DE102006053029B4 - Method for operating an electronically controlled power steering system - Google Patents

Abstract

Method for operating an electronically controlled power steering system (1) of a motor vehicle, wherein by means of a steering handle (2) a steering wheel angle (δS) is specified as a measure of a desired wheel steering angle (δFm) for steerable wheels (5a, 5b) of the motor vehicle, wherein the Steering wheel angle (δS) in the wheel steering angle (δFm) of at least one steerable wheel (5a, 5b) of the motor vehicle is implemented, characterized in that unwanted steering movements of the driver, which have a certain amplitude and a certain frequency, are detected.

Description

Technical area

The invention relates to a method for operating an electronically controlled 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 to perform such a method. Furthermore, the invention relates to an electronic control device for a motor vehicle or for an electronically controlled power steering system of a motor vehicle and an electronically controlled power steering system of a motor vehicle.

State of the art

Motor vehicles are more sensitive to steering wheel movements of the driver at higher vehicle speeds. Even when driving straight or so-called steady cornering (eg in long highway curves), a driver often steers unintentionally or unconsciously with a small amplitude. The resulting vehicle reactions must then be compensated by the driver again by appropriate countersteering. This means that the driver can rarely keep the steering wheel still, which has a negative effect on ride comfort.

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 superimposition 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 adjusts depending on the 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.

Moreover, from the DE 100 13 711 A1 a steering system known, inter alia, has a servo drive for torque assistance (power steering). The degree of torque assistance is dependent on the vehicle speed in the described steering system. While the torque assist is greater at slower vehicle speeds (eg, to operate the steering wheel with little effort when maneuvering the vehicle), torque assist is reduced at higher speeds (eg, to increase driving stability on a highway ride). The servo drive can work electrically or hydraulically. In the electric power steering system according to the invention, the torque assistance can be electrically varied. That in the DE 100 13 711 A1 described steering system has in addition to the servo drive and superimposition means which generate an additional angle and superimpose the steering handle angle predetermined by the steering handle with this additional angle.

Furthermore, from the prior art so-called steer by wire steering systems are known in which an independent specification of steering wheel torque and Radlenkwinkel, ie a mechanical decoupling of the steering movement of the driver of the steering of the wheels is present. Steering direction, steering angle and steering force are only data that feed an electronics and are converted by this into appropriate steering commands. In a steer by wire steering system, only one electrical signal connection between the steering handle and the steered wheels is effective in normal operation. In the DE 100 42 308 A1 Such a steer by wire steering system is described. The DE10 2004 022 089 A1 discloses a method for operating an electronically controlled power steering system to prevent or reduce steering rupture, which determines whether or not there is an unwanted steering wheel angle change based on an evaluation of a hand torque and a steering wheel angle, and if present, a motion damping is detected; is introduced into the steering line.

Disclosure of the invention

Technical task

The present invention has for its object to provide a method of the type mentioned, which improves ride comfort.

Technical solution

The solution of this object is achieved by a method for operating an electrically controlled power steering system of a motor vehicle having the features of claim 1, by a computer program with program code means having the features of claim 12, by a computer program product with program code means having the features of claim 13, by an electronic Control unit with the features of claim 14 and by an electronically controlled power steering system of a motor vehicle having the features of claim 15. Advantageous developments emerge from the dependent claims.

The inventive measures can be reliably detected in a simple and advantageous manner unwanted or unwanted steering movements of the driver, which have a certain amplitude and a certain frequency. In order to distinguish the intended correct steering movements of the driver from the unwanted steering movements, their frequency range and amplitude must be determined. Subsequently, such steering movements can be eliminated or eliminated, so that the driver can keep the steering wheel still, which significantly improves ride comfort and driving safety.

According to the invention it can be provided that the detection of the unwanted steering movements by means of a statistical comparison of several currently detected measured variables of the electronically controlled power steering system with stored empirical values of the corresponding measured variables, which unwanted steering movements were assigned. A steering wheel angle, a vehicle speed, a lateral acceleration, a yaw rate and / or a steering wheel torque, in particular combined with one another, can be used as measured variables or input signals. From these measurements it can be concluded whether the driver really wants to perform a movement in space, d. H. the direction changes or whether it corrects after an unwanted steering movement again.

The respective empirical values of the measured variables can be stored continuously during the journey, in particular during driving tests or test drives, in a learning phase in a database if unwanted steering movements were detected. The unwanted steering movements are therefore recorded by statistical methods, if they are identified as such. For example, if the detected steering movements prove unnecessary, because they differ from the basic direction of travel of the motor vehicle and have only a predetermined low amplitude. The learning phase can take place during test drives with the motor vehicle. Furthermore, it is possible to adaptively execute the learning phase during normal driving for different drivers, since the undesired steering movements, in particular their frequency, can differ.

Alternatively or additionally, the detection of the unwanted steering movements by means of a determined probable lane course of the motor vehicle. For this purpose, it can be provided that the probable lane course of the motor vehicle is determined by means of a camera arranged on the motor vehicle and a corresponding image recognition system, wherein road characteristics, in particular lane markings or the like, are detected by the camera. Furthermore, the probable lane course of the motor vehicle can be determined by means of a navigation system of the motor vehicle, in particular in combination with an electronic camera. As a navigation system, for example, GPS, Galileo or the like can be used, for which a corresponding receiver and in particular electronic map material is required. The determined probable lane course can also be used to hold the current lane of the motor vehicle.

After the learning phase, the driver's unwanted steering movements in a supporting phase can be advantageously at least approximately eliminated during the journey in an advantageous manner in order to increase the ride comfort. This can be done by active angular subtraction of the electronically controlled power steering system.

It is very advantageous that a rest position of the steering wheel angle -. B. with the aid of the determined probable course of the lane - is determined and the detected unwanted steering movements as deviations from the rest position are at least approximately eliminated or filtered out.

The elimination of the unwanted steering movements can be done by means of superposition of the electronically controlled power steering system for generating an additional angle by a Zusatzwinkelsteller and generating an input angle of the steering gear from a superposition of the steering wheel angle with the additional angle, the unwanted steering movements are eliminated by actively setting a corresponding opposite additional angle , Thus, the detected unwanted steering movement is subtracted by an active control intervention of an active steering in real time, that is, the sum of these two movements at least approximately zero results and Accordingly, no additional angle is placed on the steerable wheels.

Alternatively or additionally, the elimination of unwanted steering movements by means of a servo drive of the electronically controlled power steering system done. For example, torque assist steering may "harden", i. H. make it difficult for the driver to perform unwanted steering movements.

If the electronically controlled power steering system is designed as a steer-by-wire steering system, the angles of the unwanted steering movements are not placed on the wheels.

The sensor system or regulation described allows a correction of the unwanted steering movements that is not noticeable to the driver. The renewed takeover of the driver from unwanted back to targeted steering movements can be designed harmoniously and comfortably for the driver.

The method can also be used in long highway turns.

The supporting function can always be active or can be switched off by a situation detection or the like. Furthermore, the function can also activate independently when the driver of an active targeted steering again goes into a constant correcting unwanted steering movements.

The inventive method for operating an electronically controlled power steering system of a motor vehicle is implemented as a computer program on a control unit, in particular the electronically controlled power steering system or a vehicle control, with other solutions come of course in question. For this purpose, the computer program is stored in a memory element of the control unit. By processing on a microprocessor of the controller, the process is performed. 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 as a computer program product and be transferred from there into the memory element of the control unit. Such a computer program or computer program product with program code means is specified in claim 12 or claim 13.

The following is an exemplary embodiment of the invention with reference to the drawing in principle.

Brief description of the drawings

The sole figure of the drawing shows a simplified schematic representation of an electronically controlled power steering system according to the invention with superposition means and a servo drive, which is operated by means of a method according to the invention.

Preferred embodiment

The figure shows an electronically controlled power steering system 1 a motor vehicle, not shown. The electronically controlled 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 electronically controlled 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 other 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 generated to improve the driving dynamics of the motor vehicle or the comfort. 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 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 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 Transmission ratio between the steering wheel angle δ _S and the pinion angle δ _G and 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 in as a function of the vehicle speed. This makes it possible, for example, at low vehicle speeds to specify a relatively small gear ratio, in which a relatively small rotation of the steering wheel 2 to a relatively large wheel steering angle δ _{Fm of} the wheels 5a . 5b leads. It is also conceivable for reasons of stability at high vehicle speed to specify a relatively large transmission ratio. 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 overlay means 8th downstream, has the electronically controlled power steering system 1 an electric servo drive 12 on, which among other things serves the variable moment assistance. The electric servo drive 12 has an electric motor 13 for the realization of the torque support via a belt transmission 14 on. The belt transmission 14 has a drive pinion and a pulley for transmitting the torque assist via a recirculating ball gear (not shown) on the rack 6 of the electric power steering system 1 on. Furthermore, an electronic control unit 15 for controlling or regulating the electric motor 13 intended.

The invention is based on an electronically controlled power steering system 1 with a belt transmission 14 and a separate recirculating ball gear for transmitting the assisting force to the rack 6 , such as from the DE 100 52 275 known, described. For other electric power steering system technologies with torque or steering assistance, however, similar implementations according to the invention may possibly be achieved with minor changes.

In addition, the electronically controlled power steering system 1 sensors 16a . 16b . 16c on, which measure the steering wheel angle δ _S , the additional angle δ _M and the pinion angle δ _G or provide equivalent signals from which these angles δ _S , δ _M , δ _G can be determined. Furthermore, a steering torque sensor, a sum angle sensor and a tie rod sensor are provided (not shown). The controllers 11 . 15 obtain the results of the above-mentioned sensors as input signals for further processing or control or regulation of the electric motors 9 . 13 , In the figure, only the input signals for the control unit are detailed 11 represented, which via the sensors 16a . 16b . 16c and other vehicle systems, not shown, inter alia, with the input signals vehicle speed v _x , lateral acceleration a _y , yaw rate ψ., Steering wheel angle δ _S , pinion angle δ _G , steering wheel torque M _S and additional angle δ _{M is} supplied. Alternatively or additionally, a plurality of these variables could also be calculated on the basis of the other or further input variables (eg wheel speeds, etc.), in particular with the aid of suitable models.

According to the invention, the electronically controlled power steering system 1 now operated by a method in which by means of the steering handle 2 a steering wheel angle δ _S as a measure of a desired wheel steering angle δ _Fm for the steerable wheels 5a . 5b of the motor vehicle is predetermined, wherein 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 is implemented, wherein unwanted steering movements of the driver, which have a certain amplitude and a certain frequency, are detected.

The detection of unwanted steering movements by means of a statistical comparison of several, in particular combined with each other currently detected variables, namely the steering wheel angle δ _S , the steering wheel torque M _{S of} the vehicle speed v _x , the lateral acceleration a _y and / or the yaw rate ψ. the electronically controlled power steering system 1 with stored empirical values of the corresponding measured variables δ _S , M _s , v _x , a _y , ψ., which were associated with unwanted steering movements. The respective empirical values of the measured quantities δ _S , M _s , v _x , a _y , ψ. be during the journey, in particular test drive, in a learning phase in a database 17 , which on the control unit 11 is realized or to which the control unit 11 Has access, continuously stored, if unwanted steering movements were detected. On the basis of certain statistical characteristics, the empirical values are assigned to the unwanted steering movements.

Alternatively or additionally, the detection of unwanted steering movements in other embodiments, not shown, by means of a determined probable lane course of the motor vehicle. For this purpose, it can be provided that the probable lane course of the motor vehicle is determined by means of a camera arranged on the motor vehicle and a corresponding image recognition system, wherein road characteristics, in particular lane markings or the like, are detected by the camera. Furthermore, the probable lane course of the motor vehicle can be determined by means of a navigation system of the motor vehicle, in particular in combination with an electronic camera. As a navigation system, for example, GPS, Galileo or the like can be used, for which a corresponding receiver and in particular electronic map material is required. The determined probable lane course can be used to hold the current lane of the motor vehicle.

After the learning phase, the driver's unwanted steering movements in a supporting phase can be advantageously at least approximately eliminated during the journey in an advantageous manner in order to increase the ride comfort. This can be achieved by active angular subtraction of the electronically controlled power steering system 1 respectively.

For this purpose, a rest position of the steering wheel angle δ _{S is} determined and the unwanted steering movements are at least approximately eliminated as deviations from the rest position.

The elimination of unwanted steering movements by means of superposition means 8th the electronically controlled power steering system 1 by actively setting a corresponding opposite additional angle δ _M.

In a further embodiment, the elimination of unwanted steering movements by means of the electric servo drive 12 the electronically controlled power steering system 1 respectively.

The inventive method for operating the electronically controlled 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.

The invention is based on a superposition steering system with an electronic servo drive 12 (Active Front Steering / AFS) as an electronically controlled power steering system 1 described. For other electronic power steering system technologies with torque or steering assistance (electric power steering / EPS, manual torque adjuster or the like), steer-by-wire functionality or meaningful combinations thereof, however, can be achieved with possibly minor changes same inventive implementations. If the electronically controlled power steering system be designed in other embodiments as a steer-by-wire steering system, the unwanted steering movements can not be made on the wheels.

LIST OF REFERENCE NUMBERS

1

electronically controlled power steering system

2

steering wheel

3

propeller shaft

4

Steering gear / steering column

5a, 5b

steerable wheels

6

rack

7

pinion

8th

Superimposing means

9

Additional angle actuator / motor

10

Superposition gear

11

electronic control device of the superposition means

12

electric servo drive

13

electric motor

14

belt transmission

15

Control unit of the servo drive

16a, 16b, 16c

sensors

17

Database

δ _Fm

Wheel steering angle or steering angle

δ _G

pinion angle

δ _S

steering wheel angle

δ _M

additional angle

δ _Md

Setpoint of the additional angle

a _y

lateral acceleration

v _x

vehicle speed

ψ.

yaw rate

M _s

steering wheel torque

Claims (15)

Method for operating an electronically controlled 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 steerable wheels ( 5a . 5b ) of the motor vehicle, wherein 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, characterized in that unwanted steering movements of the driver, which have a certain amplitude and a certain frequency, are detected. A method according to claim 1, characterized in that the detection of unwanted steering movements by means of a statistical comparison of several currently detected variables (δ _S , M _S , v _x , a _y , ψ.) Of the electronically controlled Power steering system ( 1 ) with stored empirical values of the corresponding measured variables (δ _S , M _s , v _x , a _y , ψ.), which were assigned to unwanted steering movements. A method according to claim 2, characterized in that the respective empirical values of the measured variables (δ _S , M _s , v _x , a _y , ψ) during the journey, in particular test drive in a learning phase in a database ( 17 ) are stored continuously, if unwanted steering movements were detected. A method according to claim 2 or 3, characterized in that as measured variables or input signals a steering wheel angle (δ _S ), a vehicle speed (v _x ), a lateral acceleration (a _y ), a yaw rate (ψ) and / or a steering wheel torque (M _s ) be used. Method according to one of claims 1 to 4, characterized in that the detection of the unwanted steering movements by means of a determined probable lane course of the motor vehicle takes place. A method according to claim 5, characterized in that the probable lane course of the motor vehicle is determined by means of a camera arranged on the motor vehicle and a corresponding image recognition system, wherein road characteristics, in particular lane markings or the like are detected by the camera. A method according to claim 5 or 6, characterized in that the probable lane course of the motor vehicle by means of a navigation system of the motor vehicle, in particular in combination with an electronic camera, is determined. Method according to one of claims 1 to 7, characterized in that a rest position of the steering wheel angle (δ _S ) is determined and the unwanted steering movements are at least approximately eliminated as deviations from the rest position. Method according to one of claims 1 to 8, characterized in that the elimination of unwanted steering movements by means of superimposing ( 8th ) of the electronically controlled power steering system ( 1 ) 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 ) is carried out from a superposition of the steering wheel angle (δ _S ) with the additional angle (δ _M ), wherein the unwanted steering movements are eliminated by actively setting a corresponding opposite additional angle (δ _M ). Method according to one of claims 1 to 9, characterized in that the elimination of unwanted steering movements by means of a servo drive ( 12 ) of the electronically controlled power steering system ( 1 ) he follows. Method according to one of claims 1 to 9, characterized in that the electronically controlled power steering system is designed as a steer-by-wire steering system and the unwanted steering movements are not made on the wheels. Computer program with program code means for carrying out a method according to one of Claims 1 to 11, when the program is stored on a microprocessor of a computer on an electronic control unit ( 11 . 15 ) of an electronically controlled 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 11, when the program is stored on a microprocessor of a computer on an electronic control unit ( 11 . 15 ) of an electronically controlled power steering system ( 1 ) is performed. Electronic control unit ( 11 . 15 ) for a motor vehicle or for an electronically controlled power steering system ( 1 ) of a motor vehicle configured to execute a computer program according to claim 12. Electronically controlled 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 and - an electronic control unit ( 11 ) arranged to execute a computer program according to claim 12.

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