Gear Backlash in Robot Joints (2D)

Most robot joints are driven by a fast small motor through a gear reduction, and the position controller almost always reads only the motor's own encoder — cheaper than adding a second sensor on the output side. This 2D companion plots the commanded angle against the true output angle in real time and pairs it with a zoomed view of the gear mesh itself, so the small dead-zone between the teeth (backlash) that hides between those two encoders becomes directly visible: the motor-side trace can move freely inside the gap while the output trace sits still, lags, or — with aggressive gains and a wide gap — falls into a visible limit-cycle chatter as it repeatedly crosses the dead zone and slams the opposite tooth face. Adjust the backlash gap, gear ratio and PID gains and watch the "gap consumed" and tracking-error readouts reveal exactly how much of the joint's real motion the motor-side controller can never see.