SECURING OF A DRIVING ASSISTANCE FUNCTION WITHIN A POWER STEERING

• US 20170282972A1
• Filed: 10/01/2015
• Published: 10/05/2017
• Est. Priority Date: 10/07/2014
• Status: Active Grant

• Current Assignee: Jtekt Europe (Toyota Motor Corporation)
• Original Assignee: Jtekt Europe (Toyota Motor Corporation)
• Inventors: MORETTI, Romain
• Granted Patent: US 10,407,096 B2
• Time in Patent Office: Days
• CPC Class Codes: A01B 69/00 Steering of agricultural machines or implements; Guiding agricultural machines or implements on a desired track
• CPC Class Codes: B60T 7/12 for automatic initiation; for initiation not subject to will of driver or passenger limiting speed of vehicles other than rail vehicles B60K31/00
• CPC Class Codes: B60T 8/1755 Brake regulation specially adapted to control the stability of the vehicle, e.g. taking into account yaw rate or transverse acceleration in a curve road vehicle drive control systems for control of driving stability otherwise than by controlling a particular sub-unit B60W30/02
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 30/02 Control of vehicle driving stability
• CPC Class Codes: B60W 50/04 Monitoring the functioning of the control system
• CPC Class Codes: B62D 15/025 Active steering aids, e.g. helping the driver by actively influencing the steering system after environment evaluation B62D1/28 takes precedence
• CPC Class Codes: B62D 15/0265 Automatic obstacle avoidance by steering
• CPC Class Codes: B62D 5/04 electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
• CPC Class Codes: B62D 5/0406 including housing for electronic control unit
• CPC Class Codes: B62D 5/046 Controlling the motor
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input
• CPC Class Codes: B62D 5/0472 for damping vibrations
• CPC Class Codes: B62D 5/0481 monitoring the steering system, e.g. failures
• CPC Class Codes: B62D 6/00 Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits means for initiating a change in direction B62D1/00; steering valves B62D5/06; combined with means for inclining the vehicle body or wheels on bends B62D9/00
• CPC Class Codes: G06F 17/00 Digital computing or data processing equipment or methods, specially adapted for specific functions information retrieval, database structures or file system structures therefor G06F16/00

Abstract

A method of controlling a power steering system including at least one course control function, whereby a position setpoint is determined automatically according to a reference course that a vehicle is to be made to follow, then a motor setpoint applied to an assistance motor is adjusted accordingly, the method including a safety function which is distinct from the course control function and meets a higher ASIL safety level according to ISO-26262 standard, said safety function including a diagnostics subfunction according to which a control parameter such as the angular position of the steering wheel, the driver torque applied to the steering wheel, or the rate at which the steering wheel is turned is monitored in order to detect the onset of an alert situation considered to be hazardous, then an intervention subfunction according to which, if an alert situation is detected, the course control function is neutralized.

Claims

1. A method for managing a power steering of a vehicle comprising at least one path control function, according to which a motor setpoint is automatically adjusted and applied to an assist motor of the power steering so that the vehicle automatically follows an actual path which is close to, or which coincides with, a reference path that the vehicle is desired to follow, the method comprising a securing function, distinct from the path control function and which meets an ASIL safety level higher than said path control function according to the safety standard ISO-26262,the securing function comprising a diagnosis sub-function according to which is monitored a control parameter, representative of the behavior of the vehicle, in order to detect, by comparison of the control parameter with a predetermined alert threshold, the occurrence of a predefined alert situation, considered as dangerous, the securing function comprising afterwards an intervention sub-function according to which, in case of detection of an alert situation, the moderation and/or the neutralization of the path control function is forced.

2. The method according to claim 1, wherein the diagnosis sub-function includes a comparative analysis step, during which the instantaneous value of the control parameter is compared with the predetermined alert threshold, and then a validation step during which is assessed, in case of a crossing of the alert threshold, the holding duration during which the control parameter is kept above the alert threshold, and the occurrence of an alert situation is concluded if the holding duration exceeds a predetermined duration threshold.

3. The method according to claim 2, wherein the validation step uses an incremental counter whose increment step is adapted depending on the rotational speed of the steering wheel.

4. The method according to claim 1, wherein the intervention sub-function constitutes a neutralization sub-function according to which the path control function is neutralized if an alert situation is detected by the diagnosis sub-function, so as to deprive the path control function of any influence on the determination of the motor setpoint.

5. The method according to claim 1, wherein the securing function comprises a driver torque permanent restricting sun-function, distinct from the diagnosis sub-function and from the intervention sub-function, and which acts in parallel with the diagnosis and intervention sub-functions, by dynamically adjusting a weighting coefficient that it applies to the path control function so as to permanently keep the driver torque, which is effectively felt by the driver at the steering wheel, below an admissible maximum driver torque.

6. The method according to claim 1, wherein the securing function includes an adaptive filtering sub-function according to which a low-pass filter is activated and applied to the control parameter in order to reduce the noise therefrom, when the control parameter is in a range of values, called critical range, predefined in the vicinity of the alert threshold, and on the contrary, the low-pass filter is deactivated when the control parameter is outside the critical range.

7. The method according to claim 1, wherein the alert threshold of the securing function is adjusted according to the linear speed of the vehicle.

8. The method according to claim 1, wherein the alert threshold of the securing function is adjusted according to the driver torque exerted by the driver on the steering wheel.

9. The method according to claim 8, wherein the securing function comprises a prolongation sub-function, intended to virtually prolong a held steering wheel state, wherein the prolongation sub-function is activated when an increase, in absolute value, of the driver torque is perceived, and is deactivated when a decrease, in absolute value, of the driver torque is perceived, and according to which, when the prolongation sub-function is in its activated state, taking into consideration the measured value of the driver torque for adjusting the alert threshold of the securing function is delayed, so as to delay, for a predetermined prolongation duration after a release of the steering wheel, the modification of the alert threshold.

10. A module for managing a power steering comprising a path control branch which includes a position setpoint determination unit for defining a reference path that the vehicle is desired to follow, a follower unit which calculates the deviation between the actual path of the vehicle and the reference path in order to output an adjustment setpoint which is used at the input of a motor setpoint calculation unit which in turn emits a motor setpoint toward an assist motor, so that the adjustment setpoint could be taken into consideration for adjusting the motor setpoint applied to the assist motor in order to reduce the deviation between the actual path of the vehicle and the reference path, the management module comprising a securing branch, forming a ramification which is distinct from the path control branch and the ASIL safety level of which is higher than the ASIL safety level of said path control branch according to the safety standard ISO-26262, the securing branch comprising a diagnosis unit which receives at the input a control parameter, representative of the vehicle behavior, a measurement or an estimate of the driver torque exerted by the driver on the steering wheel, or a measurement or an estimate of the angular rotational speed of the steering wheel, and which compares the control parameter with a predetermined alert threshold, in order to detect a predefined alert situation, considered as dangerous, and which transmits, in case of detection of an alert situation, a trigger signal to an intervention unit interposed on the connection branch which links the output of the follower unit to the input of the motor setpoint calculation unit, so as to force the reduction or even the cancelling of the adjustment setpoint by opening of the connection branch.

11. The power steering management module according to claim 10, wherein the path control branch includes a position setpoint determination unit for defining a position setpoint of the power steering from the reference path that the vehicle is desired to follow, a follower unit which calculates the deviation between the effective position of the steering and the position setpoint in order to output an adjustment setpoint which is used at the input of a motor setpoint calculation unit which in turn emits a motor setpoint toward an assist motor, so that the adjustment setpoint could be taken into consideration to adjust the motor setpoint applied to the assist motor in order to reduce the deviation between the effective position of the power steering and the position setpoint.