A Variable-Stiffness Planning Method Considering Both the Overall Configuration and Cable Tension for Hyper-Redundant Manipulators

In order to realize the flexible capture of noncooperative targets, a variable-stiffness planning method considering both the overall configuration and cable tension for a hyper-redundant manipulator is proposed in this article. First, combining its kinematics and statics, an analytical stiffness model of the hyper-redundant manipulator is developed to evaluate its stiffness. The overall configuration and cable tension of the hyper-redundant manipulator are both identified as main factors that affect the stiffness. Then, a concept of configuration-stiffness mesh and tension-stiffness mesh is proposed to characterize the stiffness trend which can be optimized by active control points. On one hand, the gradient projection method is used to change the overall configuration of the hyper-redundant manipulator to optimize its stiffness. On the other hand, the cascade proportional integral differential control law is used to change the cable tension of the hyper-redundant manipulator to optimize its stiffness. Finally, simulations and experiments are carried out to validate the analytical stiffness model and variable-stiffness planning method considering both the overall configuration and cable tension for hyper-redundant manipulators.