Design Of Capacitive Torque Sensor And Research Of Electric Power Steering System

Owning to the development of intelligent control of automotive electronics, Electric Power Steering System (EPS) has replaced the Mechanical Steering System (MS) in automobile steering applications. As the core component of EPS, torque sensor represents high precision technology of EPS. The invention of a practical torque sensor is of great significance to the improvement of state-owned automobile technology.This thesis focuses on the design of a differential capacitive torque sensor and the performance test with a corresponding system. The main contents of this thesis are as follows:1) The development status and trend of power steering system and torque sensor are introduced.2) The analysis, design and manufacture of torque sensor are given. Two related patents about torque sensor are introduced. The advantages and disadvantages of my design are analyzed by the comparison with these two patents.3) My system architecture is put forward based on the study on EPS. With the circuit simulations and result analysis, the differential pulse width modulation circuit is selected as the C-V conversion circuit. Two test schemes are proposed for the detection of voltage signals after conversion.4) Reasonable devices are selected to implement the hardware design.5) Software design is carried out for the two test schemes.6) The test results and analysis of the two test schemes are given by the software and hardware joint debugging. Two conclusions are obtained through the analysis. Firstly, the design of capacitive torque sensor meets the design requirements. Secondly, the test scheme one is better than the test scheme two.The innovation of this thesis lies on the design of a differential capacitive torque sensor and a series of detections of the weak sensor capacitance signal. The patent application of the torque sensor design has been submitted.