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Reliable Fault Identification for Aircraft Control Surface Damage
No full textFault Detection and Diagnosis system (FDD) is used to isolate the aircraft fault which provides information to reconfiguration mechanism to recover its operation during the fault occurrence. Using FDD, only anticipated faults can be tackled by design. Inaccurate information from the FDD and if interpreted incorrectly by the reconfiguration mechanism, can lead to a complete loss of system stability. Robust fault identification methods need to be explored especially for the unanticipated fault scenarios. In this paper, single control surface damage fault scenario arising due to either bird strike or battle damage is considered. A typical mathematical model of the aircraft is simulated with single control surface damage which captures the dynamics of high performance aircraft. The real-time parameter estimation of augmented aircraft is essential for reconfigurable flight control. Fault detection and identification is solved with extended Kalman filter considering only state and observation equations for lateral and directional axis
Gain Enhancement of Annular Ring Patch Using Cascaded EBG
No full textIn this paper, the concept of cascaded EBG for an annular ring patch antenna excited by coaxial feed designed for 6.8 GHz is proposed. The bandwidth and gain obtained for the annular patch are 267 MHz and 7.3 dB respectively. The impedance bandwidth of the antenna is enhanced from 4 % to 18 % by introducing two complementary split ring resonators (CSRR) near the feed. By the introduction of CSRR, the antenna resonates at three different frequencies 6.4 GHz, 6.8 GHz and 7.3 GHz with gain 5.5 dB, 7.3 dB, and 0.2 dB. The gain at 6.8 GHz and 7.3 GHz are enhanced to 8.3 dB and 2 dB respectively using cascaded mushroom EBG with circular symmetry arranged around the patch
Impact Localization and Severity Estimation on Composite Structure Using Fiber Bragg Grating Sensors by Least Square Support Vector Regression
No full textLow-velocity impact (LVI) events in carbon fiber reinforced plastic (CFRP) structures are a major concern as they result in barely visible impact damage which can reduce the strength and stiffness of impacted structure. Detection of such impact events in terms of location and severity will be a significant milestone for aerospace structural health monitoring applications.
This can result in well-targeted inspection programs thereby reducing the time and cost of periodic inspections. One of the easy and efficient ways of getting the impact response of a structure is through strain measurement. LVI event monitoring using fiber Bragg grating sensors has evolved as an attractive choice in recent years along with various soft computing algorithms and advanced signal processing techniques. Machine learning techniques such as artificial neural networks and support vector machine are widely used to localize impact events. Getting information regarding the ensuing damage due to LVI event from the strain response is not straight forward as it could involve estimation of intermediate parameters like energy/force of impact, which are further related with probable damage size. This paper demonstrates least square support vector regression-based algorithm to localize impact event in terms of X - and Y -coordinates and its energy on a CFRP plate-like structure and its comparison with other algorithms cited in the literature
Properties of C f /SiC-ZrB 2 -Ta x C y composite produced by reactive hot pressing and polymer impregnation pyrolysis (RHP/PIP)
No full textC f /SiC-ZrB 2 -Ta x C y composite was synthesized by reactive hot pressing (RHP) of C f cloth, polycarbosilane (PCS), ZrB 2 , and Ta powders at 4 MPa and 1200 °C. PIP cycle influenced sintering process by increasing density of the composite from 2.34 to 2.82 g/cc. Residual carbon produced during the PIP cycles at 1200 °C was utilized to yield Ta x C y by the addition of Ta. SEM images illustrate that by increasing the number of PIP cycles, SiC derived from the PCS cover the C f fibre, micropores, and cracks. PIP cycles and Ta x C y phase improved flexural strength of the composite from 20 to 114 MPa. Mass and linear ablation resistance studies at 1600–2000 °C exhibited that oxide formation at the outer surface caused a barrier; further, no oxidation underneath the composite was observed. SEM images display that at 2000 °C, SiO 2 and Ta x O y were molten and sealed the pores. Hence, ablation resistance was enhanced by blocking the penetration in high-temperature flame
Improved fatigue crack growth resistance by retrogression and re-aging heat treatment in 7010 aluminum alloy
No full textAircraft grade 7010 aluminum alloy was heat treated to two different conditions: (1) standard peak aging (T6) and (2) retrogression and re-aging (RRA). The microstructures of these alloys were characterized by using transmission electron microscope. Fatigue crack growth rate (FCGR) tests were conducted using standard compact tension specimens, following ASTM standards. Tests were conducted at various stress ratios, R ranging from 0.1 to 0.7. The RRA-treated alloy was observed to contain coarsened ηʹ (MgZn2) precipitates with higher inter-particle spacing when compared with T6-treated alloy. The grain boundary precipitates (GBPs) were also coarsened and discontinuous in RRA-treated alloy as compared with continuous GBPs in T6 condition. The FCGR was lower and ΔKth was higher in RRA-treated alloy compared with T6-treated alloy at all the stress ratios investigated. Improved fatigue crack growth resistance in RRA-treated alloy was correlated to the modified microstructure and enhanced crack closure level
Geo-Localization of Target in 3-Dimensional Coordinate Using SRTM Data
Get PDFThis paper deals with Estimation of 3-Dimensional Geo-Location Coordinate (Latitude,
Longitude and Elevation) of a given target location using the image of a Target captured from a
Gimballed Camera mounted on an Unmanned Aerial Vehicle (UAV). The 2-Dimensional Geo-Location Coordinate (Latitude and Longitude) is estimated by the application of Geo-Location Algorithm based on the knowledge of target pixel location in the image. The Target Elevation is estimated by
Elevation Estimation Algorithm using the 2-Dimensional Geo-Location Coordinate of target and
Elevation Database such as NASA Shuttle Radar Topography Mission (SRTM) Database, National
Geospatial-Intelligence Agency (NGA) SRTM Database and Advanced Space borne Thermal Emission and
Reflection Radiometer Global Digital Elevation Model Version 2. This paper illustrates the Target Geo-Location Coordinate Estimation for two different experimental setup: UAV Simulation Setup and a Real Time Setup. The Geo-Location Estimation result obtained from the Simulation Setup is found to have localization error around 0.3 m, while the estimates from the Real Time Setup are found to have a higher localization error of around 2.3 m. The elevation result obtained using Elevation Estimation Algorithm for SRTM 1-Arc Second database is proved to be more accurate but this comes with a downside of having longer processing time when compared with other databases. NGA 3-Arc Second database provides the result with the shortest computation period
Characterization of MEMS based Inertial Measurement Unit
No full textInertial system consisting of 10 DoF MEMS IMU has been brought to deploy on the stores of high performance fighter aircraft to estimate the separation trajectory of released stores from
the aircraft. The IMU calibration has been carried out as it is prerequisite for accurate estimation of stores separation trajectory. This paper presents calibration methodology and test procedure followed to calibrate IMU. The intent is to find out stochastic and deterministic errors in tri-Axial rate gyroscopes and tri-Axial accelerometers of a MEMS IMU. For this, rate table tests are conducted to calibrate gyroscopes and tumble tests are carried out to calibrate accelerometers. In this paper, the sensor axis misalignment factors in IMU is obtained from gaussnewton optimization algorithm. Thus obtained calibration constants are further used in an EKF based fusion algorithm. A 6-state a 9-state Extended Kalman filters are presented to estimate Euler angles and position respectively. Effect of calibration on Euler angles and position estimation is clearly brought out
Transition metal based CuxNiyCoz-x-yO4 spinel composite solar selective absorber coatings for concentrated solar thermal applications
No full textSolar selective absorber coatings, combining of nanostructured, ternary transition metal spinel structure and composite oxides were prepared by a series of transition metal (Co, Ni and Cu) based nitrate salts. A single-layered structure of crystalline phase spinel-type oxide AB2O4 in the framework of simple wet chemical route and dip coating method was prepared in the crystalline structure of CuxNiyCoz-x-yO4. The X-ray diffraction profile of the oxide film was found to coincide with that of crystalline [Cu2+0.31Co3+0.16Co2+0.53]A[Cu2+0.17Ni3+0.16Co3+1.67]BO4 in the ICDD database. Precursor salts were heated at a particular temperature to form hydroxy nitrate solution followed by suitable solvent with different binders to form adherent sol for dip coating technique. By optimizing sol concentration, withdrawal speed and annealing temperature, uniform absorber layer with solar absorptance of 0.91 and emittance of 0.14 were achieved in a single layer coating with a composite oxide formation. The optical, structural and morphological properties of the optimized coatings of single layer CuxNiyCoz-x-yO4 spinel and composite oxide have been characterized by UV–Vis–NIR spectrophotometer, emissometer, X-ray diffraction, field emission - scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy
Multifunctional properties of ceria nanocubes synthesized by a hydrothermal method
No full textNanosized ceria is an extremely versatile and commercially valuable material because of its industrially important applications. The present work describes the synthesis of ceria nanocubes by a simple hydrothermal method. The size of the synthesized ceria nanocubes are 8–20 nm. The formation of ceria phase has been corroborated by X-ray photoelectron spectroscopy and X-ray diffractometry. Selected area electron diffraction patterns obtained for the nanocubes are also precisely indexed to the cubic ceria phase. The synthesized ceria nanocubes exhibit a high surface area of 26 m2 g−1 and also high catalytic activity. The work also investigates the influence of ceria nanocubes on the corrosion resistance of sol–gel hybrid coatings in 3.5% NaCl solution on AA2024 substrates. The corrosion behaviour of the sol–gel coatings revealed that ceria nanocubes reinforce the barrier properties of the sol–gel coatings and confer longer active protection to the metallic substrate
Evaluation of nanosecond laser ablation and scratch resistance of tantalum carbide coated graphite substrates
No full textThe present work aimed at investigating the effect of nanosecond laser parameters on ablation characteristics such as ablation depth and surface roughness of plasma sprayed tantalum carbide coated graphite substrates. The micro scratch tests were performed on the laser ablated and as-sprayed coatings to evaluate the critical loads and coefficient of friction. The laser ablated surface with minimum ablation depth and surface roughness was found to exhibit 18% higher critical loads when compared to that of as-sprayed surface. However, laser ablated surfaces exhibited slightly higher friction coefficient than as-sprayed surfaces due to formation of metastable oxide layer (Ta6O) on the top surface of TaC coatings as indicated by XRD. The maximum ablation and scratch resistance could be found at maximum pulse energy of 250 μJ, maximum scanning speed of 1000 mm/s and moderate hatch spacing of 20 μm. While, the failure of as-sprayed TaC coatings was attributed to local collapsing of material due to degradation of mechanical properties such as elastic modulus, surface porosity and surface roughness, laser ablated surfaces exhibited wedge spallation at the end of scratch zone only