Robust supervisor synthesis for automated manufacturing systems using Petri nets

In order to engage automated manufacturing systems in practice, a prerequisite is that they must be immune to deadlocks, which have been extensively investigated for decades by numerous researchers. To ease their effort, resources are presumptively and arbitrarily assumed never to fail; nevertheless, this is quite the opposite in reality. Actually, failures occur frequently due to various causes. In this paper, resource failures will be taken into consideration. In the paradigm of Petri nets, a robust control supervisor is developed to guarantee that the system will not be in stagnation when failures occur unexpectedly. Processes not requiring the failed resources can continue their progress smoothly. Three algorithms are proposed to achieve the tractability in deadlock-freeness, robustness, and concurrency matters, respectively. At each state, they are executed in sequence so as to attain a set of fireable transitions. Anyone of them is legal to fire by obeying these three properties. As a consequence, an appropriate firing sequence is derived so as to lead the system to a desired state. Experimental results show that the proposed approach is effective in response to resource failures.