柔性制造系统一般Petri网模型内在活性结构研究

As an indispensable component of contemporary advanced manufacturing systems, flexible manufacturing systems (FMSs) possess flexibility and agility that traditional ones lack. Deadlocks may arise in a fully automated FMS and bring about a series of disturbing issues, from degraded and deteriorated system productivity and performance to low utilization of some critical and expensive resources and even long system downtime. Therefore, an analysis and solution to deadlock problems are imperative for both a theoretical investigation and practical application of FMS. From the perspective of the behavioral logic, this work focuses on the intrinsically live structures (ILSs) and deadlock control of generalized Petri nets modeling FMSs. Being different from the existing siphon-based methods, a concept of ILSs becomes the starting point to analyze, control, optimize, simulate, and validate a novel deadlock control and liveness-enforcing method. The characteristics of ILSs are identified and derived from subclasses of generalized Petri nets modeling FMS with complex resource usage styles. Additionally, the numerical relationship between initial markings and weights of connecting arcs is investigated and used to design a restriction that ensures the intrinsical liveness of local structures. With the structural theory, graph theory, and number theory, the work achieves the goals of deadlock control and liveness-enforcement superior over the traditional siphon-based ones with a lower computational complexity or a higher computational efficiency, a lower structural complexity, and a better behavioral permissiveness of the controlled system. The binary decision diagram is used to enumerate all ILSs in a generalized Petri net model, while mixed integer programming is employed to realize a multi-objective optimization of the deadlock control and liveness-enforcing method. The results of the theoretical research are to be simulated, validated, and evaluated by running on an experimental platform. This project is a cutting-edge research work in the field of FMS and will enable advancements of both the theoretical study and the practical application of advanced manufacturing systems.

本项目致力于研究柔性制造系统一般Petri网模型中的活性结构和死锁控制问题。作为21世纪先进制造技术的重要组成部分，具有柔性的自动制造系统自诞生之日起就始终面临死锁问题。死锁会降低生产率，甚至造成整个系统停机。要实现真正的自动化柔性制造，就必须研究和解决死锁问题。本项目在逻辑层面上进行死锁控制研究，不同于基于信标的传统方法，以活性结构为切入点，对系统中死锁问题进行分析、控制、优化、仿真和验证，并从计算复杂度、受控系统结构复杂性和受控系统行为许可性三大指标出发，对基于活性结构的死锁控制策略进行定量的评估和综合。本项目充分研究一般Petri 网模型权值与标识之间的特殊数值关系，结合结构分析理论、图论、数论等数学领域，应用混合整数规划和二值决策图等数学工具，研究具有复杂资源使用方式的柔性制造系统死锁控制问题，并进行多目标优化和模拟仿真验证。这一研究工作将从理论和应用上共同推进先进制造技术的发展。

本项目以柔性制造系统为研究背景，以死锁控制和活性实现等问题为研究对象，使用一般Petri网模型进行建模、分析、控制和优化。研究工作针对一般Petri网模型不同类别(SRS、WS3PR、S4PR、G-system等)中的各种特殊活性结构进行了深入分析，围绕死锁控制和活性实现，提出了若干种基于活性结构分析的死锁控制或优化方法。(1) 对比研究了面向过程(POPN)和面向资源(ROPN)两类一般Petri网模型中内在活性结构的对应关系，将POPN中的研究成果推广到ROPN中，使得可以有效辨识结构更加精简的活性结构，并在此基础上设计实现代价更小的控制器。(2) 对经典的S3PR类Petri网模型、S3PR的特殊子类、更加一般化的S4PR类、G-system类网模型进行活性结构分析，扩展信标的表达形式，设计其死锁预防和活性实现控制器，通过实例验证和对比，新方法的计算结构可以有效改善以前所使用的控制策略。(3) 结合使用基于可达图和结构分析的方法，设计了一种迭代控制策略，用于控制目前资源使用形式最为复杂的一般Petri网模型。这种方法可以降低每一次迭代的控制对象计算负担，并且迭代次数受所分析的网模型规模限制，迭代算法具有较好的收敛性，所设计出的控制器控制效果也可有效降低控制器实现代价，从而得到更加简化的、行为许可更好的受控系统。本研究的成果具有在自动制造系统、自动化医学分析系统、多机器人协调控制系统等领域应用的潜力。