A day of PID tuning showed that the motion-control problem was probably cable routing, not only firmware.
2025-02-02 / 5 min
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I am building a motion-control rig for repeatable camera moves on miniature shots. The Y-axis servo oscillates when it hits loaded movement: exactly the kind of slow, smooth pan a corridor flythrough needs.
PID tuning helped, but only to a point. Kp, Ki, and Kd changes kept getting close and then the servo would hunt at the end of a move. More voltage headroom, cleaner encoder routing, and a firmware patch improved the sweep without fully removing the problem.
The repeated 20-second sweeps are now smooth enough for wide shots, but there is still minor vibration in the top end. The likely cause is mechanical: the encoder cable runs through a drag chain that changes tension as the axis moves.
Next step is additional damping on the cable path. If that fixes it, the solution is boring and useful, which is usually the best kind of hardware fix.
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