No abstract

In this paper, a grasp force feedback control method of a robot hand attached to a single-link robot arm is proposed, and the usefulness of the grasp force feedback control method is confirmed theoretically and experimentally. The robot hand consists of two permanent-magnet-type stepping motors, reduction gears and plate springs. In the design of the grasp force feedback control system, the start-stop performance without missing steps concerning stepping motors is effectively utilized. For the shock reduction of the robot hand mechanism using stepping motors, the stepping motors should be stopped at a lower pulse rate. Therefore, the grasp force feedback control system is designed to finish the grasp force feedback control at a lower pulse rate of the stepping motors. For this purpose, the control method of the stepping motors using the angular velocity pattern of trapezoidal shape with a constant-velocity time and an estimated finish-time determined by the grasp force feedback control is devised. Then, numerical simulations using the equations of motion of the robot and the grasp force feedback control law have been carried out, and it is ascertained theoretically that the grasping force can be precisely controlled by the present grasp force feedback control method. Furthermore, experiments have been carried out, and the excellent performance of the grasp force feedback control is confirmed experimentally.

In this study, the grasp transfer control system by a Cartesian coordinate two-link robot arm with a prototype robot hand is presented. The prototype robot hand consists of permanent-magnet-type stepping motors, gears and plate springs. The grasp force control of the robot hand is performed by a feedforward control of the stepping motors based on the dimension of a grasped object. The Cartesian coordinate two-link robot arm consists of ball screws and hybrid stepping motors. Then the numerical simulations and experiments of the grasp transfer control have been carried out, and it is confirmed that the grasp transfer control could be successfully performed, and the grasp force could be accurately controlled among the motion control of the Cartesian coordinate two-link robot arm.