Search results for "Nonlinear system"
showing 10 items of 1446 documents
Nonlinear concave-convex problems with indefinite weight
2021
We consider a parametric nonlinear Robin problem driven by the p-Laplacian and with a reaction having the competing effects of two terms. One is a parametric (Formula presented.) -sublinear term (concave nonlinearity) and the other is a (Formula presented.) -superlinear term (convex nonlinearity). We assume that the weight of the concave term is indefinite (that is, sign-changing). Using the Nehari method, we show that for all small values of the parameter (Formula presented.), the problem has at least two positive solutions and also we provide information about their regularity.
A velocity–diffusion method for a Lotka–Volterra system with nonlinear cross and self-diffusion
2009
The aim of this paper is to introduce a deterministic particle method for the solution of two strongly coupled reaction-diffusion equations. In these equations the diffusion is nonlinear because we consider the cross and self-diffusion effects. The reaction terms on which we focus are of the Lotka-Volterra type. Our treatment of the diffusion terms is a generalization of the idea, introduced in [P. Degond, F.-J. Mustieles, A deterministic approximation of diffusion equations using particles, SIAM J. Sci. Stat. Comput. 11 (1990) 293-310] for the linear diffusion, of interpreting Fick's law in a deterministic way as a prescription on the particle velocity. Time discretization is based on the …
Nonlinear FE analysis of out-of-plane behaviour of masonry walls with and without CFRP reinforcement
2014
Abstract The out-of-plane behaviour of unreinforced and CFRP reinforced masonry wall is studied by means of experimental investigation and numerical FE modelling. The latter is based on a linear constitutive law both for ashlars and mortar joints constituting masonry and the lines of potential delamination are taken into account by means of an interface element with bi-linear law, reproducing the opening failure mode. When reinforcement is introduced, an interface element with bi-linear law is also used, reproducing sliding failure mode. Comparison between numerical and experimental results show the reliability of the modelling. Moreover, a parametric analysis is carried out in order to inv…
Numerical modelling of out-of-plane response of infilled frames: State of the art and future challenges for the equivalent strut macromodels
2017
Abstract Infill-frame interaction constitutes a still open question both in research and in practicing engineering. Computational models used to predict this interaction are, in most cases, addressing the estimation of the response of the infilled frames when subjected to actions parallel to their plane. However, the observation of the post-earthquake damage has demonstrated that infills, weakened by the in-plane actions, may fail out-of-plane increasing the risks associated to the earthquake scenarios. In spite of this, different studies have shown that infills, if properly designed and supported by the frame, exhibit a significant strength and displacement capacity when called to resist t…
Comments on “Finite-Time $H_{\infty }$ Fuzzy Control of Nonlinear Jump Systems With Time Delays Via Dynamic Observer-Based State Feedback”
2014
This paper investigates a defect appearing in “Finite-time H∞ fuzzy control of nonlinear jump systems with time delays via dynamic observer-based state feedback,” which the observer-based finite-time H∞ controller via dynamic observer-based state feedback could not ensuring stochastic finite-time boundedness, and satisfying a prescribed level of H∞ disturbance attenuation for the resulting closed-loop error fuzzy Markov jump systems. The corrected results are presented, and the improved optimal algorithms and new simulation results are also provided in this paper.
Observer-based stabilization of spacecraft rendezvous with variable sampling and sensor nonlinearity
2013
Published version of an article in the journal: Mathematical Problems in Engineering. Also available from the publisher at: http://dx.doi.org/10.1155/2013/902452 Open Access This paper addresses the observer-based control problem of spacecraft rendezvous with nonuniform sampling period. The relative dynamic model is based on the classical Clohessy-Wiltshire equation, and sensor nonlinearity and sampling are considered together in a unified framework. The purpose of this paper is to perform an observer-based controller synthesis by using sampled and saturated output measurements, such that the resulting closed-loop system is exponentially stable. A time-dependent Lyapunov functional is devel…
A sliding mode approach to H∞ non-fragile observer-based control design for uncertain Markovian neutral-type stochastic systems
2015
This paper is focused on designing an H ∞ sliding-mode control for a class of neutral-type stochastic systems with Markovian switching parameters and nonlinear uncertainties. An H ∞ non-fragile observer subjected to the transition rates of the switching mode is firstly constructed. By some specified matrices, the connections among the designed sliding surfaces corresponding to every mode are established. Then, the state-estimation-based sliding mode control law is designed to guarantee the reachability of the sliding surface in finite time interval. Furthermore, a stochastic stability criterion is established for all admissible uncertainties, which can guarantee the error system and sliding…
Identification of a Hammerstein model for DC/DC converters operating in CCM
2005
This paper deals with a method for identification of a Hammerstein model of DC-DC converters operating in continuous conduction mode (CCM). This model has the duty cycle and the output voltage as input and output, respectively; it consists of a static nonlinearity and a linear and time-invariant model. The aim of the modeling the system by means of a Hammerstein model is due to its capability of describing the converter in a range of steady-state operating points instead of a desired well defined operating point as occurs for the small-signal models which are the more common mathematical description to approach the study of the converters themselves. The nonlinear characteristic of the Hamm…
Nonlinear Modeling of DC/DC Converters Using the Hammerstein's Approach
2007
This paper deals with the modelling of highly nonlinear switching power-electronics converters using black-box identification methods. The duty cycle and the output voltage are chosen, respectively, as the input and the output of the model. A nonlinear Hammerstein-type mathematical model, consisting of a static nonlinearity and a linear time-invariant model, is considered in order to cope with the well-known limitations of the more common small-signal models, i.e. the entity of the variations of the variables around a well-defined steady-state operating point and the incorrect reproduction of the steady-state behavior corresponding to input step variations from the above steady-state operat…
Galerkin Scheme-Based Determination of Survival Probability of Oscillators With Fractional Derivative Elements
2016
In this paper, an approximate semi-analytical approach is developed for determining the first-passage probability of randomly excited linear and lightly nonlinear oscillators endowed with fractional derivative elements. The amplitude of the system response is modeled as one-dimensional Markovian process by employing a combination of the stochastic averaging and the statistical linearization techniques. This leads to a backward Kolmogorov equation which governs the evolution of the survival probability of the oscillator. Next, an approximate solution of this equation is sought by resorting to a Galerkin scheme. Specifically, a convenient set of confluent hypergeometric functions, related to …