Method and apparatus for thermal management of an electric power assist steering control system by compensating steering motor current

A vehicle steering system of the type including an electric motor actuator, a motor driver circuit for generating and applying a motor current to the electric motor actuator, a current sensor for measuring the motor current from the motor driver circuit and generating a feedback signal, a torque sensor for sensing an applied steering torque and providing a torque command signal having a value indicative of the applied steering torque, said steering system comprising:

• a controller for calculating a temperature of the electric motor actuator by evaluating the motor current applied to the electric motor actuator and generating a temperature signal and having a temperature reduction factor which correlates to the temperature signal for reducing the motor current and the controller for providing a control signal to the motor driver circuit based on the feedback current signal and the torque command signal wherein the motor current is reduced by the temperature reduction factor when the temperature of the electric motor actuator is determined by the controller to be greater than a predetermined temperature.