Development of a Lightweight and High-efficiency Compact Cycloidal Reducer for Legged Robots

Actuating systems for the proprioceptive control of legged robots must have a high mechanical efficiency and mechanical bandwidth for high torque transmission to avoid power transmission losses. We developed a high-efficiency compact cycloidal reducer for legged robots that uses needle roller bearings in all parts where contact occurs during the power transfer process inside the reducer, which greatly improves the efficiency compared to a cycloidal reducer using free rollers. We also proposed a subcarrier structure that distributes the load and allows the cycloidal reducer to respond robustly to impacts that may occur during the locomotion of the legged robot. The subcarrier increases the stiffness, which improves the mechanical bandwidth. A cycloidal reducer was manufactured with > 90% efficiency in most operating ranges; it weighs 766 g and can withstand a torque of more than 155 Nm. The cycloidal reducer module coupled with the motor indicated a torque control bandwidth of 72 Hz, so it can be used for legged robots with agile motions.