F2008-05-074
Development of the High Speed Distributed Control System Based on FlexRay: The Independent Steer-By-Wire System
The advanced technology in automotive electronics will enable to make more comfortable, more convenient and safer vehicle. This can be achieved by the proper communication between several ECUs in the vehicle. The Controller Area Network (CAN) which has developed by Bosch was the main communication protocol for the automotive industry in 1990s. But now they focus on the FlexRay communication for future in-vehicle network system.
The joint development of the "FlexRay" standard by BMW, Daimler, Motorola and Philips started in 2000 to fulfill the requirements for future in-vehicle control applications include the combination of higher data rates, deterministic behavior and the support of fault tolerance. The FlexRay is a time-triggered communication system for high performance in-vehicle applications. It supports both synchronous and asynchronous data transmission to achieve the benefits of the familiar synchronous and asynchronous protocols like as CAN. It supports the dual channel for fault tolerant and extension of bandwidth and data rates of up to 10 Mbps per one channel. The FlexRay protocol also supports fault-tolerant clock synchronization algorithm via a global time base which are generated automatically in the FlexRay communication controller. These properties open the possibility for controlling the high speed distributed control system. Especially it is required by advance safety vehicle like as x-by-wire. It will enable to communicate with several ECUs within same time zone in milliseconds period.
We applied the FlexRay protocol to the independent steer-by-wire system which is actuated by two disconnected front wheel actuators. Each actuator includes two motors, and each motor is controlled by one ECU. There are 5 ECUs to control the independent steer-by-wire system. They are connected with FlexRay communication network, and controlled every 1ms period in same time based on global time which was generated by FlexRay communication controller. It is enhanced by the network management vector which is configured in FlexRay static frame for fault tolerant of the SBW. So we could achieve the fast recovery function from failure of one unit within 10ms. We also have made an optimal task schedule which is synchronized with FlexRay global time and the FlexRay communication schedule for high speed distributed control. And we have implemented and verified it in the independent steer-by-wire system.
Session: System Architecture