Design and Implementation of a Fault Tolerant Time Triggered CAN System and the Related Issues

The continuous demand for fuel efficiency requires the use of drive-by-wire technology. Steer-by-wire and brake-by-wire are examples of drive-by-wire technology. CAN is a good protocol for various vehicle modules to communicate over a single bus. With CAN, safety critical messages might not be received and transmitted within certain specified latencies. The need to receive and deliver safety critical messages on time pushed the researchers to come up with a better communication protocol. The time-triggered CAN (TTCAN) system can guarantee deterministic latencies provided there are no faults in the system. TTCAN protocol does not allow retransmission of a message if the message failed to go due to the presence of errors. Thus, if a fault occurs during the transmission of a safety critical message, the message will not be able to go to its destination node. As a result, the safety of the vehicle and the occupants will be compromised. This paper presents the design and implementation of a fault tolerant TTCAN system on the top of a standard CAN system without requiring any modifications within the CAN controller chips. The paper also discusses some issues related to the implementation of the fault tolerant TTCAN system.