D. Braun, C. W. Mathews, Human Adaptable Variable Stiffness Springs, US Patent Application 18/226,204, 2023.
Various examples of systems, methods, and applications of variable stiffness springs are described. In one example, a variable stiffness joint apparatus can include a torsional spring; a variable stiffness mechanism comprising a self-locking mechanism and a linkage system, the self-locking mechanism comprising an auxiliary spring; and an actuator in communication with the auxiliary spring of the self-locking mechanism. When the actuator changes position, a force is applied to the auxiliary spring by the actuator and a stiffness is adjusted at an energy cost that is independent of the stiffness of the spring and the energy stored by the spring. In another example, a self-adjusting variable stiffness mechanism can include a compression spring. The energy stored by compressing the compression spring and the mechanism can self-adjust a stiffness to enable energy accumulation using a same maximal compression force which is not dependent on the energy accumulated in the spring.