Design of a high-level software architecture for real-time advanced motion control of Variable Stiffness Actuators and non-invasive observation of variable stiffness

In this thesis a novel high-level real-time control architecture for VSAs (Variable Stiffness Actuators) is presented and discussed as well as a new non-invasive model-less methodology to estimate the stiffness at the output joint shaft. VSAs, and VIAs (Variable impedance Actuators) at large, are growing more and more popular in robotics, and many different prototypes have been produced in the recent years by both the research and industrial communities. In comparison with off-the-shelf electromechanical actuators, VSAs present the possibility to control the mechanical stiffness at the output joint shaft, thus leading to the need of new performance and classification criteria, measuring systems and more generally control policies. Thanks to the adoption of the CANopen model at the ISO/OSI application layer, the proposed controller, developed under Linux-Xenomai, is able to real-time communicate over CANbus to retrieve sensor related information such as encoder positions, and recruit to the motor drivers the current related commands. Moreover, mainly thanks to the modularity and the multi-process real-time arrangement of the overall architectural framework, it is able to precisely estimate and control the stiffness of the particular mechanical device only relying on force and positioning data, with no reference to the current mechanical implementation or its model. Some experiments illustrating the effectiveness of the overall architecture are carried out and results are discussed as well as some considerations related to the overall reliability and accuracy of the estimator with respect to the external disturbances and measuring errors