Time optimized smooth trajectory generation for 2DOF and 3DOF redundantly actuated cable suspended parallel robots

Abstract

Cable Suspended Parallel Robots (CSPR) are a type of cable driven parallel manipulators (CDPR) that has recently become popular for large workspace operations. They possess many advantages over common parallel robot architectures. They also possess the disadvantage of limited dynamics in motion due to the inability to exert compression and the constant limited downward force, gravity. Further, the redundancy in actuation in planar and spatial robots of certain footprints makes it challenging to determine the cable tensions and suitable dynamics for trajectories. This thesis introduces an analytical model to circumvent the cable tension determination problem using a concept termed as ‘Feasible Acceleration Diagram’. It then designs a novel methodology to generate time optimized point to point straight line trajectories with smooth dynamics for redundantly actuated 2DOF and 3DOF point-mass cable suspended parallel robots while ensuring positive cable tensions. The procedure of determination of kinematics for the trajectory is explained in detail with a test case for the 3DOF 4 cable scenario. Finally, the results obtained are verified by a simulation followed by a numerical method.