Energy-based approach for friction identification of robotic joints

In this paper a new open-loop (off-line) identification approach to determine the friction parameters in the joints of robotic manipulators is presented. These friction parameters are the Coulomb friction, Static friction, Stribeck velocity constant and Viscous damping coefficient, referred to as the CSSV.The new friction identification approach introduced in this paper permits the CSSV to be determined by solving a nonlinear optimization problem which is derived using work-energy principle. The corresponding nonlinear optimization problem is solved using an efficient technique which does not require iteration or any initial estimate of the parameters. This new open-loop approach, compared to the available open-loop approaches, has the advantages that do not require the values of the manipulator’s parameters; such as mass or mass moment of inertia of links. Moreover, since this new identification approach is open-loop, it has the superiority that does not require any controller, which is the vital component in the closed-loop identification approaches.The new identification approach proposed here is applicable to the joints of earth-based robotic manipulators whose corresponding links move in the horizontal plane or the joints of space manipulators. The new approach was experimentally verified on a robotic manipulator available in the Robotics Laboratory at the University of Saskatchewan.

Research highlights
► A new approach to determine the friction parameters in the joints of robotic manipulators is introduced.
► This approach has the advantage that does not require a controller.
► In additions, it does not need the values of manipulator’s parameters.
► The method has been experimentally verified.