DE102010032150A1 - Method for determining steering system play in vehicle, involves determining position signal of sensor to detection time point and another position signal of sensor to another detection time point - Google Patents

Abstract

The method involves determining a position signal of a sensor to a detection time point and another position signal of the sensor to another detection time point. The steering system play is determined in dependence of the two position signals of the sensor. The former detection time point is a time point, at which another sensor generates a predetermined position signal of the latter sensor. An independent claim is also included for a device for determining a steering system play.

Description

The invention relates to a method and a device for determining a steering system clearance in a vehicle with a steering assistance.

Steering systems with steering assistance means (power steering systems) are well known. In such power steering systems, an assisting torque is applied by means of an actuator to a steering column or, preferably, a rack of the steering system. This reduces a by a motor vehicle driver z. B. applied by means of a steering handle manual steering torque. Electromechanical servomotors are widely used to generate the support torque. Also known are hydraulic actuators for generating the assist torque.

The actuator in this case comprises an output shaft or a rotor of the actuator, via a transmission, for. B. via a ball screw (KGT), can be coupled to the rack. A position or position of the output shaft can in this case be detected by means of a sensor, wherein the sensor usually detects a relative position of the output shaft.

A resulting steering force on the rack of the steering system is dependent in a power steering system on the manual steering torque applied by the motor vehicle driver and the assist torque applied by the actuator. Here, the assist torque or a magnitude of the assist torque is usually dependent on a magnitude of the manual steering torque. In simple terms, the higher a manual steering torque, the higher the assist torque applied by the actuator.

The manual steering torque is here z. B. by means of a steering handle, such as a steering wheel, applied to a so-called input shaft of the steering. The input shaft corresponds to the aforementioned steering column and is also known as the torsion bar. The steering column is mechanically connected via a further gear, in particular a so-called steering pinion, with the rack.

Thus, the input shaft is thus mechanically coupled to the output shaft via mechanical elements. Ideally, the mechanical transmission path between the output shaft and the input shaft is free of play. Due to manufacturing or use-related mechanical tolerances, however, a game, for. B. a backlash of the KGT and / or the steering pinion, occur in the mechanical transmission path. This game can also be called a steering system game.

This mechanical play has a direct effect on a feel perceived by a motor vehicle driver feel.

From the DE 10 2007 000 958 A1 It is known to detect a voltage applied to the steering column steering angle by means of an index device. Further, the document discloses that a rotor position angle can be sensed by means of a sensor which is associated with a power assistance unit.

It raises the technical problem to provide a method and apparatus for determining a steering system game in a vehicle with a steering support, which determines an existing game as possible with existing elements of the steering system.

The solution of the technical problem results from the objects with the features of claims 1 and 6. Further advantageous embodiments of the invention will become apparent from the dependent claims.

A method for determining a steering system clearance is proposed.

In this case, a first sensor detects a position of an output shaft of an actuator for generating a support torque. The actuator may be an electromechanical servomotor, for example. The sensor can be a rotor position sensor. This can detect either an absolute position of the output shaft or a relative position of the output shaft. A position can also be understood to mean an angular position.

A second sensor detects a position of an input shaft of a steering system. The second sensor can also detect the position of the input shaft either absolute or relative. The second sensor is preferably arranged below a torque sensor for detecting a steering torque applied manually to the input shaft.

In the steering system according to the invention in this case the steering torque by means of a steering handle, such as a steering wheel, are applied to the input shaft. The steering torque is transmitted by means of a transmission, such as a steering pinion, on a rack of the steering system. Further, the output shaft of the actuator via a transmission, such as a ball screw, be coupled to the rack.

Furthermore, a first position signal of the first sensor is determined for at least one first detection time, for example by means of a suitable evaluation unit. The first position signal corresponds to a first position of the output shaft. The thus detected first position signal of the first sensor can be stored, for example, in a memory unit. Furthermore, at least one further position signal of the first sensor is determined for at least one further detection time. The first and the at least one further detection time are different here. The at least one further position signal corresponds to at least one further position of the output shaft.

The first detection time is in this case a time at which the second sensor detects a predetermined position signal of the second sensor. The predetermined position signal corresponds to a predetermined position of the input shaft, wherein the predetermined position signal of the second sensor is generated if the input shaft assumes the predetermined position or the position of the input shaft by a predetermined amount, for. B. deviates from the predetermined position by a predetermined tolerance dependent measure. If the predetermined position signal of the second sensor is detected, for example by means of the evaluation unit or a further evaluation unit, then the position signal of the first sensor is determined.

The at least one further detection time is a time at which the second sensor generates the predetermined position signal of the second sensor again.

Again, this means that the second sensor between the first and the at least one further detection time at least temporarily generates an output signal which does not correspond to the predetermined position signal of the second sensor. If the input shaft is in the predetermined position, is deflected out of this and returned to the predetermined position, the second sensor again generates the predetermined position signal of the second sensor. Consequently, the at least one further position signal of the first sensor is determined.

The steering system clearance is then determined as a function of the first and the at least one further position signal. For example, the steering system clearance can be determined as a signed difference or absolute value of the difference between the first and the at least one further position signal.

Alternatively, the at least one further position signal of the first sensor is determined if the second sensor generates a second predetermined position signal. In this case, the first predetermined position signal from the second predetermined position signal of the second sensor and thus also the position of the input shaft corresponding to the first predetermined position signal are different from the position of the input shaft corresponding to the second predetermined position signal. A difference between the position of the input shaft corresponding to the first predetermined position signal and the position of the input shaft corresponding to the second predetermined position signal may be previously known. Furthermore, an ideal conversion factor between a position signal of the first sensor and a position signal of the second sensor may also be known, wherein the ideal conversion factor does not take account of steering system play. The conversion factor can z. B. gear ratios and mechanical properties (torsional stiffness, etc.) of mechanical elements of the steering system into account.

Thus, the difference between the first predetermined position signal and the second predetermined position signal of the second sensor can be converted into a difference in the respective corresponding position signals of the first sensor.

The steering system clearance is then determined as a function of the first and the at least one further position signal. In this case, the at least one further position signal can be corrected by the difference between the first predetermined position signal and the second predetermined position signal of the second sensor converted to the position signal of the first sensor, resulting in a corrected further position signal of the first sensor. For example, the steering system game then as a signed difference or absolute value of the difference between the first and the at least one corrected further. Position signal to be determined.

To determine the steering system clearance, a position signal of the first sensor must therefore be determined at least two different detection times, wherein the position signal of the first sensor is always detected if the second sensor generates predetermined position signals of the second sensor. If play, in particular gear play, occurs in the steering system, then the first position signal and the at least one further position signal or the at least one further corrected position signal of the first sensor can be different. The difference depends on the size of the game. If no play occurs, then the first position signal of the first sensor is equal to the at least one further position signal of the first sensor or equal to the at least one corrected further position signal of the first sensor.

As a result, a steering system clearance can be determined in an advantageous manner. That way determines steering system game can be used to generate an error signal, which z. B. is then generated if the steering system game exceeds a predetermined value. In this case, the steering system clearance thus determined serves to diagnose the steering system, for example in the context of customer service or manufacturing services. Furthermore, the steering system game thus determined can be used to adjust or adapt mechanical elements of the steering system. The steering system game thus determined can also be used for the software-related parameterization of control functions of a steering control device. In the case of a known steering system clearance, this can be compensated, for example, by suitable methods for control / regulation, for example for precontrol. Also, depending on a steering system game, an assisting force or moment of the actuator can be reduced. If it is detected, for example, that the steering system clearance increases above a predetermined value, then an assisting force or an assisting torque can be reduced in order to reduce further mechanical loading of the steering system and thus possibly further generation of play.

In a further embodiment, the second sensor is an index signal generator. In this case, an index signal transmitter is understood to mean a sensor unit comprising one or more elements which generates a binary output signal. In this case, the index signal generator generates a first output signal if the index signal generator detects a reference mark. For this purpose, one or more reference marks can be arranged on the input shaft. For example, a reference mark can be arranged on the input shaft, wherein the index signal generator detects this reference mark in each case after a complete rotation of the input shaft, ie a rotation through 360 °. It is also conceivable that reference marks are arranged on the input shaft such that a reference mark is detected in predetermined angular steps, for example 20 °. Of course, even smaller or larger angular steps are conceivable. Also, rising or falling or characteristic of a particular steering direction angle steps are conceivable, from these characteristic angle steps, a steering direction can be determined. In this case, the index signal transmitter detects a reference mark each time the input shaft has been deflected by a predetermined angle, for example 20 °, with respect to a previously detected reference mark. If no reference mark is detected, the index signal generator generates a second output signal. The first output signal can be a binary "1", z. Example, an output signal with a first predetermined voltage level, for example 5 volts be. The second output signal may then be a binary "0", e.g. B. an output signal with a second predetermined voltage level, for example, 0 volts or -5 volts to be. Of course, also the first output signal may be a binary "0" and the second output signal may be a binary "1".

The index signal transmitter can in this case comprise an optical, inductive, capacitive or mechanical sensor. In particular, the index signal transmitter may comprise a Hall sensor.

By reference marks results in an advantageous manner an absolute reference system for the position of the input shaft and the output shaft, which may be particularly advantageous if the first sensor detects only a relative position of the output shaft. Further advantageous results that an index signal generator is less expensive than a relative or absolute angle or position sensor.

In a further embodiment, the steering system clearance is determined as a function of a predetermined number of position signals of the first sensor. In this case, more than just two position signals, for example 5 or more position signals, of the first sensor are preferably detected at predetermined position signals of the second sensor, the steering system game then also being determined as a function of more than just two position signals of the first sensor. For example, all position signals or adjusted position signals of the first sensor can be stored and an average value or median of these position signals and a standard deviation can be determined. Depending on z. B. the standard deviation can then be determined a size of the steering system game. Also, maximum deviations between the position signals of the first sensor or between the position signals of the first sensor and the mean or median can be determined, whereby a maximum game can be determined.

Via the mean value or the median, it is also possible to determine as far as possible a game-independent reference of a relative position signal of the first sensor to a position signal of the second sensor, which is generated at a reference mark and thus an absolute position of the input shaft. In this way, the relative position signal of the first sensor can be converted into an absolute reference system or a specific position signal of the first sensor can be assigned to a specific position of the input shaft. If, for example, a position signal of the second sensor corresponding to a zero or straight running angle, in particular the position signal generated at a reference mark, or a reference between a zero or straight running angle and a predetermined position signal, in particular the position signal generated at a reference mark, of the second sensor, so This can also be a corresponding to this zero or straight running angle position signal of the first sensor are determined, which is as possible independent of the game and thus accurate.

In a further embodiment, the first and the at least one further position signal of the first sensor are additionally determined as a function of a steering direction, wherein the steering system clearance is additionally determined as a function of the steering direction. In this case, a steering direction is additionally determined in the evaluation of the position signal of the second sensor. The steering direction can, for. B. be determined via a known relationship between changes in the position signals of the first or second position sensor and the steering direction. It is also conceivable that the index signal generator generates two output signals, which are offset from each other by a predetermined phase angle depending on the direction of rotation. Preferably, this method is used when a position signal of the first sensor is always determined when the position signal of the second sensor is the same predetermined position signal, that is, the input shaft is ideally in the same position.

Here, therefore, a first position signal and at least one further position signal of the first sensor is determined for a first direction of rotation and z. B. stored in a first storage unit. Also, a first position signal and at least one further position signal of the first sensor for a second direction of rotation is determined and z. B. stored in a second storage unit. Of course, in each case a first and at least one further corrected position signal of the first sensor can be determined for the first and for the second rotational direction.

Depending on the first and the at least one further position signal of the first sensor or of the at least one further corrected position signal of the first sensor, a clearance for the first direction of rotation and a clearance for the second direction of rotation can then be determined. The first direction of rotation is different from the second direction of rotation, in particular this opposite. From a plurality of position signals of the first sensor for the first and second rotational direction, an average or median of position signals of the first sensor for the first direction of rotation can be determined, whereby a spielunabhängigerer relationship between the position signal of the first sensor and the predetermined position signal of the second sensor calculated can be. Similarly, an average or median of position signals of the first sensor for the second direction of rotation can also be determined. Also, depending on z. B. the standard deviation a size of the steering system game for the first or second rotational direction are determined. Also, maximum deviations between the position signals of the first sensor or between the position signals of the first sensor and the mean or median for the first or second rotational direction can be determined, whereby a maximum play per direction of rotation can be determined.

In a further embodiment, a center position of the input shaft is determined from at least one difference of a first position signal of the first sensor for a first direction of rotation and a position signal of the first sensor for a second direction of rotation. Here, it is assumed that a predetermined position signal of the second sensor for the first rotational direction is generated when the input shaft is deflected by a predetermined angle in the first rotational direction relative to the center position of the input shaft. Further, a predetermined position signal of the second sensor for the second rotational direction is generated when the input shaft is deflected by the predetermined angle in the second rotational direction relative to the center position of the input shaft. Preferably, the center position or the zero angle of the input shaft can be determined if the second sensor is an index signal generator, which detects a reference mark in each case in a complete rotation of the input shaft in the first or second rotational direction.

Preferably, a center position of the input shaft is determined from a difference of the mean value or median of position signals of the first sensor for the first and for the second rotational direction. The center position of the input shaft can thus be determined with respect to the position signal of the first sensor, d. H. a certain position signal of the first sensor can be assigned to the center position of the input shaft.

Further proposed is a device for determining a steering system game. The device in this case comprises at least a first sensor, a second sensor and an evaluation unit. By means of the first sensor, a position of an output shaft of an actuator for generating a support torque can be detected. By means of the second sensor, a position of an input shaft of a steering system can be detected.

According to the invention, by means of the evaluation unit, a first position signal of the first sensor at a first detection time and at least one further position signal of the first sensor at least one further detection time determined, wherein the first detection time is a time at which by means of the second sensor, a first predetermined position signal of the second Sensor is generated, wherein the at least one further detection time is a time at which by means of the second sensor, the first predetermined position signal of the second sensor again or a second predetermined position signal is generated. By means of the evaluation unit, furthermore, the steering system clearance can be determined as a function of the first and the at least one further position signal of the first sensor.

Furthermore, the device may comprise one or more memory units for storing position signals of the first sensor. By means of the proposed device, one of the previously described methods can be carried out in an advantageous manner.

The invention will be explained in more detail with reference to an embodiment. The figures show:

1 a schematic overview of a steering system and

2 a schematic representation of a determination of a steering system game.

In 1 is a schematic block diagram of an electromechanical steering 1 shown. The electromechanical steering 1 includes a steering handle 2 For example, a steering wheel. The steering handle 2 is with an input shaft 3 coupled. The input shaft 3 is via a mechanical clutch 4 , For example, a steering pinion, with a steering rack 5 coupled. Furthermore, the electromechanical steering comprises a servomotor 6 that has a gearbox 7 , For example, a ball screw, also with the steering rack 5 is mechanically coupled. A rotor position of an output shaft 13 of the servomotor 6 is powered by a rotor position sensor 8th detected. The rotor position sensor 8th is data technology with a control unit 9 coupled, the control unit 9 is a so-called PID controller. Here, one of the servomotor 6 applied auxiliary torque by means of the control unit 9 be determined from the rotor position information. Next includes the electromechanical steering 1 an evaluation unit 10 , which also data technology with the rotor position sensor 8th connected is. In the input shaft 3 Here is a steering torque sensor 11 and an index buzzer 12 arranged. The steering torque sensor 11 is also data technology with the control unit 9 and the evaluation unit 10 connected, the index signal generator 12 is in this embodiment only with the evaluation 10 connected technically, but of course also with the control unit 9 get connected.

The index buzzer 12 produces an output signal with a voltage level of +5 volts, if one on the input shaft 3 arranged, but not shown, reference mark is detected. Here, the reference mark after each complete rotation of the input shaft 3 detected.

The evaluation unit 10 determines a game of the steering system and parameterizes the control parameters of the control unit as a function of the game 9 what it is related to data related to this.

In 2 is a schematic representation of a determination of a steering system game shown. Here, a position signal of the rotor position sensor is on the ordinate 8th out 1 which is detected at detection times T1 _A , T2 _A ,..., T5 _A , T1 _B , T2 _B ,..., T5 _B. Here, the detection times T1 _A , T2 _A , ..., T5 _A , T1 _B , T2 _B , ..., T5 _B detection times, to which the index signal generator 12 the reference mark is recorded. The time t is shown on the abscissa. Here, A denotes a first steering direction and B a second steering direction of the steering handle 2 that is opposite to the first steering direction A. The applied on the ordinate section A position signal of the rotor position sensor 8th , which is marked with an "x", so is a position signal, which by means of the evaluation 10 at detection times T1 _A , T2 _A , ..., T5 _{A is} determined, so if the steering handle 2 is deflected in the first direction and the index signal generator 12 the reference mark is recorded. The applied on the ordinate section B position signal of the rotor position sensor 8th , which is marked with an "o", is analogous to a position signal, which by means of the evaluation 10 at detection times T1 _B , T2 _B , ..., T5 _{B is} determined, so if the steering handle 2 is deflected in the second direction and the index signal generator 12 the reference mark is recorded. It can be seen here that the respective position signals of the rotor position sensor for the first and second steering directions A, B vary. The dashed line 14 in each case denotes an average value of the position signals of the rotor position sensor 8th for the first and for the second steering direction A, B. The dotted lines 15 each designate a maximum and minimum value of the position signals of the rotor position sensor 8th for the first and for the second steering direction A, B. From a difference between the maximum and minimum value of the position signals of the rotor position sensor 8th For example, a maximum clearance S _A for the first steering direction A and a maximum clearance S _B for the second steering direction can be determined.

LIST OF REFERENCE NUMBERS

1

electromechanical steering system

2

Steering handle

3

input shaft

4

clutch

5

Steering rack

6

servomotor

7

transmission

8th

Rotor position sensor

9

control unit

10

evaluation

11

Steering torque sensor

12

Index signal generator

13

output shaft

14

Average

15

minimum and maximum value

A

first steering direction

B

second steering direction

S _A

maximum play in the first steering direction

S _B

maximum play in the second steering direction time

T1 _A

Detection time

T2 _A

Detection time

T3 _A

Detection time

T4 _A

Detection time

T5 _A

Detection time

T1 _B

Detection time

T2 _B

Detection time

T3 _B

Detection time

T4 _B

Detection time

T5 _B

Detection time

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102007000958 A1 [0008]

Claims (6)

Method for determining a steering system clearance, wherein a first sensor detects a position of an output shaft ( 13 ) of an actuator for generating an assist torque, wherein a second sensor detects a position of an input shaft ( 3 ) of a steering system, characterized in that a first position signal of the first sensor at a first detection time and at least one further position signal of the first sensor is determined at least one further detection time, wherein the first detection time is a time at which the second sensor is a first generates predetermined position signal of the second sensor, wherein the at least one further detection time is a time at which the second sensor generates the first predetermined position signal of the second sensor again or a second predetermined position signal, wherein the steering system clearance in response to the first and the at least one further position signal of the first sensor is determined. Method according to Claim 1, characterized in that the second sensor is an index signal transmitter ( 12 ). Method according to one of the preceding claims, characterized in that the steering system clearance is determined in dependence on a predetermined number of position signals of the first sensor. Method according to one of the preceding claims, characterized in that the first and the at least one further position signal of the first sensor additionally in response to a steering direction (A, B) are determined, the steering system game is additionally determined in dependence of the steering direction (A, B) , A method according to claim 4, characterized in that a center position of the input shaft of at least one difference of a first position signal of the first sensor for a first direction of rotation (A) and a position signal of the first sensor for a second direction of rotation (B) is determined. Device for determining a steering system clearance, wherein the device comprises at least a first sensor, a second sensor and an evaluation unit ( 10 ), wherein by means of the first sensor, a position of an output shaft ( 13 ) of an actuator for generating an assist torque is detectable, wherein by means of the second sensor, a position of an input shaft ( 3 ) of a steering system can be detected, characterized in that by means of the evaluation unit ( 10 ), a first position signal of the first sensor at a first detection time and at least one further position signal of the first sensor at least one further detection time can be determined, wherein the first detection time is a time at which the second sensor generates a first predetermined position signal of the second sensor, wherein the at least one further detection time is a point in time at which the second sensor generates the first predetermined position signal of the second sensor again or a second predetermined position signal, wherein the steering system clearance is determined as a function of the first and the at least one further position signal of the first sensor.

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