Task sequence planning using fuzzy Petri nets

The authors discuss the problem of representation and planning of operations in a robotic assembly system using the fuzzy Petri net reasoning presented by C.G. Looney (1988) and S. Chen et al. (1990). Even though assembly and disassembly operations do not alter the properties of the parts. some processes may be introduced which do alter the parts and introduce associated sequencing constraints. In the fuzzy Petri net representation, those objects whose properties are altered are termed soft objects, and the process steps where alterations may occur are labeled key transitions. All feasible and complete assembly sequences must satisfy these process sequence constraints. The correct precedence relationships and the characteristics of completeness of all sequences are guaranteed by the prime number marking algorithm to mark the fuzzy Petri net before the search process starts. The fuzzy values for all objects in the system can be mapped to real-sense fuzzy values which show the degrees of completion for the changes of properties for all soft objects