Priority assignment algorithms for resolving blocking in modular control of discrete event systems

Several design techniques that can systematically assign priorities to individually nonblocking supervisors to generate a nonblocking modular supervisor are presented and studied. The work is set in the modular control with priorities scheme, which is an extension of earlier works on modular supervisory control of discrete event systems. The modular control with priorities scheme is motivated by theoretical and practical considerations; it employs a priority mechanism based on the priority functions of individual supervisors in combining individual control actions together. This mechanism provides a way to resolve blocking via the appropriate selection of priority functions. In this paper, we first provide an updated overview of the design and synthesis procedure to be followed in modular control with priorities. We then present different assignment algorithms that either always favor or do not always favor a designated supervisor in assigning priorities in order to generate a nonblocking controllable behavior.