Low gain feedback for fractional-order linear systems and semi-global stabilization in the presence of actuator saturation

Nonlinear Dynamics - This paper presents a low gain feedback design for fractional-order linear systems. A family of linear state feedback laws, parameterized in a positive low gain parameter...     

Single-parameter-learning-based robust adaptive control of dynamic positioning ships considering thruster system dynamics in the input saturation state

Nonlinear Dynamics - The focus of this paper is presented on robust adaptive dynamic positioning control in the face of thruster system dynamics. In the maritime domain, it considers the issues of...     

IMPULSIVE CONTROL FOR THE STABILIZATION AND SYNCHRONIZATION OF LUR＇ E SYSTEMS

An impulsive control scheme of the Lur‘e system and several theorems on stability of impulsive control systems was presented, these theorems were then used to find the conditions under which the Lur‘e system can be stabilized by using impulsive control with varying impulsive intervals. The parameters of Lur‘e system and impulsive control law are given, a theory of impulsive synchronization of two Lur‘e system is also presented. A numerical example is used to verify the theoretical result.     

Passivity-based control for a flexible spacecraft in the presence of disturbances

The attitude regulation control problem for flexible spacecraft is investigated in this paper. Two extended PD+variable structure controllers are proposed using passivity-based control technique instead of sliding mode control approach. The first controller is a basic one, while the second one is an extension of the first one which relaxes the bound requirement for the external disturbances. In the presence of model uncertainties and external disturbances, both controllers presented in this research can make the flexible spacecraft UGAS (uniformly globally asymptotically stable). By virtue of related analysis tools, stability of the proposed controllers is proven theoretically. Numerical simulations are also included to demonstrate the performance of the developed controllers.     

Robust identification for fault detection in the presence of non-Gaussian noises: application to hydraulic servo drives

Nonlinear Dynamics - Intensive research in the field of mathematical modeling of hydraulic servo systems has shown that their mathematical models have many important details which cannot be...     

Transient-state flow of a conducting liquid in an MHD generator at constant flow rate in the presence of side walls

It is usual in studies of transient [nonsteady] flow for a viscous incompressible conducting fluid in an MHD channel to take the distance between the side walls as infinite, which allows the initial equations to be simplified, these reducing to a single equation for the velocity if the magnetic Reynolds number is small [1–3]. A real system has a finiteratio of the sides, so it is desirable to establish the effects of the side walls.     

A mathematical model for an alloy solidification problem in the presence of an electric field

A one-dimensional mathematical model for a process of solidification of a binary alloy in the presence of an electric field is studied. A situation in which the thermal properties of each phase are different and the latent heat is non-zero is considered. A quasi-static approximation for the thermal and electric fields is used. Local existence and uniqueness of a classical solution to the resulting free boundary problem are proved for two kinds of boundary conditions. Moreover, under particular hypotheses, the monotonicity of the free boundary and the global existence of the solution is proved.

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Sommario Si studia un modello matematico unidimensionale per un processo di solidificazione di una lega binaria in presenza di un campo elettrico. Si considera una situazione in cui le proprietà termiche di ogni fase sono differenti e il calore latente è non nullo. Si usa una approssimazione quasi-statica per i campi elettrico e termico. Si dimostra l'esistenza locale e l'unicità di una soluzione classica per il problema di frontiera libera risultante con due tipi di condizioni di bordo. Inoltre si dimostra, sotto particolari ipotesi, la monotonia della frontiera libera e l'esistenza di soluzione globale.

     

On iterative learning control for MIMO nonlinear systems in the presence of time-iteration-varying parameters

In this study, the problem of adaptive iterative learning control (AILC) is considered for a class of multiple-input-multiple-output discrete-time nonlinear systems where the initial condition and reference trajectory could be randomly varying in the iteration domain. It is assumed that the considered systems are subjected to time-iteration-varying unknown parameters. The iteration-varying parameters are generated by a known high-order internal model (HOIM) that is formulated as a polynomial between two consecutive iterations. By incorporating the HOIM into the controller design, the learning convergence of ILC is guaranteed through rigorous analysis under Lyapunov theory. The illustrative example is presented to demonstrate the effectiveness of AILC method.     

Two-dimensional interaction between an incident shock and a turbulent boundary layer in the presence of an entropy layer

The results of an experimental and numerical investigation of flow and heat transfer in the region of the interaction between an incident oblique shock and turbulent boundary layers on sharp and blunt plates are presented for the Mach numbers M_∞ = 5 and 6 and the Reynolds numbers Re_∞L = 27×10⁶ and 14×10⁶. The plate bluntness and the incident shock position were varied. It is shown that the maximum Stanton number St _m in the shock incidence zone decreases with increase in the plate bluntness radius r to a certain value and then varies only slightly with further increase in r. In the case of a turbulent undisturbed boundary layer heat transfer is diminished with increase in r more slowly than in the case of a laminar undisturbed flow. In the presence of an incident shock the bluntness of the leading edge of the flat plate results in a greater decrease in the Stanton number than in the absence of the shock. With increase in the bluntness of the leading edge of the plate the separation zone first sharply lengthens and then decreases in size or remains constant.     

Proposition of an uncoupled approach for the identification of cyclic heat sources from temperature fields in the presence of large strains

A methodology is proposed to define an equivalent geometry allowing the use of an uncoupled algorithm to solve thermomechanical problems when cyclic large strain occurs. This methodology is set up on the case of a simple bar and is then challenged on a structural sample for cyclic loadings. It is shown that the definition of the equivalent geometry is dependent on the thermal boundary conditions, which are usually unknowns of the thermal problem. The proposed approach is finally applied to the identification of cyclic dissipation from infrared thermography measurements.     

Resonance phenomena in cylindrical shell with a spherical inclusion in the presence of an internal compressible liquid and an external elastic medium

In the present paper a method is proposed to investigate the behaviour of the axisymmetric system consisting of an infinite thin elastic cylindrical shell submerged in an unbounded elastic medium, filled with an ideal compressible liquid and containing a vibrating spherical inclusion, under periodic dynamic action. The goal is the analysis of the so-called “resonance” phenomena; namely: finding conditions for their appearance, and possible control by means of characteristic parameters of the hydroelastic system under consideration. The technique presented in this work was developed during the realization of a project on elaboration of methods of renewal of oil production in foul wells at the Theory of Vibration Department of the S.P. Timoshenko Institute of Mechanics of the Ukrainian Academy of Science. This mathematical technique allows rewriting the general solution of the corresponding mathematical physics equations from one coordinate system to another, so as to get an exact analytical solution (as a Fourier series) of the interaction problem for a collection of rigid and elastic bodies.     

Uniaxial extension of an isothermal fluid cylinder in the presence of inertia,surface tension and gravity

Effects of inertia, surface tension and gravity in the constant force stretching of isothermal cylindrical filaments of Newtonian, power-law and Maxwell-type fluids were analysed in Lagrangian coordinates. Solution for the purely gravitational extension of Newtonian fluid cylinder was found to be as simple as = 1 – C ₃ (1 – ) where designates the cross sectional area, the Lagrangian distance and the time. Analytical solutions were also available for the case of inertialess Newtonian and power-law fluids.A first-order backward differencing scheme and minimal computer time were sufficient to numerically analyse the constant force extension of Maxwell-type fluids in the presence of inertia, gravity and surface tension. Effects of inertia, surface tension and gravity on the severity of neck down occurring at either end of the filament are summarized in diagrams. The present approach is valid on any other constitutive model as far as there is a numerical scheme to analyse thehomogeneous extension of a cylinder of that particular fluid.