Direct derivation of the dynamic regressors for serial manipulators with mixed rigidelastic joints

In this paper, the regressor form of the dynamic equations is extended to include the case of serial manipulators with mixed rigid/elastic joints. Under the mild assumption of linearity of the nonlinear joint stiffness characteristics with respect to properly defined elastic parameters, a direct approach to the calculation of an augmented form of the regressor is proposed, where both inertial and elastic parameters appear in factored form. This allows off-line and on-line schemes to be applied for the concurrent identification of both inertial and elastic parameters. In the paper, the proposed methodology is fully detailed, and its application to a simple robot shows its effectiveness.