Automatic generation of motion sequence for error recovery in programmable logic control using plant information

In this research, we discuss how to automatically generate the motion sequence of actuators for error recovery, including parallel path divergence in the programmable logic control (PLC). Since the sequential path in PLC can be expressed by a state flow, the goal of our research is to find an optimal shortest path from the initial state to the final state. In order to solve this problem, we propose a new search strategy, which consists of two search stages. In the first stage, real-time A* (RTA*) algorithm is used to find a suboptimal sequential path from the initial state to the final state. Based on the suboptimal solutions found by RTA*, the second stage tries to pick up some underlying parallel path divergences among solutions obtained in the first stage. From some simulation results, we have verified that our proposed method could search a suboptimal motion sequence including parallel path divergences with less computational amount.