Genetic algorithms and flexible process planning in the design of fault tolerant cell control for flexible assembly systems

This paper presents a methodology for the advancement of fault tolerance in cell control when applied to a class of flexible assembly system. A literature survey of flexibility in manufacturing was conducted, which leads to the formulation of a flexible process planning (FPP) scheme which efficiently encodes all possible operation plans of products to be manufactured in typical automated manufacturing systems. Genetic algorithms are designed which can retrieve all working operation plans (WOP) from a FPP database, and can determine a production schedule and assignment of operations to workplaces which minimise the overall makespan of the job orders in near real-time. The FPP scheme and the genetic algorithm are successfully integrated into a prototype colour Petri net (CPN) based cell control system which allows the system to regenerate its control logic and the production schedules whenever system faults occur, and therefore enable it to continue in operation. The successful implementation of this fault recovery cell control system within a demonstrator assembly cell indicates that the framework proposed provides a foundation for the further development and application of advanced cell control.