A Conditional Stop Capable Trajectory Planner for Cable-Driven Parallel Robots

This paper presents a new method for cable-driven parallel robots (CDPR) to generate point-to-point (PTP) trajectories with the consideration of CDPR workspace. Similar to existing trajectory planners that work on position level using a quintic or higher polynomial, here the complete acceleration process is planned referring to a double-S trajectory, but with quintic polynomial for acceleration. Due to workspace considerations, the method had to be extended for the opportunity to trigger well-defined stops. Adapted to practical use of CDPRs, the method allows to specify distance, maximum velocity and maximum acceleration while limiting jerk where the latter is indirectly influenced. A feasibility check for user-given parameters leads to a reduction of acceleration and/or velocity to ensure reaching the goal while limiting the jerk to reduce actuator wear. To decouple the dynamics of standard trajectories and conditional stops, the braking acceleration is separately defined. The method has been tested on a cable robot prototype, called SEGESTA. The results show the capabilities of the new method especially for the real-time halt performance and the consideration of workspace boundaries.