Research On Adaptive Scheduler And Its Key Technologies For Shop Floor Under Dynamical Enviorment

In the twenty-first century, the rapid development of new products, coupled with promoted customer delivery, is the foundation of the time-based competition strategies, which have been adopted by many manufacturing enterprises. Accordingly, firms need to react adequately to dynamically changing job orders. The shop floor must posses sophisticated operation management mechanisms for various delivery criteria (e.g. throughput, cycle time, and so forth).Manufacturing Execution System (MES) has been adopted in the 21-century enterprises, which aims at realizing flexibility and response to the changing market requirements as quick as possible. In the researches on MES, how to make the resources and the control structure (scheduling method of resources) of enterprise's production system adapt to the market requirements quickly, high-efficiently and economically is the core idea. To Chinese manufacturing enterprises, most of them have had the hardware conditions to implement agile manufacturing. However, they still lack effective and proper software technologies to support scheduling and etc. Therefore, to research control structure in the shop floor manufacturing system and their complex optimization problems from MES viewpoint will be a powerful guidance and propulsion.According to features of MES and practical requirements, and based on the research work of the adaptive scheduling techniques done by international and domestic scholars as well. This thesis provides a systematic research on the key techniques of adaptive scheduler under the complex dynamical environment in the shop floor. The research works have been done as follows:The framework of adaptive scheduler, which contains a scheduling knowledge acquisition algorithm, a scheduling knowledge-based system and a controller, was established. The scheduler utilized an Extended Adaptive Scheduling Strategy (EASS) and a Model Reference Adaptive Control (MRAC) theory-based architecture. These technologies make the scheduler adapt harsh requirements of the complex dynamical environment in the respects of strategy and architecture. The process specification language ontology-based representation of process plan information used can enable seamless integration of the scheduler and other heterogeneous information systems in a shop floor.A hybrid inductive learning-based scheduling knowledge acquisition algorithm was proposed. As a mutation operator of GA, SA was in series with GA to develop a hybrid optimization method which called GA&SA. DT and GA&SA were combined in the way of Wrapper. GA&SA was utilized to resolve the optimal subset of manufacturing system attributes and determine the optimal parameters of DT under different scheduling objectives; DT was used to evaluate the fitness of chromosome in the method and generate the scheduling knowledge after obtaining the optimal attributes subset, optimal DT's parameters.A model for the Scheduling Knowledge-Based System (SKBS), using the object-oriented technology was presented. It employed object-oriented modeling language to describe the requirement model, design model and implementation model of SKBS, so various views were built up to explore the static structure and dynamic behavior of SKBS. The semantics of class in the design model was exactly constrained by using object constraint language.A controller that can deploy the scheduling strategy with a three-phase working approach was proposed. An entire process of the scheduling strategy was divided into three phases which contains monitoring, decision-making and execution. It matched well the mechanism of EASS. It was a guideline to design the basic structure and the function module of the controller. According to the requirement of the controller, the composition of the simulate model was researched and the procedure of the model generation was given. The complexity of the search space was also analyized. This working way strengthens the effectuation and rightness of the control strategy.A prototype system named AS2-SCHED(Adaptive Strategy and Adaptive Structure-based SCHEDuler ) is developed based on the kernel technique mentioned above. AS2-SCHED supports the scheduler in the shop floor in a natural and intuitive manner. The function model and architecture of proposed system are introduced practically. Finally, the application of the system is illustrated to validate these key techniques.