Workspace and stability analysis of a 6-DOF cable-driven parallel robot using frequency-based variable constraints

Because of lots of advantages such as a large workspace, high dynamics and high payload capacity, CDPRs have been widely used in various applications. In this study, kinematics and dynamics of CDPRs was derived for considering dynamic characteristics of CDPRs. This research considered two effective excitation frequencies which are the vibration induced by frame structural characteristics and acceleration profiles. Also, two main frequencies were considered as the variable constraints. They are the fundamental frequencies of each cable and the whole system. By considering them, the wrench-feasible workspace was determined and analyzed at conditions of various accelerations. In comparing the fixed and the frequency-based variable constraints, the size of the workspace was decreased slightly. However, the frequency-based variable constraint method raised stiffness of cables and end-effector. The stability of cables and end-effector was raised. Especially, the stability of cables was highly improved. Finally, the variable constraints method was verified with experiments. This method leads to high stability system.