Parameter identification of variable stiffness actuators for a humanoid robot

In recent years, robots with elastic joints have been attracting increasing interest in the robotics community. Some of the main advantages introduced by elastic joints are the ability to interact safely with humans and the remarkable adaptability to environmental changes. ALTER-EGO, a humanoid robot born from the joint efforts of the Italian Institute of Technology and the Research Center "E. Piaggio" of the University of Pisa, belongs to this category. It is a robust and versatile mobile system with a functional anthropomorphic upper body which boasts six degrees of freedom for each arm. Both are driven by variable stiffness actuators, whose operation is inspired by that of a pair of human muscles. In the real world, elastic actuators are susceptible to wear and tear over time, which can lead to changes in their parameters. This paper presents a parameter identification method based on the estimation of the actual elastic torque through the residual method, aimed at improving control accuracy.