Normal form method for large/small amplitude instability criterion with application to wheelset lateral stability

2014 ◽  
Vol 14 (03) ◽  
pp. 1350073 ◽  
Author(s):  
H. Dong ◽  
J. Zeng
Keyword(s):  
Normal Form ◽  
Small Amplitude ◽  
High Speed ◽  
Order Approximation ◽  
Algebraic Approach ◽  
Instability Criterion ◽  
Lateral Stability ◽  
Subcritical Bifurcation ◽  
Large Amplitude Oscillation ◽  
The Stability

Subcritical and supercritical bifurcations are two typical behaviors that exist in high speed railway vehicles. In the presence of instability, the former and the latter behaviors may lead to large amplitude oscillation and small amplitude swaying, respectively. The normal form (NF) method of Hopf bifurcation provides a way to study the supercritical and subcritical bifurcation. The wheelset is a key component in the vehicle system and it plays an important role in vehicle lateral stability. To study the lateral stability problems, three wheelset models are considered, which involve the NF theory. This method is an algebraic approach as opposed to the integration approach. Like the sign of Re (λ) that determines the stability of linear system, the sign of Re c1(0) determines the two bifurcation modes, meaning that Re c1(0) > 0 for supercritical bifurcation and Re c1(0) < 0 for subcritical bifurcation. Furthermore, if the ordinary differential equation (ODE) is local linear near the equilibrium position, it leads to the condition of Re c1(0) = 0, resulting in the jumping phenomenon. Besides, the expression of the 1/2-order approximation of limit cycle can be further obtained.

Effects of Phase Relation between Forewing and Hindwing on Aerodynamic Performance in Dragonfly Flight

2014 ◽  
Vol 709 ◽  
pp. 245-251
Author(s):  
Jin Zhao Yan ◽  
Meng Zong Zheng ◽  
Zhi Ping Li ◽  
Qiu Shi Li
Keyword(s):  
Phase Relation ◽  
High Frequency ◽  
Small Amplitude ◽  
High Speed ◽  
Micro Air Vehicles ◽  
Aerodynamic Performance ◽  
Stability And Control ◽  
High Acceleration ◽  
The Stability ◽  
And Control

Dragonflies possess one of the most maneuverable flights among various insects. As the bionic Micro Air vehicles (MAVs) with the flight capabilities like dragonflies have been widely applied, detailed studies of dragonfly flight become critical and necessary for improvement and accomplishment of MAVs design. The phase relation between the forewings and hindwings is the most distinct feature of dragonfly flight and it plays an important role in the aerodynamic performance. In this paper, both tethered and quasi-free flapping flight of the dragonfly Pantala flavescens was filmed using a high-speed camera in indoor laboratory. Dragonflies tend to flap in-phase when an additional force is expected, while out-of-phase flapping is conducive to the stability and control of flight. In the takeoff maneuver, the large-and small-amplitude wingbeat alternated. Dragonflies obtain a high acceleration rapidly by the suddenly enlarged wingbeat amplitude which increases by 42%, and maintain the velocity and make ready for following acceleration by the small-amplitude but high-frequency wingbeat with amplitude decreases by 51% and frequency increases by 30% relatively.

Vehicle Dynamics Control for Tractor Semitrailer Lateral Stability

2009 ◽  
Vol 16-19 ◽  
pp. 544-548 ◽  
Author(s):  
Shu Wen Zhou ◽  
Hai Shu Chen ◽  
Si Qi Zhang ◽  
Li Xin Guo
Keyword(s):  
Rigid Body ◽  
Vehicle Dynamics ◽  
High Speed ◽  
Stability Control ◽  
Dynamics Simulation ◽  
Lateral Stability ◽  
Yaw Rate ◽  
The Stability ◽  
Vehicle Dynamics Control ◽  
Body Method

Rollover and jack-knifing of tractor semitrailer on high speed obstacle avoidance under emergency are serious threats for motorists. A tractor semitrailer model was built with multi-rigid-body method in this paper. The steering performance of tractor semitrailer has been analyzed, as well as the stability control theory, including yaw rate following, anti-rollover. The dynamics simulation for yaw rate following and anti-rollover has been performed on the dynamic tractor semitrailer. The results show that the vehicle dynamics control proposed in this paper can stabilize the tractor semitrailer, rollover and jack-knifing are prevented and the tractor semitrailer more accurately follows the driver's desired path.

A Statistical Study of Process Variables to Optimize a High Speed Curtain Coater: Part I

TAPPI Journal ◽  
2009 ◽  
Vol 8 (1) ◽  
pp. 20-26 ◽  
Author(s):  
PEEYUSH TRIPATHI ◽  
MARGARET JOYCE ◽  
PAUL D. FLEMING ◽  
MASAHIRO SUGIHARA
Keyword(s):  
Boundary Layer ◽  
Experimental Design ◽  
High Speed ◽  
Statistical Study ◽  
Process Variables ◽  
High Speeds ◽  
The Stability ◽  
Air Removal ◽  
Removal System

Using an experimental design approach, researchers altered process parameters and material prop-erties to stabilize the curtain of a pilot curtain coater at high speeds. Part I of this paper identifies the four significant variables that influence curtain stability. The boundary layer air removal system was critical to the stability of the curtain and base sheet roughness was found to be very important. A shear thinning coating rheology and higher curtain heights improved the curtain stability at high speeds. The sizing of the base sheet affected coverage and cur-tain stability because of its effect on base sheet wettability. The role of surfactant was inconclusive. Part II of this paper will report on further optimization of curtain stability with these four variables using a D-optimal partial-facto-rial design.

LANDSLIDE RISK MANAGEMENT IN THE COASTAL ZONE OF THE KUIBYSHEV RESERVOIR DUE THE DESIGN OF HIGH-SPEED LINE "MOSCOW-KAZAN"

2017 ◽  
Author(s):  
Nikolai Petrov ◽  
Nikolai Petrov ◽  
Inna Nikonorova ◽  
Inna Nikonorova ◽  
Vladimir Mashin ◽  
...  
Keyword(s):  
High Speed ◽  
Computational Models ◽  
Stable State ◽  
Landslide Risk ◽  
Kuibyshev Reservoir ◽  
Stepped Surface ◽  
The Stability ◽  
Landslide Slope ◽  
The Village

High-speed railway "Moscow-Kazan" by the draft crosses the Volga (Kuibyshev reservoir) in Chuvashia region 500 m below the village of New Kushnikovo. The crossing plot is a right-bank landslide slope with a stepped surface. Its height is 80 m; the slope steepness -15-16o. The authors should assess the risk of landslides and recommend anti-landslide measures to ensure the safety of the future bridge. For this landslide factors have been analyzed, slope stability assessment has been performed and recommendations have been suggested. The role of the following factors have been analyzed: 1) hydrologic - erosion and abrasion reservoir and runoff role; 2) lithologyc (the presence of Urzhum and Northern Dvina horizons of plastically deformable rocks, displacement areas); 3) hydrogeological (the role of perched, ground and interstratal water); 4) geomorphological (presence of the elemental composition of sliding systems and their structure in the relief); 5) exogeodynamic (cycles and stages of landslide systems development, mechanisms and relationship between landslide tiers of different generations and blocks contained in tiers). As a result 6-7 computational models at each of the three engineering-geological sections were made. The stability was evaluated by the method “of the leaning slope”. It is proved that the slope is in a very stable state and requires the following measures: 1) unloading (truncation) of active heads blocks of landslide tiers) and the edge of the plateau, 2) regulation of the surface and groundwater flow, 3) concrete dam, if necessary.

Dynamic Performance of High-Speed Electric Multiple Unit within Multi-Body System Simulation

2019 ◽  
Vol 12 (4) ◽  
pp. 339-349
Author(s):  
Junguo Wang ◽  
Daoping Gong ◽  
Rui Sun ◽  
Yongxiang Zhao
Keyword(s):  
High Speed ◽  
Rapid Development ◽  
Dynamic Performance ◽  
Body System ◽  
High Speed Railway ◽  
Evaluation Indexes ◽  
Actual Operation ◽  
Multiple Unit ◽  
The Stability ◽  
Multi Body

Background: With the rapid development of the high-speed railway, the dynamic performance such as running stability and safety of the high-speed train is increasingly important. This paper focuses on the dynamic performance of high-speed Electric Multiple Unit (EMU), especially the dynamic characteristics of the bogie frame and car body. Various patents have been discussed in this article. Objective: To develop the Multi-Body System (MBS) model of EMU, verify whether the dynamic performance meets the actual operation requirements, and provide some useful information for dynamics and structural design of the proposed EMU. Methods: According to the technical characteristics of a typical EMU, a MBS model is established via SIMPACK, and the measured data of China high-speed railway is taken as the excitation of track random irregularity. To test the dynamic performance of the EMU, including the stability and safety, some evaluation indexes such as wheel-axle lateral forces, wheel-axle lateral vertical forces, derailment coefficients and wheel unloading rates are also calculated and analyzed in detail. Results: The MBS model of EMU has better dynamic performance especially curving performance, and some evaluation indexes of the stability and safety have also reached China’s high-speed railway standards. Conclusion: The effectiveness of the proposed MBS model is verified, and the dynamic performance of the MBS model can meet the design requirements of high-speed EMU.

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 High-Speed Video Analysis of the Process Stability in Plasma Spraying

2021 ◽  
Author(s):  
K. Bobzin ◽  
M. Öte ◽  
M. A. Knoch ◽  
I. Alkhasli ◽  
H. Heinemann
Keyword(s):  
Plasma Spraying ◽  
High Speed ◽  
Plasma Jet ◽  
Plasma Jets ◽  
Time Dependent ◽  
Acquisition Time ◽  
Fast Fourier Transformation ◽  
Frequency Spectra ◽  
Dependent Signal ◽  
The Stability

AbstractIn plasma spraying, instabilities and fluctuations of the plasma jet have a significant influence on the particle in-flight temperatures and velocities, thus affecting the coating properties. This work introduces a new method to analyze the stability of plasma jets using high-speed videography. An approach is presented, which digitally examines the images to determine the size of the plasma jet core. By correlating this jet size with the acquisition time, a time-dependent signal of the plasma jet size is generated. In order to evaluate the stability of the plasma jet, this signal is analyzed by calculating its coefficient of variation cv. The method is validated by measuring the known difference in stability between a single-cathode and a cascaded multi-cathode plasma generator. For this purpose, a design of experiment, covering a variety of parameters, is conducted. To identify the cause of the plasma jet fluctuations, the frequency spectra are obtained and subsequently interpreted by means of the fast Fourier transformation. To quantify the significance of the fluctuations on the particle in-flight properties, a new single numerical parameter is introduced. This parameter is based on the fraction of the time-dependent signal of the plasma jet in the relevant frequency range.

Stability of Milling Operations With Asymmetric Cutter Dynamics in Rotating Coordinates

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Alptunc Comak ◽  
Orkun Ozsahin ◽  
Yusuf Altintas
Keyword(s):  
Time Domain ◽  
Machine Tools ◽  
High Speed ◽  
End Mill ◽  
Spindle Shaft ◽  
Milling Operations ◽  
Stability Model ◽  
Principal Directions ◽  
The Stability ◽  
Rotating Coordinates

High-speed machine tools have parts with both stationary and rotating dynamics. While spindle housing, column, and table have stationary dynamics, rotating parts may have both symmetric (i.e., spindle shaft and tool holder) and asymmetric dynamics (i.e., two-fluted end mill) due to uneven geometry in two principal directions. This paper presents a stability model of dynamic milling operations with combined stationary and rotating dynamics. The stationary modes are superposed to two orthogonal directions in rotating frame by considering the time- and speed-dependent, periodic dynamic milling system. The stability of the system is solved in both frequency and semidiscrete time domain. It is shown that the stability pockets differ significantly when the rotating dynamics of the asymmetric tools are considered. The proposed stability model has been experimentally validated in high-speed milling of an aluminum alloy with a two-fluted, asymmetric helical end mill.

Transition of streamwise streaks in zero-pressure-gradient boundary layers

2002 ◽  
Vol 472 ◽  
pp. 229-261 ◽  
Author(s):  
LUCA BRANDT ◽  
DAN S. HENNINGSON
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
High Speed ◽  
Plate Boundary ◽  
Transition Process ◽  
Free Stream Turbulence ◽  
Tollmien Schlichting ◽  
Streamwise Streaks ◽  
The Stability ◽  
Optimal Disturbances

A transition scenario initiated by streamwise low- and high-speed streaks in a flat-plate boundary layer is studied. In many shear flows, the perturbations that show the highest potential for transient energy amplification consist of streamwise-aligned vortices. Due to the lift-up mechanism these optimal disturbances lead to elongated streamwise streaks downstream, with significant spanwise modulation. In a previous investigation (Andersson et al. 2001), the stability of these streaks in a zero-pressure-gradient boundary layer was studied by means of Floquet theory and numerical simulations. The sinuous instability mode was found to be the most dangerous disturbance. We present here the first simulation of the breakdown to turbulence originating from the sinuous instability of streamwise streaks. The main structures observed during the transition process consist of elongated quasi-streamwise vortices located on the flanks of the low-speed streak. Vortices of alternating sign are overlapping in the streamwise direction in a staggered pattern. The present scenario is compared with transition initiated by Tollmien–Schlichting waves and their secondary instability and by-pass transition initiated by a pair of oblique waves. The relevance of this scenario to transition induced by free-stream turbulence is also discussed.

Sensorless Grey Prediction Fuzzy Direct Torque Control for High-Speed Permanent Magnet Synchronous Motor

2012 ◽  
Vol 220-223 ◽  
pp. 1040-1043
Author(s):  
Hong Cui ◽  
You Qing Gao
Keyword(s):  
Permanent Magnet ◽  
High Speed ◽  
High Performance ◽  
Permanent Magnet Synchronous Motor ◽  
Direct Torque Control ◽  
Synchronous Motor ◽  
Torque Control ◽  
Adjustment Process ◽  
Grey Prediction ◽  
The Stability

High-speed permanent magnet synchronous motor (PMSM) is more and more widely applied in high precision processing and high-performance machines. It is very important to research practical control strategy for the stability operation of the high-speed PMSM. The strategy of sensorless grey prediction fuzzy direct torque control (DTC) is proposed which is suitable for high-speed PMSM control system. The method of prediction fuzzy control based on DTC is used to gain the flux, torque and flux oriented angle through the prediction model of the motor parameters. The best control scheme is gained by fuzzy reasoning to overcome the lag on the system making the adjustment process stable and realizing accurate predictive control. Thereby, the dynamic response of the system, anti-disturbance capability and control accuracy can be improved.

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