Environmental torque estimation for flexible-link manipulators based on nonlinear disturbance observer

Estimation of environmental torques exerted on a flexible-link manipulator is studied in this paper. To achieve this goal, a nonlinear disturbance observer is proposed. Moreover, in order to estimate the robot flexural rates, another observer is integrated with this nonlinear disturbance observer. However, the obtained integrated observer can estimate the total disturbance torques which is the combination of the environmental torques and internal disturbance torques. To cope with this problem, a robust control law is employed such that it attenuates the effects of uncertainties on the performance of the observer. The accuracy of the proposed approach is investigated via numerical simulations.