A distinct software implementation in a vehicle controller

The reliability and safety of a system can be improved by distinct software, which is a method of executing a common software design by two distinct algorithms and comparing the results. The methods of implementing distinct software are still being devised and are based on little experience. This paper discusses an implementation of distinct software in the vehicle control unit of an automated vehicle. Each module in the vehicle control unit which is considered to be safety critical is performed by two sets of distinct algorithms in pseudoparallel (one after the other) in the same micro-processor. There are two identical microprocessors with identical software to detect a single processor failure. Within each processor the distinct algorithms are compared. The output of the distinct algorithms detect common mode software errors and common mode hardware failures in the two processors, thus, improving the safety of the vehicle control unit. This paper describes the safety related software concepts being used in the design for the Advanced Group Rapid Transit (AGRT) on-board computers with extended discussion of intra-channel distinct software.