Transforming series elastic actuators into Variable Stiffness Actuators thanks to structured H∞ control

Conference of European Control Conference, ECC 2015 ; Conference Date: 15 July 2015 Through 17 July 2015; Conference Code:118225International audienceSoft Robotics and Variable Stiffness Actuation (VSA) are active research domains in robotics. The aim is to design human-friendly machines that can perform safely dexterous tasks close to or in contact with humans. Whereas most of current works focus on biomimetic VSA by using two antagonistic motors to simultaneously deal with motion control and stiffness adaptation, in this work, we present a control approach that takes advantage of the mechanical reversibility of series elastic actuators and the recent availability of structured H∞ synthesis. The paper introduces a methodology for the design of a control law that allows to turn a force-sensorless actuator that includes a flexible link into a variable stiffness actuator where the stiffness can be set arbitrarily in some interval. With the proposed framework, it has been possible to accurately control the motion and the stiffness of a cable-screw actuator