AND/OR precedence constraint traveling salesman problem and its application to assembly schedule generation

An AND/OR precedence constraints problem is formulated as a state-constrained traveling salesman problem (SCTSP) and applied to the assembly scheduling problem. Generally, the assembly operation involves precedence relationships in joining components; that is, the order of assembling components crucially determines whether the desired object can be constructed from these components. The precedence relationships of assembly operations result from the geometric constraints of the assembled objects and can be formulated as AND/OR precedence constraints. The precedence knowledge reduces the complexity of solving the ordering problem for both the acquisition and generator procedures. Two kinds of constrained TSPs, the cost-constrained TSP (CCTSP) and the SCTSP, are used to find the assembly schedule. The CCTSP method usually sets the cost of all the prohibited moves between two cities to very large values, which ensures that the precedence constraints are satisfied. The SCTSP method prohibits the generation of next valid states. Detailed algorithms, analysis, and examples are discussed.<<ETX>>