多自由度人間形人工の手の開発 : 5本指,腕の構成

抄録

Studies on artificial hands are done at many laboratories all over the world. The necessary functions for artificial hands hereafter may be dexterity, speediness, flexible handling, intelligence, and so forth. The playing of keyboards can be considered human activity which is highly dependent on these functions. This study aims to have an anthropomorphic robot play a keyboard (an electric organ in the first step of this study), with a focus on its degree-of-freedom mechanism and speediness, with the intent of developing artificial hands for more universal uses. The following three points are keys for the development of an anthropomorphic robot with the capability to play keyboards: 1) the integration of multiple degrees of freedom at the fingers, 2) the speed of finger and arm motions, and 3) the composition of a microcomputer system to control the mechanism for the multiple degrees of freedom. The design was to have 2 degrees of freedom for the thumb and 3 degrees for each finger, totalling 14 degrees, based on the analysis of motions of human fingers. As to finger driving units, it is impossible for actuators (DC sevomotors), which drive the multiple freedom mechanism, to be installed at the fingers. Therefore, actuators are installed in the body of the robot, and their power is transmitted through reduction gears to the fingers by wires and outer-wire tubes. Moreover, spring elements are introduced in the power transmission units to minimize the effects of friction forces between wires and outer-wire tubes on the responses of finger motions. Fingers are made of CFRP (Carbon Fiber Reinforced Plastics) to reduce the load on the arm. The experiments on a five-finger model have resulted in realization of 10 (Hz) tapping. In terms of an arm, the basic necessary data for design and control methods of an artificial arm were obtained through the analysis of human postures and of motions of the arm as a linking mechanism. The artificial arm is designed to be humanlike in size, shape, and functions, and to have 7 degrees of freedom including one redundant degree. Actuators are DC servomotors, sensors are velocity and position sensors, and the arm is made of CFRP, as are the fingers. Velocity and position control have enabled speedy, smooth motion of the arm. Concerning the computer system, a hierarchically structured multi-micro computer system has been composed, because total degrees of freedom are near to 50 when the degrees of freedom of four limbs are totalled. As a result, this robot system has realized the fluent play of tunes for beginners on a keyboard instrument.