Abstract
In the context of automated manufacturing, this work proposes a new special class of timed Petri nets, namely, Timed ratio-enforced Augmented Marked Graph (TAMG) and its low-cost and high-performance supervisor synthesis methodology. A supervisor is composed of a set of control places (monitors), each of which is easy to be algebraically specified by a generalized mutual exclusion constraint (GMEC) to prevent certain siphons from being undermarked. In order to make a good tradeoff between the supervisor implementation cost and system performance, a mixed integer programming (MIP) approach is formulated to synthesize the monitors. An example is used to validate the effectiveness and efficiency of the proposed method. The results show that the proposed method remarkably outperforms any existing ones.
Note to Practitioners-For an automated manufacturing systems (AMS), the application of Petri nets facilitates the design of liveness-enforcing supervisors whose ingoing and outgoing transitions are in practice associated with certain observation and control operations, respectively. Different supervisors lead to different implementation cost and system throughput. By associating both cost and duration information to each transition, this paper proposes a method to evaluate and synthesize a supervisor. This work allows industrial engineers to design a supervisory controller that can achieve low implementation cost and high throughput for AMS.