A Novel Continuum Manipulator Design Using Serially Connected Double-Layer Planar Springs

There is a surge of research interest in the field of "continuum robotics." Robots created under this paradigm offer many advantages and represent unique features in terms of flexibility, dexterity, safety, and weight reduction. This paper introduces a novel continuum manipulator that integrates multiple layers of compliant planar springs - a structure that provides several notable advantages over existing designs. First, it possesses precise linear large-displacement motion. In this context, we utilize the linear output motion of each layer of springs. With the serial connection of multiple conjoined layers, the manipulator demonstrates linear predictable bending even when executing large bends. An analytical method is provided to study the compliance characteristics of the planar spring and derive the compliance matrix to represent the force-deflection relationships, allowing an accurate motion prediction. Second, compared with work elsewhere, this structure demonstrates an effective way of decoupling bending from contraction and expansion. It reduces the uncontrolled compression when generating normal deflections, thus controlling robot bending is simplified. Third, the reachable workspace of the end effector is enlarged by means of varying the length of the continuum manipulator via controlled contraction and expansion. A 3-D printed prototype of this continuum manipulator is experimentally evaluated. The conducted experiments demonstrated validity of our approach.