Output Torque Transition of the Coupled Driven Variable Transmission Mechanism While Varying Its Gear Ratio

Abstract

We developed a variable transmission mechanism that can switch its gear ratio between 1/75 and 1/375 by changing the rotation directions of two driving motors. For robot joints, variable transmissions allow the actuators to operate with high energy efficiency. However, conventional variable transmission units are not appropriate for robot joints because they need to cut off the power or rotate output shaft continuously while varying gear ratio. The proposed variable transmission mechanism can vary its gear ratio by changing rotating direction of one of the motors. During the change, one motor needs to maintain the output torque for an instant. The experimental result shows the proposed variable transmission mechanism can vary its gear ratio without falling off of its output torque.