TESTING A SOFTWARE-BASED PID CONTROLLER USING METAMORPHIC TESTING

The Proportional-Integral-Derivative (PID) controller is ubiquitous in industrial and military systems. Almost all PID controllers are now implemented as software in a microcontroller. Control systems are required to have very high reliability, particularly as they are regularly used in safety-critical systems. An effective testing technique is essential to achieve reliable PID controller software. Unlike simple control algorithms, PID controllers are capable of manipulating the process inputs based on the history and rate of change of the signal. It is very difficult to know whether the computation of the software is correct from the computed outputs. Previous research in other areas has shown that metamorphic testing is an effective technique for this kind of problem. In this paper, we examine metamorphic testing in the context of testing an embedded software PID controller based on the free sample code from ATMEL Corporation. We show that metamorphic testing killed all mutants inserted into the controller software, demonstrating the utility of the technique in testing control systems.