DE102009004772A1 - Method for operating vehicle, involves adjusting sheer amplification by active rear axle steering system, where sheer amplification is adjusted by target steering angle of rear axle steering system - Google Patents

Abstract

The method involves adjusting a sheer amplification by an active rear axle steering system. The sheer amplification is adjusted by a target steering angle (beta-HA) of the rear axle steering system. The target steering angle is determined by the multiplication of a guide lateral acceleration (a-Y) with a change of the floating angle gradients (delta SG) in dependence of the driving speed (v-X).

Description

The The invention relates to a method for operating a vehicle the features of the preamble of claim 1.

From the publication DE 41 39 009 C2 a control device for a four-wheel steering system for a vehicle is known, which comprises adjusting devices for the front wheels and the rear wheels and generates control signals which act on the adjusting devices in accordance with predetermined steering laws. The specified steering laws are intended to allow influencing the yawing behavior and the lateral acceleration behavior of the vehicle with the aim to produce an optimal response with respect to the slip angle structure when hinging.

Another control device is known from the published patent application EP 0 150 856 B1 known, according to this control device, an auxiliary steering system is to be created, with the disturbances and influences, such as crosswind, can be better taken into account. In the control device, depending on the vehicle speed and the yaw rate and / or the lateral acceleration in accordance with a stored calculation rule, actuating signals for acting on a steering actuator for setting the front wheels are generated.

In the invention DE 198 13 945 C2 an approach is described, based on a determined from steering wheel angle and driving speed guide lateral acceleration set a defined stationary swimming behavior of the vehicle in the form of the specification of a target slip angle gradient.

Of the Invention is based on the object, an improved method to indicate a yaw gain setting.

The The object is achieved by a method solved with the features of claim 1.

preferred Embodiments and developments of the invention are in the dependent Claims specified.

at the inventive method for operating a Vehicle is the yaw gain through active rear axle steering set.

The Yaw reinforcement indicates with what yaw reaction a vehicle responds to adjusting a steering angle. By adjusting the yaw gain can thus be responsive Simply optimize steering movements.

When active rear axle steering is called a change a steering angle at a rear axle of the vehicle. The steering angle at the rear axle becomes in the same direction to a steering angle at a Front axle adjusted for greater stability of the vehicle and to achieve better directional stability. As well can the steering angle on the rear axle in opposite directions to the steering angle be adjusted at the front to ensure maneuverability of the vehicle to increase.

The Setting the yaw gain only by means of an active Rear axle steering leads to cost advantages compared to conventional overlay steering and / or Four-wheel steering.

in the Below is an embodiment of the invention based explained in more detail by drawings.

there demonstrate:

1 a schematic representation of a method according to the invention,

2 a diagram of a change of the Schwimmwinkelgradienten depending on a vehicle speed, and

three a diagram of a different yaw gain as a function of the vehicle speed.

each other corresponding parts are in all figures with the same reference numerals Mistake.

l_W = Lenkwinkel, i_GES = Gesamtlenkübersetzung der Vorderachse, v_X = Fahrgeschwindigkeit, EG_Passiv = Eigenlenkgradient des passiven Fahrzeugs, ΔSG = Änderung des Schwimmwinkelgradienten, l = Radstand 1 shows a schematic representation of a method according to the invention. The method is implemented in a control unit of a vehicle. The controller comprises a number of functional modules whose functions are described below. In a function module FG for reference variable determination, a guide lateral _acceleration a _{Y is} automatically determined according to the following formula:

l _W = steering angle, i _GES = total steering ratio of the front axle, v _X = driving speed, EG _Passive = self-steering gradient of the passive vehicle, ΔSG = change of the slip angle gradient, l = wheelbase

The Reference variable determination FG becomes for example automatically executed by a control unit.

The steering angle l _W is z. B. determined by means of a steering angle sensor to a steering column of the vehicle.

The overall steering ratio i _{GES of} the front axle is structurally determined and stored as a vehicle-dependent constant in a memory of the control unit.

The driving speed v _X is determined by means of a sensor, for. B. a Hall sensor or an inductive sensor, determined on a transmission or a wheel of the vehicle.

The self-steering gradient EC _{passive of} the passive vehicle is the self-steering gradient of the vehicle without activated rear-axle steering.

The change of the slip angle gradient .DELTA.SG is a default value and is stored as a characteristic in the control unit. This characteristic is speed-dependent and is determined in driving tests. 2 shows an example of such a speed-dependent characteristic.

By changing the float angle gradient .DELTA.SG, a change of the self-steering gradient EG _passive associated with the laws of driving physics is effected. By a speed-dependent change of the Schwimmwinkelgradienten ΔSG and thus the self-steering gradient EC _passive the yaw gain of the vehicle is adjusted.

Yaw reinforcement is the ratio between yaw rate and steering angle l _W.

Of the Wheelbase l of the vehicle is designed and construed as a constant Depending on the vehicle, stored in the control unit.

The determined lateral lateral acceleration a _Y can be displayed 2 be displayed visually in the vehicle interior.

In a further function module SL for the determination of the desired steering angle, a desired steering angle β _HA at the rear axle is determined according to the following formula: β HA = a Y · ΔSG (v X )

This determined target steering angle β _HA at the rear axle is then by means of an actuator 1 set at the rear axle of the vehicle.

In three the setting of the yaw gain is qualitatively mapped over the vehicle speed. There are two graphs three . 4 the different yaw amplifications of a vehicle without rear axle steering (= graph three ) and a vehicle with rear axle steering (= graph 4 ).

In the area below 100 km / h is on the vehicle 4 with rear axle steering a greater yaw gain compared to the vehicle three set without rear axle steering. This leads to agilization in the range below 100 km / h 6 the driving behavior, ie the vehicle responds more dynamically to steering movements.

In the range above 100 km / h is on the vehicle 4 with rear axle steering a smaller yaw gain compared to the vehicle three set without rear axle steering. This leads to stabilization in the range above 100 km / h 5 the driving behavior, ie the vehicle has an improved straight-line stability.

The Speed limit of 100 km / h was merely exemplary is chosen and is also dependent on one Vehicle type and / or a preferred driving behavior predetermined.

FG

function module for reference variable determination

SL

function module for target steering angle determination

l _W

steering angle

v _X

driving speed

ΔSG

modification the float angle gradient

β _HA

Target steering angle at the rear axle

l

wheelbase

i _GES

Overall steering ratio the front axle

EC _Passive

self-steering gradient of the passive vehicle

_aY

Leadership lateral acceleration

1

actuator

2

display

3

graph the yaw reinforcement of a vehicle without rear axle steering

4

graph the yaw reinforcement of a vehicle with rear axle steering

5

stabilization

6

Agilisierung

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 4139009 C2 [0002]
• - EP 0150856 B1 [0003]
• - DE 19813945 C2 [0004]

Claims (5)

A method of operating a vehicle, characterized in that the yaw gain is adjusted by an active rear axle steering. A method according to claim 1, characterized in that the yaw gain by means of a desired steering angle (β _HA ) of the rear axle steering is adjusted. A method according to claim 2, characterized in that the target steering angle (β _HA ) by multiplying a Führungsquerbeschleunigung (a _Y ) with a change of a Schwimmwinkelgradienten (.DELTA.SG) depending on a vehicle speed (v _X ) is determined. Method according to claim 3, characterized that the change of the slip angle gradient (ΔSG) determined from a speed-dependent characteristic becomes. Method according to Claim 3 or 4, characterized in that the lateral lateral acceleration (a _Y ) is determined according to:

is determined.