N. Luo

Discretization and FIR filtering of continuous linear systems with internal and external point delays

A discrete quasi-autoregressive moving average (QARMA) model and an equivalent impulse response (IR) description are established for linear continuous systems with internal and external point delays which are discretized through a sampler and zero-order-hold device. The QARMA-model is proved to differ from the standard autoregressive moving average (ARMA) models because of its infinite input memory caused by the delays. Based on the IR-model, a finite impulse response (FIR)-filter is proposed to approximate the input-output description under exponential stability of the unforced system. Its implementation is discussed by using fast filtering design tools.

Sliding mode control of a class of uncertain coupled systems: application to base isolated structures

The problem of feedback stabilization is addressed for a class of uncertain nonlinear mechanical systems with n degrees and n/sub c/<n control inputs. Each system of the class has the structure of two coupled subsystems with n/sub c/ and n/sub r/ degrees of freedom, respectively, n=n/sub c/+n/sub r/. A practical prototype of such systems is an uncertain base isolated structure with n degrees of freedom actively controlled via actuators applying forces to the base movement of n/sub c/<n degrees of freedom. A variable structure feedback strategy is proposed, under appropriate assumptions on the system uncertainties, to guarantee the asymptotic stability of the overall system.

Active model reference SMC schemes for vibration reduction of flexible cable-stayed bridges

Abstract In this paper, robust model reference sliding mode controllers are designed to reduce the magnitude of the transversal vibrations of a flexible cable-stayed bridge structure induced by a seismic excitation. The dynamic behaviour of the bridge is described by a mathematical model which takes into account the inherent nonlinearities due to the stay cables geometry. A numerical simulation example is presented to illustrate the effectiveness of the proposed control schemes.

Composite sliding mode control of seismically excited structures with actuator dynamics

A composite sliding mode control scheme is proposed for a class of nonlinear base isolated structures in the presence of unknown seismic excitation, parametrical uncertainties and actuator dynamics. Only the information on state variables of the base and the first floor has been used in the control design. A numerical simulation example is given for a 10-storey base isolated structure under the El Centro earthquake.

Decentralized Sliding Mode Control of a Two-Cable-Stayed Bridge

One of the main objectives in the design of cable-stayed bridge structures is to mitigate the hazards caused by external forces such as traffic, heavy winds and earthquakes and thus to lengthen its life (see [1] and [2]). Both linear and nonlinear mathematical models were developed to describe the dynamic behaviour of the cable-stayed bridges in [2] and [3]. In the recent years, several active tendon control schemes have been proposed to reduce the transversal vibration of the bridge deck, among which the centralized linear active control in [4], [5] and [6] and decentralized nonlinear active control in [3] and [7] have received a great of attention. In this paper, a new robust stabilizing decentralized controller is presented to attenuate the transversal vibration of a two-cable-stayed bridge structure induced by seismic excitation. Control design is made based on the principle of sliding mode, in which the information on the exact value of the system parameters, structural disturbances and the seismic excitation does not need to be known a priori. Conditions for the generation of sliding motion are given. Stability and robustness of the closed-loop system are analized.

Robust Stabilization of Internally Delayed Uncertain Systems via Sliding Mode Control

SummaryThe problem of robust stabilization of internally delayed uncertain systems via sliding mode controllers (SMCs) is studied in this paper. The robustness property and assymptotic stability of the system are discussed. Some sufficient conditions for the design of SMC and the switching hyperplane are given. Further generalization results, which lead to a simple design and implementation, are made for the system being described in companion form. A method is suggested for the elimination of limit cycles in systems being regulated by a relay SMC while allowing the generation of sliding motion and thus ensuring the closed-loop asymptotic stability.

Output feedback stabilization of a class of uncertain internally delayed systems

Abstract This paper is concerned with the problem of output feedback stabilization of a class of uncertain internally (i.e. in the state) delayed systems, in which only the upper bounds of nonlinear uncertainties are given. The designs of both static and dynamic output feedback controllers are considered. Some sufficient conditions for the stabilization of closed-loop systems are proposed, based upon the use of Lyapunovs stability criteria

Robust Stability and Stabilisation of Uncertain Time-delay Systems Under Sliding Mode

Abstract This paper addresses the problem of robust stabilisation of uncertain time-delay systems by using sliding mode controllers. In the regulated process, both internal (i.e., in the state) point delay, externill (i.e., in the input) point delay and a class of nonlinear uncertainties are involved. Sufficient conditions for the design of robust asymptotically stabilising sliding mode controllers are given.

Dynamic Output Feedback Control of a Class of Uncertain Time Delay Systems

This paper is concerned with the problem of stabilization of a class of SISO uncertain time-delay systems by using output feedback controllers. The uncertainties are described in terms of upper-bounds on their possible sizes. The designs of both static and dynamic output feedback controllers are considered. Some sufficient conditions for stabilization are proposed based upon tre use of Lyapunovs stability criteria.