Research And Simulation On Coordination Mechanism For Distributed Autonomous Manufacturing System

Complex dependency relationship rising from the complexity of discrete product, the complexity of its part production and the complexity of system composition is an outstanding feature of discrete manufacturing system. The management of the inherent complex dependency relationship is a necessary and important job for the running of discrete manufacturing system. To satisfy market demands much better and acclimate the manufacturing system's component change, distributed autonomous manufacturing systems, which is provided with better flexibleness, agility, extensibility, reliability and fault-tolerance, are recognized as the bright future of manufacturing system. When heterarchical control architecture is applied to manufacturing system, proper coordination mechanism must be equipped to manage dependency relationship successfully and satisfy manufacturing constraints and optimize the performance of manufacturing system. This dissertation investigates the coordination problem and mechanism of distributed autonomous manufacturing system. Three element of coordination mechanism, which is coordination strategy, coordination language and coordination protocol, is pointed out, the importance of coordination mechanism to manufacturing system is amply discussed and dependency relationship is classified. In order to form a stable theory basis for the research of distributed autonomous manufacturing system's coordination problem and coordination mechanism and facilitate the implementation of distributed autonomous manufacturing system, the coordination problem model, explicit coordination model and implicit coordination model of distributed manufacturing system is established. The management of dependency relationship of two main explicit coordination mechanisms, namely mediated commitment and control information exchange, is analyzed. Their optimization performance, robustness, communication overhead and realizability are contrasted. The employment of collaborative plan exchange between manufacturing resource agents is put forwarded and the action blue print of manufacturing system in the achievement of resource-task matching using bidding mechanism, estimating the satisfaction of dependency relationship, dealing with disturbance attack and realizing nonlinear process plan-based scheduling. Making use of collaborative plan exchange and contract net protocol, an explicit coordination prototype manufacturing system CPE is developed. The scheduling performance experiment, disturbance-dealing experiment and the nonlinear process plan experiment on CPE revealed that collaborative plan exchange can successfully optimize the performance of manufacturing systems, smoothly deal with the attack of disturbance, efficiently accomplish the management of nonlinear process plan's complex dependency relationship and effectively exert the advantage of nonlinear process plan. Inspired by the research fruit of ethology, the application of implicit coordination mechanism to manufacturing system is put forward and pheromone-based machine-choosing algorithm and coordination framework is established. Optimization ability analysis for implicit coordinated manufacturing systems revealed that pheromone-based machine-choosing algorithm's modification of pheromone would result in the increasing of the manufacturing system's probability of converging on optimum solution, if it exists. The advantage and disadvantage of implicit coordination mechanism is analyzed and it is pointed out that the implicit coordination mechanism can search optimum by an auto-catalysis process, stably adapt to the change of manufacturing system's configuration and disturbance. It is also pointed out that the implicit coordination mechanism has the advantage of less communication overhead and good realizability of agents and the disadvantage of worse openness and indispensable adaptation period. Making use of the pheromone-based machine-choosing algorithm and coordination framework, an implicit coordination prototype manufacturing system PSMS is developed. In the double-product and double-stage hybrid flow shop experiment on PSMS demonstrated that the implicit coordination mechanism has better performance by contrast with local dispatch rules and can be applied to stochastic machining time problem in which other coordination mechanisms and scheduling algorithms is invalid. In experiment which aims at investigating the implicit coordination mechanism's adaptability by changing manufacturing system's configuration and input, PSMS showed very good adaptability, in which other scheduling algorithms and coordination mechanism is deficient. In the experiment imitating the painting stage of GM Motors'truck factory, PSMS also showed better performance and confirmed that the in the scheduling of hybrid flow shop implicit coordination mechanism has better performance than contract net protocol.