Online Time-Optimal Trajectory Planning in Dynamic Workspace of Cable Suspended Robots

This paper presents a method for online trajectory planning of cable suspended robots. A three degrees-of-freedom spatial cable robot is studied in this analysis. By deriving dynamic model of the robot, cable force restrictions will induce a set of algebraic inequalities in dynamic equations. Direction of required tracking acceleration reveals feasible motion of the robot, which guarantees non-violation of cable force bilateral bounds. Required tracking acceleration is in the direction of instantaneous minus desired velocity vectors with specified magnitude. Furthermore, alternative recipes are employed to decrease negative impacts of unwanted inputs and applying actuator constraints in trajectory planning. Finally, several simulations are presented to demonstrate success of the method. Proposed approach can be used in online trajectory tracking for all cable-driven parallel suspended robots akin to what is realized for the presented three degrees-of-freedom robot.