Energy efficient scheduling of a two machine robotic cell producing multiple part types

This paper studies robot speed control decisions and the energy consumption objective in a cyclic robotic cell scheduling problem. The study considers a two-machine flow shop cell that produces multiple part types. A robot handles the parts between the machines and buffers. We assume that the energy consumption of the robot during a move is a convex function of its speed. The problem is to sequence the parts, construct a robot move sequence, and plan the robot’s speed levels to minimize two conflicting objectives: cycle time and energy consumption of the robot. We propose mathematical models that find Pareto-efficient solutions to the problem. For large instances, we propose heuristic search algorithms. Numerical results show that integrating robot speed decisions into the scheduling problem leads to significant energy saving.