Especially advantageous is the speed difference between a non-driven and to determine a driven wheel and the transferable from the clutch Moment to control such that a certain relative speed difference not exceeded becomes.

Alternatively or additionally, the angular deceleration of a driven wheel can be determined and the torque that can be transmitted by the clutch can be controlled such that a predetermined angle delay is not exceeded.

In Further embodiment of the method according to the invention, the transferable Clutch torque corresponding to an output signal of a control unit for Capture driving conditions to be controlled.

The under claims 7 to 14 are on implementation forms directed the method, as in particular by his prime mover driven motor vehicle are used.

• – Ermitteln des Schlupfes wenigstens eines angetriebenen Rades,
• – Ermitteln des Schlupfes der Kupplung,
• – Ermitteln des Schlupfmoments des bzw. der angetriebenen Räder,
• – Vorsteuern des von der Kupplung übertragbaren Moments derart, dass es dem ermittelten Schlupfmoment des bzw. der angetriebenen Räder etwa gleich ist und
• – Steuern des von der Kupplung übertragbaren Moments derart, dass der Schlupf des bzw. der angetriebenen Räder abnimmt.

An advantageous embodiment of such a method is characterized by the following steps:

• Determining the slip of at least one driven wheel,
• Determining the slip of the clutch,
• Determining the slip moment of the driven wheel (s),
• Pre-controlling the torque transferable by the clutch such that it is approximately equal to the determined slip torque of the driven wheel (s) and
• Controlling the torque transmittable by the clutch such that the slip of the driven wheel (s) decreases.

advantageously, the control of the slip of the at least one driven Rades by controlling the clutch torque with the aid of a PI controller.

alternative can control the clutch torque while controlling the speed the at least one driven wheel to a target speed.

With Advantage is the clutch torque timed after reduction of the wheel slip enlarged and the reduction of the wheel slip occurs by reducing the clutch torque again as soon as the wheel slip exceeds a predetermined value.

there may be the value of the maximum clutch torque at which substantially no wheel slip occurs, are stored.

• – Ermitteln des Schlupfes wenigstens eines angetriebenen Rades,
• – Ermitteln des Schlupfes der Kupplung,
• – Ermitteln des Schlupfmoments des wenigstens einen angetriebenen Rades,
• – Vorsteuern des von der Kupplung übertragbaren Moments derart, dass es dem ermittelten Schlupfmoment des bzw. der angetriebenen Räder etwa gleich ist und
• – Steuern des von der Kupplung übertragbaren Moments derart, dass die Winkelbeschleunigung des bzw. der angetriebenen Räder einen von dem Schlupfmoment abhängigen Wert annimmt.

An alternative embodiment of the method according to the invention is characterized by the following steps:

• Determining the slip of at least one driven wheel,
• Determining the slip of the clutch,
• Determining the slip moment of the at least one driven wheel,
• Pre-controlling the torque transferable by the clutch such that it is approximately equal to the determined slip torque of the driven wheel (s) and
• Controlling the torque transmittable by the clutch such that the angular acceleration of the driven wheel (s) assumes a value dependent on the slip torque.

During the change or control of the transmissible by the clutch torque takes place an engine intervention advantageously such that the engine speed while the change of the transferable from the coupling Moments at least approximate remains constant.

advantageously, can control the torque transmitted by the driven wheel (s) used at least one other setting of a vehicle parameter become.

A Device for controlling the driving stability of a motor vehicle includes a between a drive motor of the motor vehicle and at least one driven wheel arranged clutch whose transmissible moment means an actuator is adjustable, sensors for determining the slip the at least one driven wheel, sensors for detection the slip of the clutch and an electronic control device, which the actuator of the clutch to carry out one or more of controls the aforementioned method.

The Invention will be described below with reference to schematic drawings, for example and explained in more detail.

In the figures represent:

1 a schematic diagram of a drive train of a motor vehicle with units for its control and

2 a block diagram for explaining the implementation of a method according to the invention.

According to 1 has a total of 4 designated motor vehicle drive motor 6 on that with a gear 8th via a clutch 10 connected is. The coupling 10 is advantageously self-adjusting, ie the wear of friction linings of the clutch is compensated such that a constant, low release force is ensured. Such friction clutches are for example in the DE 42 39 291 A1 . DE 42 39 289 A1 and DE 43 06 505 A1 described.

The transmission output is via a cardan shaft 12 and a differential 14 with the driven in the example shown rear wheels 16 connected to the motor vehicle.

The coupling 10 , which can be carried out pressed or pulled, is via an actuating lever 18 from an actor 20 actuated.

The transmission, in the example shown, an automated manual transmission, by means of two actuators 22 and 24 operated, one of which performs a selector operation and the other a switching operation.

The actors 20 . 22 and 24 be from an electronic transmission control unit 26 controlled with wheel speed sensors 28 . 30 the driven rear wheels and wheel speeds 32 and 34 the non-driven front wheels 36 and 38 connected is. Next is the transmission control unit 26 with in the respective actuators 20 . 22 and 24 associated position encoders connected, so that the respective position of an associated actuator is known. Individual driving programs can be achieved with the help of a selector lever 40 be selected, its position by means of a position transmitter 42 to the transmission control unit 26 is transmitted.

The position encoders of the actuators 20 . 22 and 24 are usually designed as incremental encoders, with the help of which the respective actuator position can be determined with respect to a reference point. A determination of the actuator position is in particular for the clutch actuator 20 important because the gripping point of the clutch 4 a certain position of the actuating lever 18 is assigned and the transmissible each of the clutch torque on the further actuating travel of the actuating lever 18 , starting from the gripping point, ori entiert. Advantageously, the gripping point of the coupling 10 therefore repeatedly determined during commissioning and during operation.

For controlling the drive motor 6 is an engine control unit 44 provided, whose inputs with a sensor 46 for detecting the position of an accelerator pedal 48 , a sensor 50 for detecting the rotational speed of the crankshaft or the clutch input rotational speed, a position sensor 51 for detecting the position of a load actuator 52 , a flow sensor 54 for detecting the air flow rate of the drive motor, a temperature sensor 56 and possibly other sensors connected. The engine control unit 18 controls an actuator 58 that the load actuator 52 actuated.

Furthermore, the drive train contains an ABS control unit 60 , by means of which blocking of the vehicle wheels in a brake operation can be prevented. Inputs of the ABS control unit 60 For example, they are connected to the wheel speed sensors. In the event of a blockage detection, the control unit delivers 60 an output signal to a brake control unit 62 one by pressing a brake pedal 64 caused brake pressure in the brake system so modulated that the wheel brakes 66 do not block. With the help of other sensors, such as a sensor 68 for detecting rotations of the vehicle about a vertical axis, a steering angle, etc., the controller 60 be supplemented to a driving stability control unit.

The controllers 18 . 26 and 60 communicate via a bus system 70 with each other, so that a comprehensive bidirectional data exchange is possible, within which, for example, the control unit 60 Activities of the controller 44 and vice versa.

Structure and function of the units described are known per se and are therefore not explained in detail. The vehicle drive train is shown only by way of example and can be modified in various ways. For example, the transmission may be a manually operated transmission, with only the clutch being automated. The transmission can be a conventional automatic transmission with planetary gear sets his or a gearbox with continuously variable translation. The vehicle may have front-wheel or four-wheel drive, etc.

In the following, developments according to the invention, in particular of the controls of the exemplified drive train will be explained.
If the vehicle is moved on surfaces with low adhesion, such as icy surfaces, it may come in overrun to a blocking of the driven wheels when the transmitted via the clutch from the engine to the driven wheels thrust torque is greater than that of the wheels on the Roadway transmissible friction torque.

das durch Drehzahländerungen des Rades bedingt ist. Um ein Blockieren des Rades zu verhindern, muss somit die Beziehung erfüllt sein (alle Momente negativ):

In order to prevent blocking of the driven wheels in such situations, according to the invention, the clutch is deliberately opened so far that it slips and the torque transmissible by it is lowered such that the wheel torque + M _{Rad is} less than the sum of the tire _friction torque M _Reib (moment transferred from the wheel to the road) and the dynamic tire moment

which is caused by changes in the speed of the wheel. In order to prevent a blocking of the wheel, the relationship must be fulfilled (all moments negative):

wobei iges die zwischen der Kupplung und dem Rad wirksame Gesamtübersetzung ist und η der Wirkungsgrad des betroffenen Antriebsstrangs ist, der beispielsweise bei etwa 0,95 liegt.The wheel torque depends in a two-wheel drive vehicle on the transmitted clutch _torque M _üK in the following manner:

where iges is the effective between the clutch and the wheel total gear ratio and η is the efficiency of the affected powertrain, which is for example about 0.95.

Lifting M _≥ M can _raise M _Wheel (reduce contribution) _until the wheel continues to turn.

To the Recognizing a risk of locking and the strategy to control the For example, coupling offers the following options:

Option A:

In order to detect the situation and then control the clutch torque if necessary, in two-wheel drive vehicles the brake slip S between the driven and non-driven wheels can be detected:

If S exceeds a critical slip value Sc, it comes to blocking and the wheel can not side guide take over more. One for Sc assumed value may be, for example, 0.1.

The wheel speeds φ. can be detected via the corresponding wheel sensors, so that S can be determined. By means of a example in the transmission control unit 26 implemented control strategy, the slip S by appropriate control of the actuator 20 be controlled so that S remains below the critical value Sc. It may be particularly advantageous to regulate S to a value close to Sc, so that the largest possible braking torque of the engine corresponding to the respective conditions can be transmitted to the wheels, without causing a dangerous driving condition.

If the slip S, for example, when engaging after a downshift or when braking with an engine thrust torque of -50 Nm over 0.1 increases, the clutch is opened controlled, so that the wheel torque changed so is that S stays smaller than 0.1. The absolute amount of the transferred Clutch torque is thus during the regulation or when the vehicle is driving on a road at which would cause a clutch torque of 50 Nm to block under 50 Nm.

Variant B:

In all-wheel drive vehicles, there is usually no slip between driven and non-driven wheels. Here, the angular acceleration φ .. _Rad can be used as a reference variable for the clutch torque. If the wheel becomes jammed φ .. _wheel suddenly becomes negative. The clutch torque is then adjusted such that φ .. _wheel remains above a "stall threshold" φ .. _{wheel, c} . It goes without saying that this procedure is also possible with two-wheel drive vehicles.

Variant C:

A critical situation with a risk of locking may also be caused by an external control device, such as the control unit 60 or the controller 26 , are detected, for example, when the engine speed decreases rapidly, without this being associated with a corresponding vehicle deceleration. The clutch can then be controlled as a function of output signals of the respective control unit and / or further signals derived therefrom.

In one with a clutch or a torque transmission device with variable torque capacity equipped powertrain can the clutch and the wheels slip. If the coupling adheres, i. there is no slippage at her, determines the drive motor, the drive train torque and thus can check the wheel slip. When the clutch slips (for example when starting, shifting or in slip-controlled driving situations) the drive train torque is determined by the clutch torque.

at automated or actuated by an actuator clutches is the drive train torque modulated in slip phases, so that a wheel slip control in Connection with an automated clutch also in phases with Drive of the vehicle by the engine is possible.

The following is based on the 2 explains the principle of an exemplary slip control of the wheels by means of an automated clutch:
With 84 are sensors, such as wheel speed sensors, referred to the speed φ. from wheels corresponding output signals to a computing unit 86 deliver. In the arithmetic unit 86 is calculated from the speed signals with additional plausibility with the help of, for example, the wheel accelerations from the speed signals of the driven and non-driven wheels a wheel slip SR, which another computing unit 88 is supplied. From sensors 90 signals ω are derived due to which in a computing unit 92 the slip SK of the clutch can be calculated. This calculation is possible, for example, directly by comparing the engine speed with the speed of the propeller shaft taking into account the respective gear ratio. Alternatively, for example, the rotational speeds of the non-driven wheels can be used, from which, taking into account the total ratio, the output speed of the clutch can be calculated. The clutch slip SK is another input of the arithmetic unit 88 supplied, in which the slip torque of the wheels M _wheels or the torque transmitted by the wheels can be calculated according to the following formulas:

The acceleration of the drivetrain (clutch disc, transmission, differential and wheels) is determined by its inertia and by the difference between the clutch torque and wheel torque. The respective torque transmitted by the clutch is out of the position of the actuator 20 ( 1 ) known.

The Slip moment of the wheels depends on different influencing factors, such as the road surface, the acceleration of the vehicle, the load condition of the vehicle, etc.

berechnet und dieses in der Schlupfphase bestimmte Radmoment wird als Vorsteuergröße MVS zur Ansteuerung des Aktors 20 bzw. der Vorsteuerung der Kupplung verwendet. Somit gilt:

In the arithmetic unit 88 is the wheel torque according to the formula

calculated and this determined in the slip phase wheel torque is used as a pilot control variable MVS to control the actuator 20 or the pilot control of the clutch used. Thus:

there lends itself to the calculable factors influencing the wheel torque, such as the dependence on vehicle acceleration, etc. With the help of Feedforward is first Achieves a balance between clutch torque and wheel torque, in whose presence the wheels are not would accelerate further.

The feedforward control is superimposed on a control that safely degrades the wheel slip. It makes sense to regulate the acceleration of the wheels. In this case, a negative target value of the acceleration is to be selected in order to ensure a reduction of the wheel slip. For example, a PI controller can be used, with the aid of which a control variable MS for the clutch superimposed on the pilot control variable MVS is calculated as follows: ω. instinctual aim <0

In 2 is with 94 denotes a computing unit that calculates the control variable MS and this as a second input to an adder 96 whose other input with the arithmetic unit 88 connected is. At the output of the adder 96 is thus the signal MK, which is the sum of the pilot control variable MVS and the control variable MS and with which the actuator 20 is controlled. Thus, the feedforward control is superimposed on a PI control.

The above based on the 2 explained acceleration control can be replaced by a speed control, if the target speed of the driven wheels is known, which can be determined, for example, from the speed of the non-driven wheels.

If the Zielraddrehzahl is known, an extension of the basis of the 2 explained accelerator. The target acceleration would then be made dependent on the slip speed. In this way, for large slip values, a correspondingly large negative target acceleration could be defined, which is reduced for smaller slip values. For the functionality characteristics could be used, which in the arithmetic unit 94 are stored.

If the wheel slip is reduced, the clutch torque is advantageous timed rebuilt. As soon as this comes to a renewed Radschlupf leads, resumes the regulation.

In addition, can the maximum clutch torque at which no wheel slip occurs, get saved. The clutch torque can be up to this value be increased without a renewed Radbeschleunigung occurs.

bestimmten Reib- bzw. Radmoment der Räder zu regeln. In diesem Fall könnte der Regler gemäß 2 unter Vorgabe einer positiven Beschleunigung verwendet werden. Die Regelparameter müssten auf das geschlossene System abgestimmt bzw. umgeschaltet werden. Die Beschleunigungsvorgabe ergibt sich bei haftenden Rädern näherungsweise aus der Massenträgheit des Fahrzeugs und dem Radreibmoment nach folgender Formel:

It is also possible the wheel acceleration depends on the formula

to regulate certain friction or wheel torque of the wheels. In this case, the controller could according to 2 under specification of a positive acceleration. The control parameters would have to be tuned or switched to the closed system. The acceleration specification results for adhering wheels approximately from the inertia of the vehicle and the wheel friction torque according to the following formula:

It It is understood that the aforementioned controls or regulations can be combined with each other in any way and that other regulations are used instead of PI control can be.

During the Phases of slip control by means of the coupling, it is advantageous to control the drive motor such that its speed at least approximately remains constant. For this example, the engine torque accordingly lowered the clutch engagement (with decreasing clutch torque the engine torque is lowered accordingly or the speed of the Motor is directly regulated).

at not slipping clutch can basically the engine control the Take over slip control. Especially in connection with the engine and the clutch engagement is it is advantageous to the wheel slip control by the clutch slip or the change the clutch torque alone or in conjunction with the engine intervention to regulate.

Out according to the above versions determined maximum wheel torque at which no slip occurs, are conclusions on the respective road condition possible. If this wheel torque falls below a certain limit value, then for example Driving programs can be switched, for example, to a winter program be switched, in which with reduced clutch torque or Wheel torque is approached. This starting can also be reduced Starting speed and an additional, slippage-controlled intervention in the clutch torque.

In summary A wheel slip control is performed using an automated clutch in slip phases, the frictional torque of the wheels is determined. This information can be used on the one hand to an acceleration control to assist by means of a precontrol; to the other one can Target value for set an optimal acceleration at the adhesion limit of the wheels become. The controller provides first for one controlled removal of wheel slip and then for building the optimal Acceleration.

4

motor vehicle

6

drive motor

8th

transmission

10

clutch

12

propeller shaft

14

differential

16

rear wheel

18

actuating lever

20

actuator

22

actuator

24

actuator

26

Transmission control unit

28

wheel speed sensor

30

wheel speed sensor

32

wheel speed sensor

34

wheel speed sensor

36

front

38

front

40

selector lever

42

position transmitter

44

Engine control unit

46

sensor

48

accelerator

50

sensor

51

locator

52

Load actuator

54

Flow Sensor

56

temperature sensor

58

actuator

60

ABS control unit

62

Brake control unit

64

brake pedal

66

wheel brake

68

sensor

70

Bus system

84

sensors

86

computer unit

88

computer unit

90

sensors

92

computer unit

94

computer unit

96

adder

Claims (15)

A method for controlling the driving stability of a motor vehicle, wherein the method depending on the respective operating condition of the motor vehicle transmissible by a arranged between a drive motor and driven wheels of the motor vehicle automatic transmission torque is changed, characterized in that a slip of the driven wheels directly by controlling the of the clutch transmissible torque is controlled. Method according to claim 1, characterized in that that blocking the driven wheels in the overrun mode by reducing of the transferable from the coupling Moments is prevented. Method according to claim 2, characterized in that that the speed difference between a non-driven and a driven wheel is determined and the transferable from the clutch Moment is controlled such that a predetermined speed difference not exceeded becomes. Method according to claim 2, characterized in that that the speed difference between a non-driven and a driven wheel is determined and the transferable from the clutch Moment is controlled such that a predetermined relative speed difference not exceeded becomes. Method according to one of claims 1 to 4, characterized that the angular delay a driven wheel is determined and the transferable from the clutch Moment is controlled so that a predetermined angular delay does not exceed becomes. Method according to one of claims 1 to 5, characterized that the transferable Clutch torque corresponding to an output signal of a control unit for Capture driving conditions is controlled. Method according to claim 1, characterized by the following steps - Determine the slip of at least one driven wheel, - Determine the slip of the clutch, - Determining the slip moment the driven wheel (s), - input tax of the transferable from the coupling Moments such that it the determined slip torque of the or driven wheels is about the same and - Taxes of the transferable from the coupling Moments such that the slip of the driven wheels or decreases. Method according to claim 7, characterized in that that the regulation of the slip of at least one driven Rades by controlling the clutch torque with the aid of a PI controller he follows. Method according to claim 7 or 8, characterized that the control of the clutch torque while controlling the speed the at least one driven wheel is at a target speed. Method according to one of claims 7 to 9, characterized that after reduction of the wheel slip, the clutch torque time-controlled is enlarged and the reduction of wheel slip by reducing the clutch torque again as soon as the wheel slip exceeds a predetermined value. Method according to claim 10, characterized in that that the value of the maximum clutch torque at which substantially no wheel slip occurs, is stored. Method according to claim 1, characterized by the following steps - determining the slip of at least one driven wheel, Determining the slip of the clutch, determining the slip moment of the at least one driven wheel, pre-controlling the torque transmittable by the clutch such that it is approximately equal to the determined slip torque of the driven wheel (s) and controlling the torque transmittable by the clutch such that the angular acceleration of the driven wheel (s) assumes a value dependent on the slip moment. Method according to one of claims 7 to 12, characterized that an engine intervention takes place such that the engine speed during the change of the transferable from the coupling Moments at least approximate remains constant. Method according to one of claims 7 to 13, characterized that the torque transmitted by the driven wheel (s) is for control used at least one other setting of a vehicle parameter becomes. Device for controlling the driving stability of a motor vehicle, comprising one between a drive motor ( 6 ) of the motor vehicle and at least one driven wheel ( 16 ) arranged coupling ( 10 ), the transferable moment of which by means of an actuator ( 20 ) is adjustable, sensors ( 28 . 30 . 32 . 34 ) for determining the slip of the at least one driven wheel, sensors ( 50 . 28 . 30 ) for determining the slip of the clutch and an electronic control device ( 26 ), which controls the actuator of the clutch for carrying out the method according to one of claims 1 to 14.