Key Technologies Research Of Electric Power Steering System Based On CAN Bus

Electric power steering(EPS) is a new technology for improving the convenience and security of steering. It can make the driver offset part of the steering resistance in low speed and static state by means of motor power just with a smaller force. While when at a high speed, increase steering resistance improves the safety of steering. In addition, with the development of automobile electronic communication technology and CAN bus technology, the development of electric power steering system has opened up a new direction. Therefore, the EPS system must support the CAN communication protocol for realizing the linkage with other vehicle electronic control system, in order to better play its power characteristics and improve the driveing safety of automobile. Therefore, it is vary important to support the development of CAN communication technology.EPS system designed in this thesis is based on the existing electric power technology, which is mainly consist of five modules: the automobile speed acquisition module, steering car wheel angle collection module, electric control module,assisted motor execution module and slave computer module. The above modules are connected together by two CAN bus and a CAN gateway. Automobile speed acquisition module and steering wheel angle acquisition module is used for collecting vehicle speed, steering wheel angle and then send the data to the CAN bus. And the electric control and power assisted motor execution module are responsible for transferring speed and direction wheel angle information on the CAN bus according to the control strategy and the PID control algorithm, which control the drive power steering motor running. Besides the lower computer console module is responsible for assistting the host computer module debugging and monitoring of electric assisted motor control and execution module, and fault detection of the whole system and the running log backup system.Compared with other steering system, paper adopt Embedded uC/OS-II system and FATFS file system as the running platform for the main control module, which makes the system has strong scalability and debugging ability, file storage and backup function providing space for the development of the reference data for the application of EPS system upgrade later. In addition, each module designed in this paper using two CAN bus communication improve the security and stability of the bus communication system.The main content of the work: Study automobile electric power steering system model and control strategy with feedback control algorithm; Finishing the hardware design of the speed collection module, handwheel angle collection module, electric control and assisted motor module, the slave computer module, and the transplantation of embedded C/OS-II system and FATFS file system; Write applications in each module to complete the function.The test answer of illustrate that, the system meet the requirements of designed, in which the system voltage range is 9-16 v, the assisted motor’s minimum torque output is 0.1Nm, time of response less than 180 ms.