Continuous uniformly finite time exact disturbance observer based control for fixed-time stabilization of nonlinear systems with mismatched disturbances.

This paper presents a continuous composite control scheme to achieve fixed-time stabilization for nonlinear systems with mismatched disturbances. The composite controller is constructed in two steps: First, uniformly finite time exact disturbance observers are proposed to estimate and compensate the disturbances. Then, based on adding a power integrator technique and fixed-time stability theory, continuous fixed-time stable state feedback controller and Lyapunov functions are constructed to achieve global fixed-time system stabilization. The proposed control method extends the existing fixed-time stable control results to high order nonlinear systems with mismatched disturbances and achieves global fixed-time system stabilization. Besides, the proposed control scheme improves the disturbance rejection performance and achieves performance recovery of nominal system. Simulation results are provided to show the effectiveness, the superiority and the applicability of the proposed control scheme

Chattering-Free Time Scale Separation Sliding Mode Control Design with Application to Power System Chaos Suppression

This paper presents a novel chattering-free sliding mode control method for a class of disturbed nonlinear systems, which achieves fast and exact disturbance estimation, eliminates chattering, and recovers the performance of nominal system and nominal control input. The proposed approach combines time scale separation design and sliding mode control. Different from the existing disturbance estimation based sliding mode control methods, the proposed scheme achieves fast and exact disturbance estimation through time scale separation and eliminates discontinuous switching term, thereby achieving good chattering alleviation effect and providing good transient response. The proposed control method is applied to suppress chaos in power system and simulation results confirm the effectiveness and robustness of proposed control scheme and highlight the advantages of the proposed control scheme over the existing disturbance estimation based sliding mode control methods in terms of chattering alleviation effect and transient response

Time response of system states under disturbance observer based control and baseline control.

<p>Time response of system states under disturbance observer based control and baseline control.</p

Sketch diagram of DC-motor.

<p>Sketch diagram of DC-motor.</p

Curves of the disturbances <i>d</i>₁, , <i>d</i>₂ and their estimated values under the proposed disturbance observer.

<p>Curves of the disturbances <i>d</i>₁, , <i>d</i>₂ and their estimated values under the proposed disturbance observer.</p

Convergence time versus the logarithm of norm of initial condition.

<p>Convergence time versus the logarithm of norm of initial condition.</p

Time response of system states under the proposed control scheme.

<p>Time response of system states under the proposed control scheme.</p

Time response of system states under the control scheme proposed in [26].

<p>Time response of system states under the control scheme proposed in [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0175645#pone.0175645.ref026" target="_blank">26</a>].</p

Curves of the disturbances , , and their estimated values.

<p>Curves of the disturbances , , and their estimated values.</p