A Trajectory Planning Approach for Delta Robots Considering Both Motion Smoothness and Dynamic Stress

By considering both motion smoothness and dynamic stress, a trajectory planning method for delta robots, with the goal of determining the two optimal normalized time factors that dominate the motion path in operation space, is presented in this article. First, based on the semianalytical elastodynamics model of parallel robots, which considers the compliance of the limbs and joints, a dynamic stress model of the kinematic chain was built. Two indices were proposed to reflect the motion smoothness and dynamic stress. A sensitivity analysis and an optimization of the normalized time factors for a modified fifth-order B-spline approach were conducted in isight and matlab. The results show that the two normalized time factors have important impacts on the motion smoothness and dynamic stress. A comparison showed that the trajectory planning approach based on the modified fifth-order B-spline reduced the dynamic stress while improving the motion smoothness. The approach proposed in this work can also be applied in trajectory planning for other parallel or hybrid robots.