High-speed and high-backdrivable actuation system considering variable-structured elastic design

This paper proposes a high-speed high-backdrivable actuator using a new actuation structure. To realize a small-sized high-torque actuator, a reduction gear is usually used. Because of the current saturation and friction effect of the actuator, the actuator has maximum values of acceleration and rotation speed. A gear with a high gear ratio reduces these two maximum values because of the presence of a reduction mechanism. The trade-off between the output torque and rotation speed exists. Consequently, it is difficult to achieve high-speed motions using a gear. Moreover, the reduction mechanism increases the friction of the motor and deteriorates its backdrivability. Therefore, in this study, a new actuation mechanism is utilized to solve such problems. The new mechanism consists of an electromagnetic clutch and elastic spring. High backdrivability and high-speed motion are achieved by releasing the clutch and transforming the elastic potential energy accumulated by the geared motor into kinetic energy, respectively. In the proposed system, the output rotation speed exceeds the maximum rotation speed obtained after it is reduced by the gear. Finally, the validity of the proposed method is verified experimentally.