Aircraft Vibration Research Articles

ПСЕВДОГРАДИЕНТНАЯ ФИЛЬТРАЦИЯ СИСТЕМ КВАЗИПЕРИОДИЧЕСКИХ ПРОЦЕССОВ НА ОСНОВЕ ЦИЛИНДРИЧЕСКИХ ИЗОБРАЖЕНИЙ

The object behavior in many practical situations has a quasi-periodic character, that is, it has a noticeable periodicity with random variations of quasi-periods, for example speech signals, aircraft engine noise and vibration, etc. An object can have several parameters, so it is described by a system of random processes observed in a mixture with noise. In this paper an autoregressive model is used in the form of sweeps along spirals of several coaxial cylindrical images to represent systems of quasi-periodic processes. For filtering, an adaptive pseudo-gradient analogue of the Kalman filter is proposed, which does not require setting the parameters of the process system model and its observations. Filter optimization is carried out recurrently as the observations are received. In the case of homogeneous processes, the filter converges to the optimal one, constructed with known parameters of observations, and in the case of inhomogeneous processes it performs close to optimal filtering. Examples of imitation of systems of two quasi-periodic processes and their filtering are given.

О применении алгоритмов оценивания и коррекции в системе измерения параметров вибрации элементов конструкции летательного аппарата

Nowadays, high-precision measurement of aircraft vibration parameters during its main operations modes, including in-flight operation mode, is still considered an important scientific and technical field of study and research. These kinds of measurements are usually conducted in order to analyze the airplane vibration properties and characteristics, which serves in diagnosing the state of its structure, predicting the appearance and development of defects and deformations, as well as to prevent or avoid the influence of dangerous phenomena such as flutter, buffeting, etc. In this article, the authors present the primary results of their work to build a system designed to measure such airplane vibration parameters. In comparison with the existing analogous systems, the new proposed system makes use of traditional vibrometric measurement methods in combination with approaches typical for solving orientation and navigation problems. So, the article discusses the principles of constructing a measurement system of vibration parameters of aircraft structural elements using the example of a system for measuring aircraft wing vibrations using MEMS IMU units and data fusion technology. A brief review of the main existing solutions in this research field is carried out, and the relevance and expediency of the proposed version of the system is substantiated. The basic components and structure of the proposed system are presented, including MEMS IMU units, a displacement sensor, and an onboard navigation system. The basic principles of the system operation are described based on the use of data from the displacement sensor, inertial measurements and optimal Kalman estimation. The main algorithms for the system operation are presented, including algorithms for inertial measurements, estimation and correction, as well as the actual algorithm for calculating vibration parameters. In addition, the mathematical errors models of the main measurements units of the system are presented. The article also presents simulation results, which are encouraging, and they demonstrate the performance of the system and its expected relatively high accuracy characteristics, which in turns confirms the expected efficiency of its application and the prospects of the chosen direction of research and development.

Monitoring System of Vibroacoustic Parameters of a Working Zone

This article discusses the safety problems of the use of aviation technology associated with the influence of operational vibration of aircraft. The topical issue of timely detection and prevention of a dangerous state of critical machines and mechanisms is analyzed. Modern means of measuring vibration parameters, principles of measurement, as well as characteristics of the sensitive element of the measuring transducer, are considered. The block diagram and operation algorithm of the proposed system for monitoring vibroacoustic parameters, which is built on the basis of a piezoelectric transducer, is presented. This system can measure the parameters of noise and vibration and analyze the measured data, signal about exceeding the permissible ranges for human work, display the measured data. The advantage of the proposed system is the connection of the measuring channels with the mainboard using the Bluetooth module, which allows the sensors to measure noise and vibration to be placed in any part of the working area.

Analyzing mechanical vibrations of an aircraft opposed piston engine

The paper presents the results of the bench tests to measure mechanical vibrations of a new aircraft opposed piston engine with reciprocating pistons. The PLZ-100 engine is a three-cylinder, six-piston, two-shaft drive unit with a two-stroke diesel cycle. This type of engine is dedicated for powering light aircraft, e.g. autogyros. The tests were carried out on a test bench at the Lublin University of Technology. The engine was loaded with constant torque, for several fixed values of rotational speed of a crankshaft. The angle of the start of diesel injection was changed for each of the rotational speeds. The mechanical vibrations that accompanied the operation of this drive unit were recorded with three measurement transducers and a National Instruments conditioning system. Each of the transducers was mounted on a different axis of the engine. The signals were analyzed from their courses with the DIAdem software. The results were the courses of effective speed and vibration acceleration to conduct a vibration-acoustic evaluation of the PLZ-100, detect and prevent various types of defects or failures.

Aircraft Detection Using Phase-Sensitive Optical-Fiber OTDR.

Aircraft detection plays a vital role in aviation management and safe operation in the aviation system. Phase-Sensitive Optical Time Domain Reflectometry (Φ-OTDR) technology is a prevailing sensing method in geophysics research, structure inspection, transportation detection, etc. Compared with existing video- or radio-based detection methods, Φ-OTDR is cost-effective, suitable for long-distance detection, and resistant to severe weather conditions. We present a detection system using Φ-OTDR technology and analyze the character of the acoustic signal of aircraft. Instead of runway monitoring in the airport or noise detection in the air, this study focuses on the detection of seismic vibration signal excited by the sound of aircraft. The Chebyshev filter is adopted to eliminate the impact of background noise and random noise from the original vibration signal; the short-time Fourier transform is used for time-frequency analysis. The experimental results showed that the seismic vibration signal excited by the aircraft sound is mainly low-frequency, which is under 5 Hz. Time delay of aircraft vibration signal in different locations of the optic fiber is recorded by the sensing system. The Doppler effect is also revealed by the time-domain analysis: the frequency increases when the aircraft is approaching and decreases when the aircraft moves away.

Spatial correlation effect of a multidimensional force on vibration suppression

The spatial correlation of a multidimensional force produced by different aircraft components is an important factor that affects the structural vibration of aircraft. To predict the structural response by external forces with a certain phase difference, determined by the spatial correlation of external forces, an analytical method based on structural response integration is developed and adopted. The characteristics of the external forces, especially the phase difference of the structural vibration, are investigated to reduce structural vibration by utilizing the spatial correlation of the external forces. Additionally, to suppress structural vibration by a propagation wavefield, corresponding to complex flow excitation, the developed integration method is used to estimate the accuracy of the propagation wavefield replaced by concentrated forces. Finally, a measurement is designed and performed, which further reveals the spatial correlation effect of the external forces on the structural vibration.

Nonlinear Noise Reduction for the Airborne Transient Electromagnetic Method based on Kernel Minimum Noise Fraction

The airborne transient electromagnetic method has become a powerful tool to explore deep resource and tectonic structures. However, aircraft vibrations and flight environments produce very strong and complex nonlinear noise and result in poor data quality compared to ground transient electromagnetic methods. Consequently, the reduction of airborne electromagnetic noises is of vital importance to data inversion and imaging. To suppress and remove the nonlinear noise, we propose using kernel minimum noise fraction (KMNF), which is a nonlinear generalized method of minimum noise fraction. First, an adaptive variable window-width filtering algorithm is used to evaluate the noises and perform the preliminary denoising. Then, we adopt the two filter methods, which are minimum noise fraction (MNF) and KMNF to suppress the noise. The results show that these two methods can both suppress noise and make the decay curves smooth, but kernel MNF is more effective for the nonlinear characteristics of noise and it does not weaken the anomaly. Finally, field data from the Qinling mine area is processed, using the MNF and KMNF methods. The results show that nonlinear noise is suppressed by both methods but the results of KMNF are better than those of the linear MNF method.

Spectrum parameters for runway roughness based on statistical and vibration analysis

ABSTRACT Airport runway roughness can be characterised by power spectral density (PSD) and two spectrum parameters, namely, the unevenness index and waviness. In order to find suitable spectrum parameters for airport runway roughness, seven runway profiles in China were measured to expand the current database of runway profiles. The statistical distributions of the spectrum parameters for runway roughness then were calculated, and the effects of the spectrum parameters on aircraft vibrations were analysed. The results show that the mode of the unevenness index is 0.13, which is a little lower than that of an A-level road, and the mode of waviness is 2.2, which is higher than the waviness recommended in ISO road classification. Moreover, as the unevenness index and the waviness increase, the aircraft vibrations become more severe. The aircraft vibration responses can be represented as a function of waviness, unevenness index, and speed, with a high correlation. At a constant speed, the relationship between the threshold values of the unevenness index and waviness can be shown as a straight line in a log plot. Finally, taking 200 km/h as the representative speed, threshold curves of the spectrum parameters, which are based on ride comfort levels and statistical analysis are proposed for the the simulation of aircraft vibration.

Improvement of Boeing Bump Method Considering Aircraft Vibration Superposition Effect

Pavement evaluation is critical for the decision-making process of pavement preservation and rehabilitation. Roughness is a key airport pavement characteristic that has been linked to impacts such as safety and service life. The Boeing Bump is one of the few roughness evaluation methods that has been developed specifically for runways. Although it is superior to the widely used International Roughness Index (IRI), it does not take into account the superposition effect of continuous runway bumps. Based on the ADAMS/Aircraft virtual prototype platform, this paper establishes and verifies five typical models (B737, B747, B757, B777, and B787) and then analyzes the most unfavorable speed (in terms of aircraft vibration) of each model and the dynamic responses caused by multiple bumps. The original Boeing Bump is improved and optimized by determining dynamic response thresholds for the various aircraft types. The results show that the revised Boeing Bump is more realistic than the original version, especially with regard to medium and long wave bands.

Modeling and experimental analysis on the effect of carrier aircraft vibration on the imaging quality of an aspherical aerial camera

As one of the important factors, the vibration of the carrier aircraft has its impact on the imaging quality of an aspherical aerial camera. To analyze the imaging quality of the aspherical aerial camera under the vibration of the carrier aircraft, a mathematical model is established in this paper based on the theory of the transfer function and the carrier aircraft vibration principle to describe the influence of the carrier aircraft vibration on the modulation transfer function (MTF) of the aspherical optical system. The imaging quality of the aerial camera is based on MTF, and the effect of carrier aircraft vibration on the MTF of the aspherical aerial camera is investigated by simulation analysis and experiment analysis respectively. As per the results of both analyses, the variation trend of the results is in good agreement with the outcome of the mathematical model, and the mathematical model is validated. Therefore, the mathematical model is available to investigate the effect of carrier aircraft vibration on the MTF of the aspherical aerial camera, and provide theoretical guidance for aerial camera optimization design.

Vibration Response Aspects of a Main Landing Gear Composite Door Designed for High-Speed Rotorcraft

One of the crucial issues affecting the structural safety of propeller vehicles is the propeller tonal excitation and related vibrations. Propeller rotation during flight generates vibrating sources depending upon its rotational angular velocity, number of blades, power at shaft generating aircraft thrust, and blade geometry. Generally, the higher energy levels generated are confined to 1st blade passing frequency (BPF) and its harmonics, while additional broadband components, mainly linked with the blade shape, the developed engine power, and the turbulent boundary layer (TBL), also contribute to the excitation levels. The vibrations problem takes on particular relevance in the case of composite structures. The laminates in fact could exert damping levels generally lower than metallic structures, where the greater amount of bolted joints allow for dissipating more vibration energy. The prediction and reduction of aircraft vibration levels are therefore significant considerations for conventional propeller aircrafts now entering the commercial market as well as for models currently being developed. In the Clean Sky 2 framework, the present study focuses on a practical case inherent to the AIRBUS-Racer program aiming to design and develop a multi-tasking fast rotorcraft. This paper defines a finite elements (FE)-based procedure for the characterization of the vibration levels of a main landing gear (MLG) composite door with respect to the expected operating tonal loads. A parametric assessment was carried out to evaluate the principal modal parameters (transfer functions and respective resonance frequencies, mode shapes, and damping coefficients) of the landing gear-door assembly in order to achieve reduced vibration levels. Based on the FE analysis results, the influence of the extra-damping, location, and number of ballast elements, the boundary conditions were investigated with respect to failure scenarios of the kinematic line opening the study towards aeroelastic evaluations. Further experimental ground test results serve as a validation database for the prediction numerical methods representative of the composite door dynamic response.

Optimization of International Roughness Index Model Parameters for Sustainable Runway

Pavement roughness is a critical airport pavement characteristic that has been linked to impacts such as safety and service life. A properly defined roughness evaluation method would reduce airport operational risk, prolong the life of aircraft landing gear, and optimize the decision-making process for pavement preservation, which together positively contribute to overall airport sustainability. In this study, we optimized the parameters of the International Roughness Index (IRI) model to resolve the current poor correlation between the IRI and aircraft vibration responses in order to adapt and extend the IRI’s use for airport runway roughness evaluation. We developed and validated a virtual prototype model based on ADAMS/Aircraft software for the Boeing 737–800 and then employed the model to predict the aircraft’s dynamic responses to runway pavement roughness. By developing a frequency response function for the standard 1/4 vehicle model, we obtained frequency response distribution curves for the IRI. Based on runway roughness data, we used fast Fourier transform to implement the frequency response distribution of the aircraft. We then utilized Particle Swarm Optimization to determine more appropriate IRI model parameters rather than modifying the model itself. Our case study results indicate that the correlation coefficient for the optimized IRI model and aircraft vibration response shows a qualitative leap from that of the original IRI model.

Maximum Likelihood Estimation of Time-Varying Sparsity Level for Dynamic Sparse Signals

In the field of Compressed Sensing, estimation of sparsity level is very essential as the sparsity level determines the minimum number of (i) measurements to be obtained of a sparse signal during acquisition and (ii) iterations to be performed for many of the greedy techniques for the perfect recovery of the sparse signal from the obtained measurements. In this paper, we propose a Maximum Likelihood (ML) estimator to estimate the instantaneous sparsity level during acquisition and an ML sequence (MLS) estimator of sparsity levels during recovery. As the sparsity level varies in time due to the continuous birth of newer supporting components and death of existing supporting components, this paper models the sparsity level variation as a stochastic birth-death process. The real-world applications of the proposed estimators are presented on the compression of aircraft vibration signals and the estimation of wireless channels. The simulation results on real-world and model-generated data demonstrate the performance merits of the proposed estimators compared to other existing methods.

Research on Contact Performance of Aviation Electrical Connector under Atmospheric Turbulence

Electrical connectors are the basic components of the electric system in automobiles, aircrafts and ships to realize the current and electrical signal transmission. In the aviation electrical system, the electrical connectors are indispensable supporting devices accessories, which play important roles in connecting electrical system, monitoring and controlling equipment, and provide a guarantee for the reliable transmission of electrical signals between the aviation equipment and system. Whether aviation electrical connectors work reliably directly affects the safety and reliability of the entire aircraft aviation system. The random vibration of aircraft caused by turbulence during flight is one of the main factors affecting the contact performance of the electrical connectors. In this paper, the contacts of the circular four-slot three-pin electrical connectors were chosen as the research specimens. The theoretical model of the contact force for contacts of electrical connectors was established. The test method for contact force measurement was determined. According to the test scheme, the detecting device for the contact force and contact resistance of the electrical connectors was designed, and the turbulence test of the electrical connectors was carried out. Through the analysis of the test data, the influence rule of the turbulence degree, flight speed and flight height on the contact force and contact resistance of the aviation electrical connectors was obtained.

Healable, memorizable, and transformable lattice structures made of stiff polymers

Emerging transformable lattice structures provide promising paradigms to reversibly switch lattice configurations, thereby enabling their properties to be tuned on demand. The existing transformation mechanisms are limited to nonfracture deformation, such as origami, instability, shape memory, and liquid crystallinity. In this study, we present a class of transformable lattice structures enabled by fracture and shape-memory-assisted healing. The lattice structures are additively manufactured with a molecularly designed photopolymer capable of both fracture healing and shape memory. We show that 3D-architected lattice structures with various volume fractions can heal fractures and fully restore stiffness and strength over two to ten healing cycles. In addition, coupled with the shape-memory effect, the lattice structures can recover fracture-associated distortion and then heal fracture interfaces, thereby enabling healing of lattice wing damages, mode-I fractures, dent-induced crashes, and foreign-object impacts. Moreover, by harnessing the coupling of fracture and shape-memory-assisted healing, we demonstrate reversible configuration transformations of lattice structures to enable switching among property states of different stiffnesses, vibration transmittances, and acoustic absorptions. These healable, memorizable, and transformable lattice structures may find broad applications in next-generation aircraft panels, automobile frames, body armor, impact mitigators, vibration dampers, and acoustic modulators.

基于最小二乘法的飞机发动机安装节动态力识别

For aircraft noise and vibration control, it is vitally important to identify dynamic forces on engine mounts caused by engine operation. Although such dynamic forces are needed to predict and control structural vibration and structure-borne noise in the cabin, they cannot be measured directly in the flight state. The least squares method was employed to identify the dynamic forces based on the frequency response function (FRF) between excitation points and response positions with the actual acceleration measurements in the flight state. A norm condition number criterion was used to evaluate the accuracy of the inverse calculation process, and relative errors of the predicted dynamic forces were calculated. The results show that, the identified forces meet engineering requirements.

Aircraft vibration and other factors related to high systolic blood pressure in Indonesian Air Force pilots

AbstrakLatar belakang: Penerbangan dapat berdampak pada sistem kardiovaskular manusia. Penerbang terpajan antara lain pada bising dan vibrasi pesawat. Penelitian bertujuan untuk mengetahui pengaruh beberapa faktor penerbangan pada tekanan darah sistolik.Metode: Penelitian nested case-control dilakukan pada penerbang Angkatan Udara Republik Indonesia yang melakukan pemeriksaan fisik tahunan di Lembaga Kesehatan Penerbangan dan Ruang Angkasa (LAKESPRA) Saryanto tahun 2003–2008. Data yang diperoleh dari rekam medik berupa umur, jumlah jam terbang, jenis pesawat, kadar glukosa puasa dan kadar kholesterol darah, lingkaran pinggang, tinggi dan berat badan, tinggi badan, serta tekanan darah.Hasil: Dari 336 penerbang, terdapat 16 penerbanga dengan tekanan sistolik ³ 140 mmHg. Penerbang dengan rata-rata jam penerbangan 300-622 jam per tahun dibandingkan dengan 29-299 jam per tahun mempunyai risiko peningkatan tekanan darah sistolik tinggi sebesarf 5 kali [rasio odds suaian (ORa) = 5,05, 95% interval kepercayaan (CI) = 0,88 -23,30, P = 0,070]. Menurut jam terbang total, mereka yang memiliki 1.401-1,1125 jam dibandingkan 147-1.400 jam berisiko 3,6 kali mengalami tekanan darah sistolik tinggi (ORa = 3,58, 95% CI = 1,24-10,38). Selain itu, mereka dengan denyut nadi istirahat tinggi dibandingkan dengan denyut nadi normal istirahat memiliki 2,4 kali mengalami tekanan darah sistolik tinggi (ORa = 2,37, CI = 0,74-7,50 95, P = 0,147].Kesimpulan: Vibrasi pesawat terbang tinggi, rata-rata jam terbang per tahun tinggi, dan frekuensi nadi istirahat yang tinggi meningkatkan risiko tekanan sistolik tinggi.Kata kunci:tekanan darah sistolik, vibrasi pesawat terbang, frekuensi nadi istirahat, pilotAbstractBackground:Flight may affect the human cardiovascular system. Pilots are exposed among others to aircraft noise and vibration. This study aimed to investigate the effects of aircraft flight on systolic blood pressure.Methods:A nested case-control study was conducted on Indonesian Air Force pilots doing annual medical check-ups at the Saryanto Institute for Medical and Health Aviation and Aerospace (LAKESPRA) from 2003 – 2008. The data extracted from medical records were age, total flight hours, type of aircraft, fasting blood glucose and cholesterol levels, waist circumference, height and weight (Body Mass Index), and blood pressure.Results: Of 336 pilots, there were 16 with systolic pressure 140 mmHg. The pilot who had high vibration than low vibration had 2.8-fold to be high systolic blood pressure [adjusted odds ratio (ORa) = 2.83; 95%confidence interval (CI) =1.16-22.04). In term of average flight hours, those who had average flight hours of 300-622 hours per year compared to 29-299 hours per year had 5-fold increased risk to be high systolic blood pressure (ORa = 5.05; 95% CI =1.16-22.04]. Furthermore, those who had high than normal resting pulse rate had 2.4 times to be high systolic blood pressure (ORa = 2.37; 95 CI =0.81-6.97; P = 0.115).Conclusion:High aircraft vibration, high average flight hours per year, and high resting pulse rate increase risk high systolic blood pressure in air force pilots.Keywords: systolic blood pressure, aircraft vibration, resting pulse rate, pilots

Design of Multichannel and Multihop Low-Power Wide-Area Network for Aircraft Vibration Monitoring

Vibration-based condition monitoring among all the components of the aircraft structure is an important approach to improve the flight safety before any component in aircraft reaches resonance. This paper presents multichannel and multihop low-power wide-area network (MCMHL) architecture suitable for vibration monitoring on aircraft. First, microelectro mechanical system-long Range (LoRa)-based sensor node architecture in light of hardware cross-layer algorithm is proposed for implementing the tradeoff among hardware cost, power consumption, and performance. To achieve high accuracy of synchronous acquisition, multihop slot segmenting scheduling and multichannel data communication algorithm are proposed. In addition, the beacon transmission delay, of beacon between sink and sensor nodes is calculated, and further synchronization compensation algorithm is designed. The experiments of the proposed approach in aircraft vibration test and data synchronization test on aircraft skin are validated, showing that the proposed MCMHL approach has these abilities of data synchronous collections, remote communication, and data stream uploading in a wide monitoring area.

Design of vibration standard device based on random comparison method

In order to meet the needs for aircraft vibration transducer and measurement equipment to be calibrated at the job site, it is necessary to design a compact, dynamic and functional vibration standard device. This paper introduces a vibration standard device based on random comparison method. The structure and working principle of software and hardware are described in detail. Unlike the calibration requirements under laboratory conditions, on-site calibration requires that the calibration process be more consistent with the actual operating conditions. A random vibration comparison calibration method using random signals as excitation sources is designed. The vibration standard device can be maneuvered from the laboratory environment to the aircraft maintenance site. It has been proved measurement uncertainty of the system is 1.0 % (k= 2) by the method of control accuracy.

항공기 진동 범위 충족을 위한 레이다센서 장착구조물의 구조적 안정성 검증

In this paper, the structural stability of a radar sensor mounting structure satisfying aircraft vibration range is described. Vibration measurement of mounting structure and radar sensor for aircraft vibration was performed for the mounting structure for flight test of radar sensor. In order to design the mounting structure satisfying the structural stability, it was designed by referring to the propeller aircraft vibration standard of MIL-STD-810G. To verify the structural stability of the constructed structure, a dummy radar sensor was mounted on the aircraft using the designed and constructed mounting structure, and the amount of vibration applied to the mounting structure was measured using an acceleration sensor. Structural stability of the mounting structure was confirmed by using the vibration data measured in the dynamic operating environment such as takeoff, cruising, and landing.