Electric power steering control

• US 5,668,722 A
• Filed: 10/02/1995
• Issued: 09/16/1997
• Est. Priority Date: 10/02/1995
• Status: Expired due to Term

• Current Assignee: GM Global Technology Operations Incorporated (General Motors Company), Steering Solutions IP Holding Corporation (Nexteer Automotive Group Ltd.)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Collier-Hallman, Steven James, Chandy, Ashok, Kaufmann, Timothy Wesley
• Primary Examiner(s): Chin, Gary
• Application Number:
  US08/537,605
• Time in Patent Office: 715 Days
• Field of Search: 364/424.051, 364/424.052, 180/412, 180/413, 180/421, 180/422, 180/443, 180/446
• US Class Current: 701/41
• CPC Class Codes: B62D 5/0466 for returning the steering wheel to neutral position

Abstract

An electric power steering control apparatus comprising a torque sensor coupled to a vehicle steering system for measuring steering wheel torque provided by a vehicle operator, a steering angle sensor coupled to the steering system for measuring steering wheel angle, a controller, responsive to the measured steering wheel torque and a vehicle speed, providing a sum return-to-center command, and a motor responsive to the sum return-to-center command, wherein the controller determines a low speed return-to-center command responsive to the measured steering wheel torque and a first predetermined function, determines a high speed return-to-center command responsive to the measured steering wheel torque and a second predetermined function and blends the low and high speed return-to-center commands to obtain the sum return-to-center command.

Claims

1. An electric power steering control, according to the steps of:

measuring steering wheel torque;

measuring steering wheel angle;

measuring vehicle speed;

responsive to the measured steering wheel torque and vehicle speed, determining a power assist command;

determining a low vehicle speed return-to-center command responsive to the measured steering wheel angle and a first predetermined function;

determining a high vehicle speed return-to-center command responsive to the measured steering wheel angle and a second predetermined function; and

blending the low and high vehicle speed return-to-center commands responsive to the vehicle speed to determine a sum return-to-center command

subtracting the sum return-to-center command from the power assist command to obtain a motor command; and

commanding a power assist motor responsive to the motor command.

2. An electric power steering control according to claim 1, wherein the step of blending comprises the sub-steps of:

determining, responsive to the vehicle speed, a blend signal in a normalized range between 0 and 1;

multiplying the blend signal by the low vehicle speed return-to-center command to determine a first fractional component signal;

multiplying a quantity (1--the blend signal) by the high vehicle speed return-to-center command to determine a second fractional component signal;

summing the first and second fractional component signals to determine the sum return-to-center command.

3. The electric power steering control of claim 1, also comprising the step of ramping out the sum return-to-center command when the vehicle speed is below a break speed.

4. An electric power steering control apparatus comprising:

a torque sensor coupled to a vehicle steering system for measuring steering wheel torque provided by a vehicle operator;

a steering angle sensor coupled to the steering system for measuring steering wheel angle;

a controller, responsive to the measured steering wheel torque and a vehicle speed signal, providing a sum return-to-center command; and

a motor responsive to the sum return-to-center command to provide power assist to the steering system, wherein the controller comprises

means for determining a low speed return-to-center command,

means for determining a high speed return-to-center command,

means for blending the low and high speed return-to-center commands to obtain the sum return-to-center command,

a high resolution filter comprising a high gain amplification stage and a low pass filter stage, wherein the high resolution filter receives the vehicle speed signal and provides a high resolution filtered speed signal responsive thereto, and

means for ramping out the sum return-to-center command when the high resolution filtered speed signal is below a break speed.

5. An electric power steering control apparatus comprising:

a torque sensor coupled to a vehicle steering system for measuring steering wheel torque provided by a vehicle operator;

a steering angle sensor coupled to the steering system for measuring steering wheel angle;

a controller, responsive to the measured steering wheel torque and a vehicle speed, providing a sum return-to-center command; and

a motor responsive to the sum return-to-center command to provide power assist to the steering system, wherein the controller comprises

means for determining a low speed return-to-center command,

means for determining a high speed return-to-center command, and

means for blending the low and high speed return-to-center commands to obtain the sum return-to-center command.