Linear Active Disturbance Rejection Control Design for a Single-Link Flexible-Joint Manipulator with Uncertainties

A robust design method based on Linear Active Disturbance Rejection Control (LADRC) is proposed for the trajectory tracking control (TTC) of single-link flexible-joint manipulator (SLFJM) affected by uncertainties. By using diffeomorphic coordinate transformation, the manipulator is first modeled as a linear system with nonlinear uncertainties. Then it regards all the uncertainties, including the nonlinear dynamics, parameter perturbations, and exogenous disturbances as a new extended disturbance state. An extended state observer is designed to estimate and compensate the total disturbance, and the original manipulator nonlinear system becomes a linear integral series one. A state error feedback control law is finally designed to achieve the TTC. The advantages of the proposed control method are that it does not require an exact model information of the manipulator, and only the measurement of the link angle is utilized. The stability of the closed-loop control system is assured under the assumptions of bounded disturbances and small change rates of uncertainties. Simulations are carried out to verify the effectiveness and superiority of the proposed method.