Design of Non-Contact Torque Sensor for Electric Power Steering System

It is important to make a reliable and precise measurement about the torque on the steering wheel in an electric power steering system (hereinafter EPS system), thus a non-contact photoelectric torque sensor has been developed, which converts the torque exerted on the steering wheel into an output voltage and works as a “photo potentiometer”. The torque sensor is composed of a torsion bar which is built into the steering shaft and converts the torque into angular displacement, a slider which changes angular displacement into linear displacement, and a “photo potentiometer” which switches the linear displacement into an output voltage. Inside the “photo potentiometer”, a light emitter attached to the pivot, two photo cells fixed on the housing, and an IC amplifier are adopted. The working principle and the structure of this “photo potentiometer” are proposed in detail, some tests are performed and the test results are given out and analyzed.