Actuators

Actuators turn energy into movement giving humanoid robots the strength, speed, and precision to walk, lift, balance, and recover. Without them, even the smartest robot is just a statue.

Most humanoids rely on electric motors with gear reductions (precise but rigid) or hydraulic systems (powerful but heavy and complex). Some joints also use strain-wave, planetary, or ball screw drives to balance torque density, weight, and backlash — each suited for different loads from hips to wrists. But new trends are shifting the landscape:

• Series Elastic Actuators (SEAs) add compliance and impact absorption, improving safety and resilience.
• Direct-drive motors offer smoother, quieter control without bulky gearboxes.
• Sensorized actuators integrate force and position sensing for real-time feedback.
• Modular designs make repair and iteration easier at scale.
  

Some of the most radical advances come from emerging research in soft robotics — like fiber-based actuators inspired by rope weaving, which offer programmable elasticity in lightweight, flexible forms.