Coreless Motor

A small motor whose rotor has no iron core — just a self-supporting cup of windings — light and fast-responding.

A coreless motor is a small DC motor whose rotor skips the laminated steel core and instead forms the copper windings into a self-supporting, cup-shaped coil. Removing the core brings several benefits: the rotor is very light with low rotational inertia, so it starts, stops, and changes speed quickly; there's no eddy-current or hysteresis loss in a core, so efficiency is high; and there's no cogging torque (the notchy, step-by-step feel some motors have while turning), giving smoother motion at low speed. The trade-offs are poorer heat dissipation, a lower power ceiling, and a higher price. It's long been used in medical devices, precision instruments, and model aircraft, with Switzerland's Maxon and Germany's FAULHABER as the leading makers. In embodied AI, it's mainly used in the finger joints of dexterous hands, paired with a miniature lead screw or reduction gears to drive each finger.

ExampleMany dexterous hands pack a coreless motor and a miniature lead screw into the palm or a finger, with one motor driving one degree of freedom.

Also called

Ironless Motor, Coreless DC Motor

Related

Dexterous Hand · Brushless DC Motor · Micro Lead Screw · Cogging Torque · maxon · FAULHABER

Sources

Coreless DC motor - Wikipedia