Optimal Scheduling and Model Predictive Control for Trajectory Planning of Cooperative Robot Manipulators

摘要

A hierarchical control approach for cooperative pick-and-place tasks in a narrow shared workspace is proposed. A scenario with two robot arms performing pick-and-place tasks with moving objects while ensuring collision-free planning and execution of their respective trajectories is specifically addressed. To this end, we consider a hierarchical architecture with two-layer optimization-based control policies involving task scheduling in the top layer and path planning, along with the motion constraints, at the bottom one. On the one hand, for task allocation, a distance minimization algorithm is introduced, leading to an integer optimization problem with linear constraints and a bilinear cost function. On the other hand, we invoke model-based collision-free minimum-time planning of robot trajectories. Hereby, inverse robot dynamics and time scaling appear to be useful tools. The former accounts for the compensation of nonlinear robot dynamics, while the latter converts the trajectory planning to a fixed-time optimization problem, thus enabling synchronous robot task executions.