With fully-body humanoid robots on the rise, the motor controllers, power electronics, and cooling systems that keep them moving must deliver more power, more precision, and more efficiency than ever.
To replicate a similar range of motion as a human, approximately 40 servo motors — often permanent magnet synchronous motors (PMSMs) or brushless DC (BLDC) motors — are usually deployed throughout the robot. The motors are distributed through different parts of the body, primarily located in the neck, torso, arms, legs, toes, and other joints, excluding the hands. To simulate a human’s dexterity, a single robotic hand can integrate more than 10 additional motors to control individual fingers and grasping mechanisms.
The power demands of these motors vary depending on their specific functions. The motors driving the delicate manipulation of the wrist or fingers possibly only require several amps, while motors embedded in hips or knees can require more than 100 A to handle the full body weight. In most cases, these robots run on a 48-V power distribution architecture, with each power board delivering around 500 W to 1 kW to the motors. At such power levels, thermal management is a top challenge
Given the rising demands for power density, these motors must be compact, lightweight, and efficient to fit within human-sized joints while still enabling the precise movements of humans. High-bandwidth, real-time control often facilitated by field-oriented control (FOC) is critical for coordinating the motion of different joints to maintain balance. At the same time, accurate position sensing — provided by compact sensors in each joint — is key to keeping movement smooth and adroit.
The GaN Plan for Motor Design
Gallium nitride (GaN) is increasingly being used to tackle these unique demands, said Ryan Wang, director of systems engineering and marketing at Texas Instruments. Thanks to their lower switching losses, GaN power FETs can handle pulse-width-modulation (PWM) frequencies of over 100 kHz, which allows for more accurate motor control.
