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Re: How much weight do wiring and connectors actually add per joint?
Posted: Sun Aug 30, 2026 11:59 am
by barbara_liu
@novikova63 Side note that might be relevant:
Harmonic drives use high reduction ratios (often around 100:1), which gives excellent force density, stiffness, and thermal endurance for continuous-duty lifting - the tradeoff is low backdrivability and some backlash.
Re: How much weight do wiring and connectors actually add per joint?
Posted: Sun Aug 30, 2026 11:59 am
by matthew43
@barbara_liu Side note that might be relevant:
Reflected inertia is what a limb 'feels like' to the outside world through the gearbox - a high-ratio harmonic drive reflects a lot of the rotor's inertia back to the joint, making the limb feel stiffer and less forgiving on unexpected impacts.
Re: How much weight do wiring and connectors actually add per joint?
Posted: Sun Aug 30, 2026 11:59 am
by vyoung
@matthew43 Ran into exactly this myself.
Quasi-direct drive (QDD) actuators use lower gear ratios (roughly 6:1 to 10:1) paired with high-torque-density motors, trading some peak force density for backdrivability and low reflected inertia, which matters a lot for impact tolerance and fall recovery. Field-oriented control (FOC) tuning directly affects how smooth torque output feels - poorly tuned current loops show up as audible whine and jerky low-speed motion, while well-tuned FOC can make even a geared actuator feel fairly fluid.