Brushless DC Motor

A DC motor that swaps mechanical brushes for electronic commutation — the workhorse motor in robot joints.

A brushless DC motor puts permanent magnets on the rotor and coils on the stator; a driver switches current through the coils electronically based on the rotor's position (sensed by Hall-effect sensors or an encoder), replacing the brushes and commutator that wear out in a brushed motor. As a result it lasts longer, runs more efficiently, and concentrates heat in the stator where it's easier to dissipate, while also giving higher torque density. Most motors in robot joints, drones, and dexterous hands are brushless, usually paired with field-oriented control (FOC) for precise current and torque control. It's structurally similar to a permanent magnet synchronous motor, and the two are often used interchangeably in engineering talk, with the main technical difference being in back-EMF waveform and drive method.

ExampleA quadruped robot's joint module is typically an outrunner brushless motor plus a planetary gearbox and an encoder, with a driver using FOC to control the output torque.

Also called

BLDC Motor

Related

Permanent Magnet Synchronous Motor (PMSM) · Field-Oriented Control · Outrunner Motor · Servo Drive (Motor Driver) · Hall-Effect Sensor · Joint Actuator Module

Sources

Wikipedia: Brushless DC electric motor