Evaluation of process controller fault tolerance using simulation

The paper presents a study of several alternatives of a fault-tolerant process controller design. We compare controller architectures based on different amount of hardware redundancy with those using time redundancy. The system behaviour is evaluated by means of a process-oriented simulation model enabling software injection of faults. As an overall measure of controller design quality (which includes both performance and reliability) we use the numerical error of the output. The results obtained on the model are used to show the dependence of the output error upon the relative speed of computation and upon the rate of faults damaging the data. Thus for every set of parameters, a system configuration which gives the best results, can be determined.