張力拮抗方式による骨格型肘・前腕関節機構とその制御

抄録

The driving system of a manipulator is divided into two groups of movements. One group is driven directly by the actuator on each joint, and the other is driven indirectly by an actuator which is set apart from the manipulator. The second type of movement allows the manipulator to be made small. We have researched a mechanism and control method that can move as softly as the human arm, and we have adopted wire cables for the driving system of our human-type manipulator. The cable transmits the force from another, separate motor. This is similar to the human muscle system. But in most cases in which a cable is used to drive the manipulator, it is used as the means of transmitting the rotational torque from separated motors to each joint. But this is basically different from the action of a muscle. The muscles contend with each other, and one acts on the joints. Making the most of the characteristics of human mechanisms, we aim to achieve a skilled motion, like that of the human arm, that can control the position and force precisely. In the study reported in this paper, we looked at the human elbow joint and made a manipulator joint that has a similar mechanism that is characteristic of the human elbow joint. This joint consists of three links which correspond to the bones of the human arm and has 2 degrees of freedom (d. o. f.), flexion and rotation. This mechanism is driven by three cables which transmit the force from a separate motor. One cable has 2 d. o. f., and others work in contention. The basic control method is PI feedback control. Besides the main feedback loop, this algorithm has minor feedback loops that return the tension of the cables. We examined the position control. From the results of the numerical simulation and the experiment on this joint, we found that the algorithm of the contending force for 1 d. o. f. motion is able to extend to the control of 2 d. o. f. motions which are driven by three cables. The coefficient of the feedback loop does not influence the time response of the joint angle. This minor feedback of tension is restrained from being excessive, but excessive feedback makes the position control unstable.