DE102004041616B4 - Method for steering assistance in a vehicle - Google Patents

Abstract

method for steering assistance in a vehicle with a steering wheel (1), a steering shaft (2) and a steering gear (3), one acting on the steering gear (3) Motor (9) depending a steering torque (Ms) measured by a steering torque sensor (4) is characterized in that the measured steering torque (Ms) one from a moment of inertia (Jl) and a rotational acceleration (bs) of the steering wheel (1) formed Correction size (K) reduced becomes.

Description

The The invention relates to a method for steering assistance in a vehicle with a steering wheel, a steering shaft and a steering gear, with an on the steering gear acting engine in response to one of a steering torque sensor measured steering torque is controlled.

electrical Steering support systems - also power steering called - included usually a mounted on the steering shaft steering torque sensor, which should detect the steering torque applied by the driver. Further is a motor connected to the steering gear, which is the assist torque applies.

In order to give the driver the feeling of unsupported steering, especially with rapid movements of the steering wheel, various proposals have been made. For example, the generic US 6,360,151 B1 the compensation of the moment of inertia of the electric motor described. Further, in DE 102 01 704 A1 an electric motor control apparatus for a power steering apparatus is described, which can deliver an appropriate steering force to a steering wheel according to the driving conditions. In this case, the angular velocity of the steering wheel is taken into account.

The torque determined by the steering torque sensor is not exclusive to that from the driver applied steering torque, but a superposition this and the moment that comes from the acceleration of the steering wheel arises.

It However, it has turned out to be better for many steering functions is the pure steering torque that the driver applies to the control to use the power steering.

These The object is achieved in the method according to the invention in that the measured steering torque by one of the moment of inertia and the spin the steering wheel formed correction variable is reduced. Preferably is provided that the correction value by multiplying a Input size with a stored moment of inertia of the steering wheel is formed.

The Formation and application of the correction quantity - in control engineering as well Observers called - allow a more exact steering assistance and therefore a more precise steering. The spin of the Steering wheel is also called steering angle acceleration below.

Provided a sensor for the steering wheel acceleration is present or a value for it already derived from other systems in the vehicle can, in the method according to the invention be provided that the input variable the steering wheel acceleration is.

to Using a steering angle sensor, the inventive method be configured such that the input from the steering angle by two-fold derivative is formed. The for the inventive method required arithmetic functions are preferably using a suitable processor. A derivative can then easily by subtraction two successive values of the input variable - provided There is a steering angle sensor with sufficient resolution and dynamics in front.

Stands a sensor for measuring the rotational speed of the steering shaft to available so can the inventive method Also be designed such that the input through Derivative from the rotational speed of the steering shaft is formed.

to Control of the engine are common anyway sensors required, such as rotation angle sensors. these can for the inventive method be used by that the input from the rotation angle of the motor through twice derivative is formed and that in the correction quantity multiplicatively the reduction ratio the steering gear is received.

In similar Way can also be used by a speed sensor of the engine be that input size through Derivation of the speed of the engine is formed and that in the Correction size multiplicative the reduction ratio of Steering gear is received.

embodiments The invention are illustrated in the drawing with reference to several figures and explained in more detail in the following description. It shows:

1 a schematic representation of a known power steering,

2 a schematic representation of a steering aid according to the inventive method,

3 to 7 Block diagrams of observers for the inventive method, which are adapted to different sensors.

The 1 and 2 each show a steering wheel 1 with a steering shaft 2 indicating the rotation of the steering wheel 1 on a steering gear 3 transfers. At the steering shaft 2 there is a steering torque sensor 4 . the from the torsion of the steering shaft 2 derives a size corresponding to the steering torque Ms. This is done via the components EPS Basic Support 5 and EPS steering function 6 as well as an adder 7 a motor control device 8th fed to the output of a motor 9 It is connected to the steering gear 3 acts. In addition, the engine has 9 via a motor position sensor 10 (Angle of rotation sensor), the respective engine position to the engine control unit 8th reports. This is required, for example, in brushless DC motors. The EPS basic support 5 (EPS = Electronic Power Steering) includes the basic functions while the EPS steering function 6 contains additional functions that may vary from vehicle to vehicle or from vehicle to vehicle manufacturer.

At the in 2 shown power steering according to the inventive method is between the steering torque sensor 4 and the entrances of the facilities 5 . 6 an observer 11 inserted. This receives from the engine position sensor 10 the respective motor position, from which a correction quantity K is derived. The derivative of the correction quantity in the observer 11 is for this embodiment later with reference to 6 explained in more detail. The output is then the steering torque Mf, which is applied by the driver.

The driver steering torque Mf is calculated as follows from the application of the twist set: Jl · bl = Mf + Ms, is there
Jl the moment of inertia of the steering wheel,
bl the steering angular acceleration,
Mf the torque applied by the driver and
Ms the torque measured by the steering torque sensor.

If one converts this equation to Mf, one obtains the following equation, as it is to be implemented for the observer: Mf = Jl · bl - Ms.

3 shows an observer 11.1 who is a subtractor 12 and a multiplier 13 contains. From the steering torque sensor 4 the moment Ms is fed while from a sensor 14 the steering angular acceleration bs is supplied. By multiplying the steering angular acceleration bs with that from a memory 15 read out moment of inertia Jl of the steering wheel at 13 creates a correction value that the subtractor 12 is supplied. This results in the steering torque Mf applied by the driver. This will be over the output 16 the other components of the power steering system 2 fed.

At the in 4 illustrated embodiment of an observer 11.2 is a steering angle sensor 17 whose output ws is derived twice after the time to arrive at the steering angular acceleration. This is done in the observer 11.2 the size to be deduced 18 to 21 each delayed by a time element Z-1 and subtracted from the instantaneous magnitude, each resulting in a time derivative.

The observer 11.3 to 5 is from a sensor 22 the steering angle velocity vs is supplied and at 20 and 21 once derived, so that the steering angular acceleration bl arises.

The embodiment of an observer 11.4 to 6 receives information about the steering angle acceleration from the motor angle sensor 10 whose size is wm at 18 to 21 is derived twice, whereupon the angular acceleration bm of the engine arises. However, since the correction quantity K is to be formed with the steering angular acceleration, the observer becomes 11.4 from a store 23 the reduction ratio 1: x read out. Thus, the moment of inertia Jl of the steering wheel becomes 24 multiplied. The result then becomes like the other observers with the multiplier 13 multiplied by the steering angular acceleration bs.

According to the embodiment 7 the observer gets 11.5 from a sensor 25 the speed of the engine dm, from the by at 20 . 21 the acceleration bm of the engine is derived. The reduction ratio of the transmission is as in the embodiment after 6 considered.

1

steering wheel

2

steering shaft

3

steering gear

4

Steering torque sensor

5

EPS basic support

6

EPS steering function

7

adder

8th

Motor controller

9

engine

10

Motor position sensor

11

observer

12

subtractor

13

multipliers

14

sensor

15

Storage

16

output

17

Steering angle sensor

18

delay

19

subtractor

20

delay

21

subtractor

22

sensor

23

Storage

24

multipliers

25

sensor

Claims (7)

Method for steering assistance in a vehicle with a steering wheel ( 1 ), a steering shaft ( 2 ) and a steering gear ( 3 ), one on the steering gear ( 3 ) acting engine ( 9 ) in response to a steering torque sensor ( 4 ) measured steering torque (Ms), characterized in that the measured steering torque (Ms) to one of an inertia (Jl) and a rotational acceleration (bs) of the steering wheel ( 1 ) Correction size (K) is reduced. A method according to claim 1, characterized in that the correction quantity (K) by multiplying an input variable with a stored moment of inertia (Jl) of the steering wheel ( 1 ) is formed. Method according to claim 2, characterized in that that the input quantity is the steering wheel acceleration (bs) is. Method according to claim 2, characterized in that that the input from a Steering angle is formed by two-fold derivative. A method according to claim 2, characterized in that the input variable by derivation from a rotational speed (vs) of the steering shaft ( 2 ) is formed. A method according to claim 2, characterized in that the input variable from a rotation angle (wm) of the motor ( 9 ) is gebil det by two-fold derivative and that in the correction value (K) multiplicatively a reduction ratio of the steering gear ( 3 ) received. A method according to claim 2, characterized in that the input variable by derivation of a rotational speed (dm) of the engine ( 9 ) is formed and that in the correction value (K) multiplicatively the reduction ratio of the steering gear ( 3 ) received.