Electric power steering control

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.

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.