Automating the addition of fault tolerance with discrete controller synthesis
Tolerating the value failures of sensors is an important problem in automated control processes and plants. In this paper, we address this problem in a theoretical framework in order to demonstrate the feasibility of an automatic method based on discrete controller synthesis. We consider a fault-intolerant program whose job is to control an automated process, here a liquid tank equipped with level sensors that can be subject to value faults. This fault-intolerant program is modeled as a finite labeled transition system. We then specify formally a fault hypothesis, i.e., how many sensors can fail simultaneously. We use discrete controller synthesis to obtain automatically a program, having the same behavior as the initial fault-intolerant one, and satisfying the fault tolerance requirements under the fault hypothesis. We advocate that, thanks to the use of discrete controller synthesis, our method offers flexibility, reliability, separation of concern, and it is automatic.