On the automatic generation of assembly plans

This paper describes the XAP/1 assembly planning system. It begins by comparing the version of the assembly planning problem addressed by the XAP/1 system to other systems in terms of the range of operations allowed in plans, the degree of detail in which plans are described, the type of input data required, and the degree of optimization done on plans. The XAP/1 system is strongly oriented toward plan optimization, which requires it to plan to somewhat greater detail than other planners. Its range is currently more limited in that it cannot generate plans with subassemblies. The paper then summarizes some results on the computational complexity of assembly planning and describes the operation of the XAP/1 planner. XAP/1 generates plans by successively adding sequencing and trajectory assertions to a set until it describes only one plan. The geometric feasibility of the resulting plan is enforced by a single form of constraint. The search for an optimal plan is guided by advice from a set of plug-in criterion modules and an arbitration module. These criteria provide not only estimates of the quality of partially formed plans, they also provide advice on which planning decisions should be considered next. The paper concludes by summarizing the performance of the system on some sample problems and brieey discussing how the approach can be extended.