Abstract-A method for automatic generation of non-blocking controllers that generate collision-free flexible manufacturing cells is presented in this paper. Today, industry demands on flexible production sometimes require significant changes in location, orientation and configuration of industrial robots and other moving devices, when new products are introduced. All these changes pose a threat to the devices to collide while sharing workspace. Although the use of simulation software to facilitate these changes is gaining popularity, the coordination of collisionfree flexible manufacturing systems is still at best a semi-manual trial-and-error procedure. To avoid this, a formal model of the operations in a manufacturing system is generated, and for each operation state a corresponding 3D simulation shape is created. A collision-free system is then achieved by considering pairs of colliding shapes as forbidden states. The automatic generation also includes a synthesis procedure, where a non-blocking and controllable supervisor is generated based on guard generation. The guards are computed by binary decision diagrams, which means that complex systems can be handled, still generating comprehensible restrictions that are easily included in PLC-code.

Abstract-An abstraction method for Extended Finite Automata (EFAs), i.e., finite automata extended with variables, using transition projection is presented in this work. A manufacturing system modeled by EFAs is abstracted into subsystems that embody internal interacting dependencies. Synthesis and verification of subsystems are achieved through their model abstractions rather than their global model. Sufficient conditions are presented to guarantee that supervisors result in maximally permissive and nonblocking control. An examples demonstrate the computational effectiveness and practical usage of the approach.

In flexible manufacturing systems a large number of operations need to be coordinated and supervised to avoid blocking and deadlock situations. The synthesis of such supervisors soon becomes unmanageable for industrial manufacturing systems, due to state space explosion. In this paper we therefore develop some reduction principles for a recently presented model based on self-contained operations and sequences of operations. First sequential operation behaviors are identified and related operation models are simplified into one model. Then local transitions without interaction with other operation models are removed. This reduction principle is applied to a synthesis of nonblocking operation sequences, where collisions among moving devices are guaranteed to be avoided by a flexible booking process. The number of states in the synthesis procedure and the computation time is reduced dramatically by the suggested reduction principle.

Abstract-A limitation of the Ramadge and Wonham (RW) framework for the supervisory control theory is the explicit state representation using finite automata, often resulting in complex and unintelligible models. Extended finite automata (EFAs), i.e., deterministic finite automata extended with variables, provide compact state representation and then make the control logic transparent through logic expressions of the variables. A challenge with this new control framework is to exploit the rich control structure established in RW's framework. This paper studies the decentralized control structure with EFAs. To reduce the computational complexity, the controller is synthesized based on model abstraction of subsystems, which means that the global model of the entire system is unnecessary. Sufficient conditions are presented to that guarantee the decentralized supervisors result in maximally permissive and nonblocking control to the entire system.

No abstract