Impedance Regulation in Human Movements During a Rotation Task
Koji Ito, Toshio Tsuji, and Minoru Sugino
Faculty of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-hiroshima-shi, Hiroshima 724, Japan
In this paper, we discuss how the human subject controls the hand position and force depending upon the task objects and what roles the arm redundancy and muscle impedance regulation play in rotation. From the measurement of the hand force and arm posture in the execution of crank rotations, it was found that the subject made wrist joint impedance large and generated hand force in the both directions normal and tangential to the crank rotation. Impedance analysis demonstrated that the high impedance of the wrist joint, realized by simultaneous activities of the flexor and extensor muscles, provided for the posture of redundant arm without limiting the hand manipulatability. It was also shown that the hand force in the outer and normal directions contributed to an increase in the robustness of the hand manipulation against external disturbances.