Scheduling method of robotic cells with machine–robot process and time window constraints

Abstract

Robotic cells are widely used in the fields of incorporate automation and repetitive processing. Throughput analysis and scheduling of robotic cells with machine process have been well studied, while research work on robotic cells with machine–robot process in which robots concurrently perform collaborated tasks in addition to part transportation is still at an early stage. After defining the concepts of internal and external time window constraints, we propose a robotic cell scheduling problem with machine process and machine–robot process simultaneously, when processing time window is an essential constraint. According to the constraints in real engineering practice, a mathematic model of single-gripper robotic cells is established to minimize the average manufacturing cycle time. A shifting bottleneck searching algorithm is proposed based on the basis of analyses. In addition, a lower bound for the average manufacturing cycle time is established. Finally, through extensive simulation experiments, the numerical and experimental results demonstrate that the shifting bottleneck searching provides optimal or near optimal solutions.