DE102011121612A1 - Method for detecting operating condition of steering wheel of electronically controlled power steering system for vehicle, involves adjusting damping factor of steering retraction based on detected operating condition of steering wheel - Google Patents

Abstract

The method involves detecting an operating condition (BZ) of a steering wheel based on steering angle acceleration (b) and a steering moment (LM) during steering retraction. A damping factor of the steering retraction is adjusted based on the detected operating condition. The operating condition is distinguished between guided and non-guided steering retractions. The damping factor is increased to a predeterminable value during the guided steering retraction, where the predeterminable value is adjusted based on driving speed of a vehicle.

Description

The invention relates to a method for detecting an operating state of a steering wheel of an electronically controlled power steering system according to the features of the preamble of claim 1.

The DE 10 2008 031 729 A1 describes a method for electronically controlling a steering assist for a vehicle. In this case, an instantaneous desired steering torque for a voltage applied to the steering wheel of the vehicle steering torque in dependence on a driving speed, a steering wheel angle and a steering speed and predetermined vehicle-specific parameters using stored maps is determined and is used as a reference variable for the scheme.

The DE 10 2009 028 647 A1 describes a method to detect the operating state of a steering wheel in a vehicle, wherein a current, high-resolution steering wheel angle and a current steering torque are determined. Depending on the steering wheel angle and the steering torque, a driver's hand torque currently applied by the driver is determined. In dependence on a progression of the driver's manual torque, the operating state of the steering wheel is then determined or it is detected whether the driver has his hands on the steering wheel or whether the driver has taken his hands off the steering wheel. The method can be carried out with the sensors already present in an EPS steering system.

The invention is based on the object to provide a method for detecting an operating state of a steering wheel of an electronically controlled power steering system.

The object is achieved by a method for detecting an operating state of a steering wheel of an electronically controlled power steering system with the features of claim 1.

Advantageous embodiments of the invention are the subject of the dependent claims.

In the method for detecting an operating state of a steering wheel of an electronically controlled power steering system with a steering torque controller for a vehicle, the operating state is detected during a steering return of a steering angle acceleration and a steering torque, wherein a damping factor of the steering return is set in dependence of the detected operating state.

As a result, a target conflict between such a steering feel or a steering comfort in a guided steering return, wherein the driver with at least one hand touches the steering wheel, and an unguided steering return, wherein the driver does not touch the steering wheel, is advantageously solvable. By means of the method according to the invention, corresponding power steering systems are tunable such that a good steering feel in a guided steering return can be combined with a particularly rapid steering return at an unguided steering return by a corresponding increase in the damping factor.

As a result, a steering comfort of the vehicle is steigerbar in a particularly advantageous manner.

Embodiments of the invention are explained in more detail below with reference to drawings.

Showing:

1 schematically a flowchart for detecting or determining an operating state of a steering wheel of an electronically controlled power steering system and

2 schematically a sequence program for the determination of a damping factor.

Corresponding parts are provided in all figures with the same reference numerals.

1 schematically shows a flowchart for detecting or determining an operating state BZ of a steering wheel of an electronically controlled power steering system of a vehicle, not shown. Such a vehicle comprises a conventional, for example in the DE 10 2008 031 729 A1 revealed electronically controlled steering assistance.

Such a conventional steering torque controller generates an instantaneous setpoint steering torque for a steering torque LM applied to the steering wheel of the vehicle from the driving state variables driving speed v and steering angle w. In this case, the target steering torque is formed additively from a basic steering torque and an additional steering torque.

By means of the additional steering torque are thereby preferably taken into account the steering comfort improving properties of the steering. These include, for example, a steering stabilizing friction and damping within the steering system, without which the steering would be nervous and the driver would be taught an unsafe driving experience.

Steering should reset itself in city traffic, especially in turning maneuvers, independently from a steering position to a middle position as soon as a driver turns the steering wheel lets go. At this also called steering return reset process high demands are to be made. Too fast steering return is perceived by the driver as inharmonious and can lead in extreme cases to leave the desired vehicle trajectory. Too slow steering return requires manual intervention by the driver and is therefore perceived as uncomfortable.

A steering torque controller allows the adjustment of the steering return, in particular their damping, on the adjustment of friction and damping.

In some driving maneuvers vehicle drivers prefer a guided steering return, in which the driver with at least one hand touches the steering wheel and leads such. This is the case, for example, when driving through a roundabout in which multiple turns have to be made.

In general, drivers will not let go of the steering wheel as the next steering operation will start directly after the steering reset. In such guided steering return, it is preferred if the steering return is done with a strong damping.

Damping values or factors DF, which are required for this, lead to unsatisfactory steering reset, in which the driver does not touch the steering wheel, to unsatisfactory, in particular too slow, steering provisions.

It is in such power steering systems thus a conflict between a steering feel or a steering comfort in a guided steering return, the driver with at least one hand touches the steering wheel, and an unguided steering return, the driver does not touch the steering wheel.

By means of the method according to the invention, corresponding power steering systems are tunable such that a good steering feel in a guided steering return can be combined by a corresponding increase in damping with a particularly fast steering return at an unguided steering return.

In order to make this possible, the operating state BZ of the steering wheel is detected on the basis of a steering angular acceleration b and a steering torque LM during a steering return, whereby a damping factor DF of the steering return is set as a function of the detected operating state BZ. This is preferably done by a temporary change of the steering torque damping defined by the steering torque controller. If a guided steering reset is detected, the steering torque damping is increased by a predefinable amount.

In this case, a distinction is preferably made between two operating states BZ, between a guided and an unguided steering return.

The applied in such power steering systems on the steering wheel of the vehicle steering torque LM is detected or measured in a conventional manner. This measurement is preferably carried out by means of a torsion bar on the steering wheel side steering gear input. The steering torque LM is fed directly to a control unit SE.

Furthermore, in a conventional manner, a steering angle w, a steering speed u and a steering angular acceleration b are detected. The imbalance U of the steering wheel, the phase P of the imbalance U of the steering wheel, the primary friction PR, and the inertia M of the steering wheel are constant quantities and are generally known by the vehicle. These factors or values go through as shown in FIG 1 mathematical functions mF1 to mF3 and / or multiplier MG1 to MG3 and are then fed to the control unit SE.

The control unit SE evaluates the incoming signals and calculates such a resulting steering torque deviation rLM between the steering wheel torque acting on the steering wheel and the steering torque resulting from the steering angular acceleration b and the inertia M of the steering wheel. The resultant steering torque deviation rLM calculated in this way is fed to a further mathematical function mF4 and then fed to a first evaluation unit AE1.

In the evaluation unit AE1, the resulting steering torque deviation rLM is analyzed. If the resulting steering torque deviation rLM is almost zero, the moment on the steering wheel corresponds to the torque which is required for the intended steering angular acceleration b. If this is the case, obviously no additional torque on the steering wheel attacks, as is the case with an unguided steering return.

If the resulting steering torque deviation rLM has a clear deviation from zero, it is to be concluded that an additional torque is introduced into the steering wheel, in particular that the steering wheel is held by the driver, as is the case with a guided steering return.

Subsequently, a signal representing the operating state BZ is output on the basis of these calculations.

2 schematically shows a sequence program for the determination of a damping factor DF.

In this case, the steering speed u is processed by means of a mathematical function mF5 and then fed with the steering angle w to a multiplier element MG4. An outgoing signal is fed in a second evaluation unit AE2. Within the evaluation unit AE2 it is determined whether the steering angle w and the steering speed u have different signs. If this is the case, a steering return is detected. Otherwise, a normal Zulenkvorgang is closed. A corresponding signal is fed to a multiplier MG5.

The vehicle speed v is fed to a third evaluation unit AE3, within which a characteristic map is stored, in which each vehicle speed v is assigned a maximum damping factor DF. Thus, the damping factor DF is set as a function of a vehicle speed v of the vehicle. A corresponding signal is fed to a multiplier MG5.

Furthermore, the multiplier MG5 the operating state BZ is forwarded. The multiplier MG5 causes a damping increase or an increase of the damping factor DF to be actuated only when a guided steering reset is detected. The output signal of the multiplier element MG5 is fed to an adder AD and then processed in a low-pass filter TF.

The resulting damping factor DF is passed to the conventional steering torque controller where it is multiplied by the standard damping for that driving condition.

In this case, this standard damping is set such that a fast and safe steering return is possible with unguided steering provisions.

LIST OF REFERENCE NUMBERS

BZ

operating condition

v

driving speed

w

steering angle

b

Steering angle acceleration

LM

steering torque

DF

damping factor

SE

control unit

U

unbalance

P

phase

PR

primary friction

u

steering speed

M

inertia

mF1 to mF5

mathematical function

MG1 to MG5

multiplier element

RLM

resulting steering torque

AD

addition element

AE1 to AE3

evaluation

TF

Low Pass Filter

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 102008031729 A1 [0002, 0015]
• DE 102009028647 A1 [0003]

Claims (5)

Method for detecting an operating state (BZ) of a steering wheel of an electronically controlled power steering system with a steering torque controller for a vehicle, characterized in that during a steering return the operating state (BZ) of the steering wheel is detected on the basis of a steering angular acceleration (b) and a steering torque (LM), wherein a damping factor (DF) of the steering return is set in dependence on the detected operating state (BZ). A method according to claim 1, characterized in that is distinguished as the operating state (BZ) between a guided and an unguided steering return. A method according to claim 2, characterized in that at a guided steering return of the damping factor (DF) is increased by a predetermined value. A method according to claim 3, characterized in that the predeterminable value is set as a function of a driving speed (v) of the vehicle. A method according to claim 2, characterized in that at an unguided steering return of the steering torque regulator vorgebebene or set attenuation factor (DF) is maintained.

Images