Time-optimal task scheduling for two robotic manipulators operating in a three-dimensional environment

The present paper introduces a method for determining the optimal task scheduling for a two-robot work cell. This problem is reminiscent of the classic Travelling Salesman Problem (TSP), but the measure to be optimized is the time instead of the distance. In addition, this is a much more complex problem, since it involves two robots (salesmen), which have to visit different task-points (cities) considering the multiplicity of the robots' inverse kinematics. The optimization problem addressed in this work concerns the determination of the (near-)optimum sequence of task-points that should be visited by each one of the two robots while ensuring minimum total cycle time and collision avoidance among their links. The proposed approach is based on genetic algorithms and a special encoding is used to incorporate the division of the task-points for both robots and the multiple solutions of the inverse kinematics. The method was tested in different scenarios and the experimental results demonstrated the efficiency and effectiveness of the proposed approach.