Continuous Finite-Time Active Disturbance Rejection Control With Application to DC Motor

In this paper, we propose a continuous finite-time-convergent active disturbance rejection control design scheme for a class of second order uncertain nonlinear systems. A continuous finite-time-convergent extended state observer is first developed to estimate the total disturbance which includes the nonlinear time-varying uncertain dynamics and the external disturbances. A continuous finite-time active disturbance rejection control design scheme is proposed by using saturation method. The key idea is using the estimate of the total disturbance to compensate the uncertainty such that the output tracks a given setpoint in finite time and stays at the setpoint afterwards, and all states of the closed-loop system remain uniformly bounded. By this dynamic compensation and saturation strategy, the finite-time stability of the error system is established under some weak restrictions on nonlinearities of the system. Experiments on a DC motor platform are carried out to illustrate the effectiveness of the proposed method.