We propose the use of a second-order sliding-mode controller (2-SMC) to stabilize an autonomous underwater vehicle (AUV) which is subject to modeling errors and often suffers from unknown environmental disturbances. The 2-SMC is effective in compensating for the uncertainties in the hydrodynamic and hydrostatic parameters of the vehicle and rejecting the unpredictable disturbance effects due to ocean waves, tides, and currents. The 2-SMC is comprised of an equivalent controller and a switching controller to suppress the parameter uncertainties and external disturbances, and its closed-loop system is exponentially stable in the presence of parameter uncertainties and unknown disturbances. We performed numerical simulations to validate the proposed control approach, and experimental tests using Cyclops AUV were conducted to demonstrate its practical feasibility. The proposed controller increased the accuracy of trajectory tracking for an AUV in the presence of uncertain hydrodynamics and unknown disturbances.

Second-order sliding-mode controller for autonomous underwater vehicle in the presence of unknown disturbances

In this article, a novel sliding mode control (SMC) approach is proposed for the control of a class of underactuated systems which are featured as in cascaded form with external disturbances. The asymptotic stability conditions on the error dynamical system are expressed in the form of linear matrix inequalities. The control objective is to construct a controller such that would force the state trajectories to approach the sliding surface with an exponential policy. The proposed SMC has a simple structure because it is derived from the associated first-order differential equation and is capable of handling system disturbances and nonlinearities. The effectiveness of the proposed control method is validated using intensive simulations. © 2014 Wiley Periodicals, Inc. Complexity, 2014

Design of LMI-based sliding mode controller with an exponential policy for a class of underactuated systems

This paper investigates a robust adaptive second-order sliding mode control method for tracking problem of a class of uncertain linear systems with matched and unmatched disturbances. The fundamental idea of the suggested control method is that the discontinuous sign function is used for the time-derivative of the control signal and hence the smooth control input achieved after an integration process is continuous and removes the chattering problem. Using a PID sliding surface, the finite-time convergence of output tracking errors is obtained. The adaptive gain-tuning control law removes the necessity of gaining information about the upper bounds of the external disturbances. The control system is in the sliding mode and then, tracking errors converge to the origin in a finite time under the presence of the external disturbances. Simulation results on an uncertain numerical system and a turntable servo-system are presented to indicate the effectiveness and feasibility of the proposed scheme.

A novel robust adaptive second-order sliding mode tracking control technique for uncertain dynamical systems with matched and unmatched disturbances

We propose and analyze a scheme to enhance optomechanically-induced-transparency (OMIT) based on parity-time-symmetric optomechanical system. Our results predict that an OMIT window which does not exist originally can appear in weak optomechanical coupling and driving system via coupling an auxiliary active cavity with optical gain. This phenomenon is quite different from these reported in previous works in which the gain is considered just to damage OMIT phenomenon even leads to electromagnetically induced absorption or inverted-OMIT. Such enhanced OMIT effects are ascribed to the additional gain which can increase photon number in cavity without reducing effective decay. We also discuss the scheme feasibility by analyzing recent experiment parameters. Our work provide a promising platform for the coherent manipulation and slow light operation, which has potential applications for quantum information processing and quantum optical device.

/pdf/parity-time-symmetry-enhanced-optomechanically-induced-18nokdm4xr.pdf

Parity-time-symmetry enhanced optomechanically-induced-transparency

In this paper, a pinning impulsive control scheme is adopted to investigate the synchronization of fractional complex dynamical networks. An effective method has been applied to select controlled nodes at each impulsive constants. Based on the Lyapunov function method and the connection between the exponential function and Mittag-Leffler function, sufficient conditions for achieving exponential synchronization of fractional complex networks have been derived. Finally, numerical simulations are exploited to verify the effectiveness of the theoretical results, and some discussions about synchronization region are given.

Exponential synchronization of fractional-order complex networks via pinning impulsive control

Projective synchronization of a class of complex networks is investigated using second-order sliding mode control. The sliding surface and the control input are designed based on stability theory. The Burgers system with spatiotemporal chaotic behavior in the physics domain is taken as nodes to constitute the complex network, and the Fisher–Kolmogorov system is taken as the tracking target. The artificial simulation results show that the synchronization technique is effective.

Projective synchronization of a class of complex network based on high-order sliding mode control

This paper investigates the signal synchronization transmission among uncertain discrete networks with different nodes based on Lyapunov theorem. A novel synchronization technique and an identification law of adjustment parameter are designed. In order to testify the effectiveness of synchronization technique, laser phase-conjugate wave, Gibbs electro-optical system and Bragg acousto-optical system are taken as the nodes of the complex networks to make a simulation. It shows the synchronization technique can be applied to any network connected arbitrarily, and the network number and the number of network nodes can be selected freely.

The signal synchronization transmission among uncertain discrete networks with different nodes

In this paper, we research the outer synchronization among discrete networks with different topologies. Based on Lyapunov theorem, a novel synchronization technique is designed. Further, the control inputs of the networks and the adaptive laws of configuration matrix element are obtained. In the end, a numerical example is given to illustrate the effectiveness of the synchronization technique. It is found that the designed control input of the networks ensures the convergence of the errors among the networks to zero. And the designed adaptive law of configuration matrix element can replace effectively configuration matrix element in networks.

Shuo Liu

Papers

Projective synchronization of a class of complex network based on high-order sliding mode control

The signal synchronization transmission among uncertain discrete networks with different nodes

Determination of configuration matrix element and outer synchronization among networks with different topologies