Introduction

Wijker, Jaap

doi:10.1007/978-90-481-2728-3_1

Cited by 9 publications

(17 citation statements)

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“…The random response in any system excited by random vibration can be represented as a correlation function. 26…”

Section: Mathematical Analysis Of Random Vibrations In Uavsmentioning

confidence: 99%

Random vibrations in unmanned aerial vehicles, mathematical analysis and control methodology based on expectation and probability

Аl-Мashhadani

2018

Journal of Low Frequency Noise, Vibration and Active Control

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The analysis of the random vibrations that occur during the flight of the unmanned aerial vehicles is important, as these random vibrations have random characteristic properties and have the ability to decrease the endurance of such systems. The accuracy of data collected from sensors in the unmanned aerial vehicle system is important for the flight control system. The transferring of these data among different sensors such as inertial measurement unit, axis accelerometers, GPS or cameras is usually affected by many factors. One of the important factors is the random vibration, which is usually caused by aerodynamic excitation or air turbulence. The problem of random vibrations has been studied for a long time and explained in many text books. In this study, the author introduces a mathematical analysis for random vibrations that are independent of their sources by considering these vibrations as a random and non-stationary process and designs a control methodology based on expectations and probability theory to reduce the effect of these vibrations. The analysis used in this research is based on the assumptions of practical approximation techniques.

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“…The random response in any system excited by random vibration can be represented as a correlation function. 26…”

Section: Mathematical Analysis Of Random Vibrations In Uavsmentioning

confidence: 99%

Random vibrations in unmanned aerial vehicles, mathematical analysis and control methodology based on expectation and probability

Аl-Мashhadani

2018

Journal of Low Frequency Noise, Vibration and Active Control

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“…Let us assume a highly dynamic host vehicle with an installed crystal oscillator ( Figure 1 ). Dynamic loads applied by the highly dynamic host vehicle on the crystal oscillator are divided into [ 7 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]:…”

Section: Dynamic Loads and Its Affection To Instability Of Crystalmentioning

confidence: 99%

“…Mechanical random vibration of the Ariane 4 launch vehicle is shown in Figure 20 a [ 32 ]. Generally, this load is defined by Acceleration Spectral Density (ASD) in (g 2 /Hz).…”

Section: Impacts Of Dynamic Loads On Stability Of Crystal Oscillatmentioning

confidence: 99%

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Novel Gyroscopic Mounting for Crystal Oscillators to Increase Short and Medium Term Stability under Highly Dynamic Conditions

Abedi

Tian

Sun

2015

Sensors

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In this paper, a gyroscopic mounting method for crystal oscillators to reduce the impact of dynamic loads on their output stability has been proposed. In order to prove the efficiency of this mounting approach, each dynamic load-induced instability has been analyzed in detail. A statistical study has been performed on the elevation angle of the g-sensitivity vector of Stress Compensated-cut (SC-cut) crystals. The analysis results show that the proposed gyroscopic mounting method gives good performance for host vehicle attitude changes. A phase noise improvement of 27 dB maximum and 5.7 dB on average can be achieved in the case of steady state loads, while under sinusoidal vibration conditions, the maximum and average phase noise improvement are as high as 24 dB and 7.5 dB respectively. With this gyroscopic mounting method, random vibration-induced phase noise instability is reduced 30 dB maximum and 8.7 dB on average. Good effects are apparent for crystal g-sensitivity vectors with low elevation angle φ and azimuthal angle β. under highly dynamic conditions, indicating the probability that crystal oscillator instability will be significantly reduced by using the proposed mounting approach.

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“…The principle of usage of the SRS consists of the assumption that any acceleration time-history which results in a SRS in accordance with a given specification will cause the same damage in the space element under testing. 11 A shock test specification is usually provided with tolerances that allow to find reproducible shock profiles that could generate equally feasible SRSs. This is an important property because the generated acceleration time history is usually limited by the selected testing method.…”

Section: Introductionmentioning

confidence: 99%

Shock environment design for space equipment testing

Morais

Vasques

2016

Proceedings of the Institution of Mechanical Engineers, Part G:

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The main specification in the verification by testing of space hardware vulnerability to shock excitations is the shock response spectrum. Although it compiles the most relevant information needed to describe the overall shock environment characteristics, shock testing still poses various difficulties and uncertainties concerning the suitability and operation of the shock test system used, and the adequate definition of the underlying test parameters. The approach followed from the interpretation of typical shock testing specifications to the development, validation, and characterization of the developed shock test system, including the definition and design of the relevant parameters influencing the attained shock environment, is described in this paper. The shock testing method here presented consists of a pendular in-plane resonant mono-plate shock test apparatus where the structural response of the ringing plate depends upon welldefined controllable parameters (e.g. impact velocity, striker shape, mass, and contact stiffness), which are parametrically determined to achieve the target shock environment specification. The concept and analytical model of two impacting bodies are used in a preliminary analysis to perform a rigid body motion analysis and contact assessment. A detailed finite element model is developed for the definition of the ringing plate dimensions, analysis of the plate dynamics and virtual shock testing. The assembled experimental apparatus is described and a test campaign is undertaken in order to properly characterize and assess the design and test parameters of the system. The developed shock test apparatus and corresponding finite element model are experimentally verified and validated. As a result of this study, a reliable finite element modeling methodology available for future shock test simulation and prediction of the experimental results was created, being an important tool for the adjustment of the shock test input parameters for future works. The developed shock test system was well characterized and is readily available to be used for shock testing of space equipment with varying specifications.

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Introduction

Cited by 9 publications

References 0 publications

Random vibrations in unmanned aerial vehicles, mathematical analysis and control methodology based on expectation and probability

Random vibrations in unmanned aerial vehicles, mathematical analysis and control methodology based on expectation and probability

Novel Gyroscopic Mounting for Crystal Oscillators to Increase Short and Medium Term Stability under Highly Dynamic Conditions

Shock environment design for space equipment testing

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