Use of a power-steering motor to simulate an end-of-travel stop for said steering

Patent metadata

Field	Value
Publication number	US-9950735-B2
Application number	US-201414896296-A
Country	US
Kind code	B2
Filing date	Jun 3, 2014
Priority date	Jun 4, 2013
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

A method for managing a power-steering motor configured to supply a force to assist the movement of a steering rack involves the steering rack being mounted such as to be movable between at least a first position and a second position in order to be able to change the steering angle of a steered wheel. The method includes the steps of defining a virtual end-of-travel threshold strictly between the first position and the second position. If the rack is detected as having crossed the virtual end-of-travel threshold in a predetermined crossing direction, simulating, by the power-steering motor, an end-of-travel stop by including in the assistance instruction a resistance instruction that simulates the effect of a mechanical stop, such as a spring-damper or a mass-spring-damper, preventing the actuator member from progressing further beyond the virtual end-of-travel threshold.

First claim

The invention claimed is:

1. A method of managing a power-steering motor, during which an assistance setpoint (Ctot) is established for a power-steering motor for providing an assistance force (Assistance force) to assist in maneuvering a steering actuator member, of steering rack type, said actuator member being moveably mounted at least between a first position and a second position, distinct from each other, which delimit a functional travel of said actuator member such that the actuator member can modify an orientation angle of a steering effector member, of steered wheel type, the method includes the following steps:
a step (a) of defining a virtual end of travel threshold, during which at least one virtual end of travel threshold is chosen which corresponds to a fictional engaging position of the actuator member against a virtual stop, wherein said fictional engaging position strictly lies between the first position and the second position,
a step (b) of evaluating a position, during which an instantaneous position of the actuator member is evaluated and compared with the virtual end of travel threshold so as to detect a crossing of said virtual end of travel threshold by said actuator member, and, when it is detected that the actuator member has crossed said virtual end of travel threshold in a predetermined crossing direction,
a step (c) of simulating an end of travel stop during which is included in the assistance setpoint (Ctot) a resistance setpoint (Torque stop ) which simulates the effect of a mechanical stop by opposing to the progression, in a considered crossing direction of the actuator member beyond the virtual end of travel threshold,
wherein the resistance setpoint (Torque stop )is obtained

by an expression of the first order simulating a spring-damper stop and which comprises to this end an elastic component (F E =K P VRE ·X Rack ) simulating a spring effect, which is proportional, according to a predetermined stiffness coefficient (K P VRE ), to a displacement amplitude (X Rack ) of the actuator member beyond the virtual end of travel threshold and a viscous component (F V =K D VRE ·{dot over (X)} Rack ), simulating a damping force, which is proportional, according to a predetermined coefficient of viscosity (K D VRE ), to a displacement speed ({dot over (X)} Rack ) of the actuator member,
or by an expression of the second order simulating a mass-spring-damper stop and which comprises to this end an elastic component (F E ), a viscous component (F v ), and an inertial component (F 1 =K D2 VRE ·{umlaut over (X)} Rack ), simulating a moveable mass effect, which is proportional, according to a predetermined coefficient of inertia (K D2 VRE ), to an acceleration ({umlaut over (X)} Rack ), of the actuator member,
and wherein the virtual end of travel threshold and/or the coefficients of stiffness (K P VRE ), of viscosity (K D VRE ), and of inertia (K D2 VRE ), are modified according to at least one parameter selected from the group consisting of a speed of displacement (V v ) of a vehicle on which the power-steering motor is set, a torque (τ v ) exerted by a driver on a steering wheel which controls a displacement of the actuator member, the position (Pt, X rack ) of the actuator member, the speed ({dot over (X)} Rack ) of the actuator member, and the acceleration ({umlaut over (X)} Rack ) of the actuator member.

2. The method according to claim 1 , wherein when a speed of the vehicle exceeds a predetermined high speed threshold, a damping of the virtual stop is increased.

3. The method according to claim 1 , wherein the displacement of the actuator member being controlled by a steering wheel, the virtual end of travel threshold precedes by 30 degrees to 60 degrees, an extreme steering angular position of said steering wheel which corresponds to a mechanical displacement limit of the actuator member in a considered steering direction.

4. The method according to claim 1 , further comprising parameterizing the virtual end of travel threshold to use the power-steering motor to lock a the displacement of the steering actuator member in an invariable position, or restrict said displacement within a predetermined restraining range, less than 50%, the displacement range corresponding to the normal functional travel of said actuator member.

5. The method according to claim 4 , wherein an adjustment of the virtual stop corresponds to values of the coefficients of stiffness (K P VRE ), of viscosity (K D VRE ) and/or of inertia (K D2 VRE ), strictly higher than those used for the virtual stops implemented during normal driving.

6. The method according to claim 1 , further comprising adjusting a symmetry of a running gear of a vehicle including at least one effector member formed by a steered wheel, during which is set a first left virtual end of travel threshold and a second right virtual end of travel threshold such that the first virtual end of travel threshold and the second virtual end of travel threshold are located at equidistance on either side of a central median position which corresponds to an absence of turning of steered wheel(s) of the running gear.

Assignees

• Jtekt Europe Sas

Inventors

• Barthomeuf Julien
• Moulaire Pascal
• Pilaz Pierre-Willem

Classifications

• B62D5/0469 Primary

  End-of-stroke control · CPC title

• B60R25/02

  operating on the steering mechanism · CPC title