| This thesis studies robotic scheduling problems arising in automated electroplating lines.In such lines,robots are often used for material handing between workstations.These robots play a crucial role in the performance of the lines and an optimal schedule of the robot operations is a key factor in guaranteeing product quality and maximizing productivity.We focus on extended lines(i.e.with multi-function and/or multi-capacity workstations)with a single robot.This research investigates three robotic scheduling problems: robust optimization for cyclic robotic scheduling problem,dynamic robotic scheduling problem in extended lines and cyclic robotic scheduling problem in extended lines.We first study the robust optimization for a cyclic robotic scheduling problem.The robustness of a cyclic robot schedule is defined in terms of the free slacks in robot traveling times.A bi-objective mixed-integer linear programming(MILP)model is developed to optimize the cycle time and the robustness simultaneously.It is proved that the optimal cycle time strictly increases with the robustness,thus there is an infinite number of Pareto optimal solutions.We established lower and upper bounds of these two objectives.Computational results on several benchmark instances and randomly generated instances indicate that the proposed approach can effectively solve the problem.We then examine a dynamic robotic scheduling problem with multi-function and multi-capacity tanks.We demonstrate that an existing model for a similar problem can lead to sub-optimality.To deal with this issue,a new MILP model is developed to generate an optimal reschedule.It can handle the case where a multi-function tank is also multi-capacity.Computational results on instances with and without multi-function tanks indicate that the proposed model always yields optimal solutions and is more compact and effective than the existing one.Finally,we investigate a cyclic robotic scheduling problem with multi-function and multi-capacity tanks.An MILP model is developed for the problem.The key issue is to formulate the time-window constraints and the workstation capacity constraints.We adapt the formulation of time-window constraints for a simpler cyclic robotic scheduling problem to the studied case.The workstation capacity constraints are handled by dealing with the relationships between robot moves so that there is always an empty processing slot for new parts.Computational experiments on numerical examples and randomly generated instances indicate that the proposed model can effectively solve the problem. |
