Modularization and task sequencing of complex assembly systems

We provide a mathematical proof that sequencing of tasks according to their ascending reliabilities (in which each step has higher probability of success than the step before) leads to a minimum expected cost. A general heuristic can be driven from this proof that states: start with the most difficult task when dealing with complex problems. We also show that modularization and subassembly formation can reduce the cost saving effects of task sequencing. The paper illustrates the importance of considering task modularization prior to task sequencing for complex assemblies.