Abstract: A new smooth and near time-optimal trajectory planning approach is proposed for a parallel manipulator along a specified path. Compared with conventional planning algorithms based on dynamics, the fully dynamic model of the robot is constructed by virtual work principle with consideration of friction torque in every revolute joint. The kinematic and dynamic constraints can be converted to a pseudo-velocity limitation curve, and then a pseudo-acceleration boundary curve is calculated, both of which can determine the constraints to be obeyed by the planning algorithm. The five-order polynomial spline is applied to intersect the motion curves smoothly for the state, velocity, and acceleration in phase plane, which can guarantee the continuity of the torque, joint velocity and acceleration. The effectiveness of the planning algorithm is verified by an experiment for a parallel robot. The results show the differences between the trajectory planning of serial and parallel robot, and the feasibility of the method which can be used to online application for similar industrial robots.

Key words: parallel manipulator;trajectory planning;time-optimal;friction torque