|Disturbance-observer Based Adaptive Control for Second-order Nonlinear Systems Using Chattering-free Reaching Law
Liang Tao, Qiang Chen*, and Yurong Nan
International Journal of Control, Automation, and Systems, vol. 17, no. 2, pp.356-369, 2019
Abstract : "In this paper, an adaptive sliding mode control incorporating with a nonlinear disturbance observer is
proposed for a class of second-order nonlinear systems with unknown parameters and matched lumped disturbance.
A double hyperbolic reaching law with chattering-free characteristic is first constructed, and an adaptive sliding
mode controller is designed to guarantee the satisfactory tracking performance and fast error convergence. The
chattering problem is eliminated by means of the infinitely approaching equilibrium point instead of crossing it by
employing two hyperbolic functions. In order to identify the unknown parameters accurately, an adaptive parametric
update law is presented through constructing a set of auxiliary filtered variables. Then, a nonlinear disturbance
observer is proposed to improve the tracking performance and compensate for the lumped disturbance including
perturbations and uncertainties. The stability analysis is provided by the Lyapunov stability theory, and a numerical
simulation on a mass-spring damper system is given to demonstrate the effectiveness of the proposed method."
"Disturbance observer, double hyperbolic reaching law, parametric identification, second-order nonlinear systems, sliding mode control."