Some Bond Graph Structural Properties: Eigen Spectra and Stability

1989 ◽  
Vol 111 (3) ◽  
pp. 382-388 ◽  
Author(s):  
A. Zeid
Keyword(s):  
Canonical Form ◽  
Bond Graph ◽  
Design Tool ◽  
System Stability ◽  
Stability Estimates ◽  
Graphical Modeling ◽  
Linear And Nonlinear ◽  
The Stability ◽  
Time Invariant

What does the structure of the bond graph reveal about the eigenvalues of linear systems and about the stability of the linear and nonlinear systems they represent? In an earlier work, estimates of the eigen spectra of systems were given based on the structural classification of a canonical form of the bond graph. This work provides stability criteria based on the structure of the bond graph canonical form for linear and nonlinear time invariant dynamic systems. Tighter bounds on the eigen spectrum are also provided for the class of systems with uniform tree simple full graphs. It is shown that if a system is modeled by a standard bond graph whose canonical form is of the simple full or simple partial class, then estimates of the system stability, asymptotic stability, or instability can be obtained directly from the properties of the resistance field. The stability estimates can be automated and are obtained prior to the derivation of the dynamic equations. The stability properties can be used also as a design tool to suggest stabilizing feedback at the graphical modeling stage of the design process.

Stability Analysis of Two-Layered Finite Hydrodynamic Porous Journal Bearing Using Linear and Nonlinear Transient Method

2007 ◽  
Author(s):  
S. K. Kakoty ◽  
S. K. Laha ◽  
P. Mallik
Keyword(s):  
Journal Bearing ◽  
Journal Bearings ◽  
Operating Conditions ◽  
System Stability ◽  
Rigid Rotor ◽  
Transient Method ◽  
Porous Bearing ◽  
Nonlinear Transient ◽  
Linear And Nonlinear ◽  
The Stability

A theoretical analysis has been carried out to determine the stability of rigid rotor supported on two symmetrical finite two-layered porous oil journal bearings. The stability curves have been drawn for different eccentricity ratios and Sommerfeld numbers. The effect of bearing feeding parameter, L/D ratio on the stability is also investigated. This paper also deals with a theoretical investigation of stability using a non-linear transient method. This analysis gives the journal centre locus and from this the system stability can be determined. With the help of graphics, several trajectories of the journal centre have been obtained for different operating conditions. Finally a comparison between single-layered porous bearing and the two-layered porous bearing is presented here.

Stability and Control of a Parametrically Excited Rotating Beam

1998 ◽  
Vol 120 (4) ◽  
pp. 462-470 ◽  
Author(s):  
S. C. Sinha ◽  
Dan B. Marghitu ◽  
Dan Boghiu
Keyword(s):  
Equations Of Motion ◽  
System Stability ◽  
Flexible Beam ◽  
Parametrically Excited ◽  
Stability And Control ◽  
Rotation Parameters ◽  
The Stability ◽  
And Control ◽  
Time Invariant ◽  
Time Periodic

In this paper the stability and control of a parametrically excited, rotating flexible beam is considered. The equations of motion for such a system contain time periodic coefficients. Floquet theory and a numerical integration are used to evaluate the stability of the linearized system. Stability charts for various sets of damping, parametric excitation, and rotation parameters are obtained. Several resonance conditions are found and it is shown that the system stability can be significantly changed due to the rotation. Such systems can be used as preliminary models for studying the flap dynamics and control of helicopter rotor blades and flexible mechanisms among other systems. To control the motion of the system, an observer based controller is designed via Lyapunov-Floquet transformation. In this approach the time periodic equations are transformed into a time invariant form, which are suitable for the application of standard time invariant controller design techniques. Simulations for several combinations of excitation and rotation parameters are shown.

scholarly journals A Simplified Method for Predicting the Stability of Aerodynamically Excited Turbomachinery

2006 ◽  
Vol 129 (4) ◽  
pp. 724-729 ◽  
Author(s):  
Albert F. Storace
Keyword(s):  
Natural Frequencies ◽  
Design Tool ◽  
System Stability ◽  
Squeeze Film ◽  
Real Eigenvalue ◽  
Turbine Engine ◽  
Squeeze Film Dampers ◽  
Simplified Method ◽  
Stability Method ◽  
The Stability

A modal stability (MS) method is presented for the quick and accurate prediction of the stability of aerodynamically excited turbomachinery using real eigenvalue/eigenvector data obtained from a rotordynamics model. The modal stability method provides a means to compare the work of stabilizing damping forces to the work of destabilizing aerodynamic cross-coupled stiffness forces to predict the onset of whirl instability. The MS method thus indicates that unstable or self-excited whirling (sometimes called whipping) at one of the system’s natural frequencies is initiated when the destabilizing work equals or exceeds the stabilizing work. This approach provides a powerful design tool to quickly ascertain the effects of squeeze-film dampers, and turbine engine architecture, including bearing locations and bearing support structure stiffness, on system stability.

Modeling and Analysis of Soft Contact in Robotic Grasping Using Bond Graph Methods

2011 ◽  
Vol 189-193 ◽  
pp. 1786-1792
Author(s):  
A. Khurshid ◽  
A. Ghafoor ◽  
M.A. Malik
Keyword(s):  
Viscoelastic Material ◽  
Bond Graph ◽  
Contact Forces ◽  
System Stability ◽  
Modeling And Analysis ◽  
Graph Modeling ◽  
Novel Approach ◽  
Bond Graph Modeling ◽  
The Stability ◽  
Soft Finger

Soft fingers contribute to dexterous grasping on account of the area contact and high friction involved. This paper presents a novel approach in modeling of soft contacts between soft fingertip and object using viscoelastic material and analyses its characteristics employing BondGraph Methods (BGM). The fingers are made viscoelastic by using springs and dampers. Detailed bond graph modeling of the contact phenomenon with two soft-finger contacts considered to be placed against each other on the opposite sides of the grasped object as is generally the case in a manufacturing environment is presented. The stiffness of the springs is exploited in order to achieve the stability in the soft-grasping which includes friction between the soft finger contact surfaces and the object. It is shown in the paper that the system stability depends on the viscoelastic material properties of the soft interface. Method of root locus is used to analyze this phenomenon. The paper shows how the weight of the object moving downward is controlled by the friction between the fingers and the object during the application of contact forces by varying the damping and the stiffness in the soft finger.

Influence of internal and external risks on sustainability of financial system of Аltai krai

2018 ◽  
Vol 35 (4) ◽  
pp. 133-136
Author(s):  
R. N. Ibragimov
Keyword(s):  
Sustainable Development ◽  
Financial Stability ◽  
Management Strategy ◽  
Financial System ◽  
Risk Management Strategy ◽  
The Sustainable Development ◽  
The Stability ◽  
The Impact

The article examines the impact of internal and external risks on the stability of the financial system of the Altai Territory. Classification of internal and external risks of decline, affecting the sustainable development of the financial system, is presented. A risk management strategy is proposed that will allow monitoring of risks, thereby these measures will help reduce the loss of financial stability and ensure the long-term development of the economy of the region.

DEVELOPMENT OF THE BASIC CRITERIA FOR RUSSIAN COASTS TYPIFICATION

2017 ◽  
Author(s):  
Рубен Косян ◽  
Ruben Kosyan ◽  
Viacheslav Krylenko ◽  
Viacheslav Krylenko
Keyword(s):  
Coastal Zone ◽  
Coastal Area ◽  
Economic Activity ◽  
Basic Information ◽  
Dynamic Features ◽  
Static State ◽  
Evolutionary Features ◽  
Coastal Features ◽  
The Stability

There are many types of coasts classifications that indicate main coastal features. As a rule, the "static" state of the coasts is considered regardless of their evolutionary features and ways to further transformation. Since the most part of the coastal zone studies aimed at ensuring of economic activity, it is clear that the classification of coast types should indicate total information required by the users. Accordingly, the coast classification should include the criterion, characterizing as dynamic features of the coast and the conditions and opportunities of economic activity. The coast classification, of course, should be based on geomorphological coast typification. Similar typification has been developed by leading scientists from Russia and can be used with minimal modifications. The authors propose to add to basic information (geomorphological type of coast) the evaluative part for each coast sector. It will include the estimation of the coast changes probability and the complexity of the coast stabilization for economic activity. This method will allow to assess the dynamics of specific coastal sections and the processes intensity and, as a result – the stability of the coastal area.

scholarly journals Can Vaccination Trigger Autoimmune Disorders? A Meta-Analysis

Vaccines ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 821
Author(s):  
Marek Petráš ◽  
Ivana Králová Lesná ◽  
Jana Dáňová ◽  
Alexander M. Čelko
Keyword(s):  
Meta Analysis ◽  
Autoimmune Disorders ◽  
Risk Of Bias ◽  
Extensive Literature ◽  
Primary Analysis ◽  
Measures Of Association ◽  
Assessment Development ◽  
Extensive Literature Search ◽  
The Stability

Vaccination as an important tool in the fight against infections has been suggested as a possible trigger of autoimmunity over the last decades. To confirm or refute this assumption, a Meta-analysis of Autoimmune Disorders Association With Immunization (MADAWI) was conducted. Included in the meta-analysis were a total of 144 studies published in 1968–2019 that were available in six databases and identified by an extensive literature search conducted on 30 November 2019. The risk of bias classification of the studies was performed using the Newcastle–Ottawa Quality Assessment Scale. The strength of evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation. While our primary analysis was conducted in terms of measures of association employed in studies with a low risk of bias, the robustness of the MADAWI outcome was tested using measures independent of each study risk of bias. Additionally, subgroup analyses were performed to determine the stability of the outcome. The pooled association of 0.99 (95% confidence interval, 0.97–1.02), based on a total of 364 published estimates, confirmed an equivalent occurrence of autoimmune disorders in vaccinated and unvaccinated persons. The same level of association reported by studies independently of the risk of bias was supported by a sufficient number of studies, and no serious limitation, inconsistency, indirectness, imprecision, and publication bias. A sensitivity analysis did not reveal any discrepancy in the primary result. Current common vaccination is not the cause of any of the examined autoimmune disorders in the medium and long terms.

Stability of Ring-Type MEMS Gyroscopes Subjected to Stochastic Angular Speed Fluctuation

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Samuel F. Asokanthan ◽  
Soroush Arghavan ◽  
Mohamed Bognash
Keyword(s):  
Angular Velocity ◽  
Degrees Of Freedom ◽  
Microelectromechanical Systems ◽  
Damping Ratio ◽  
Operating Conditions ◽  
System Stability ◽  
System Response ◽  
Ring Type ◽  
Mems Gyroscopes ◽  
The Stability

Effect of stochastic fluctuations in angular velocity on the stability of two degrees-of-freedom ring-type microelectromechanical systems (MEMS) gyroscopes is investigated. The governing stochastic differential equations (SDEs) are discretized using the higher-order Milstein scheme in order to numerically predict the system response assuming the fluctuations to be white noise. Simulations via Euler scheme as well as a measure of largest Lyapunov exponents (LLEs) are employed for validation purposes due to lack of similar analytical or experimental data. The response of the gyroscope under different noise fluctuation magnitudes has been computed to ascertain the stability behavior of the system. External noise that affect the gyroscope dynamic behavior typically results from environment factors and the nature of the system operation can be exerted on the system at any frequency range depending on the source. Hence, a parametric study is performed to assess the noise intensity stability threshold for a number of damping ratio values. The stability investigation predicts the form of threshold fluctuation intensity dependence on damping ratio. Under typical gyroscope operating conditions, nominal input angular velocity magnitude and mass mismatch appear to have minimal influence on system stability.

scholarly journals An Ensemble Feature Selection Approach to Identify Relevant Features from EEG Signals

2021 ◽  
Vol 11 (15) ◽  
pp. 6983
Author(s):  
Maritza Mera-Gaona ◽  
Diego M. López ◽  
Rubiel Vargas-Canas
Keyword(s):  
Feature Selection ◽  
Sensitivity And Specificity ◽  
Eeg Signals ◽  
Specificity And Sensitivity ◽  
Selection Approach ◽  
Feature Selection Approach ◽  
The Stability ◽  
Selection Algorithms ◽  
Epileptiform Events

Identifying relevant data to support the automatic analysis of electroencephalograms (EEG) has become a challenge. Although there are many proposals to support the diagnosis of neurological pathologies, the current challenge is to improve the reliability of the tools to classify or detect abnormalities. In this study, we used an ensemble feature selection approach to integrate the advantages of several feature selection algorithms to improve the identification of the characteristics with high power of differentiation in the classification of normal and abnormal EEG signals. Discrimination was evaluated using several classifiers, i.e., decision tree, logistic regression, random forest, and Support Vecctor Machine (SVM); furthermore, performance was assessed by accuracy, specificity, and sensitivity metrics. The evaluation results showed that Ensemble Feature Selection (EFS) is a helpful tool to select relevant features from the EEGs. Thus, the stability calculated for the EFS method proposed was almost perfect in most of the cases evaluated. Moreover, the assessed classifiers evidenced that the models improved in performance when trained with the EFS approach’s features. In addition, the classifier of epileptiform events built using the features selected by the EFS method achieved an accuracy, sensitivity, and specificity of 97.64%, 96.78%, and 97.95%, respectively; finally, the stability of the EFS method evidenced a reliable subset of relevant features. Moreover, the accuracy, sensitivity, and specificity of the EEG detector are equal to or greater than the values reported in the literature.

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