Design and Kinematics of Cable-Driven Soft Module Coupled with Spring

Abstract

Soft robot has become a hot point because it has excellent adaptability and safety with environment However, poor motion accuracy and low stiffness have limit its applications. This paper proposes a cable-driven soft module coupled with spring. It has compact structure, large range of motion, standard plug-and-connect connector, and can be easily assembled into a soft manipulator or a gripper. The kinematics of the module and modular manipulator are established based on the piece-wise constant curvature (PCC) method. The nonlinear friction of cables and the gravity of the modules have been analyzed to obtain an accurate model. Experiments on modules and manipulators with different sizes and stiffness have demonstrated its accuracy. The modules can reach a maximum bending angle of 180°, and the error is within 2.5°. The manipulators can reach a total bending angle more than 270°, and the error does not exceed 5°. Finally a gripper equipped with three modules is developed. It can grasp objects with different shapes, fragility and weights range from 1g to 0.43kg. It also demonstrates the good flexibility and load capacity of the module.