Cable Force Distribution and Motion Control for a Cable-Driven Super-Redundant Robot Under Stiffness Constraints

Abstract

Cable-driven super-redundant robots (CDSSR) with slender and flexible bodies have wide application potential in narrow spaces. However, the control accuracy of the robot is affected by the instability of the operating stiffness during motion, which is related to the diversity of the cable tension distribution solutions. To solve this problem, an analytical stiffness model of the cable-driven super-redundant robot is first constructed based on the virtual work principle. Then, an optimal cable tension distribution model based on energy optimization and stiffness constraint is proposed. Third, a motion control framework of cable-driven super-redundant robot with stiffness constraints is proposed. Finally, constant stiffness control experiments and repeated positioning accuracy experiments of robot end under different end stiffness conditions are carried out on a 21-DOF cable-driven super-redundant robot. The results show that the proposed control strategy can achieve constant stiffness control. When the stiffness of the robot is adjusted from 200 N/m to 300 N/m, the repeated positioning accuracy in the X, Y, and Z directions is increased by 40.00%, 27.62%, and 53.09%, respectively. When the end stiffness is adjusted from 300 N/m to 400 N/m, the repeated positioning accuracy in the X, Y, and Z directions is increased by 40.81%, 58.08%, and 64.99%, respectively. The experimental results show that the proposed cable force distribution model and control strategy are effective.