Nonlinear disturbance observer for flexible-link manipulators based on flexural rate estimation

In this paper, a nonlinear disturbance observer (NDO) is designed to estimate the environmental torques exerted on a flexible-link manipulator. To avoid differentiation from noisy data in order to get the estimate of flexural rates, another reduced order observer is employed. Then, the stability analysis of the integrated observer errors based on Lyapunov stability criterion is studied. Finally, the performance of the proposed observer is investigated by numerical simulations.