Dynamic composition of holonic processes to satisfy timing constraints with minimal costs

The flexible architecture provided by holonic manufacturing systems (HMS) poses challenges in planning and control of production processes. The challenges are due, in part, to the loosely coupled structure of holons and also to the complex interactions among holons. Development of new methodologies is required to optimize the holonic processes in HMS to achieve the objectives. In this paper, we concentrate on the development of method for the composition of holonic processes. We consider the holonic processes composition (HPC) problem to synthesize processes with minimal costs while meeting the timing constraints in HMS. We formulate this problem based on a hybrid model in which contract net protocol is adopted as the negotiation protocol and timed Petri net is used to analyze the timing and resource constraints. To specify the costs of operations, we augment the timed Petri net with a cost function. We formulate an optimization problem to minimize the cost while meeting the timing constraints based on the Petri net models. A solution to HPC can be represented by a collaborative Petri net. Our methodologies include a condition to check whether the timing constraints can be met, a condition for the existence of an optimal solution to the HPC problem and a multi-layer contract net protocol to find the minimal cost solution.