scholarly journals Lyapunov Based Estimation of Flight Stability Boundary under Icing Conditions

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Binbin Pei ◽  
Haojun Xu ◽  
Yuan Xue
Keyword(s):  
Equilibrium Point ◽  
External Disturbance ◽  
Stability Boundary ◽  
Wind Tunnel Test ◽  
Test Results ◽  
Theoretical Support ◽  
Effect Model ◽  
Short Period ◽  
The Stability ◽  
Period Model

Current fight boundary of the envelope protection in icing conditions is usually defined by the critical values of state parameters; however, such method does not take the interrelationship of each parameter and the effect of the external disturbance into consideration. This paper proposes constructing the stability boundary of the aircraft in icing conditions through analyzing the region of attraction (ROA) around the equilibrium point. Nonlinear icing effect model is proposed according to existing wind tunnel test results. On this basis, the iced polynomial short period model can be deduced further to obtain the stability boundary under icing conditions using ROA analysis. Simulation results for a series of icing severity demonstrate that, regardless of the icing severity, the boundary of the calculated ROA can be treated as an estimation of the stability boundary around an equilibrium point. The proposed methodology is believed to be a promising way for ROA analysis and stability boundary construction of the aircraft in icing conditions, and it will provide theoretical support for multiple boundary protection of icing tolerant flight.

STABILITY BOUNDARY CHARACTERIZATION OF NONLINEAR AUTONOMOUS DYNAMICAL SYSTEMS IN THE PRESENCE OF A SUPERCRITICAL HOPF EQUILIBRIUM POINT

2013 ◽  
Vol 23 (12) ◽  
pp. 1350196 ◽  
Author(s):  
JOSAPHAT R. R. GOUVEIA ◽  
FABÍOLO MORAES AMARAL ◽  
LUÍS F. C. ALBERTO
Keyword(s):  
Dynamical Systems ◽  
Equilibrium Point ◽  
Equilibrium Points ◽  
Stability Boundary ◽  
Complete Characterization ◽  
Center Manifolds ◽  
The Stability ◽  
Hyperbolic Equilibrium ◽  
Autonomous Dynamical Systems

A complete characterization of the boundary of the stability region (or area of attraction) of nonlinear autonomous dynamical systems is developed admitting the existence of a particular type of nonhyperbolic equilibrium point on the stability boundary, the supercritical Hopf equilibrium point. Under a condition of transversality, it is shown that the stability boundary is comprised of all stable manifolds of the hyperbolic equilibrium points lying on the stability boundary union with the center-stable and\or center manifolds of the type-k, k ≥ 1, supercritical Hopf equilibrium points on the stability boundary.

The Stability Analysis of the Driving Rod of the Wind Tunnel Test Model Based on Workbench

2015 ◽  
Vol 799-800 ◽  
pp. 538-542
Author(s):  
Zi Yan Shao ◽  
Wen Jia Chen ◽  
Yong Jin Hu ◽  
Guan Jian Li
Keyword(s):  
Wind Tunnel ◽  
Degrees Of Freedom ◽  
Wind Tunnel Test ◽  
Future Research ◽  
Response Analysis ◽  
Test Model ◽  
Main Research ◽  
Theoretical Support ◽  
Harmonic Response Analysis ◽  
The Stability

The ANSYS Workbench is used in this paper to analyse a kind of wind tunnel test model support platform with 5 degrees of freedom. The driving rod of the pitch motion is chosen as the main research project. By using static structural analysis, modal analysis and harmonic response analysis, a detailed analysis is made on the stress, deformation and frequency of the driving rod, and provides theoretical support for the future research on the stability of the institution.

scholarly journals A New Adaptive Fuzzy PID Control Method and Its Applicance in FCBTM

2016 ◽  
Vol 11 (3) ◽  
pp. 394 ◽  
Author(s):  
Jingang Lai ◽  
Hong Zhou ◽  
Wenshan Hu
Keyword(s):  
Control Method ◽  
External Disturbance ◽  
Testing Machine ◽  
Three Dimensional ◽  
Test Results ◽  
Motor Speed ◽  
Fuzzy Pid Control ◽  
Adaptive Fuzzy ◽  
The Stability ◽  
Adaptive Fuzzy Pid Control

<p class="Abstract">The process of tension control for material testing using the Flexible ircuit Board testing machine (FCBTM) is featured with multi-variable, nonlinearity, ime delays and time variation. In order to ensure the tension precision, the stability of ervo motor’ speed and the reliability of test results, this paper establishes an accurate ystem model for the FCBTM, in which a novel three-dimensional adaptive fuzzy ID controller is designed. Specially, the simulation results show that the proposed daptive fuzzy control method is not only robust to the external disturbance but also ith more excellent dynamic and steady-state characteristics than traditional ones.</p>

scholarly journals Stability analysis of long hydrodynamic journal bearings based on the journal center trajectory

Friction ◽  
2020 ◽  
Author(s):  
Yu Huang ◽  
Haiyin Cao ◽  
Zhuxin Tian
Keyword(s):  
Stability Analysis ◽  
Equilibrium Point ◽  
Journal Bearing ◽  
Stability Boundary ◽  
Initial Point ◽  
Journal Bearings ◽  
Bearing Surface ◽  
Rotating Speed ◽  
Stability Threshold ◽  
The Stability

AbstractIn this study, we observe that there are two threshold speeds (stability threshold speed and second threshold speed) for the long journal bearing, which is different for the short bearing. When the rotating speed is below the stability threshold speed, the stability boundary nearly coincides with the clearance circle, and the journal center gradually returns to the equilibrium point after being released at an initial point. If the rotating speed is between the stability threshold speed and the second threshold speed, after being released at an initial point, the journal center converges to a contour containing the equilibrium point. In this situation, for a higher rotating speed, the corresponding contour is also larger. When the rotating speed exceeds the second threshold speed, the journal gradually moves towards the bearing surface after being released at an initial point.

Rancang Bangun Piranti Lunak Pengolah Data Pasca Pengujian Terowongan Angin Kecepatan Rendah Indonesia

2016 ◽  
Vol 7 (2) ◽  
pp. 131-138
Author(s):  
Ivransa Zuhdi Pane
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Test Results ◽  
Effective Solution ◽  
Post Processing ◽  
Prototype Development ◽  
Design Activities ◽  
Index Terms ◽  
Test Objects ◽  
Processing Requirement

Data post-processing plays important roles in a wind tunnel test, especially in supporting the validation of the test results and further data analysis related to the design activities of the test objects. One effective solution to carry out the data post-processing in an automated productive manner, and thus eliminate the cumbersome conventional manual way, is building a software which is able to execute calculations and have abilities in presenting and analyzing the data in accordance with the post-processing requirement. Through several prototype development cycles, this work attempts to engineer and realize such software to enhance the overall wind tunnel test activities. Index Terms—software engineering, wind tunnel test, data post-processing, prototype, pseudocode

scholarly journals Influence of Whey Protein Micro-Gel Particles and Whey Protein Micro-Gel Particles-Xanthan Gum Complexes on the Stability of O/W Emulsions

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2301
Author(s):  
Man Zhang ◽  
Bin Liang ◽  
Hongjun He ◽  
Changjian Ji ◽  
Tingting Cui ◽  
...  
Keyword(s):  
Oxidative Stability ◽  
Whey Protein ◽  
High Speed ◽  
Xanthan Gum ◽  
Physical Stability ◽  
Theoretical Support ◽  
Gel Particles ◽  
Oil In Water ◽  
The Stability ◽  
The Impact

Appropriate pretreatment of proteins and addition of xanthan gum (XG) has the potential to improve the stability of oil-in-water (O/W) emulsions. However, the factors that regulate the enhancement and the mechanism are still not clear, which restricts the realization of improving the emulsion stability by directional design of its structure. Therefore, the effects of whey protein micro-gel particles (WPMPs) and WPMPs-XG complexes on the stability of O/W emulsion were investigated in this article to provide theoretical support. WPMPs with different structures were prepared by pretreatment (controlled high-speed shear treatment of heat-set WPC gels) at pH 3.5–8.5. The impact of initial WPC structure and XG addition on Turbiscan Indexes, mean droplet size and the peroxide values of O/W emulsions was investigated. The results indicate that WPMPs and XG can respectively inhibit droplet coalescence and gravitational separation to improve the physical stability of WPC-stabilized O/W emulsions. The pretreatment significantly enhanced the oxidative stability of WPC-stabilized O/W emulsions. The addition of XG did not necessarily enhance the oxidative stability of O/W emulsions. Whether the oxidative stability of the O/W emulsion with XG is increased or decreased depends on the interface structure of the protein-XG complex. This study has significant implications for the development of novel structures containing lipid phases that are susceptible to oxidation.

scholarly journals An unusually low density ultra-short period super-Earth and three mini-Neptunes around the old star TOI-561

2020 ◽  
Author(s):  
G Lacedelli ◽  
L Malavolta ◽  
L Borsato ◽  
G Piotto ◽  
D Nardiello ◽  
...  
Keyword(s):  
Transit Time ◽  
Time Variation ◽  
Planetary System ◽  
Radial Velocities ◽  
Low Density ◽  
Outer Planets ◽  
Short Period ◽  
The Stability

Abstract Based on HARPS-N radial velocities (RVs) and TESS photometry, we present a full characterisation of the planetary system orbiting the late G dwarf After the identification of three transiting candidates by TESS, we discovered two additional external planets from RV analysis. RVs cannot confirm the outer TESS transiting candidate, which would also make the system dynamically unstable. We demonstrate that the two transits initially associated with this candidate are instead due to single transits of the two planets discovered using RVs. The four planets orbiting TOI-561 include an ultra-short period (USP) super-Earth (TOI-561 b) with period Pb = 0.45 d, mass Mb = 1.59 ± 0.36 M⊕ and radius Rb = 1.42 ± 0.07 R⊕, and three mini-Neptunes: TOI-561 c, with Pc = 10.78 d, Mc = 5.40 ± 0.98 M⊕, Rc = 2.88 ± 0.09 R⊕; TOI-561 d, with Pd = 25.6 d, Md = 11.9 ± 1.3 M⊕, Rd = 2.53 ± 0.13 R⊕; and TOI-561 e, with Pe = 77.2 d, Me = 16.0 ± 2.3 M⊕, Re = 2.67 ± 0.11 R⊕. Having a density of 3.0 ± 0.8 g cm−3, TOI-561 b is the lowest density USP planet known to date. Our N-body simulations confirm the stability of the system and predict a strong, anti-correlated, long-term transit time variation signal between planets d and e. The unusual density of the inner super-Earth and the dynamical interactions between the outer planets make TOI-561 an interesting follow-up target.

scholarly journals Investigation of the Time Dependence of Wind-Induced Aeroelastic Response on a Scale Model of a High-Rise Building

2021 ◽  
Vol 11 (8) ◽  
pp. 3315
Author(s):  
Fabio Rizzo
Keyword(s):  
Wind Tunnel ◽  
Time Dependence ◽  
Wind Tunnel Test ◽  
Structural Response ◽  
Cumulative Distribution ◽  
Scale Model ◽  
Acquisition Time ◽  
Test Results ◽  
High Rise ◽  
High Rise Building

Experimental wind tunnel test results are affected by acquisition times because extreme pressure peak statistics depend on the length of acquisition records. This is also true for dynamic tests on aeroelastic models where the structural response of the scale model is affected by aerodynamic damping and by random vortex shedding. This paper investigates the acquisition time dependence of linear transformation through singular value decomposition (SVD) and its correlation with floor accelerometric signals acquired during wind tunnel aeroelastic testing of a scale model high-rise building. Particular attention was given to the variability of eigenvectors, singular values and the correlation coefficient for two wind angles and thirteen different wind velocities. The cumulative distribution function of empirical magnitudes was fitted with numerical cumulative density function (CDF). Kolmogorov–Smirnov test results are also discussed.

scholarly journals Gust Alleviation Control using Prior Gust Information: Wind Tunnel Test Results

2019 ◽  
Vol 52 (12) ◽  
pp. 128-133
Author(s):  
Yoshiro Hamada ◽  
Kenichi Saitoh ◽  
Noboru Kobiki
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Test Results ◽  
Gust Alleviation
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