Hardware

Backlash

Backlash is the mechanical play between mating gear teeth or transmission elements, manifesting as a small dead zone where the output does not move when the input reverses direction. It introduces hysteresis and nonlinearity that degrade positioning accuracy and can cause limit cycles in feedback control. Zero-backlash transmissions such as harmonic drives, preloaded ball screws, and split-gear arrangements mitigate it at added cost and friction.

Why it matters for physical AI

Unmodeled backlash corrupts the assumption that commanded and actual motion match, injecting noise into demonstration data and blurring the fine positioning that learned insertion and assembly policies must achieve.