Module, Electric Power Steering (EPS): Operation

The Electric Power Steering (EPS) module uses input signals received from sensors to vary the 12 volt current to the electric motor for the desired power steering torque. The boost or assist is variable and speed sensitive, responding to sensors monitoring steering torque, steering wheel speed, angle, and vehicle speed. The steering system is fully integrated with the vehicle's Electronic Stability Control (ESC) system and helps to compensate in split-traction, torque steer, and pull-drift (crowned road) situations. Communication is received and transmitted to the EPS module on the Controller Area Network (CAN) line.

The EPS module outputs the following actions based on input received:

• Basic Operation:  Based on vehicle speed, assists the column rotation based on driver input to decrease steering effort.
• Variable Servo Steering:  As vehicle speed increases, the module reduces the amount of assistance to the column.
• Active Return:  The EPS module commands the motor to assist the steering wheel in returning to the center position.
• Damping of Steering Return Oscillations:  After a steering maneuver, the chassis may produce steering wheel oscillation. The EPS module uses the electric motor to help dampen these oscillations.
• Selectable Power Assistance:  Instrument panel driver selectable modes vary the level of power steering assistance in three ways:
  1. "Comfort" provides a balance of steering feel and steering effort
  2. "Normal" increases steering feel and effort by one level
  3. "Sport" provides the greatest amount of steering feel and requires the highest steering effort.