Estimation of decenteralized unknown dynamics for a 2DOF manipulator using a time varying extended state observer

Abstract

In this paper, an estimation of the dynamics of a 2 degrees of freedom robot manipulator with uncertainties, is derived, using an extended state observer. Decentralizing approach in multivariable systems, is an methodolgy used in an increasing number of practical systems to simplify the controller design. On the other hand, these systems usually contain uncertainties, and also parts of the system's dynamics are unknown. Due to the robust characteristics of extended state observers, these observers would be able to estimate these unknown dynamics, which has been discussed in the literature thoroughly. In this paper, a special class of extended state observers, namely the time varying extended state observer, will be discussed to estimate the dynamics and the disturbances related to the couplings in a manipulator with 2 degrees of freedom. The proposed observer significantly reduces the estimation error's peaking phenomenon, using time variant gains. Thus, it has a better performance compared to similar observers in the literature. This specific class, has time varying parameters, which makes its design simpler and presents a better performance, compared to other linear or nonlinear observers available. As shown in the simulations, the estimation error pick phenomena reduces drastically.