Assessing the impact of redundancy on performance and reliability in a drive-by-wire system

Many next-generation automotive control systems, such as brake-by-wire, will feature the replacement of mechanical linkages between the driver and vehicle actuators by sensors communicating with computer-controlled electromechanical actuators. For such systems, redundancy is often employed to achieve the required fault tolerance and reliability. In this paper, we investigated the effect of hardware redundancy on the timing, control performance and reliability of an automotive drive-by-wire system. From an initial, minimal system design, we then added redundancy to provide fault-tolerance in the most critical areas of the system. To investigate if the software architecture had an influence on the effects of this redundancy, we implemented two different approaches to the software design for each implementation. We then used a Hardware-In-the-Loop (HIL) testing facility to record performance metrics for each of the four implementations. These metrics are presented and discussed. Finally, we applied reliability modeling techniques to consider the changes in overall system reliability that can be expected between systems.