Trajectory generation and tracking control methods for a multiple transfer robots system

This paper proposes trajectory generation and tracking control methods for the advanced transportation system METROS (Multiple Transfer Robots System). The methods enable several transfer robots to transfer materials cooperatively in an automated factory. The material´s reference trajectory guaranteeing smooth motions of robots is represented by simple combinations of line trajectories with constant velocity profiles and transition ones with 8th order polynomials. In order to transfer the material stably along the reference trajectory, a cooperative control architecture which consists of a master robot and slave ones is introduced. The master robot determines a behavior of the material for the specified reference trajectory, and thereafter distributes the forces required to realize the desired behavior to the slaves. Each slave robot generates its own trajectory and controls the speed and steering so as to exert the force commanded by the master robot. An impedance model is defined to determine the behavior of the material so that the material can behave as a desired mass-spring-dashpot system. The simulation results justify both the proposed methods