A Switchable Rigid-Continuum Robot Arm: Design and Testing

This paper presents a novel robot arm that is capable of switching between a rigid robot arm and a continuum robot arm. Therefore, the novel robot arm can perform adaptive physical interaction and manipulation against complex working environments and tasks. The switch-ability of the robot arm is achieved with two types of joints: knee-like flexible joints and continuum flexible joints, with which the continuum segment of the robot arm is capable of locking and losing, hence the degree of freedom of the robot arm is capable to be switched. In this work, kinematics is established for specifying the relationship between joints space and global coordinates in both rigid and continuum configurations. Then, the posture and workspace in rigid and continuum configurations are analyzed and illustrated with numerical simulations, and compared based on the established kinematic model. Finally, a series of preliminary experimental testing toward the joint motion and stiffness has been carried out to validate the design, the kinematic model, and the motion performance of the proposed robot arm. Both the numerical and experimental results show that the knee-like joints can guarantee favorable motion accuracy, and the motion of continuum segment from the testing is well aligned with the motion calculated from the theoretical model. Moreover, the stiffness of rigid configuration is larger than the continuum configuration based on the stiffness experiment results. Therefore, the proposed novel robot arm is capable to handle adaptive interaction and manipulation in a diverse environment through the switching between the rigid and continuum configurations.