Design and implementation of a fault-tolerant drive-by-wire system

Abstract

This thesis presents the design and implementation of a prototype for a drive-by-wire system in road vehicles. The prototype extends an existing (non-fault-tolerant) prototype with fault tolerance by implementing distributed brake system and dual modular redundancy for a central control unit. The steering is made redundant by utilizing the distributed brakes and using the braking capability on either side of the car. This will cause the car to turn in corresponding direction, i.e., steer-by-brakes. A hardware monitor is designed and implemented in the redundant central control units. The purpose of the hardware monitor is to restart the control unit in case of a failure. The non–fault-tolerant prototype is being used as a reference design when analysing the reliability and safety of the fault tolerant design. An analysis is made to verify the lowest failure rate that the design must tolerate in order to meet a target reliability of 99.999% after 10 years. The thesis follows the guidelines of the standard for functional safety in road vehicles, ISO 26262.