Self-lock carrier: Realize low-backlash characteristic in 3 K planetary gearbox

Advanced manufacturing equipment heavily relies on gearboxes for optimal performance, especially in heavy-duty applications like industrial robot joints and advanced machine tools where precision and stiffness are paramount. While harmonic and cycloid gearboxes are common for their low backlash characteristic, conventional 3 K planetary gears excel in efficiency, torque density and stiffness but they are rarely utilized in high precision scenario due to backlash issue. In this study, a deformable planet carrier system (DPCS) is proposed for backlash restrain by center distance compensation. The DPCS incorporates a self-lock design, preserving low backlash feature while upholding load capacity and stiffness, meeting the demands of precision industrial equipment. To illustrate its principles, statics models demonstrate its force analysis, and FEM simulations reveal its self-lock feature. Backlash compensation model theoretically analyzes its anti-backlash effect from kinematics and geometry aspects. To validate its feasibility, the first prototype is manufactured and designated as H3K-40K-104. Experiment result prove that prototype achieves significant low backlash characteristic, with the maximum dynamic transmission error (DTE) of 20.5 arcsec and backlash of 6.561 arcsec. Stiffness hysteresis curve indicates a minimal lost motion of 20.01 arcsec. This paper provides an effective method to greatly refine precision performance in 3 K gear trains.