Electric power steering torque compensation

Patent metadata

Field	Value
Publication number	US-11014606-B2
Application number	US-202016776422-A
Country	US
Kind code	B2
Filing date	Jan 29, 2020
Priority date	Jan 29, 2019
Publication date	May 25, 2021
Grant date	May 25, 2021

Abstract

Among other things, we describe techniques for electric power steering torque compensation. Techniques are provided for a method implemented by a computer, e.g., a computer onboard an autonomous vehicle. A planning circuit onboard the vehicle and connected to an EPS of the vehicle determines a compensatory torque signal to modify an actual steering angle of a steering wheel of the vehicle to match an expected steering angle of the steering wheel. The planning circuit transmits the compensatory torque signal to a control circuit that controls the steering angle of the steering wheel. The EPS modifies the actual steering angle based on the compensatory torque signal resulting in a modified steering angle. The control circuit operates the vehicle based on the modified steering angle.

First claim

What is claimed is:

1. A computer-implemented method comprising:
determining, by a planning circuit onboard a vehicle and connected to an electric power steering (EPS) system of the vehicle, a compensatory torque signal to modify an actual steering angle of a steering wheel of the vehicle to match an expected steering angle of the steering wheel;
transmitting, by the planning circuit and to a control circuit, a base torque signal that applies a torque on the steering wheel;
modifying the base torque signal in accordance with the compensatory torque signal, wherein at least one of the compensatory torque signal or the base torque signal is a voltage;
transmitting, by the planning circuit, the compensatory torque signal to the control circuit that controls the steering angle of the steering wheel;
modifying, by the EPS system, the actual steering angle based on the compensatory torque signal resulting in a modified steering angle; and
operating, using the control circuit, the vehicle based on the modified steering angle characterized in that the method comprises:
generating a plurality of compensatory torque signals, each generated compensatory torque signal comprising a respective torque signal to transmit to the EPS system for applying a torque to the steering wheel, wherein generating the plurality of compensatory torque signals comprises, for each generated compensatory torque signal:
determining an expected steering angle of the steering wheel for the respective torque signal;
applying the respective torque signal to the EPS system, resulting in a steering angle;
operating the vehicle at the steering angle at a pre-determined speed;
determining an actual steering angle of the steering wheel for the respective torque signal; and
storing the generated compensatory torque signal and the actual steering angle as a data pair.

2. The method of claim 1 , wherein modifying the base torque signal in accordance with the compensatory torque signal comprises adding a magnitude of the compensatory torque signal to a magnitude of the base torque signal.

3. The method of claim 1 , wherein the compensatory torque signal is transmitted to the control circuit as a feedforward signal.

4. The method of claim 1 , wherein determining the expected steering angle of the steering wheel for the respective torque signal comprises curve fitting a polynomial surface that relates vehicle speed and steering angle to applied torque.

5. The method of claim 1 , further comprising:
determining a difference between the expected steering angle and the actual steering angle; and
in accordance with a determination that the difference exceeds a predetermined threshold, operating the vehicle to a target location.

6. The method of claim 1 , further comprising:
determining, by the planning circuit, operating conditions of the vehicle; and
modifying the compensatory torque signal according to the operating conditions.

7. The method of claim 6 , wherein the compensatory torque signal is modified according to the operating conditions in real-time.

8. The method of claim 6 , wherein the operating conditions comprise weather conditions in which the vehicle is operated.

9. The method of claim 6 , wherein the operating conditions comprise road conditions on which the vehicle is driven.

10. The method of claim 6 , wherein the operating conditions comprise load carried by the vehicle.

11. The method of claim 6 , wherein the operating conditions comprise driving conditions stored by the planning circuit in a passenger profile comprising driving preferences of one or more passengers of the vehicle.

12. The method of claim 6 , further comprising receiving, by the planning circuit, an instruction to modify the compensatory torque signal from a remote location remote to the vehicle, wherein the compensatory torque signal is modified in response to receiving the instruction from the remote location.

13. A vehicle comprising:
a planning circuit;
memory; and
at least one program stored in the memory, the at least one program including instructions executable by the planning circuit to perform the method of claim 1 .

14. A non-transitory computer-readable storage medium comprising at least one program for execution by a planning circuit of a vehicle, the at least one program including instructions which, when executed by the planning circuit, cause the vehicle to perform the method of claim 1 .

Assignees

• Motional Ad Llc

Inventors

• Wu Ning
• Andersen Hans
• Seccamonte Francesco

Classifications

• B60W2556/45

  External transmission of data to or from the vehicle · CPC title

• B60W2050/0075

  Automatic parameter input, automatic initialising or calibrating means · CPC title

• B62D15/025 Primary

  Active steering aids, e.g. helping the driver by actively influencing the steering system after environment evaluation (B62D1/28 takes precedence) · CPC title

• B62D5/0463

  calculating assisting torque from the motor based on driver input · CPC title

• B60W2050/0024

  Variable gains · CPC title