Fault Diagnosis and Fault Tolerant Control for a Class of Re-Entrant Manufacturing Systems

In practical manufacturing scenarios, re-entrant manufacturing systems (RMSs) are vulnerable to uncertain workstation faults, which may cause sudden changes in the work-in-process (WIP) level and impair the overall production capacity. To ensure agile response to market demands and to maintain stable system behavior under fault scenarios, an active fault-tolerant control scheme via fault diagnosis for RMSs is developed in this paper. Firstly, a hybrid hyperbolic partial differential equation continuum model is developed to describe the evolution of WIP dynamics, where the workstation faults result in the discarding of defective products during processing. Subsequently, a fault diagnosis scheme is presented to detect and estimate the uncertain faults in real time, by integrating an observer-based fault detection method and an adaptive fault estimation algorithm. Utilizing the estimated fault information, a fault-tolerant control strategy is then proposed to compensate for fault-induced state jumps and achieve agile production control. Finally, a numerical simulation is conducted to demonstrate the effectiveness of the proposed fault-tolerant control approach. It is believed the proposed theory enriches the theory, analysis, design of control circuit systems and has potential of practical implementations to industrial manufacturing systems.