DE102009000246A1 - Automatic calibration method for index sensor of electronic servo steering system of motor vehicle in driving operation, involves emitting electronic index signal during deflections of servo steering system in neutral position - Google Patents

Abstract

The automatic calibration method involves emitting an electronic index signal (idx) during the deflections of a servo steering system (1) in a neutral position, particularly straight line driving position of the servo steering system. The neutral position of the electronic servo steering system is characterized by a pre-determined steering angle value or a pre-determined angle value of the servo steering system, where the angle value is correlated with the steering angle. Independent claims are also included for the following: (1) a computer program with program code units; (2) a computer program product with data carrier; and (3) an electronic servo steering system with steering handle.

Description

The The invention relates to an automatic calibration method for an index sensor of an electronic power steering system of a motor vehicle. The The invention also relates to a computer program and a computer program product with program code means, for such an automatic calibration method perform. Furthermore, the invention relates to a electronic power steering system of a motor vehicle.

An active steering system or 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 predefined 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 may also have superposition means.

As already stated above, in an active steering system to the actual Steering angle or steering wheel angle, which from the driver via the steering wheel is introduced, an additional steering angle (additional angle or motor angle) added. The actual steering angle on the front wheels of the motor vehicle is therefore off the steering wheel angle and the additional motor angle to a Total steering angle superimposed. The absolute added motor angle is required for engine position control.

Problematic However, the engine position sensors are usually have only a limited, absolute measuring range and therefore not cover the entire steering range, so only the information about a relative angle can be detected, but not the absolute angle. In order to determine the absolute angle, is an additional Counter for counting engine revolutions the servomotor or actuator required; the counting device but is coupled to a power supply. If this is interrupted, For example, when disconnecting the battery, the information goes on lost the revolution of the engine and it is not without further action absolute angle determination for the steering wheel and the steered Wheels more possible. For cost reasons is often not a motor position angle sensor of the active steering motor absolute incremental sensor used. To the motor angle over need to capture several revolutions the angle increments are counted. The amount of angle increments may be arbitrary in principle, but less than the required Measuring range of the motor position angle. Adding the angle increments is often done in a control unit. The sum is stored in a non-volatile memory. In certain Situations, such as B. a sudden voltage loss can Nevertheless, there is a loss of the summed up motor position angle. At a restart of the active steering system, this can be a so-called obliquity of the steering wheel lead, d. H. the Steering wheel is not in the usual straight ahead driving position when driving straight ahead.

A steering system for a vehicle according to the DE 10 2005 059 883 A1 with a steering handle, a steering column, a steering linkage and at least one steerable vehicle wheel comprises a motor-driven adjusting device, an angle sensor and a further measuring device whose measurement signal is related to an angle signal. The signal of the angle sensor is subdivided into a plurality of signal periods, wherein the signal of the further measuring device is associated with a predetermined angle value of a signal period of the angle sensor. The further measuring device may be an index sensor for generating an index signal at a specified steering angle value.

It is therefore known to use for the determination of straight ahead another sensor, the so-called index sensor. The index sensor is a simple sensor which sends an electrical signal or index signal in the straight-ahead position and thus when deflecting the index sensor, for example in conjunction with a steering wheel kelsensor the engine correction angle to compensate for the steering wheel tilt by the active steering system can be calculated.

There the index sensor for manufacturing reasons not exactly at 0 degrees relative to the straight-ahead position installed must be, the offset or the offset of the angle, which produced by the manufacture and installation of the sensor, calibrated become. This calibration process is currently at the end of production or in case of customer service (eg when changing the active steering system or its controller). The calibration process of the index sensor is via a diagnostic device initiated. It must be on a Achsvermessprüfstand be ensured the straight-ahead position of the front wheels and the steering wheel angle sensor in the straight-ahead position of the steering wheel output nominal 0 degrees. By deflecting the index sensor becomes in conjunction with the steering wheel angle sensor the offset angle or the offset value in relation to the steering wheel angle or steering angle determined and stored in the control unit. Desirable it would be if this elaborate manual calibration or learning process should no longer be performed explicitly.

Of the The present invention is therefore based on the object, a simple automatic calibration procedure for an index sensor to provide an electronic power steering system of a motor vehicle.

These The object is achieved by claim 1 solved.

The Automatic calibration method according to the invention for an index sensor of an electronic power steering system a motor vehicle while driving, which in its Überlenken in a neutral position, in particular a straight-ahead position of the electronic power steering system, an electrical index signal outputs, wherein the neutral position of the electronic power steering system by a predetermined steering angle value or a predetermined with the Steering angle correlating angle value of the electronic power steering system is characterized, wherein during driving to Calibration of the index sensor in each case with an output electrical Index signal when the index sensor is deflected as the offset single value of the index sensor, an offset or a difference of the current steering angle value or the current angle value correlating with the steering angle of the predetermined neutral steering position predetermined steering angle value or from the predetermined angle value correlating with the steering angle determined and stored, has the advantage that no calibration more explicitly or manually must be performed.

Of the Teach-in process no longer has to be carried out explicitly but is done automatically. At the end of the tape or at the end of the production process will only be used as before in vehicles without active steering system the steering wheel angle sensor is in straight ahead position to zero degrees set. Then the wheels go straight posed. By straightening the front wheels is The steering wheel is rotated and the steering wheel angle gives the now resulting Steering wheel slant off. The active steering controller is Now given the command, from the steering angle to the required motor angle calculate to correct the steering angle angle error. The vehicle is now moved normally while driving. In the thereby necessary Überlenken of the index sensor while driving becomes the index offset or the offset of the index sensor measured or determined. Subsequently can the straight-ahead position by means of the offset / offset adjusted index sensor are always determined.

Very It is also advantageous if as offset mean of the index sensor, an average of the stored offset single values is formed and stored. Furthermore, the number of Specified to be determined or stored offset individual values or be limited.

Around the highest possible security of the determined value will reach the index offset at each override and successful determination of the index sensor offset in a non-volatile Memory stored and from the multiplicity of these values as final Calibration value of the mean value formed. The number of the mean contributing values may be limited. Is the number to the mean contributing index offset values, the teach-in process is completed.

According to the invention be further provided that the the neutral position of the electronic power steering system characteristic predetermined steering wheel angle value or the specified angular value correlated with the steering angle by means of measured wheel speeds of the motor vehicle is determined.

If the motor angle is lost, for example, by a loss of voltage before an index offset value has been learned, the straight-ahead position of the steering gear can advantageously be determined alternatively or additionally on the basis of the measured wheel speeds. Ie. at almost identical wheel speeds (at a vehicle speed greater than 0 km / h), the resulting steering wheel angle is used in the control unit for obliquity correction. Subsequently, this is invented The automatic calibration method according to the invention is carried out.

Of the predetermined or current steering angle value can be an input angle be the steering gear of the electronic power steering system. When preset or current correlating with the steering angle value Angle value, a steering wheel angle value can be used.

The Automatic calibration method according to the invention for an index sensor of an electronic power steering system a motor vehicle while driving is for example in the frame a method for operating an electronic power steering system preferably as a computer program on a control unit implemented the electronic power steering system. This is the computer program in stored a memory element of the controller. By Processing is done on a microprocessor of the controller the procedure is carried out. The computer program can open a computer-readable medium (floppy disk, CD, DVD, Hard disk, USB memory stick or the like) or an internet server be stored as a computer program product and from there into transmit the memory element of the controller become. Such a computer program or computer program product with program code means is specified in claim 7 or claim 8.

claim 9 relates to an electronic power steering system of a motor vehicle.

advantageous Embodiments and developments of the invention are specified in the subclaims. The following is a principle with reference to the drawing an embodiment of the invention indicated.

It demonstrate:

1 a simplified schematic representation of an active or superposition steering system, in which an automatic calibration method according to the invention is used; and

2 a simplified flow chart of the automatic calibration method according to the invention.

1 shows an electronic power steering system 1 or superposition steering system or active steering system of a motor vehicle, not shown. The electronic 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 fundamentally used for the realization of one or more 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 transmission 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 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. As a rule, the desired additional angle δ _Md results from a summation of partial desired additional angles of different useful functions (eg the variable steering ratio) of the electronic power steering system 1 , For the sake of simplicity, however, the desired additional angle δ _{Md will be} equated with the partial target additional angle of the variable steering ratio below. The control or regulation of the electric motor 9 This is usually done as a function of the vehicle speed v _{x of} the motor vehicle, ie the provided by a useful function variable 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 due to the superposition of the steering wheel angle δ _S with different, speed-dependent Zu set angles δ _M as a function of the vehicle speed v _x .

So that the above-mentioned control functions can be performed, receives the control unit 11 as input signal, the current vehicle speed v _x (eg via the CAN bus of the motor vehicle). In addition, the electronic power steering system 1 sensors 12a . 12b . 12c 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, an index sensor 12d provided, which in its deflection in a neutral position, in particular a straight-ahead position of the electronic power steering system 1 an electrical index signal idx outputs, wherein the neutral position of the electronic power steering system 1 by a predetermined steering angle _value δ _{G_NEUTRAL} or a predetermined with the steering angle δ _G correlated angle value, z. As the steering wheel angle δ _S , the electronic power steering system 1 is marked.

As in 1 indicated, the control unit 11 over the sensors 12a . 12b . 12c . 12d and other vehicle systems, not shown, inter alia, supplied with the input signals vehicle speed v _x , steering wheel angle δ _S , pinion angle δ _G , additional angle δ _M and the index signal idx. Alternatively or additionally, a plurality of these variables could also be calculated on the basis of the other or further input variables, in particular wheel speeds, for example with the aid of suitable models.

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.

How out 2 It can be seen according to the invention an automatic calibration method with method steps A, B, C and D for the index sensor 12d of the electronic power steering system 1 suggested while driving. Step A is z. B. started at the end of the manufacturing process. During the driving operation, in the step B for calibration of the index sensor 12d each at the output electrical index signal idx when the index sensor is deflected 12d as offset value offset _{E of} the index sensor 12d an offset or a difference of the current steering angle _value δ _G from the predetermined neutral steering position predetermined steering angle _value δ _{G_NEUTRAL} and determined in a database DB in a non-volatile memory _{element of} the controller 11 - on successful determination - stored. Then continue with step C. The number of offset individual values offset _E to be determined or stored is predetermined or limited. In step C, it is thus checked whether the predetermined number of offset individual values offset _{E has been} reached. If this is the case, continue with step D. Otherwise, step B follows again and the next offset item Offset _E is determined. In step D, offset _{M of} the index sensor is used as the offset average 12d an average of the stored offset individual values offset _{E is} formed and stored in a non-volatile memory element on the control unit 11 (in 2 dashed lines indicated) stored. This completes the calibration procedure and the offset average Offset _M is used as the calibration value.

In the present exemplary embodiment, the pinion angle or input angle δ _G , δ _{G_NEUTRAL of} the steering gear is the given or current steering angle _value 4 of the electronic power steering system 1 used.

Alternatively, instead of the predefined or current steering angle _value δ _G , δ _{G_NEUTRAL,} a predefined or current angle value correlating with the steering angle δ _G , in particular the steering wheel angle δ _S , can be used.

Alternatively or additionally, the neutral position of the electronic power steering system 1 characteristic predetermined input _angular value δ _{G_NEUTRAL of} the steering gear 4 or with the input angle δ _{G of} the steering gear 4 correlating steering wheel angle value δ _{S are determined} by means of measured wheel speeds of the motor vehicle.

The inventive automatic calibration method for the index sensor 12d of the electronic power steering system 1 of the motor vehicle while driving is in the context of a method for operating the electronic power steering system 1 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

electronic Power 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 device of the superposition means

12a, 12b, 12c

sensors

12d

index sensor

δ _Fm

wheel steering angle or steering angle

δ _G

pinion angle

δ _{G_NEUTRAL}

given Pinion angle value

δ _S

steering wheel angle

v _x

vehicle speed

δ _M

additional angle

δ _Md

setpoint the additional angle

idx

index signal

A, B, C, D

steps

Offset _E

Offset single value

Offset _M

Offset averaging

DB

Database

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 19751125 A1 [0002]
• - DE 102005059883 A1 [0005]

Claims (9)

Automatic calibration procedure for an index sensor ( 12d ) of an electronic power steering system ( 1 ) of a motor vehicle in driving operation, which in its deflection in a neutral position, in particular a straight-ahead position of the electronic power steering system ( 1 ) outputs an electrical index signal (idx), wherein the neutral position of the electronic power steering system ( 1 ) by a predetermined steering angle _value (δ _{G_NEUTRAL} ) or a predetermined angular value (δ _S ) of the electronic power steering system correlating with the steering angle (δ _G ) ( 1 ), during the driving operation for calibration of the index sensor ( 12d ) each at an output electrical index signal (idx) when deflecting the index sensor ( 12d ) as offsetting value (offset _E ) of the index sensor ( 12d ) an offset of the current steering angle value (δ _G ) or of the current angle value (δ _S ) correlating with the steering angle (δ _G ) from the predetermined steering angle _value (δ _{G_NEUTRAL} ) characterizing the neutral _position or from the predetermined angle value correlating with the steering angle (δ _G ) (δ _S ) is determined and stored. Automatic calibration method according to claim 1, characterized in that the offset mean value (offset _M ) of the index sensor ( 12d ) an average of the stored offset individual values (offset _E ) is formed and stored. Automatic calibration method according to claim 1 or 2, characterized in that the number of offset individual values to be determined or stored (offset _E ) is predetermined or limited. Automatic calibration method according to claim 1, 2 or 3, characterized in that the neutral position of the electronic power steering system ( 1 ) characteristic predetermined steering angle _value (δ _{G_NEUTRAL} ) or the predetermined with the steering angle (δ _G ) correlating angle value (δ _S ) is determined by means of measured wheel speeds of the motor vehicle. Automatic calibration method according to one of claims 1 to 4, characterized in that the predetermined or current steering angle value is an input angle (δ _G ) of the steering gear ( 4 ) of the electronic power steering system ( 1 ). Automatic calibration method according to one of claims 1 to 5, characterized in that the predetermined or current angular value correlating with the steering angle value (δ _G ) is a steering wheel angle value (δ _S ). Computer program with program code means for carrying out an automatic calibration method according to one of Claims 1 to 6, if the program is stored on a microprocessor of a computer, in particular on an electronic control unit ( 11 ) of an electronic power steering system ( 1 ), is performed. A computer program product comprising program code means stored on a computer-readable medium for carrying out an automatic calibration method according to one of claims 1 to 6, when the program is stored on a microprocessor of a computer, in particular on an electronic control unit ( 11 ) of an electronic 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 ), - an index sensor ( 12d ), which in its deflection in a neutral position, in particular a straight-ahead position of the electronic power steering system ( 1 ) outputs an electrical index signal (idx) and - an electronic control unit ( 11 ), which is set up to execute the computer program according to claim 7 and which contains the electrical index signal (idx) of the index sensor ( 12d ) receives as input signal.