Design And Experiment Study Of Automotive Steering Wheel Speed Sensor

Steering wheel speed sensor is one of the key parts of Electro-Hydraulic Power Steering(EHPS)system, and the characteristic of EHPS system is much concerned with the output of the steering wheel speed sensor. An inductive steering wheel speed sensor was designed for the EHPS system.At first, EHPS system was introduced. Various steering wheel speed sensor around the world were analyzed and the inductive steering wheel speed sensor was decided to study. The eddy current field of the inductive steering wheel speed sensor was analyzed based on Ansoft Maxwell 3D. Design curves and magnetic field were represented, which provided basis for the design and machining of the sensor. Based on the sensor of Hella company, The structure of the sensor was analyzed and designed. Strip conductor structure and non-interleaved bend structure of the rotor and external structure of this sensor were designed.Secondly, the processing circuit of the sensor was analyzed, which includes signal detection circuit and oscillation circuit that produced the high frequent alternating current. The oscillator is LC capacitance feedback oscillation circuit. The inductance range of exciting coil when oscillator circuit operated stably was reached a conclusion, which is from2.8315μH to3.1886μH. And then, the principle of signal detection circuit was analyzed. The processing circuit and PCB were designed by Protel. Components were selected reasonably and parameter of the components was adjusted, which optimized the performance of the sensor.At last, an experimental device was designed, based on which, experiment of different rotors was carried on. 0.8mm thickness and 2.7mm space double layer annular stainless steel rotor was decided for this sensor. Copper and aluminum rotors were also appropriate for this sensor. The sensor calibration tests were completed. The result showed the precision of the sensor was±2.06%, which could satisfy the requirement of performance for EHPS system. High speed test was carried out then, the result showed that the linearity characteristic of the sensor was±2.05% when the high speed was 1350r/min, which showed the sensor can be used in high speed measure. And temperature test was done also. The linearity characteristic of the sensor was good between -40℃and 120℃.