Differential Linear Actuation for Compact Humanoid Body Joints

The actuation system is segmented into multiple smaller linear actuators arranged in pairs or groups, where each actuator handles a portion of the total actuation load. This segmentation allows the robot to achieve high performance through coordinated action of multiple compact units rather than relying on single large actuators, thereby maintaining a compact form factor within the human envelope.

The linear actuators are nested within the robot's limb structures, with actuators positioned inside or along the length of limbs. This nesting approach maximizes the use of available internal volume, allowing high-performance actuation systems to be integrated without increasing the external dimensions of the robot beyond the human envelope.

Traditional rotary actuators with complex gear trains and mechanical transmission systems are replaced with linear actuators that provide quasi-direct drive to the joints. This substitution eliminates or minimizes mechanical friction sources associated with gears and transmission mechanisms, significantly reducing energy loss while maintaining the ability to produce human-like movement patterns.

The actuation approach changes from indirect mechanical transmission to direct linear actuation, fundamentally altering the mechanical parameters of the system. This parameter change reduces friction coefficients and energy dissipation, enabling extended runtime while preserving human-like gait capabilities.