DE102006041236A1 - Operating method for electronic power-assisted steering system of vehicle, involves overlapping additional angle, which is disabled after re-start of utility function - Google Patents

Abstract

The method involves overlapping an additional angle (delta-M), which is disabled after a re-start of the utility function, with available difference between a desired additional reference partial angle (delta-MdVL) of the utility function and an instantaneous actual value. The effective difference between the additional reference partial angle of the utility function and the instantaneous actual value is determined as synchronizing input (D-Sync) from a specified operating interval of a synchronizing function, where the overlapping of the additional reference partial angle is released. Independent claims are also included for the following: (1) a computer program with a program code medium (2) a computer program product with a program code medium.

Description

Technical area

The The invention relates to a method for operating an electronic Power steering system of a motor vehicle according to the preamble of claim 1. The invention also relates to a computer program and a Computer program product with program code means for such Perform procedure. Furthermore, the invention relates to an electronic power steering system of a motor vehicle.

State of the art

A steering system with overlay means is from the DE 197 51 125 A1 known. There, the movement (additional angle or motor angle) of an actuator, ie an electric motor superimposed by means of a superposition gear (for example, a planetary gear) with the steering wheel angle. With the help of the superposition means, it is possible to superimpose a steering wheel angle predetermined by the steering handle to increase driving stability or comfort with an additional angle, so that a variable transmission ratio between steering wheel angle and mean wheel steering angle of the steerable wheels of the motor vehicle is adjusted depending on driving dynamics or comfort. As a result, it is safety z. B. possible, a motor vehicle, which threatens to break out, due to a corresponding correction of the Radlenkwinkels back into a stable driving situation. The overlay means may support other vehicle dynamics systems (eg, an electronic stability program (ESP) or an anti-lock braking system (ABS)). In terms of comfort, it is also possible to superimpose a speed-dependent additional angle on a steering wheel angle, for example. As a result, a relatively small gear ratio can be set at low vehicle speeds, ie, a relatively small rotation of the steering handle leads to a relatively large steering angle of the wheels (compared to the mechanical basic ratio direct ratio). At high vehicle speeds, however, a relatively large gear ratio (compared to the mechanical basic ratio indirect ratio) can be adjusted so that the driving stability of the motor vehicle increases. The electronic power steering system according to the invention also has superposition means.

He follows after switching off the motor vehicle or the power steering system - without a Blocking or blocking the auxiliary angle actuator, d. H. in one Error case - one change the actual additional angle, For example, when the steering wheel is rotated, especially in the Workshop on the lift, with a deadlock in the gearbox or a moment on the shaft of the electric motor, so are the utility functions when restarting of the superposition steering system, in particular the variable steering ratio, first only limited use, because the fixed or stored when switching off the system Actual additional angle of the electric motor of the superposition means not with matches the target additional angle when switching back on and thereby an unwanted one Motor angle jump would arise. The system must first be synchronized again. Such a difference between the actual additional angle and the desired additional angle of the electric motor of the superposition means, a so-called Steering wheel tilt, can also during the ride occur, especially when cornering of the Motor vehicle variable steering ratio for example, must be turned off and the steering ratio on the basic translation the steering gear is transferred.

So far In such an error case, the useful functions, in particular the variable steering ratio, first disabled. Then a synchronization function will be used steady transition between the current actual motor angle or actual additional angle and calculated by the useful function requested target motor angle or desired additional angle. If setpoint and actual value are close enough after a certain travel time together, the utility function is reactivated. Accordingly receives the driver during the synchronization process disadvantageously no support by the variable steering ratio. The full functionality the electronic power steering system or its useful functions are not immediately at the start, but only with a delay to available which considerably limits the ride comfort.

Disclosure of the invention

Technical task

outgoing It is the object of the present invention to provide a Method for operating a power steering system of a motor vehicle, a computer program, a computer program product and an electronic one Power steering system of a motor vehicle of the type mentioned to provide which allow operation of the power steering system such that after a restart of the electronic power steering system as fast as possible the full functionality the useful functions of the electronic power steering system is available.

Technical solution

This object is achieved by the features mentioned in claim 1. The task is related to the computer program by claim 6, with respect to the computer program product by claim 7 and with respect to the electronic power steering system by claim 8.

By the measures according to the invention are the useful functions, in particular the variable steering ratio an electronic power steering system, in particular when a synchronization of the Additional angle is required, available much earlier, since already from a given Turn-on a synchronization of the additional angle in parallel to provide the functionality of the variable steering ratio he follows. After starting the system is the lock of the additional angle actuator first locked, so no overlay the additional angle with the steering angle. The utility function or the variable steering ratio calculated constantly a corresponding to steering wheel angle and vehicle speed Target additional angle or partial target additional angle. To a defined or predetermined switch-on time calculates the synchronization function the difference between the current actual additional angle and that of the variable steering ratio requested desired additional angle. The calculated difference is called synchronization effort designated, which subsequent to the desired additional angle of the variable steering ratio is added by appropriate correction angle. Immediately afterwards the lock of Zusatzwinkelstellers is unlocked, causing the variable steering ratio as a utility function completely is activated, although the system has a steering wheel obliquity, which by the size of the synchronization overhead is defined. The synchronization overhead will be ongoing corrected out.

Of the Synchronization effort or steering wheel misalignment can then, depending After driving situation, be corrected slowly or quickly.

Emotional if the motor vehicle slow, so can be corrected quickly. If the vehicle speed is higher, then the synchronization speed can be in an embodiment according to the invention dependent from the vehicle speed and the steering speed. Out security Synchronization can be prevented during fast travel. As well can synchronize at low steering or steering wheel angular velocity be stopped while be synchronized faster at high steering angle speed can.

The inventive method for operating an electronic power steering system of a motor vehicle is preferably as a computer program on a control unit of the electronic power steering system realized. For this purpose, the computer program is in a memory element of the control unit saved. By processing on a microprocessor of the controller is the procedure is carried out. The computer program may be stored on a computer-readable medium (floppy disk, CD, DVD, hard disk, USB memory stick or the like) or one Internet server be stored as a computer program product and transmitted from there into the memory element of the control unit become. Such a computer program or computer program product with program code means is specified in claim 6 or claim 7.

claim 8 relates to an electronic power steering system of a motor vehicle.

following is in principle an embodiment with reference to the drawing of the invention. Brief description of the drawings

It shows:

1 a simplified schematic representation of a power steering system according to the invention, which is operated by a method according to the invention;

2 a first simplified diagram of temporal angular profiles in a fast synchronization; and

3 a second simplified diagram of temporal angular gradients in a slow synchronization. Preferred embodiment

1 shows an electronic power steering system 1 a motor vehicle, not shown. The electric power steering system 1 has a steering wheel 2 trained steering handle on. The steering wheel 2 is via a cardan shaft or steering column 3 with a steering gear 4 connected. The steering gear 4 serves to a rotation angle of the steering column 3 in a wheel steering angle δ _Fm of steerable wheels 5a . 5b implement the motor vehicle. The steering gear 4 has a rack 6 and a pinion 7 on, to which the steering column 3 attacks. The electronic power steering system 1 also includes overlay means 8th one as an electric motor 9 trained actuator or additional angle adjuster and driven by this superposition gear 10 exhibit. The superposition gearbox 10 is designed as a planetary gear. In further embodiments, the superposition gear could 10 Also be designed as a wave gear or the like. Through the steering wheel 2 is a steering wheel angle δ _s as a measure of a desired wheel steering angle δ _{Fm of} the steerable wheels 5a . 5b of the motor vehicle specified. With the help of the electric motor 9 Then, a superposition angle or additional angle δ _{M is} generated and by the superposition gear 10 with the Steering wheel angle δ _S or the angle of rotation of the steering column 3 superimposed. The additional angle δ _M is basically for the realization of useful functions, in particular for improving the driving dynamics of the motor vehicle or comfort, in particular by providing a variable steering ratio or a variable ratio between steering wheel angle δ _S and wheel steering angle δ _{Fm of} the steerable wheels 5a . 5b , generated. The sum of steering wheel angle δ _S and additional angle δ _M gives the input angle of the steering gear 4 or in the present embodiment, the pinion angle δ _G. The superposition of the additional angle is mechanically lockable (not shown).

The overlay means 8th have an electronic control unit 11 on, which among other things, the control of the additional angle δ _M and the output torque of the electric motor 9 serves. On the electronic control unit 11 For this purpose, a control process takes place, which as a control structure or as a computer program on a microprocessor, not shown, of the control unit 11 is executed. The electric motor 9 is with an electrical drive signal δ _Md , which the setpoint of the electric motor 9 to be generated additional angle δ _M , ie the desired additional angle corresponds driven. The control or regulation of the electric motor 9 usually takes place as a function of the vehicle speed of the motor vehicle, ie the variable transmission ratio between the steering wheel angle δ _Fm and the pinion angle δ _G or the wheel steering angle δ _{Fm of} the wheels 5a . 5b is set by the superimposition of the steering wheel angle δ _S with different, speed-dependent additional angles δ _M as a function of the vehicle speed. So that the above-mentioned control functions can be performed, receives the control unit 11 among other things, as an input signal, the current vehicle speed (eg via the CAN bus of the motor vehicle). The electronic power steering system 1 can in other embodiments, not shown, the overlay means 8th downstream also have an electric or hydraulic servo drive, which among other things serves the variable torque assistance.

According to the invention, the electronic power steering system 1 now operated by a method in which by means of the steering handle 2 the steering wheel angle δ _S as a measure of the desired wheel steering angle δ _Fm for the steerable wheels 5a . 5b of the motor vehicle is specified, in which for the realization of the variable transmission ratio between the steering wheel angle δ _S and the wheel steering angle δ _Fm as a useful function, the additional angle δ _M generated and the input angle δ _{G of} the steering gear 4 of the electronic power steering system 1 is generated from the superposition of the steering wheel angle δ _S with the additional angle δ _M , and in which the input angle δ _{G of} the steering gear 4 in the wheel steering angle δ _Fm for the at least one steerable wheel 5a . 5b of the motor vehicle is implemented. The inventive method is described below with reference to in the 2 and 3 illustrated simplified diagrams, which show temporal profiles of the steering angle, illustrates. The horizontal axes of the diagrams show the time in seconds (s) and the vertical axes the corresponding steering angle in degrees (°) or in 3 also the steering wheel angular velocity δ. _{S is} plotted in degrees per second (° / s). After a restart of the useful function at a time t ₀ , in the presence of a difference between the desired Teilollzusatzwinkel δ _MdVL the _Nutzfunktion and the current actual additional angle δ _M , the superposition of the additional angle δ _{M is} locked, wherein the desired by the Nutzfunktion Teilollzusatzwinkei δ _MdVL continues to be calculated continuously, after which from a predetermined switch-on time t ₁ a synchronization function, not shown in the process of the invention, the current difference between the Teilollzusatzwinkel δ _MdVL the _Nutzfunktion and the current actual additional angle δ _M or corresponding minus the control difference - as in the diagrams shown - the (total) desired additional angle δ _{Md determined} as synchronization _effort D _sync , after which the superposition of the additional angle δ _{M is} released, and then the synchronization _effort D _Sync such, preferably continuously by correction angle, to the Tei Is added addition angle δ _MdVL the _Nutzfunktion that the synchronization effort D _{Sync is} continuously reduced. The desired additional angle δ _Md is formed by adding the respective correction angle with the respective partial target additional angles δ _{MdVL of} the useful function. The synchronization is completed at a time t ₂ , wherein the synchronization _effort D _{Syac is} 0 ° and the desired additional angle δ _Md coincides with the partial target additional angle δ _{MdVL of} the useful function. The synchronization effort D _Sync is adapted to the current driving situation of the motor vehicle reduced. How out 2 can be seen at a low vehicle speed of the synchronization effort quickly - ie with a high synchronization speed - reduced. That is, relatively large correction angles are added. At a particularly higher vehicle speed, the synchronization effort is reduced as a function of the vehicle speed and the steering speed. From a predetermined higher vehicle speed, the reduction of the synchronization effort for security reasons is completely prevented. At a high steering speed synchronization takes place correspondingly faster. In 3 is a synchronization as a function of the steering wheel angular velocity δ. _S shown. With rising Steering wheel angular velocity δ. _S takes place at the switch-on time t _i, the calculation of the synchronization _effort D _Sync and the start of the synchronization. As can be seen, the synchronization at low steering wheel angular velocity δ. _S , for example, at time t _1a , prevented. At time t ₂ , the synchronization is completed.

The inventive method for operating the electronic power steering system 1 is as a computer program on the control unit 11 realized, with other solutions of course come into question. For this purpose, the computer program is in a memory element of the control unit 11 saved. By processing on a microprocessor of the controller 11 the procedure is carried out. The computer program can be stored on a computer-readable data carrier (floppy disk, CD, DVD, hard disk, USB memory stick or the like) or an Internet server, not shown, as a computer program product and from there into the memory element of the control unit 11 be transmitted.

1

Superimposed steering system

2

steering wheel

3

Drive shaft / steering column

4

steering gear

5a, 5b

steerable bikes

6

rack

7

pinion

8th

Superimposing means

9

Additional angle actuator / motor

10

Superposition gear

11

electronic control unit the overlay means

δ _Fm

wheel steering angle or steering angle

δ _G

pinion angle

δ _S

steering wheel angle

δ. _S

Steering wheel angle speed

δ _M

additional angle

δ _Md

setpoint the additional angle

δ _MdVL

Part nominal additional angle the utility function

t ₀ , t ₁ , t _1a , t ₂

timings

D _Sync

synchronization effort

Claims (8)

Method for operating an electronic power steering system ( 1 ) of a motor vehicle, in which by means of a steering handle ( 2 ) a steering wheel angle (δ _S ) as a measure of a desired wheel steering angle (δ _Fm ) for at least one steerable wheel ( 5a . 5b ) of the motor vehicle, in which an additional angle (δ _M ) is generated for realizing a useful function, in particular a variable transmission ratio between the steering wheel angle (δ _S ) and the wheel steering angle (δ _Fm ), and an input angle (δ _G ) of a steering gear ( 4 ) of the electronic power steering system ( 1 ) is generated from a superposition of the steering wheel angle (δ _S ) with the additional angle (δ _M ), in which the input angle (δ _G ) of the steering gear ( 4 ) in a wheel steering angle (δ _Fm ) for the at least one steerable wheel ( 5a . 5b ) of the motor vehicle is implemented, wherein the superposition of the additional angle (δ _M ) is mechanically lockable, characterized in that - after a restart (t ₀ ) of the Nutzfunktion, in the presence of a difference between a desired Teilollzusatzwinkel (δ _MdVL ) of the _Nutzfunktion and a momentary additional angle (δ _M ), the superimposition of the additional angle (δ _M ) is locked, wherein the Nutzoll desired Teiloll additional angle (δ _MdVL ) of the _Nutzfunktion continues to be calculated continuously, - after which from a predetermined switch-on (t ₁ ) a synchronization function the actual difference between the partial target additional angle (δ _MdVL ) of the useful function and the current actual additional angle (δ _M ) is determined as synchronization _effort (D _Sync ), - after which the superposition of the additional _angle (δ _MdVL ) is released, and - after which the synchronization _effort (D _Sync ) so to the Teilollzusatzwinkel (δ _MdVL ) of the useful function addi The synchronization effort (D _Sync ) is continuously reduced. A method according to claim 1, characterized in that the synchronization effort (D _sync ) adapted to the current driving situation of the motor vehicle is reduced. A method according to claim 1 or 2, characterized in that the synchronization effort (D _Sync ) is rapidly reduced at a low vehicle speed. A method according to claim 1, 2 or 3, characterized in that the synchronization effort (D _Sync ) at a higher vehicle speed in dependence on the vehicle speed and the steering speed (δ. _S ) is reduced. Method according to one of claims 1 to 4, characterized in that from a predetermined higher vehicle speed, the reduction of the synchronization effort (D _Sync ) is prevented. Computer program with program code means for carrying out a method according to one of Claims 1 to 5, if the program is stored on a microprocessor of a computer, in particular on a control unit ( 11 ) of a power steering system ( 1 ), is performed. A computer program product comprising program code means stored on a computer-readable medium for carrying out a method according to one of claims 1 to 5, when the program is stored on a microprocessor of a computer, in particular on a control unit ( 11 ) of a power steering system ( 1 ), is performed. Electronic power steering system ( 1 ) of a motor vehicle, with - a steering handle ( 2 ) for specifying a steering wheel angle (δ _S ) as a measure of a desired wheel steering angle (δ _Fm ) for at least one steerable wheel ( 5a . 5b ) of the motor vehicle, - a steering gear ( 4 ), which determines the steering wheel angle (δ _S ) in the wheel steering angle (δ _Fm ) of the at least one steerable wheel ( 5a . 5b ) of the motor vehicle, - superimposing means ( 8th ) for generating an additional angle (δ _M ) by an additional angle adjuster ( 9 ) and for generating an input angle (δ _G ) of the steering gear ( 4 ) from a superposition of the steering wheel angle (δ _S ) with the additional angle (δ _M ), and - an electronic control device adapted to execute the computer program according to claim 6.