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Paper WeC02.1

Sardellitti, Irene (Istituto Italiano di Tecnologia (IIT)), Medrano-Cerda, Gustavo (Italian Institute of Technology), Tsagarakis, Nikolaos (Istituto Italiano di Tecnologia), Jafari, Amir (Swiss Federal Institute of Technology (ETH) Zurich), Caldwell, Darwin G. (Italian Institute of Technology)

A Position and Stiffness Control Strategy for Variable Stiffness Actuators

Scheduled for presentation during the Regular Session "Compliance Devices and Control" (WeC02), Wednesday, May 16, 2012, 14:30−14:45, Meeting Room 2 (Chief Red Wing)

2012 IEEE International Conference on Robotics and Automation, May 14-18, 2012, RiverCentre, Saint Paul, Minnesota, USA

This information is tentative and subject to change. Compiled on December 17, 2017

Keywords Compliant Joint/Mechanism, Mechanism Design of Manipulators, Compliant Assembly

Abstract

Variable stiffness actuators (VSAs) have been introduced to improve, at the design level, the safety and the energy efficiency of the new generation of robots that have to interact closely with humans. A wide variety of design solutions have recently been proposed, and a common factor in most of the VSAs is the introduction of a flexible transmission with varying stiffness. This, on the control perspective, usually implies a nonlinear actuation plant with varying dynamics following time-varying parameters, which requires more complex control strategies with respect to those developed for flexible joints with a constant stiffness. For this reason, this paper proposes an approach for controlling the link position and stiffness of a VSA. The link positioning relies on a LQR-based gain scheduling approach useful for continuously adjusting the control effort based on the current stiffness of the flexible transmission. The stiffness perceived at the output link is adjusted to match the varying task requirements through the combination of the positioning gains and the mechanical stiffness. The stability of the overall strategy is briefly discussed. The effectiveness of the controller in terms of tracking performance and stiffness adjustment is verified through experiments on the Actuator with Adjustable Stiffness (AwAS).

 

 

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