Hierarchical Supervisory Control Under Partial Observation: Normality

Abstract

Complex systems are often composed of many small communicating components called modules. We investigate the synthesis of supervisory controllers for modular systems under partial observation that, as the closed-loop system, realize the supremal normal sublanguage of the specification. We call such controllers maximally permissive normal supervisors. The challenge in modular systems is to find conditions under which the global nonblocking and maximally permissive normal supervisor can be achieved locally as the parallel composition of local normal supervisors. We show that a structural concept of hierarchical supervisory control called modified observation consistency (MOC) is such a condition. However, the algorithmic verification of MOC is an open problem, and therefore it is necessary to find easily-verifiable conditions that ensure MOC. We show that the condition that all shared events are observable is such a condition. Considering specifications, we examine both local specifications, where each module has its own specification, and global specifications. We combine our results for normality with the existing results for controllability to locally synthesize the nonblocking and maximally permissive controllable and normal supervisor. Finally, we illustrate the results on an industrial case study of the patient table of an MRI scanner.

Safe Performance of an Industrial Autonomous Ground Vehicle in the Supervisory Control Framework

“…The second aim is the easy and robust implementation of the designed scheme to the real CPS. The main issue in SCT design is the size and complexity of the total symbolic mathematical model, including all CPS's devices and subsystems, as their size and complexity tend to grow exponentially with respect to the development of new technologies [11,12]. Another issue of SCT, which aims to provide formal and effective solutions, is cyberattacks at the level of the physical part of the CPS [13][14][15].…”