Robotic actuator

A humanoid robot, comprising:

• at least one robotic limb;
• and
• an actuator configured to move at least a portion of the at least one robotic limb, the actuator comprising:
• a mechanical ground;
• a motor coupled to the mechanical ground, the motor comprising a stator and a rotor;
• a gearbox, comprising:
• a shaft that extends through the gearbox and comprises a hollow bore;
• a first plurality of first planet gears;
• at least one sun gear that rides on the shaft and is rotationally coupled to the rotor, the at least one sun gear configured to transmit torque produced by the rotor to the first planet gears;
• a second plurality of second planet gears;
• a first ring gear coupled to the first planet gears;
• and
• a second ring gear coupled to the second planet gears;
• and
• an actuator output coupled to an output of the gearbox.