The FlexRay Implementation of By-Wire System for Electric Vehicle

In the recent years, advanced technologies of electronic devices for the communication and computer engineering have been considered to be widely implemented in the vehicle systems. Among those possible applications, the automotive network which is so-called “X-by-Wire” scheme has been developed for steering control and braking control of the vehicles. It is known that the weight reduction of vehicle systems can decrease the power consumption in the design of electric driven vehicle by replacing the mechanical components with electronic devices. Therefore, X-by-wire system combined with fault-tolerant applications will be a trend in the automotive industry. Under the automotive circumstance, the timetrigged protocol improves the network capacity and guarantees the transmission of all safety related message. In order to ensure the safety of electronic devices, an advanced networking protocol FlexRay has been recently proposed to the design of X-by-wire system. In this paper, such an X-by-wire mechanism is developed for electric vehicle. The proposed design covers the development of a hub wheel motor driven electric vehicle and the design of both electronic control braking module and communication network. For facilitating the application usage, a FlexRay communication node is developed by using microprocessor chip Freescale MC9S12XF512. An electric vehicle is also designed by using four hub wheel type AC motors with DC motor driven braking mechanism for system testing and performance evaluation. A timescheduling scheme is proposed and configured for each of nine FlexRay nodes to fulfil the tasks of driveby-wire and brake-by-wire operations. Experimental results demonstrate the success of the proposed design.