Airborne Power Research Articles

Fault Diagnosis Expert System for Electric Power System of the Large-Scale UAVs Based on Virtual Instrument

In this paper, a test system hardware platform based on PXI bus system is proposed to test the airborne power system and typical power distribution structure of large-scale Unmanned aerial vehicles (UAV). By researching system structure, analyzing failure mode and designing fault tree, fault diagnosis expert system is designed to test the airborne power system in large-scale UAVs, where a forward reasoning expert knowledge base based on extension rule is built to solve the non-exact inference in complex system via introducing certainty factor. The experiments illustrate that the proposed system can effectively improve the intelligent level of test system and has good application prospects.

Experimental study of defoaming by air-borne power ultrasonic technology

Foam is a dispersion of gas in a liquid in which the distances between the gas bubbles are very small. Foams are frequently generated in the manufacture of many products as result from the aeration and agitation of liquids, from the vaporization of the liquid and also from biological or chemical reactions. Foams are generally an unwanted product in industrial processes because they cause difficulties in process control and in equipment operation. The most efficient conventional method for defoaming is the use of chemical agents but they contaminate the product. High-intensity ultrasonic waves offer a clean procedure to break foam bubbles. The potential use of ultrasound for foam breaking that was known since many years has been recently reinforced by the application of a new type of ultrasonic defoamer based on the stepped-plate high-power transducers to generate air-borne ultrasound. This defoamer has been successfully applied in several industrial problems such as the control of excess foam produced during the filling operation of bottles and cans on high-speed canning lines and in fermenting vessels and other reactors of great dimensions.The treatment of such industrial problems requires the proper characterization and quantification of the main parameters involved in the mechanisms of the defoaming effect. This paper deals with an experimental study about the separate influence of such parameters with the aim of improving the application of the stepped-plate power ultrasonic generators for the production of the defoaming action on industrial processes

Nonlinear Current Control of Single-Phase PFC Converters

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A set of new nonlinear current control methods are presented for single-phase power factor corrected ac–dc converters. These control methods combine input current feedforward with partial feedback based on the switch current to achieve sinusoidal input current and unity input power factor. They overcome the limitations of conventional linear (average) current control in terms of control bandwidth and sensitivity to noise, resulting in high-performance input current control which can meet the most stringent harmonic current limits required by variable-frequency airborne power systems. The control methods are also ideally suited for integrated mixed-signal implementation, requiring an analog current controller which is very simple, much less sensitive to noise than conventional linear feedback control, and independent of converter and control design parameters; and a digital controller which operates with a sampling frequency much lower than the switching frequency. Detailed development of the control methods is presented along with their stability analysis and circuit implementation. A prototype converter and its operation are also presented to validate the analysis and to demonstrate the performance of the control methods. </para>

Dymola-based modeling of SRD in aircraft electrical system

A rapid-calculation nonlinear model of switched reluctance drives system (SRD) is modularly developed based on Dymola, a new object-oriented modeling software. The SRD is constructed as a subsystem model for the aircraft electrical system model library. The purpose is to build a generic, expandable, and relatively complete airborne model library, then conveniently assemble a system-level model of airborne power system to simulate its dynamic performance, and then alleviate the difficulty in design and optimization of airborne power system during the conceptual design phase.

Compact, lightweight, superconducting power generators

Many future military systems will depend heavily on high electrical power input ranging from hundreds of kilowatts up to the multimegawatt level. These weapon systems include electromagnetic launch applications as well as electrically driven directed energy weapons (DEW), such as high-power microwaves and solid-state lasers. These power generation subsystems must often be packaged using limited space and strict weight limits on either ground mobile or airborne platforms. Superconducting generators made of high-temperature superconductors (HTS) will enable megawatt-class airborne power systems that are lightweight and compact. Also discussed briefly are new advances in HTS conductors and refrigeration systems furthering the development of HTS power systems.

Synthesis of Input-Rectifierless AC/DC Converters

This paper discusses the basic construction procedure and topological possibilities of creating AC/DC converters out of simple DC/DC converters. It is shown that two separately controlled DC/DC converters are sufficient for producing a regulated DC output and shaping the input current, from an AC voltage source, without the need for input rectifiers. Some design constraints are discussed, emanating from the limitation of the conversion ratios that can be achieved by particular DC/DC converters. Selected topologies are verified experimentally. This kind of rectifierless converter find applications in airborne power supplies where zero-crossing distortions are significant because of the inevitable phase-lead effect of the input rectifier bridge.

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The aircraft brake system has an important influence on the safety of aircrafts. The traditional hydraulic brake system needs long and complicated pipelines, from the aircraft central hydraulic pumps to the brake actuators, which could cause serious vibration and leakage problem. This paper proposes a new Integrated Self-energized Brake System (ISBS) for aircrafts based on a single switching valve control. The new system needs neither external hydraulic sources nor complicated pipelines. It recovers some kinetic energy of the landing aircraft through a hydraulic pump geared by the main wheel. The recovered energy will convert into hydraulic power used for brake actuators. Compared with the traditional hydraulic brake system, the new system has a higher level of safety, economy and reliability, and has better performance than the electric brake system. Moreover, its self-energized feature makes it possible to brake as usual even in an emergency situation, such as when the airborne power is lost. In this paper, an aircraft longitudinal motion model and a hydraulic ABS model with a single switching valve are formulated. Based on these models, a switched control strategy with delay compensation is developed, which describes a switching surface derived from back-stepping to direct switching actions. The feasibility of the new system is verified by simulations. Meanwhile, an experimental prototype is designed to carry out experiments on a ground brake testing bench, whose results indicate the new system has a favorable development and application prospect.

A study of exhaust noise in a motor vehicle using statistical energy analysis

This work uses statistical energy analysis (SEA) to study noise transmission through a commercial motor vehicle and in order to do this various sound and vibration power inputs associated with flanking transmission via the exhaust and engine noise are calculated. A modern commercial motor vehicle that has an exhaust noise sensitivity problem is studied in this work. The aim of this work is to demonstrate the application of SEA and to study the effects on noise transmission when the exhaust is incorrectly fitted (misaligned). Airborne and structural paths for sound and vibration transmission to a vehicle saloon are considered. Also, the SEA framework is used to identify the relative importance of each structural and airborne power input in relation to the sound power that is transmitted to the vehicle saloon. It is shown that the importance of each sound power input varies with frequency. At low frequencies, sound transmission through the vehicle structure is most important. At high frequencies, airborne flanking noise transmission to the floor is important. In this case, exhaust vibration transmission is most important at frequencies between 250 Hz and 1 kHz when the engine is running at 5700 r/min, and the SEA model predicts the change in performance associated with exhaust misalignment.

A study of engine noise transmission using statistical energy analysis

This work uses statistical energy analysis (SEA) to study engine noise transmission through a small passenger motor vehicle and in order to do this the sound and vibration power input is calculated. An aim of this work is to identify the causes of differences between measured and SEA predicted vibration transmission in motor vehicles. To allow this to be studied a relatively simple running condition and vehicle are chosen. Airborne and structural paths for sound and vibration transmission to a vehicle saloon are considered. Also, SEA is used to identify the relative importance of each structural and airborne power input in relation to the sound power that is transmitted to the vehicle saloon. This technique can then make it possible for the power input matrix to be greatly simplified. The most important power input to the small passenger vehicle used in this study is found to be at the floor mounts of the engine subframe. At high frequencies resonant transmission through the firewall (dash) can also be important. The results indicate the difficulty of estimating the power input, which is the main cause of differences between measured and predicted results (even for the restricted running condition considered here). The work also demonstrates that SEA can be very useful for identifying important transmission paths and predicting overall performance.

The philosophy and development of an automatic checkout adapter for an air-borne electric power system

The demand for automatic checkout of complex air-borne equipment has become a major item in ground-support equipment, and as a result, many basic equipments have been developed and built for this purpose. The concept of the basic equipment is to produce a component capable of testing any present-day or proposed future electronic system. To do this the test apparatus is divided into two parts; one which is generally referred to as the automatic checkout equipment, and one which is usually called an adapter. The automatic checkout equipment for this application uses a binary coded digital program which is read from a tape and which establishes all the major functions of the test equipment. In this instance the basic unit, that is, the automatic checkout equipment, has the capability of reading four basic parameters: frequency, time, voltage, and resistance. These four functional capabilities establish the criteria for the operation of the adapter which must interrogate the air-borne electrical system and present an analog signal in terms of one of the functional categories.

Ground power equipment for support of air force weapons

THE MATERIAL that is presented in this paper was gathered during an engineering study on the same subject which was made for the Air Research and Development Command of the United States Air Force. The objective of the study was preparation of recommendations for needed development in the area of ground support for secondary power. In aviation terminology, secondary power is defined as that power which is used for purposes other than the propulsion of aircraft and missiles. Aircraft and missiles are defined as weapons, and a weapon system includes everything that is needed for maintenance, calibration, testing, and training during operational use of the weapon. ?Ground power? substitutes for air-borne secondary power during tests. The familiar secondary power systems are electric, hydraulic, and pneumatic. During the study, it was found desirable to treat air conditioning as a fourth and newly important type of secondary power.

Arc Suppression for Relay Contacts in DC Service

Available relays for control of high-power direct current are seen to be large, heavy, and adversely affected by vibration and shock. This paper shows how commonly available components of reasonable size can be used with small vibration-resistant relays to control large direct currents at high potential. Thus, control of high-power airborne power supplies on the direct current side has become possible with reasonable equipment.

Radio Telemetering for Testing Aircraft in Flight

A brief resume is given of the factors which necessitated the development of thoroughly practicable and reliable telemetering equipment for dynamic testing of high-speed aircraft in flight. An outline of a radio telemetering system is presented which was developed under contract and accepted as suitable for structural flight testing by the United States Navy Bureau of Aeronautics in April 1945. Emphasis is placed upon the electric system and circuits which are of most interest to Institute members. These include the stabilized amplitude modulated subcarrier oscillators, the master amplifier, the air-borne regulated power supply, the frequency modulated transmitter, the automatic frequency controlled frequency modulated receiver, the heterodyne analyzer, and the mobile receiving station.