Cable‐Driven Hyper‐Redundant Manipulator With Pitch‐Twist Joints: Mechatronic Design, Kinematics Analysis, and Prototype

ABSTRACT This paper proposes a cable‐driven manipulator (CDM) consisting of pitch‐twist (P‐T) joints driven by tubed cables with an optimized tightening strategy. Compared with the conventional CDMs constructed by pitch‐yaw (P‐Y) joints, the P‐T CDM has four advantages: (1) Arm twisting can be achieved without any additional motor, reducing the self‐weight to increase the load margin; (2) Many fewer joints are involved in different kinds of motions, and the same goes for driven cables, reducing the difficulty of joint linkage; (3) Each pitch or twist joint can be controlled separately by a pair of cables which are put into the corresponding tubes with fixed and redundant length to be decoupled from those of other joints, reducing control complexity; (4) The cable‐decoupling mechanism simplifies the cable‐tightening strategy to depend solely on the load direction of the corresponding joint, enabling the cable alternating driving to reduce the number of required motors. These advantages on structure and control are verified in the simulation about analysis of workspace and trajectory. Finally, the ability of obstacle avoidance, the controlling conveniency in typical trajectories, the load capacity of arm, the feasibility of cable‐tightening strategy, and the motion accuracy are all validated by series of prototype experiments.