Synthesis and Implementation of Distributed Supervisory Controllers With Communication Delays

This paper discusses a method to distribute a synthesized supervisor for implementation on multiple physical controllers. Dependency structure matrices are used to determine a distribution of a system. The supervisor is then distributed accordingly, using an existing localization method. Communication delays between the distributed components of a supervisor may affect its behavior, due to changes in the order of events. Therefore, a new delay-robustness check is proposed and where needed mutex locks are employed to make the distributed supervisor delay robust. The controller performance is analyzed and optimized through a parameter study and a mutex implementation evaluation. In a real-life case study, the method is demonstrated by synthesizing, distributing, implementing, and validating a supervisor for a road tunnel. Note to Practitioners - This article is motivated by the desire to bridge the gap between the asynchronous, discrete-event, world of synthesized supervisors and the synchronous, real-time, world of networked PLC controllers. The main focus lies on maintaining the guarantees of supervisor synthesis while taking into account all aspects of real-time implementation, such as cycle-driven code execution and communication delays.