Development of a Contactless Hall Effect Torque Sensor for Electric Power Steering

Abstract

In this paper, we will present an innovative torque sensor design which could be preferably used in Electric Power Assisted Steering (EPAS) application. This torque sensor is a non-contact Hall effect design. The specificity of this structure is its ability to measure the shift angle between two rotating shafts linked by a torsion bar. This measurement is done with stationary electronic components. This unique structure generates enough magnetic flux variation to measure angular shifts from +/-1° to +/-8° with low-cost standard Hall ASICs available from various suppliers. This torque sensor has convinced automotive industry due to its good performances, its compact dimension and a price compatible with the market expectation for this application. This paper will explain the basic magnetic principle of this torque sensor, the improvements which have lead to a structure compatible with automotive industry requirements, some measurement results and possible sensor integration in the application.