Synthesis and analysis of a flexible elephant trunk robot

This paper presents a novel synthesis and analysis of a flexible elephant trunk robot (biological continuum–style manipulator). The robot includes eight flexible segments, although it can be extended to more segments as necessary. In this study the gravity of the springs is neglected due to the fact that the manipulation force is much larger than these gravity forces. This mechanism exhibits a wide range of maneuverability and has a large number of degrees of freedom. Each segment is designed using a novel flexible mechanism based on the loading of a compression spring in both transverse and axial directions, and using cable–conduit systems. The rotational motion is transformed to tendon-like behavior, which enables the location of the actuators away from the trunk (e.g. at the end of the trunk). The forward kinematics of the mechanism is also presented and lends itself well to computer control. It is shown that the solution of the transverse deflection of each segment is obtained in a general form, while the stiffness coefficients are obtained in closed form from a two-dimensional model (small and large deflection angles) and from a three-dimensional model used in a finite element method to verify results. The friction in the analysis between the cable and the conduit is neglected in the analysis. A prototype trunk segment is experimentally tested, the results are verified and the elephant trunk robot is built. A bench-top actuation system has been developed and a control scheme used in prosthetic hand control has been implemented to control the mechanism.