The Research And Development Of Steering Wheel Angle Sensor With CAN Bus

In Adaptive Front-lighting System, Electronic Control Unit requires some dynamic parameters of the steering wheel, such as the rotation direction, the angle, the angular velocity, et cetera. These dynamic parameters are key information for the AFS. Because of the vehicle-mounted sensors have high requirement on measurement stability, production costs and other factors. And with the emergence of smart sensors, the traditional angle sensors are more and more difficult to meets these requirements. Micro Control Units are usually integrated in smart sensors, so that smart sensors can have more functionality, more easy to use, easy to update and other advantages.Based on the research of the movement of car and steering wheel, a new type method of steering wheel angle measuring was proposed in this paper. It was a new type of non-contact way to measure the steering wheel angular velocity and angle. The principle of the method was using the angular velocity of car and steering wheel in the earth reference system to calculate the angular velocity and angle of the steering wheel relative to car. The composition of the steering wheel angle measuring system was designed according to the measuring method. The design implemented a new type of steering wheel Angle sensor, which integrated C8051F040 MCU and became an intelligent sensing detection system. MEMS gyroscope chip L3G4200D was the core device of the system and Hall device A3144 was used to revise measuring error. The MCU collects angular velocity signals from two L3G4200D. The angular velocity and angle data of steering wheel can be calculated by data processing and numerical integration. The Hall element angular correction module integrated in the system can remove effectively the drift error of gyro. The system sent angular velocity and angle data of the steering wheel real time through CAN communication interface.The development of the work included hardware and software. The hardware part mainly include the MCU minimum system, MEMS gyroscope circuit, Hall element circuit, CAN communication interface and power supply circuit, etc. As to software, the method of modular design, enhance the readability of program. The entire program consists of some subroutine modules, the main program only responsible for scheduling the subroutine to complete each part of the work. The subroutine include system initialization, data acquisition, digital filtering algorithm, numerical integration algorithm, the angle correction method, the CAN interface driver, etc. Finally, the contrast experiment and AFS test was carried out. The result showed that the designed sensor has reasonable accuracy, high measurement range, simple structure and stable performance. And the angle sensor can work normally in the CAN network of AFS test bench.