The existing particle swarm optimization (PSO) algorithm has the disadvantages of application limitations and slow convergence speed when solving the problem of mobile robot path planning. This paper proposes an improved PSO integration scheme based on improved details, which integrates uniform distribution, exponential attenuation inertia weight, cubic spline interpolation function, and learning factor of enhanced control. Compared with other standard functions, our improved PSO (IPSO) can achieve better optimal results with less number of iteration steps than the different four path planning algorithms developed in the existing literature. IPSO makes the optimal path length with less than 20 iteration steps and reduces the path length and simulation time by 2.8% and 1.1 seconds, respectively.

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This article reports a transition-based control technique to prevent deadlocks for flexible manufacturing systems that can be modeled with a generalized class of Petri nets. The proposed method utilizes the structural properties of the Petri net model to avoid the computation of its reachability graph which in general leads to the state explosion problem. Three algorithms are developed. The first and second algorithms aim to compute first-met and n-met uncontrolled transitions, respectively, in an iterative manner until all the n-met uncontrolled transitions are found in the plant net model. The third algorithm is used to design n-transition controllers iteratively. The iteration terminates when all the transitions in the set of uncontrolled transitions are processed. The addition of the n-transition controllers to the plant net model is to make the n-met uncontrolled transitions controlled. The transition controllers are capable of enforcing liveness to the plant net model with all its reachable markings being retained in the controlled system, which ensures the full utilization of resources and provides the high productivity of a flexible manufacturing system.

Decentralized supervisory structure has drawn much attention in recent years to address the computational complexity in designing supervisory structures for large Petri net model. Many studies are reported in the paradigm of automata while few can be found in the Petri net paradigm. The decentralized supervisory structure can address the computational complexity, but it adds the structural complexity of supervisory structure. This paper proposed a new method of designing a global controller for decentralized systems of a large Petri net model for flexible manufacturing systems. The proposed method can both reduce the computational complexity by decomposition of large Petri net models into several subnets and structural complexity by designing a global supervisory structure that can greatly reduce the cost at the implementation stage. Two efficient algorithms are developed in the proposed method. Algorithm 1 is used to compute decentralized working zones from the given Petri net model for flexible manufacturing systems. Algorithm 2 is used to compute the global controller that enforces the liveness to the decentralized working zones. The ring assembling method is used to reconnect and controlled the working zones via a global controller. The proposed method can be applied to large Petri nets size and, in general, it has less computational and structural complexity. Experimental examples are presented to explore the applicability of the proposed method.

Deadlocks are undesirable situation in flexible manufacturing systems (FMSs), which degrades the benefit derived from flexible manufacturing systems. Many researchers are working to overcome this problem, and a lot of methods have been developed to tackle the deadlock in FMSs. However, most of the methods in the literature provide a complex supervisory structure. This paper propose a new method of deadlock prevention for a flexible manufacturing system with a minimal supervisory structure, in wh ich a new algorithm is developed to compute generalize mutual exclusion constrains (GMECs) for each process of the Petri net model of an FMS. The number of GMECs depends on the concurrent processes of the Petri net model. Control places are designed from the computed GMECs to enforce liveness of the Petri net model. The addition of control places to the uncontrolled Petri net provides a live controlled Petri net system with optimal control purposes. A flexible manufacturing system (FMS) aims to provide a special consideration to diversify the products in a medium or small batch to increase the competition ability in the world market. Deadlocks are an important issue to be considered in the design and control stage of an FMS, since there occurrences cause a lot of damage to the system or might halt the whole system from the operation [I].Several tools have been developed to tackle the deadlocks in FMSs [2]-[4]: Petri nets, automata and graph theory. Petri nets become the most essential tool to tackle deadlocks in an FMS, since they can appropriately describe an FMS' s structural and behavioral properties such as conflicts, concurrency, casual dependency, liveness and boundedness [3]-[5] . Furthermore, Petri nets are widely used in contemporary technological systems such as computer and communication networks, manufacturing process, urban traffk systems, and automation systems [2]-[8]. The performance of a deadlock prevention policy can be evaluated based on the following criteria: (i) Behavioral permissiveness, (ii) Structural complexity, and (iii) Computational complexity. A maximally permIssIve supervisor usually leads to sufficient utilization of resources and high system throughput [3]. A supervisor with a minimal number of control places can decrease both hardware and software cost in the stage of control verification, validation and implementation [3].There are mainly two types of Petri net analysis techniques, structural analysis and reachability graph analysis. For structural analysis, siphons and resource transition circuits (RTCs) are extensively used to deal with deadlocks in FMSs. The work in [4], [5] developed a method of elementary siphon analysis to cope with the deadlock problem in FMSs. The method is efficient as it provides a minimal supervisory structure and reduces the computational complexity of the siphons, which in general increases exponentially with the size of a Petri net model of an FMS, although, the method cannot provide an optimal control policy.The study in [6] developed a method of selective...