Humanoid Robot Joint Module (Rotary Actuator) Structure – Core Components

Output Flange / Connector – Connects to robot links (e.g., lower leg, forearm), outputs torque and motion.

Torque Sensor (optional but common in high-performance designs) – Ring or spoke type, used for force control / collision detection.

Harmonic Drive – Consists of a wave generator, flexspline, and circular spline; mounted on the motor output shaft.

Frameless Torque Motor – Stator fixed to the housing, rotor connected to the wave generator.

Brake (Safety Holding Brake) – Locks the joint position when power is lost.

Dual Encoders – Motor-side encoder (measures speed/position) and output-side encoder (eliminates reducer backlash error); commonly used for full closed-loop control.

Driver (Servo Drive Board) – Integrated inside the module or in a compact package.

Housing / Cooling Structure – Aluminum alloy body with cable channels.