Research Of The Sensor In Vehicle Electric Power Steering (EPS) System

In the Electric Power Steering (EPS) system, the dynamic parameters are necessary for ECU to implement the control. These parameters mainly includes steering torque,absolute angular position of the steering wheel and steering direction, which are very important for ECU. So, the sensors to get these parameters are crucial for EPS system. Because the sensors are used in vehicle, so they have to meet the demand of working environmental,costs and stability. It's the reason people keep researching and renewing the sensors in vehicle. With the development of MCU and the need of high performance sensor, intelligent sensor is the trend of the future sensor development, which has many advantages, such as easy to design and renew, high stability. The sensor described in this article has a MCU.This article has studied various methods to measure torque. Using the new angle sensor chip, we build a non-contact, smart sensor ,which can detect steering torque,absolute angular position of wheel and steering direction. First, we introduce the torsion measure principle and the angle sensor chip-TLE5011, which transform the mechanical quantity into electrical quantity. Then, we fix on the method of steering parameter measure, according to the steering characteristic and the angle sensor chip performance. The method is getting the torque by measure the torsional deflection, Using the principle of vernier caliper to measure the absolute angular position of wheel, the steering direction and speed can be computed in the MCU. In the end we bring forward the structure design plan,according to the method been fixed. The sensor system has three TLE5011 chips, IC1,IC2,IC3。There is a rotation difference between IC1 and IC2, because of the torque. There is also a rotation difference between IC1 and IC3, because of the different transmission ratio. By analysis, the relationship can be set up, between the difference with the torque and the difference with the steering angle. Finally, the steering parameter can be measured by three angle sensor chip. The sensor system includes mechanism, circuit and the software.