Search results for "Linear"
showing 10 items of 7165 documents
Nonlinear analysis of cylindrical and conical hysteretic whirl motions in rotor-dynamics
2014
Abstract The internal friction of a rotor–shaft-support system is mainly due to the shaft structural hysteresis and to some possible shrink-fit release of the assembly. The experimentation points out the destabilizing effect of the internal friction in the over-critical rotor running. Nevertheless, this detrimental influence may be efficiently counterbalanced by other external dissipative sources located in the supports or by a proper anisotropic configuration of the support stiffness. The present analysis considers a rotor–shaft system which is symmetric with respect to the mid-span and is constrained by viscous-flexible supports with different stiffness on two orthogonal planes. The cylin…
Fault Detection of Networked Control Systems Based on Sliding Mode Observer
2013
Published version of an article in the journal: Mathematical Problems in Engineering. Also availeble from the publisher at: http://dx.doi.org/10.1155/2013/506217 Open Access This paper is concerned with the network-based fault detection problem for a class of nonlinear discrete-time networked control systems with multiple communication delays and bounded disturbances. First, a sliding mode based nonlinear discrete observer is proposed. Then the sufficient conditions of sliding motion asymptotical stability are derived by means of the linear matrix inequality (LMI) approach on a designed surface. Then a discrete-time sliding-mode fault observer is designed that is capable of guaranteeing the…
Peak Power Demand and Energy Consumption Reduction Strategies for Trains under Moving Block Signalling System
2013
Published version of an article in the journal: Mathematical Problems in Engineering. Also available from the publisher at: http://dx.doi.org/10.1155/2013/940936 Open Access In the moving block signalling (MBS) system where the tracking target point of the following train is moving forward with its leading train, overload of the substations occurs when a dense queue of trains starts (or restarts) in very close distance interval. This is the peak power demand problem. Several methods have been attempted in the literature to deal with this problem through changing train's operation strategies. However, most existing approaches reduce the service quality. In this paper, two novel approaches - …
H∞ fuzzy control of DC-DC converters with input constraint
2012
Published version of an article in the journal: Mathematical Problems in Engineering. Also available from the publisher at: http://dx.doi.org/10.1155/2012/973082 Open access This paper proposes a method for designing H∞ fuzzy control of DC-DC converters under actuator saturation. Because linear control design methods do not take into account the nonlinearity of the system, a T-S fuzzy model and a controller design approach is used. The designed control not only handles the external disturbance but also the saturation of duty cycle. The input constraint is first transformed into a symmetric saturation which is represented by a polytopic model. Stabilization conditions for the H∞ state feedba…
Structural Health Monitoring Procedure for Composite Structures through the use of Artificial Neural Networks
2015
In this paper different architectures of Artificial Neural Networks (ANNs) for structural damage detection are studied. The main objective is to investigate an ANN able to detect and localize damage without any prior knowledge on its characteristics so as to serve as a real-time data processor for Structural Health Monitoring (SHM) systems. Two different architectures are studied: the standard feed-forward Multi Layer Perceptron (MLP) and the Radial Basis Function (RBF) ANNs. The training data are given, in terms of a Damage Index ℑD, properly defined using a piezoelectric sensor signal output to obtain suitable information on the damage position and dimensions. The electromechanical respon…
Neural based MRAS sensorless techniques for high performance linear induction motor drives.
2010
This paper proposes a neural based MRAS (Model reference Adaptive System) speed observer suited for linear induction motors (LIM). Starting from the dynamical equation of the LIM in the synchronous reference frame in literature, the so-called voltage and current models of the LIM in the stationary reference frame, taking into consideration the end effects, have been deduced. Then, while the inductor equations have been used as reference model of the MRAS observer, the induced part equations have been discretized and rearranged so to be represented by a linear neural network (ADALINE). On this basis, the so called TLS EXIN neuron has been used to compute on-line, in recursive form, the machi…
New Procedures of Pattern Classification for Vibration-Based Diagnostics via Neural Network
2014
In this paper, the new distance-based embedding procedures of pattern classification for vibration-based diagnostics of gas turbine engines via neural network are proposed. Diagnostics of gas turbine engines is important because of the high cost of engine failure and the possible loss of human life. Engine monitoring is performed using either ‘on-line’ systems, mounted within the aircraft, that perform analysis of engine data during flight, or ‘off-line’ ground-based systems, to which engine data is downloaded from the aircraft at the end of a flight. Typically, the health of a rotating system such as a gas turbine is manifested by its vibration level. Efficiency of gas turbine monitoring s…
A semi-empirical multipurpose steady-state model of a fuel cell for household appliances
2013
In this paper, a multipurpose model of a proton exchange membrane fuel cell for household appliances is proposed. According to a conventional mathematical approach, the proposed model is derived from the physical and electro-chemical equations that rule the fuel cell behaviour. Differently from existing models, a parametric analysis is carried out and a few tunable parameters are accurately selected and identified. Furthermore, this paper proposes an innovative technique of unique model architecture which enables the designer to solve by himself the trade-off between complexity and accuracy on the basis of the specific applications. Three different choices could be performed by the designer…
Gabor filters in industrial inspection: a review. Application to semiconductor industry
2005
This paper focuses on reviewing some recent works of the use of Gabor filters dealing with industrial applications. After a brief recall of Gabor filter basis, the two usual uses of Gabor filters are recalled: filter bank approach and filter design approach. The third part presents recent published works domain by domain. A fourth part exposes our own work with Gabor Filters for defect detection on semiconductor. A short conclusion summarizes the paper.
ALE Simulation of Orthogonal Cutting: a New Approach to Model Heat Transfer Phenomena at the Tool-Chip Interface
2007
This paper presents a new procedure to evaluate the global heat transfer coefficient in orthogonal cutting. The knowledge of the actual heat transfer conditions is a fundamental issue as far as the life, tool wear and tool substitution interval are regarded. More in detail, an Arbitrary Lagrangian-Eulerian approach was utilised to model orthogonal cutting process and the numerical simulations were validated by making experimental tests for identifying cutting forces and internal tool temperatures. A mild steel was cut utilising both an uncoated (WC) and a coated (TiN) tool. On the basis of both experimental and simulative data, a consistent model of the global heat transfer coefficient as f…