Vehicle electric power assist steering system and method using angle based torque estimation

A control system for controlling electric motor torque assist to an electric power assisted steering system for a vehicle having a steering assembly including a steering wheel connected to a steering column and an electric motor operatively engaged with the steering assembly for supplying steering torque assist, wherein said control system comprises:

• a steering angle sensor for sensing an angular position of the steering assembly;
• a torque estimator for estimating a torque signal as a function of said sensed angular position of the steering assembly, wherein the steering system does not include a torque sensor;
• and
• a controller for generating a motor control signal as a function of said estimated torque for controlling the electric motor.

A method of controlling an electric power assisted steering system having a steering assembly including a steering wheel connected to a steering column for a vehicle, and wherein said steering system does not include a torque sensor, said method comprising the steps of:

• sensing an angular position of the steering assembly;
• estimating a torque signal as a function of said sensed angular position of the steering assembly;
• generating a motor control signal as a function of said estimated torque for controlling an electric motor;
• and
• applying said motor control signal to an electric motor to generate a controlled amount of steering torque assist.