optimal trajectory planning of a cable-driven parallel robot by direct collocation approaches

Trajectory planning in cable-driven robots is more challenging than rigid-link ones. to maintain the robot control, the cable tensions must be positive during motion. this paper presents a direct collocation approach to solve the optimal trajectory planning based on the minimization of a robot's tension and tension-rate objective functions. besides, during robot motion, the cables must be tensile. the configuration of a cable parallel robot composed of a 3-cable and a prismatic actuator neutralizes the moving platform’s weight while improving tensionability. to generate smooth trajectories, the proposed method is compared with two standard approaches: gpops-ii software package which uses legendre-gauss-radu quadrature orthogonal collocation polynomials and direct collocation by using b-spline interpolation curves. despite the efficiency of using b-spline functions in trajectory planning, numerical simulations demonstrate that the hermite-simpson direct collocation approach has a substantial benefit in the computation cost and accuracy for trajectory planning of a cable-driven parallel robot. also, by choosing appropriate constraints and cost functions, the cable forces in the parallel robot can be well managed.