A Continuum Manipulator with Closed-form Inverse Kinematics and Independently Tunable Stiffness

Continuum manipulators can accomplish various tasks in confined spaces, benefiting from their compliant structures and improved dexterity. Confined and unstructured spaces may require both enhanced stiffness of a continuum manipulator for precision and payload, as well as compliance for safe interaction. Thus, studies have been consistently dedicated to design continuum or articulated manipulators with tunable stiffness to adapt to different operating conditions. This paper presents a continuum manipulator with independently tunable stiffness where the stiffness variation does not affect the movement of the manipulator's end-effector. Moreover, the proposed continuum manipulator is found to have analytical inverse kinematics. The design concept, analytical kinematics, system construction and experimental characterizations are presented. The results showed that the manipulator's stiffness can be increased up to 3.61 times of the minimal value, demonstrating the effectiveness of the proposed idea.