Patent ID: 6845309

Claim:
A power steering system for a vehicle, comprising: a steering system having an assist mechanism with at least one motor for power steering; a sensor for sensing at least one of a steering angle and a steering torque by a driver of the vehicle; and at least one controller for receiving inputs from the sensors and from the motor for calculating an output torque of the assist mechanism and for comparing said output with the steering torque, wherein the at least one controller uses an algorithm to calculate the output torque by the assist mechanism and determines whether a relationship between the steering wheel torque and the assist mechanism torque is within acceptable bounds; and wherein the at least one controller uses an algorithm for calculating motor assist torque, wherein torque equals sqrt (⅔) * Kt 2 *[I a *sin(Θ)+ I b *sin (Θ−2π/3)+ I c *sin (Θ+2π/3)], where Kt2 is a constant factor for a particular motor, I a , I b and I c are motor phase currents, and Θ is a rotor mechanical angle times a number of pole pairs of the motor.