Atsushi Horigome

Development of a coupled tendon-driven 3D multi-joint manipulator.

Very long-reach snake-like robotic arms in the range of 14 meters are expected to be used in decommissioning work inside nuclear reactor containers. We developed a tendon-driven system which has the advantage of placing electronic devices protected in the arms base part which stays out of the reactor container, and only few expensive highly radiation hardened sensors and tools are mounted in the arm tip. Generation of large joint torque is necessary to realize such a very long arm. We applied the concept of coupled tendon-driven mechanism formerly used to generate restricted two dimensional motions, and extended its concept by proposing a new joint arrangement which makes possible three dimensional motions in a large workspace. Mechanical design, compact storage method and derivation of the arm motion control are detailed. Moreover, we built a preliminary mechanical prototype called ”Mini 3D CT-Arm”, and the experimental results demonstrated the validity of the newly proposed concept.

Basic study for drive mechanism with synthetic fiber rope – investigation of strength reduction by bending and terminal fixation method

In this study, we investigate physical properties of synthetic fiber ropes for drive mechanism. First, we carry out experiment about the relation between tensile strength and bending ratio D / d, where D is pulley diameter and d is rope diameter. Although it is widely known that a metal wire rope gets strength reduction under small D / d, we newly detected that a synthetic fiber rope also gets strength reduction in the same way. Secondly, we evaluate the strength of various end fixation method of synthetic fiber rope. Knot fixation makes rope strength half in all kinds of knot. Clamping fixation with enough pressuring force can get large strength even if a synthetic fiber rope has low friction coefficient. Although calking fixation and sewing fixation cannot change rope length easily, they can get the largest strength around 85–90% of the rope strength in our experiment. Graphical Abstract

Design of a weight-compensated and coupled tendon-driven articulated long-reach manipulator

A weight-compensated and coupled tendon-driven mechanism which is a combination of the existing two mechanisms is proposed and its static control is discussed. This mechanism allows the long-reach manipulator with very small actuators by applying one thick tendon to a coupled tendon-driven mechanism. Static control of tension was investigated and the solution which derives the tension of the joint controlling tendons and the weight-compensating tendon from the arm posture was proposed. Moreover, tendon tension on three types of the proposed mechanism is simulated in six postures. The weight-compensation sometimes requires large tension of the joint controlling tendons, however, it reduces tendons tension under around 2 kN basically.