Evaluation of aiding and opposing load efficiency for an actuator planetary drive

Planetary gears offer compact and light solutions to achieve the high gear ratios required by robotics and actuation applications. This characteristic is usually combined to high torque density, high stiffness, and a good mechanical efficiency. In this work, we consider a particular layout of a compound planetary gearing, aiming to achieve very high gear ratios while reducing the amount of recirculating power that has a negative impact on the overall efficiency of the transmission. The efficiency of the reducer is computed in opposing and aiding load conditions, and compared to alternative solutions offering the same gear ratio and compactness, showing a better performance than commonly employed planetary drives. Additionally, the results are compared to a simplified model for mechanical transmission efficiency.