Devolepment Of Non-Contacting Steering Torque And Angle Sensor

With the rapid development of the automotive industry, increasing numbers of automotive electronics and electric equipment are applied in vehicles. Because of the advantage of energy saving, compact structure and flexibility, electric power steering system (EPS) is widely used in passenger cars. The steering sensors are important part of the EPS, which provide the driver’s steering torque and the steering angle signals to EPS. Meanwhile, the electronic stability program (ESP) and other electronic control systems also need the steering angle signal shared by the steering sensor to act as the basis for identifying the driving intention. The central purpose of this paper is to develop a simple and inexpensive torque and angle integrated steering sensor with moderate accuracy and stable performance.Firstly, this paper introduces several sophisticated solutions, both domestic and foreign, to summarize the signal processing method in steering torque measurement and steering angle measurement. After that, this paper discusses the trends of the steering sensors and puts forward overall design goals base on the trends. Combing with the analysis results of demand for angle and torque measurement, the steering torque measurement solution based on multi-pole magnet and angle measurement solution was proposed. The overall structure of the integrated solution is given subsequently.Secondly, based on the finite element analysis to the field distribution around the multi-pole magnet, the paper interprets the relationship between steering torque and magnetic field angle. Then, the hardware solution of torque measurement based on magnetic angle sensor KMA220is proposed. The signal conversion and calibration methods are designed according to the input-output relationship between the deformation of the torsion bar and outputs of KMA220.Angle measurement solution of intergrated sensor contains a gear transmission structure with three gears. This paper expounds the basic operation principle of angle measurement based on the relationship between the transmissions of gear set, and proposes the hardware solution of angle measurement based on magnetic angle sensor KMZ60. According to the input-output characteristics of KMZ60, this paper establishes the compensation method for outputs of KMZ60. The compensated signals are used to calculate the angles of gears wtih CORDIC algorithm, then the steering angle is calculated relying on the angle of gears.Finally, this paper uses the steering sensor testing platform as a testing tool to test the static characteristics of integrated steering sensor using specific algorithms. The experimental results show that the integrated steering sensor is stable, moderately accurate, and its performance can basically meets the requirements of EPS.