In this paper. an optimal PID controller is introduced for an antagonistic variable stiffness actuator (AVSA) based on Hammerstein models. A set of Hammerstein models is developed for the AVSA using the voltage difference method. For each stiffness level. https://www.ealisboa.com/special-pick-CRB-Concept-Style-Spinning-Guides-Model-YG-best-find/