Joint optimization of tow-trains dispatch and conflict-free route planning in mixed-model assembly lines

The increment of product variety and complex customer requirements has let many manufactures deliver flexible small-lot parts to mixed-model lines, causing a large consumption of energy. Tow-trains, consisting of an auto-guided vehicle(AGV) and several trailers carrying the bin filled with materials, have been widely employed in mixed-model assembly lines. This paper focuses on the joint optimization of the tow-trains dispatch and conflict-free route planning, aiming to minimize the sum of total energy consumption and delay. An integer programming model with extra conflict-free constraints is proposed for dispatching and routing problem(DRP). An approach integrated genetic algorithm and time-space graph-based ant colony algorithm is applied to jointly determine the optimal number of tow-trains and the sequence of tasks for each tow-train with a conflict-free route. Finally, a computational study is conducted to verify the performance of the proposed approach.