Trajectory planning of cooperative robotic system for automated fiber placement in a leader-follower formation

This work investigates a leader-follower trajectory planning strategy in a 13-DOF (degree of freedom) cooperative robotic system for automated fiber placement (AFP). A 6-DOF serial robot with an AFP head is employed as the leader, while a 6-RSS (revolute-spherical-spherical) parallel robot holding a Y-shape mandrel through a 1-DOF rotary stage serves as the follower. Due to the fact that the dynamic and kinematic constraints of the serial robot may interrupt the fiber layup process, a time-jerk optimal trajectory planning scheme for the serial robot is designed. Considering a desired 0 degrees fiber path, an optimal trajectory can be generated for the AFP head subject to the robot dynamic and kinematic constraints. However, the AFP head path could be deviated from the pre-planned fiber path, and the AFP head roller direction may not meet the requirement of keeping perpendicular to the mandrel surface. To compensate the serial robot motion and satisfy the AFP geometric constraints, a vision-based trajectory generation approach is developed for the parallel robot using a photogrammetry sensor C-Track 780. Based on the visual measurement results, the desired parallel robot trajectory can be determined according to the desired trajectory of the start point on the given fiber path. Experiments have been done to validate the effectiveness and superiority of the proposed strategy.