Increasing robustness and output performance of Variable Stiffness Actuators in periodic motions.

Variable Stiffness Actuators (VSAs) have been developed to address the safety and limited adaptability in interactions with uncertainties and energy efficiency issues which exist in traditional "stiff" robots. When desired performance of a VSA is given for a certain application, the question is how this desired performance can be achieved with minimum energy consumption and maximum robustness against uncertainties. This will lead to more compact, lighter but more powerful VSAs. This work develops an understanding of how to optimally design the parameters of the stiffness adjustment mechanisms by developing a framework that can robustly maximize the output performance of VSAs. Five VSA examples, each representing a different design set of stiffness adjustment mechanism, are being considered and evaluated based on the proposed optimization framework to perform a given periodic motion. The resultant optimal design of each set is then compared with the original design in terms of output performance and robustness. The proposed framework shows improvement of the output performance for the given periodic motion up to 546%, with robustness of up to 2.1% perturbation of the optimal design values. • Output performance of variable stiffness actuators is defined and formulated. • Different classes of variable stiffness actuators are being analyzed. • An interval-optimization problem for output performance is presented. • The proposed framework shows improvement of the output performance for the given periodic motions. [ABSTRACT FROM AUTHOR]