A low backlash and highly efficient gearbox for robot actuator

This paper presents a framework for a low-backlash, high-backdrivable gear based on analytical modeling and simulation. Robot actuators typically combine an electric motor with a high gear ratio gearbox to meet the high torque requirements. The 3K compound planetary gearbox, with its high gear ratio, emerges as a promising candidate for robot actuators used in physically interactive environments due to its high transmission efficiency in both forward and backward motions, thus endowing it with high back-drivability. However, compared to high-ratio gearboxes like harmonic drives, the existing 3K compound planetary gearbox is known to have high backlash. In this sense, the proposed design framework includes: 1) modeling of forward and backward transmission efficiency, 2) derivation of backlash, and 3) maximization of efficiency under bounded backlash constraints. The simulation results indicate that the backlash could be reduced from 24 arcmin to 2 arcmin. We expect that this knowledge could provide insights for designing gears with low backlash and high efficiency for robot actuators used in physically interactive tasks.