A control theory approach for analyzing the effects of data errors in safety-critical control systems

Computers are increasingly used for implementing control algorithms in safety-critical embedded applications, such as engine control, braking control and flight surface control. Addressing the consequent coupling of control performance with computer related errors, this paper develops a composite computer dependability/control theory methodology for analyzing the effects data errors have on control system dependability. The effect is measured as the resulting control error (defined as the difference between the desired value of a physical properly and its actual value). We use maximum bounds on this measure as the criterion for control system failure (i.e., if the control error exceeds a certain threshold, the system has failed). In this paper we a) present suitable models of computer faults for analysis of control level effects and related analysis methods, and b) apply traditional control theory analysis methods for understanding the effects of data errors on system dependability An automobile slip-control brake-system is used as an example showing the viability of our approach.