Air Platform Research Articles

Correction of Refracted Propagation Effects for Airborne Radar Tracking

This paper concerns the correction of refracted propagation effects for airborne radar tracking. An algorithm based on the Kalman filter (KF) is developed that compensates for range and elevation refraction errors, which were analytically derived using a simplified tropospheric model. In particular, the refraction error model applies to a spherically stratified troposphere and does not include the effects of azimuthal refraction errors, small-scale fluctuations, or ducting. The effectiveness of the proposed tracking algorithm is assessed in the presence of tropospheric parameter mismatch and measurement noise. Both theoretical and numerical results are described for a medium range scenario, and a quasi-ellipsoidal racetrack is chosen for the air platform that carries the radar.

Tidal constituents from remote sensing image sequences

We address the problem of obtaining tidal constituents from a series of shoreline positions derived from time-sequential airborne imagery of the intertidal zone. A multi-sensor experiment (Bachmann et al., 2012) conducted at the Virginia Coast Reserve Long-Term Ecological Research (VCR LTER) site11www.vcrlter.virginia.edu supplied in-situ and airborne data. Hyperspectral and infrared shoreline imagery of the VCR LTER barrier islands, shallow lagoons, and mainland coastal areas as well as topographic LiDAR data were obtained from the same air platform over a nine-day period, and LiDAR and in-situ topographic beach surveys were used to specify the beach bathymetry and derive a Digital Elevation Model (DEM) over the primary area focused on in this paper at Wreck Island, VA. The DEM and shoreline positions are used to obtain a time sequence of tidal heights; these are found to be consistent with a time series from a GPS-equipped tide gage float anchored nearby. A least-squares fit of the five largest tidal constituents (M2, N2, S2, O1, K1) to this one-week record indicates that the first three can be retrieved with only a ±15–20 % error, as determined by the one-year sea-surface height time series from a nearby NOAA Sea Surface Height (SSH) station at Wachapreague, VA.The broader question of how many images are needed to obtain tidal constituents from an annual record is also addressed. Using SSH values from a NOAA tide gage station as a surrogate for image-derived SSH values, we progressively decimate a yearlong tide record, calculating its tidal constituents at each level of decimation. We find that that only one image every ten days is needed to retrieve the five largest tidal constituents to within a 10% error.

Station-keeping control for a stratospheric airship platform via fuzzy adaptive backstepping approach

This paper presents a novel approach for station-keeping control of a stratospheric airship platform in the presence of parametric uncertainty and external disturbance. First, conceptual design of the stratospheric airship platform is introduced, including the target mission, configuration, energy sources, propeller and payload. Second, the dynamics model of the airship platform is presented, and the mathematical model of its horizontal motion is derived. Third, a fuzzy adaptive backstepping control approach is proposed to develop the station-keeping control system for the simplified horizontal motion. The backstepping controller is designed assuming that the airship model is accurately known, and a fuzzy adaptive algorithm is used to approximate the uncertainty of the airship model. The stability of the closed-loop control system is proven via the Lyapunov theorem. Finally, simulation results illustrate the effectiveness and robustness of the proposed control approach.

Retail beamed power using millimeter waves

Retail delivery of electric power through millimeter waves is relevant in developing areas where the market for communication devices outpaces the power grid infrastructure. It is also a critical component of an evolutionary path towards terrestrial and space-based renewable power generation. Narrow-band power can be delivered as focused beams to receivers near end-users, from central power plants, rural distribution points, UAVs, tethered aerostats, stratospheric airship platforms, or space satellites. The article surveys the available knowledge base on millimeter wave beamed power delivery. It then considers design requirements for a retail beamed power architecture, in the context of rural India where power delivery is lagging behind the demand growth for connectivity. A survey of technology developments relevant to millimeter wave beaming is conducted, and indicates that massive, mass-produced solid-state arrays capable of achieving good efficiency and cost effectiveness are possible in the near term to enable such retail power beaming architectures.

Impact of Flight Disturbances on Airborne Radar Tracking

This correspondence is devoted to the study of the impact of flight disturbances due to the atmospheric turbulence on airborne radar tracking. The performance of a turbulence-ignorant tracking filter is assessed in a turbulent simulated scenario. The turbulence is modelled according to the Dryden model, a correlated, zero-mean, Gaussian random process. A quasi-ellipsoidal racetrack course is chosen for the air platform that carries the radar. The performance of the turbulence-ignorant tracking algorithm is analyzed in terms of mean value and standard deviation of the estimation errors for each component of the position and velocity vectors and compared with the posterior Cramer-Rao lower bound (PCRLB), evaluated for the ideal case of absence of platform vibrations.

Multisolver Domain Decomposition Method for Modeling EMC Effects of Multiple Antennas on a Large Air Platform

We proposed herein a multisolver domain decomposition method (MS-DDM), and applied it to compute the isolations among multiple antennas mounted on a large air platform at X -band frequency. The fundamental strategy of the proposed MS-DDM is to decompose the entire computational domain into many subregions based on the local material properties and geometrical features. Subsequently, we employ the most suitable computational electromagnetic (CEM) technique for each of the subregions. Moreover, the coupling between well-separated subregions is implemented through Stratton-Chu representation formulas. However, for the touching interfaces between neighboring subregions, a Robin transmission condition is introduced to mitigate the troublesome self-integral terms with weak singular kernels. The proposed MS-DDM is, therefore, well suited for modeling multiple antennas conformally mounted on a large platform, where touching subregions are usually unavoidable. Furthermore, by using the proposed MS-DDM framework, multiple existing CEM solvers have been successfully integrated with few minor modifications.

Cold and transition season cloud condensation nuclei measurements in western Colorado

Abstract. Recent studies have shown that orographic precipitation and the water resources that depend on it in the Colorado Rocky Mountains are sensitive to the variability of the region's aerosols, whether emitted locally or from distant sources. However, observations of cloud droplet nucleating aerosols in western Colorado, climatologically upwind of the Colorado Rocky Mountains, have been limited to a few studies at a single, northern site. To address this knowledge gap, atmospheric aerosols were sampled at a ground site in southwestern Colorado and in low-level north to south transects of the Colorado Western Slope as part of the Inhibition of Snowfall by Pollution Aerosols (ISPA-III) field campaign. Total particle and cloud condensation nuclei (CCN) number concentrations were measured for a 24-day period in Mesa Verde National Park, in September and October 2009. Regression analysis showed a positive relationship between mid-troposphere atmospheric pressure to the west of the site and the total particle count at the ground site, but no similar statistically significant relationship was found for the observed CCN. These data were supplemented with particle and CCN number concentration, as well as particle size distribution measurements collected aboard the King Air platform during December 2009. A CCN closure attempt was performed and suggested that the sampled aerosol may have had a low hygroscopicity that changed little with the large-scale wind direction. Together, the sampled aerosols from these field programs were characteristic of a rural continental environment with CCN number concentrations that varied slowly in time, and little in space along the Western Slope.

First Fuel-Cell Manned Aircraft

First Fuel-Cell Manned Aircraft

Improved test capabilities for cost-effective performance evaluation of airborne electronic warfare systems

AbstractState of the art test capabilities are described that can enable optimised electronic warfare (EW) system development programmes for military air platforms. EW systems are key enablers of air platform survivability and the above is important as defence ministries and industry world-wide wrestle with affordability, technical and industrial challenges. The military end user needs improved capability quickly, with high availability; defence ministries want this at lowest possible cost and with minimum risk. Satisfying these requirements, while remaining in business against a background of fierce international competition and world financial crisis, is indeed challenging. Improvements are described that can enable improved technical performance and lower cost, time and risk programmes than hitherto, with emphasis on RF EW systems and the recent multi-£M upgrade to BAE Systems’ EW Test Facility, with its aircraft-sized anechoic chamber. This upgrade assures a further decade of world-class UK capability for testing manned and unmanned air platforms.

Complex airborne system with combined action on the conditions of risk weather phenomena

The study of the weather phenomena is one of the main concerns of scientists. Initially, the researches in this area were intended to provide military structures new ways of fighting in wars such as the wars in Korea or Vietnam and then continued with the development of technologies to combat the phenomena that affect the normal conditions of agriculture, the environment, etc. -extreme phenomena- hail, low precipitation regime, etc. Since the last decade of last century also in Romania there were a number of initiatives supported through a national program of research in the fight against hail and stimulation of precipitation. In this context, INCAS proposed in 2008 a research project to implement a complex airborne system, which carry out actions to limit the effects of extreme weather events on crops and objectives of national and strategic interest, on the basis of information received from a system of sensors located on the air platform and intended for measuring the physical characteristics of the atmosphere. Also, as a long-term effect, the action of the complex airborne system may lead to the rainfall regulation and control, with all the implications arising from this (avoiding flooding, providing protection from frost of autumn crop, etc). The aerial platform chosen for this research approach is the aircraft for school and training IAR99 SOIM, INCAS being the author of its structural design and also holding the patent for Industrial Design nr.00081 registered with OSIM. Project acronym : COMAEROPREC.

Configurations analysis for high‐altitude/long‐endurance airships

PurposeIn recent years, high‐altitude/long‐endurance airship platforms have generated great interest as a means to provide communications and surveillance capabilities. The purpose of this paper is to develop a model for airship conceptual design and help provide insight into the viability of high‐altitude/long‐endurance airships.Design/methodology/approachA configuration analysis model with the consideration of pressure difference, temperature difference, and helium purity, etc. was developed. The influences of the airship payload, size and area required of solar cell with environment and operation parameters, such as operation latitude, pressure difference, temperature difference, helium purity, seasons, latitude, and wind speed, etc. were analyzed.FindingsThe results show that the area of solar cell required for stratospheric airship is very large under the condition of low altitude, high latitude, wind, and in winter, etc. which might make the design of high‐altitude/long‐endurance airship an elusive goal. They also show that the solar cell efficiency is the key technology in the control of solar cell area required for airships, and the technology advances in regenerative fuel cells and propeller efficiency have significant effects among on the airship payload, size, and solar cell area required for airship.Originality/valueThe paper analyses the energy balance of the high‐altitude/long‐endurance airship.

Comment on �Three-Dimensional Ascent Trajectory Optimization for Stratospheric Airship Platforms in the Jet Stream�

TECHNICAL COMMENTS are brief discussions of papers previously published in this journal. They should not exceed 1500 words (where a figure or table counts as 200 words). The author of the previous paper is invited to submit a reply for publication in the same issue as the Technical Comment. These discussions are published as quickly as possible after receipt of the manuscripts. Neither AIAA nor its Editors are responsible for the opinions expressed by the authors.

Comment on "Three-Dimensional Ascent Trajectory Optimization for Stratospheric Airship Platforms in the Jet Stream"

Comment on "Three-Dimensional Ascent Trajectory Optimization for Stratospheric Airship Platforms in the Jet Stream"

A Comparison of Meteorological Observations from South Pole Station before and after Installation of a New Instrument Suite

Abstract The Amundsen–Scott South Pole surface meteorological instrument suite was upgraded in 2004. To ensure that the new and old instruments were recording similar information, the two suites of instruments ran simultaneously for a year. Statistical analysis of the time series of temperature, pressure, and wind was performed to determine if there were any significant differences in the observations. Significant differences were found in some of the winter months for temperature and wind speed. No differences were found for the wind direction distribution. There are also noticeable differences in wind speed between the Clean Air platform near the Clean Air facility and the platform at the approach end of the skiway. Wind speeds are lower at the skiway tower when the wind is from the northeast quadrant and at the Clean Air tower when the wind is from the southwest quadrant, reflecting the effect of increased surface roughness and flow distortion over and around the station structures. Because of a change in elevation of the pressure sensor, the pressure data were recalculated at a common station elevation (2836 m). Although the resulting differences are small (around 0.1 hPa), there is a systematic sign change between summer and winter. The results of this analysis, while revealing some significant differences, show that the new instrumentation at South Pole station is generally reporting observations that are similar to those of the old instrumentation, and most of the differences are within the accuracy of the instruments. However, the instrument placement and construction of official aviation routine weather reports (METARs) do have an impact on the usefulness of the data for research.

Naval Target Classification by Fusion of Multiple Imaging Sensors Based on the Confusion Matrix

This paper presents an algorithm for the classification of targets based on the fusion of the class information provided by different imaging sensors. The outputs of the different sensors are combined to obtain an accurate estimate of the target class. The performance of each imaging sensor is modelled by means of its confusion matrix (CM), whose elements are the conditional error probabilities in the classification and the conditional correct classification probabilities. These probabilities are used by each sensor to make a decision on the target class. Then, a final decision on the class is made using a suitable fusion rule in order to combine the local decisions provided by the sensors. The overall performance of the classification process is evaluated by means of the “fused” confusion matrix, i.e. the CM pertinent to the final decision on the target class. Two fusion rules are considered: a majority voting (MV) rule and a maximum likelihood (ML) rule. A case study is then presented, where the developed algorithm is applied to three imaging sensors located on a generic air platform: a video camera, an infrared camera (IR), and a spotlight Synthetic Aperture Radar (SAR).

Three-Dimensional Ascent Trajectory Optimization for Stratospheric Airship Platforms in the Jet Stream

The authors would like to thank the Korea Ministry of Commerce, Industry, and Energy for their support of this project and for the permission to publish this work.

Exfoliation detection using structurally integrated piezoelectric ultrasonic transducers

Advanced sensors and sensor network technologies are shaping the future of civilian and military air platform health assessment and monitoring. In this paper, the feasibility of applying a structurally integrated thick-film piezoelectric ceramic ultrasonic transducer for monitoring exfoliation corrosion damage is investigated. The ultrasonic transducer can easily and reliably be deposited on metallic and polymeric structures using a sol-gel spray approach. The change in material thickness due to exfoliation damage is estimated using ultrasonic time-of-flight measurements. Experimental results from two aluminium (Al.7075-T6511) specimens are presented. In comparison, conventional water-coupled ultrasonic tests were also conducted to generate a thickness map for each selected specimen before the integrated transducers were fabricated. Close correlation was obtained between both conventional and integrated thick-film ultrasonic measurements, demonstrating the effectiveness of the integrated thick-film ultrasonic transducer for exfoliation corrosion damage assessment and monitoring.

Analysis of the Motion Control Methods for Stratospheric Balloon-Borne Gondola Platform

At present, gondola platform is one of the stratospheric balloon-borne platforms being in research focus at home and overseas. Comparing to other stratospheric balloon-borne platforms, such as airship platform, gondola platform has advantages of higher stability, rapid in motion regulation and lower energy cost but disadvantages of less supporting capacity and be incapable of fixation. While all platforms have the same goal of keeping them at accurate angle and right pose for the requirements of instruments and objects installed in the platforms, when platforms rotate round the ground level perpendicular. That is accomplishing motion control. But, platform control system has factors of low damper, excessive and uncertain disturbances by the reason of its being hung over balloon in the air, it is hard to achieve the desired control precision because platform is ease to deviate its benchmark motion. Thus, in the controlling procedure in order to get higher precision, it is crucial to perceive the platform's swing synchronously and rapidly, and restrain the influence of disturbances effectively, keep the platform's pose steadily. Furthermore, while the platform in the air regard control center in the ground as reference object, it is ultimate to select a appropriate reference frame and work out the coordinates and implement the adjustment by the PC104 controller. This paper introduces the methods of the motion control based on stratospheric balloon-borne gondola platform. Firstly, this paper compares the characteristic of the flywheel and CMG and specifies the key methods of obtaining two significant states which are ‘orientation stability’ state and ‘orientation tracking’ state for platform motion control procedure using CMG as the control actuator. These two states reduce the deviation amplitude of rotation and swing of gondola's motion relative to original motion due to stratospheric intense atmosphere disturbance. We define it as the first procedure. In next procedure, we use the transfer matrix of earth reference frame to geographic reference frame to transform the data measured by the magnetic orientation sensors and the gyroscope to the space orientations, then the PC104 controller use the space orientations value as feedback to complete revises.

Shape Optimization of Stratosphere Airship

PRESENTLY, there is a strong interest in developing unmanned stratospheric airship platforms to be utilized as telecommunication relays, for environmental monitoring or surveillance purposes. Because of the large surface area of the hull, an airship shows high drag, which roughly increases with the square of the airspeed. The required propulsion power is proportional to the third power of the airspeed. Therefore, it is of essential interest to minimize the aerodynamic drag and to maximize the propulsion efficiency. The propulsive power required depends mainly on the aerodynamic drag of the airship hull, which accounts for about 2 of the total drag. Even a small reduction in hull drag can result in a significant saving of fuel, which in turn will lead to a greater payload capacity or an increased range of the airship. During the aerodynamic design of an airship, it is therefore especially important to find a drag-minimized envelope for the intended range of missions. The investigations on the shape optimization of airship were conducted by Th. Lutz et al. 1 and Nejati et al. 2 A source distribution on the body axis was chosen to model the body contour and the corresponding inviscid flowfield, with the source strengths and the lengths of respective segments being used as design variables for the optimization process. Boundary-layer calculation is performed by means of a proved integral method for attached laminar or turbulent boundary layers. To determine the transition location, Lutz used a semi-empirical method based on linear stability theory (e n method), Nejati applied forced transition criterion and concluded that the e n -method is desirable for determining the transition location. A commercial optimizer as well as an evolution strategy with covariance matrix adaption of the mutation distribution were applied as optimization algorithm in Lutz’ paper. Nejati used the genetic algorithm as the optimization algorithm and found that genetic algorithm is a powerful method for such a multidimensional, multimodel, and nonlinear objective function. In this Note, we developed a new method for shape optimization of airship body in terms of the previous investigations of shape optimization. 1−11 The airship geometry is expressed analytically as a polynomial function of eight parameters. The inviscid flow

Design of the Automatic Flight and Guidance Controller for 50m Unmanned Airship Platform

The Stratospheric Airship Platform (SAP) has a capability of performing the autonomous and guidance flight to satisfy given missions. To be used as the High Altitude Platforms (HAPs), the capabilities of controlling platform's accurate position and keeping the station point are the most important features. Under this circumstances Autonomous Flight Control System (AFCS) is a critical system and plays a key role in achieving the given requirements and succeeding in missions. In this paper, the design and analysis results of the AFCS algorithms and controller are presented. The brief summary of the AFCS hardware structure is also explained. The autopilot controller and guidance logics were designed based on the linear dynamics of the unmanned airship platform and the full nonlinear dynamics was considered to evaluate and verify their performances.