Planning link-interference-free trajectories for a parallel link manipulator

The paper develops a practical link-interference-free trajectory planning and control strategy for parallel link manipulators. An efficient algorithm for calculating the minimum distance between finite line segments is derived for online estimation of leg interference. If any of the parameters are critical, suggesting that a link collision is about to occur, then an alternative trajectory is calculated to prevent the collision while minimizing the error in the desired (commanded) trajectory. The trajectory control algorithm that results is cast in the form of a constrained minimization problem. Key to the trajectory modification algorithm is the derivation of the Jacobian matrix relating changes in platform velocity to interference velocity. Simulation results demonstrate the performance of this algorithm and experimental results verify its effectiveness