US Patent 11174850 Shape memory alloy nested rotary actuator

A plurality of shape memory alloy tubes (SMTs) of one or more shape memory alloy (SMA) types is configured as an element in a rotary actuator system in a nested manner. In various configurations, the nested SMTs provide one or more modes of multiplication (torque output or angular displacement), rotation reversibility and bias loading. The innovation provides for leveraging the modes for reductions in the rotary actuator system size, weight, or complexity or combinations thereof, or providing improved and more stable actuation capabilities in a given envelope.