Design and implementation of a biomimetic wire-driven underactuated serpentine manipulator

Inspired by the snake skeleton and octopus arm muscle arrangement, we designed and built a wire-driven underactuated serpentine robot arm. The robot arm is made of a number of rigid vertebras, which is controlled by two sets of wires. The chained vertebras make up the backbone while the wires together with the servo motor work as the muscle. The robot arm has two bending degree of freedom (DOF). An elastic tube is used to confine the joint rotation. By the piece wise constant curvature assumption, forward and inverse kinematics is developed by geometry analysis and D-H method. Trajectory of the end effector is a spheroidal surface. A prototype is built to validate the design. The positioning error of the designed robot arm is related to the overall length of the flexible part. The longer the bending section, the larger the error. For the prototype, the positioning error is less than 2%. The robot arm is highly flexible. It remains controllable when obstacles are present. This manipulator is well suited for working in confined space, especially for engineering or medical inspection.