DE102006036751A1 - Vehicle`s driving condition parameter controlling method, involves determining lateral guided force in accordance with given kinematic relation as function of rack steering force which acts in rack steering of steering system of vehicle - Google Patents

Abstract

The method involves determining a lateral guided force in a tire (10) of a vehicle for actuator in the vehicle. The lateral guided force is determined in accordance with a given kinematic relation as function of the rack steering force which acts in the rack steering (7) of a steering system (1) of the vehicle. The rack steering force is determined as a function of the steering moments that act in the steering system. An independent claim is also included for a regulating and control device for the execution of a method for regulating or controlling a driving condition parameter of a vehicle.

Description

The The invention relates to a method of control at least one driving state quantity of a Vehicle according to the preamble of claim 1.

In "ATZ Automobiltechnische Zeitschrift 96", 1994, pages 674-689 , A method for driving dynamics control in motor vehicles is described, in which the vehicle longitudinal dynamics and the vehicle transverse dynamics are taken into account. With the help of the vehicle dynamics control, the driving stability should be ensured even in border areas.

outgoing a desired yaw rate is determined from the steering wheel angle specified by the driver, which compared with a yaw rate and a yaw rate control is taken as a basis. about the yaw rate controller will do that for the vehicle transverse guidance required yaw moment provided by targeted braking interventions on individual wheels of the vehicle is implemented.

The Control of yaw rate alone, however, can be at low Static friction values on the tires to large angles of slip and thus to instability lead the vehicle. For this reason, in addition to the regulation of the yaw rate too introduced a limitation of the vehicle swimming angle in the control concept, but what the knowledge the lateral forces on the tire is required. For the determination of lateral forces become elaborate Tire models needed, However, due to the complexity of the tire dynamics always with an uncertainty factor.

From Based on this prior art, the invention has the object based, in a simple manner and with high accuracy the cornering force on a tire of a vehicle for control or regulation to determine at least one driving state variable.

These Task is according to the invention with the Characteristics of claim 1 solved. The dependent claims give expedient further education at.

at the method according to the invention for controlling or controlling a driving state quantity becomes the cornering force on a tire of the vehicle from a given, kinematic context as a function of the rack force determined in the rack the steering system of the vehicle acts. This rack power can turn be calculated as a function of the moments acting in the steering system. In this way, a relationship between the steering moments in the steering system and cornering power created for various dynamic control or control concepts is needed. In this version can basically to dispense with the use of a tire model, creating a considerable procedural simplification is achieved. In the value of determined cornering force the tire contains the information about the current coefficients of friction on the tire, but not as usual in the prior art usual tire models, but implicitly in the steering moments, which act in the steering system, are included. These steering moments can help with appropriate sensors are determined, it is at the steering torque appropriate to one generated by the driver hand torque and an engine torque of a supporting Servomotor.

There the steering torque can be determined with high accuracy and a measure of the current Friction on the tires are, can with the method according to the invention exhausted driving dynamics reserves with simple means, by becoming aware of lateral acceleration quantities and related Sizes. It can Reibwertschätzungen be performed, in particular to determine the coefficient of friction of the road. Another possibility consists in quality improvement with regard to the hand torque to be determined, which the driver during Holding the steering wheel at a certain steering wheel angle felt and the For example, during a transition of the vehicle from a road surface with high coefficient of friction on a road surface with low Friction value changes. An improvement in feedback in these cases indicates the driver the reduced coefficient of friction, so that the driver on the changed road Conditions can react accordingly. In the prior art, this immediate feedback becomes through the inertia strongly damped by the servomotor and delayed transmission, which makes an immediate driver reaction difficult or impossible. In the method according to the invention can the immediate feedback due to the knowledge of the cornering force by appropriate Vehicle-side settings are generated in the actuators.

According to an advantageous further embodiment it is provided that the rack power is calculated stationary from a proportion of the manual torque and the motor torque of the supporting servo motor, the steering ratios are taken into account on the one hand by the pinion in the steering system on the rack and on the other hand by the servo motor on the rack. This servomotor is usually an electric motor, which is provided to support and possibly reduce the steering torque to be applied by the driver in the steering system. Instead of an electric servomotor and a hydraulic servo-adjusting device may be provided, the one Hydraulic cylinder comprises, wherein the hydraulic pressure is expediently generated by an electric motor driven hydraulic pump.

According to one another preferred embodiment the rack force is calculated as a function of an estimation error that varies from the difference between calculated state variables in one mathematical vehicle model and corresponding measured quantities. The calculated state variables in the mathematical model are acting as a function of the steering system Steering moments representable. In this embodiment, the rack-and-pinion force becomes in particular in the manner of a closed loop using an estimator or Regulator from the mentioned estimation error determined, wherein the determined value of the rack force in the closed loop again the mathematical model for calculation the state variables is supplied. In this way, after the settling of the system becomes a reliable value for the Rack power achieved, the finally according to the known context considering Wheel kinematics in steering system of calculation of cornering force is based on the training tire.

In an advantageous further embodiment, the state variables of Steering wheel angle and the motor angle of the supporting Servo motor, which is calculated in the mathematical equivalent model and be compared with corresponding measured variables. These measures can usually be found in Vehicle dynamics control systems used become.

Further Advantages and expedient designs are the further claims, the figure description and the drawings. Show it:

1 a schematic representation of a steering system in a vehicle, with a servo motor for steering assistance and an upstream superposition gear,

2 a schematic representation of the kinematic conditions on a wheel,

3 a block diagram for determining the cornering force acting transversely on a tire, as a function of the manual torque and the engine torque and the transmission ratios in the steering system,

4 a block diagram for the dynamic determination of the rack force in a mathematical replacement model and the resulting cornering force.

At the in 1 schematically illustrated steering system 1 gets from the driver via the steering wheel 2 given a steering wheel angle δ _LR , via a steering shaft 3 and a steering gear 6 and a rack 7 on the steered front wheels 8th is transmitted, in which sets a wheel steering angle δ _v . For steering assistance - possibly also for reducing the steering torque to be applied by the driver - is a servo motor 9 provided that an additional steering torque T _EPS via the steering gear 6 feeds. At the servomotor 9 In particular, it is an electric motor, possibly also a hydraulic steering assistance is considered.

In the steering system 1 Optionally an additional superposition gearbox 4 be provided, which in the steering shaft 3 is interposed. This superposition gearbox 4 is a servomotor 5 associated with the operation of an additional rotation angle δ _{M is} generated, which is superimposed on the generated by the driver steering wheel angle δ _LR , so that a resulting steering wheel angle δ _LR , adjusts that of the steering gear 6 is supplied as a steering pinion angle. If the additional servomotor 5 in the superposition gearbox 4 is not actuated, no additional rotation angle δ _{M is} generated, so that the resulting steering angle δ _LR , with the driver predetermined steering angle δ _{LR is} identical. On the superposition gearbox 4 if necessary, it can also be completely dispensed with.

In 2 the wheel kinematics is shown schematically. The steering movement is via the steering gear 6 and the rack 7 on a linkage 11 transmitted, which is the kinematics of the steered front wheel 8th represents. The in the rack 7 acting rack force F _Z is related to the cornering force F _y , which in the transverse direction on the tire 10 of the steerable front seat 8th acts.

Looking at the structure on the front axle, it will be appreciated that the lateral guidance forces introduced into the suspension via the tire are transformed into a steering torque which is supported on the tie rod. With knowledge of the suspension kinematics a relationship between the axle-initiated cornering force F _y and the track or rack force F _{Z can be} specified: F y = f (v kin ) · F Z f (V _kin ) here denotes a function determined by the wheel kinematics, which may possibly also be present as a characteristic diagram.

The rack force F _Z is calculated as a function f (T) of the steering moments T acting in the steering system: F Z = f (T), wherein as a steering torque T the generated by the driver or on this retroactive hand torque T _H and the engine torque T _{EPS of} the supporting servo motor 9 be taken into account.

The embodiment has the advantage that it is also possible to take note of the current lateral force F _y acting on a tire of interest even without having to take into account a complex tire model.

The cornering forces F _y can be used for plausibility of sensor sizes. On the other hand, the slip angle in the vehicle - the deviation between the longitudinal axis and the vector of the actual speed of the vehicle - can be calculated. In addition, dynamic reserves of the vehicle, ie lateral acceleration variables or related variables, can be determined. Finally, it is possible to carry out friction coefficient estimates and, in particular, to determine the coefficient of friction between the tire and the road. Since the current cornering forces F _y for each steered wheel can be determined separately, it is also possible to detect μ-split situations in which there are different coefficients of friction at the wheels on the left and right of the vehicle.

As 3 in conjunction with the 1 and 2 can be seen, the rack-and-pinion force F _Z from a proportion of the hand torque generated by the driver T _H and a share of the engine torque T _{EPS of} the supporting servomotor 9 taking into account the known steering ratio i _R of the steering shaft 3 or the pinion in the steering system 1 on the rack 7 and also known steering ratio i _{KGT / R} from the servomotor 9 on the rack 7 be calculated: F Z = T H · i R + T EPS · i KGT / R

The cornering force F _y is, as stated above, taking into account the kinematic relationship f (V _kin ) according to F y = f (v kin ) · F Z calculated from the rack force F _Z.

An alternative method for determining the rack force F _Z is in 4 specified. In a mathematical replacement or vehicle model, which is in state form, state variables are determined as a function of the manual torque T _H , the engine torque T _EPS and the rack force F _Z. This mathematical model is in 4 in the block 12 shown.

The mathematical model is in the block 12 in the shape x. = Ax + Bu before, wherein the state vector x contains the steering wheel angle δ _LR and the motor position angle δ _EPS and the input vector u the manual torque T _H , the engine torque T _EPS and the rack force F _Z.

des Modells werden anschließend mit korrespondierenden Messgrößen

verglichen. Der daraus erhaltene Schätzfehler e mit e = x – xM wird einem weiteren Block 13 als Eingangsgröße zugeführt, der einen Schätzer bzw. Regler enthält, in welchem die Zahnstangenkraft F_Z als Funktion des Schätzfehlers e ermittelt wird: FZ = f(e) The calculated state variables x with

of the model are then given with corresponding measured quantities

compared. The resulting estimation error e with e = x - x M becomes another block 13 supplied as an input, which contains an estimator or controller in which the rack force F _{Z is determined} as a function of the estimation error e: F Z = f (e)

The rack-and-pinion force F _Z determined in this way is again displayed as an input to the input vector in the block in a feedback loop 12 fed, where again in the mathematical vehicle model, the state variables are calculated. Since there is a permanent correction between the calculated variables and the measured variables, the system oscillates to the correct values for the state variables, at the same time a correct value for the rack force F _{Z is} determined.

The rack force F _Z is finally in the other block 14 the calculation of the cornering force F _y according to the context F y = f (v kin ) · F Z based on.

The cornering force has been determined in this way for the steered front wheels. Taking into account the total lateral force on the vehicle can from the cornering force FV / y for the Vor axle also the cornering force FH / y for the rear axle can be calculated: F H y = m · a y - F V y . where m is the mass of the vehicle and a _{y is} the lateral acceleration of the vehicle.

The described method are in a control and regulation device in the vehicle carried out, in which the cornering force the determination of actuating signals for the application of various actuators and adjusting devices in the vehicle is used, for example the brake systems or the engine management.

1

steering system

2

steering wheel

3

steering shaft

4

Superposition gear

5

servomotor

6

steering gear

7

rack

8th

front

9

servomotor

10

tires

11

linkage

12

block

13

block

14

block

δ _LR

steering wheel angle

δ _M

Additional angle of rotation

δ _v

wheel steering angle

^T EPS

engine torque

T _H

manual torque

F _Z

Rack force

F _y

Cornering force

Claims (8)

Method for controlling or controlling at least one driving state variable of a vehicle, in which the cornering force (F _Y ) on a tire ( 10 ) of the vehicle for setting an actuator in the vehicle is determined, characterized in that cornering force (F _y ) is determined according to a predetermined kinematic relationship as a function (f (V _kin )) of the rack force (F _Z ) in the rack ( 7 ) of the steering system ( 1 ) of the vehicle acts: F y = f (v kin ) · F Z and that the rack force (F _Z ) as a function (f (T)) of the steering system ( 1 ) acting steering moments (T) is determined: F Z = f (T) A method according to claim 1, characterized in that as a steering torque (T) generated by the driver hand torque (T _H ) and an engine torque (T _EPS ) of a supporting servomotor ( 9 ). Method according to Claim 2, characterized in that the rack-and-pinion force (F _Z ) consists of a proportion of the hand moment (T _H ) generated by the driver and a proportion of the motor torque (T _EPS ) of a supporting servomotor ( 9 ) taking into account the steering ratio (i _R ) of the pinion in the steering system ( 1 ) on the rack ( 7 ) and the steering ratio (i _{KGT / R} ) of the servomotor ( 9 ) on the rack ( 7 ) according to the context F Z = T H · i R + T EPS · i KGT / R composed. Method according to one of claims 1 to 3, characterized in that from calculated state variables (x) and corresponding measured variables (x ^M ) an estimation error (e) according to the context e = x- x M . determined on the basis of the calculation of the rack force (F _Z ): F Z = f (e), wherein the calculated state variables (x) in a mathematical model as a function (f (T _H , T _EPS )) of the steering system ( 1 ) acting steering moments (T _H , T _EPS ) are represented: x. = f (t H , T EPS ). A method according to claim 4, characterized in that in the mathematical model in the manner of a closed loop, the rack force (F _Z ) determined from the estimation error (e) is fed back and included in the recalculation of the state variables (x). A method according to claim 4 or 5, characterized in that as state variables (x) of the steering wheel angle (δ _LR ) and the motor position angle (δ _EPS ) of the supporting servomotor ( 9 ). Method according to one of claims 1 to 6, characterized in that from the determined for the front axle cornering force (FV / y) by taking into account the Ge total lateral force on the vehicle, the cornering force (FH / y) for the rear axle is determined: F H y = m · a y - F V y . where m is the mass of the vehicle a _y denotes the lateral acceleration of the vehicle. Control and regulating device for carrying out the method according to one of the claims 1 to 7.