|A Robust Controller for Trajectory Tracking of a DC Motor Pendulum System
Carlos Aguilar-Ibañez*, Julio Mendoza-Mendoza, Jorge Davila, Miguel S. Suarez-Castanon and Ruben Garrido M.
International Journal of Control, Automation, and Systems, vol. 15, no. 4, pp.1632-1640, 2017
Abstract : "This work presents a solution to the output feedback trajectory tracking problem for an uncertain DC
motor pendulum system under the effect of an unknown bounded disturbance. The proposed algorithm uses a Proportional
Derivative (PD) controller plus a novel on-line estimator of the unknown disturbance. The disturbance
estimator is obtained by coupling a standard second-order Luenberger observer with a third-order sliding modes differentiator.
The Luenberger observer provides estimates of the motor angular position and velocity. Moreover, an
ideal disturbance estimator in terms of the Luenberger observer error and its first and second time derivatives is obtained
from the observer error formulae; these time derivatives are not available from measurements. Subsequently,
the sliding modes third-order differentiator allows obtaining estimates of these time derivatives in finite time. The
estimates replace the real values of the first and second time derivatives in the ideal disturbance estimator thus
producing a practical disturbance estimator, and also permit obtaining an estimate of the motor angular velocity. A
depart from previous approaches is the fact that the disturbance is not directly estimated by the Luenberger observer
or the third-order differentiator. Numerical simulations and real-time experiments validate the effectiveness of the
Finite time observer, PD controller, servomechanism, variable structure control.