Stop motion photography punishes any movement at all, and that is exactly the problem this build runs into. The maker, a freelance filmmaker, has put together a 6 DOF motion control arm to hold a mirrorless camera with a wide lens, and the constant headache is vibration or shake whenever the shoulder pitch and elbow pitch joints move together under load.
The hardware itself looks well thought out. The arm is built from black custom structural parts printed in PETG-CF and PAHT-CF, and it carries a set of Robstride actuators, one per joint: an EduLite 05 with 6 N·m on the shoulder pan, a pair of RS10P units with 42 N·m each on shoulder and elbow pitch, RS00 units with 14 N·m on roll and pitch, and an RS05 with 5.5 N·m on the final pan. The whole bill of parts and print material came to roughly 1k USD, which seems very reasonable for this kind of rig.
The control side is where the interesting work happens. A PC builds trajectories by polynomial interpolation between pose keyframes, smoothed with a quintic curve. An STM32 running in MIT mode plays the trajectory back on its own clock, sampling the curves at 400 Hz into MIT commands every 2.5ms. The controller layers in saved gravity and friction estimates, estimated inertia times acceleration, enabled ripple corrections, and an integral term accumulated from position error over time.
There has been real progress: major stepping issues on some actuators were fixed with differential gear calibration, and adding the integral component helped a little. The shake is not fully solved though, and the maker is still weighing a lower I action on the position loop plus local PID control per joint. The plan to pair it with a GoPro ILS and follow focus makes it worth watching.