Variable Stiffness Actuators (VSAs) are complex mechatronic devices, which belong to a class of actuators that are capable of changing their apparent stiffness independent of the output position. They achieve this by the use of a certain amount of elastic elements and the actuated degrees of freedom (DOFs) which determine the manifestation of these elastic elements at the actuator output. By accumulating negative work, the energy storing capability of elastic elements can be implemented for obtaining energy-efficient actuation. Henceforth, they can be implemented into assistive devices such as arm supports or exoskeletons, where energy efficiency is beneficial.
For this application some objectives need to be fulfilled, like the change of stiffness and simultaneously keeping a constant applied force, while minimal energy is utilized to execute this adaptation. The current cable-driven VSA is not applicable for assistive usage, since it has 4 actuated DOFs, which is too many to be feasible. A regular VSA uses 2 DOFs which may be suitable to be used in assistive devices, but does not necessarily fulfill all the desired objectives.
The aim of this project is therefore to make a revolutionary design of a VSA, based on the 4 DOFs cable-driven VSA, with reduced actuated DOFs which can then be used for such applications. A likely approach would be an intelligent mechanical coupling of the DOFs, resulting in less actuated DOFs and, therefore, a feasible design for usage in assistive applications. A prototype setup will be prepared that can prove the principle.