D Braun, C. W Mathews, Method and apparatus for human augmentation and robot actuation, US Patent App. 17/872,164, 2023.
The present disclosure relates to a parallel variable stiffness actuator. The parallel variable stiffness actuator can comprise a spring and a variable-stiffness mechanism. The variable-stiffness mechanism can be configured to modulate a stiffness of the parallel variable stiffness actuator. The parallel variable stiffness actuator can further comprise a direct-drive motor arranged in parallel with the spring. A force of the direct-drive motor can be applied directly to a load. The present disclosure further relates to a resonant energy accumulation method implemented by a parallel variable stiffness actuator. A stiffness of a spring can be changed when there is no energy stored by the spring. A resonant energy accumulation method where a force of a direct-drive motor can be applied in resonance with the oscillatory motion, while the stiffness of the parallel variable stiffness actuator can be changed to keep the amplitude of the oscillatory motion nearly constant.