Energy conscious scheduling in a two-machine robotic cell

Akhlaghi, Vahid Eghbal
Robotic cells usually operate under time pressure to minimize time related objectives such as cycle time, makespan, and tardiness. Robot moves constitute a significant portion of cycle time. Also, robots consume significant amount of energy determined by the speeds and distances of their moves. We study the tradeoff between the cycle time and energy consumption of a robot in a two machine flexible robotic cell which processes identical parts. In this system, the loading and unloading of machines are made by a robot. Each machine performs a different operation on each part and the robot moves linearly along a track. There are alternative cyclic schedules for such a cell and each cycle involves a number of different robot moves. Energy consumption of a robot can be formulated as a convex function of its speed, since the energy consumption increases with the speed. Given a cycle time, we find optimal speeds for different robot moves in robotic cell cycles. We determine the best cyclic schedule and the optimal robot speeds that minimize the total energy consumption. Furthermore, we generate efficient frontier for energy consumption and cycle time objectives for a number of examples. 


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Citation Formats
V. E. Akhlaghi, “Energy conscious scheduling in a two-machine robotic cell,” M.S. - Master of Science, Middle East Technical University, 2017.