Comparison of resonant topologies in high-voltage DC applications

Because of their tolerance of transformer nonidealities, resonant converters are considered to be well-suited to high-voltage applications. The series and parallel resonant topologies, as well as a newly discovered hybrid resonant topology are compared for high-voltage applications. Design criteria which incorporate transformer nonidealities are developed and used in the construction of high voltage prototypes for each topology. It is found that the parallel topology leads to the lowest peak switch current and the most ideal behavior     

Sequential Piecewise Recursive Filter for GPS Low-Dynamics Navigation

The design, implementation, and performance of a real-time estimation algorithm, referred to in this paper as the sequential piecewise recursive (SPWR) algorithm, for the global-positioning system (GPS) low-dynamics navigation system is described. The SPWR algorithm for this application was implemented in single precision arithmetic (32 bit, floating point). Numerical results are presented covariance and filter gains at a slower rate than the state measurement update, and it uses U-D factor formulation to perform covariance computations. The SPWR algorithm saves real-time processing requirements without appreciable degradation of filter performance. Another important feature of the SPWR algorithm is that it incorporates pseudorange and delta-range data from each GPS satellite sequentially for navigation solution. The SPWR algorithm, for this application, was implemented in single precision arithmetic (32 bit, floating point). Numerical results are presented.     

Causes of aircraft electrical failures

The results of a survey of data on failures of aircraft electronic and electrical components that was conducted to identify problematic components are reported. The motivation for the work was to determine priorities for future work on the development of accident investigation techniques for aircraft electrical components. The primary source of data was the Airforce Mishap Database, which is maintained by the Directorate of Aerospace Safety at Norton Air Force Base. Published data from the Air Force Avionics Integrity Program (AVIP) and Hughes Aircraft were also reviewed. Statistical data from these three sources are presented. Two major conclusions are that problems with interconnections are major contributors to aircraft electrical equipment failures, and that environmental factors, especially corrosion, are significant contributors to connector problems     

Beamspace ML bearing estimation incorporating low-angle geometry

A problem in low-angle radar tracking, namely, bearing estimation in the presence of a strong specular multipath component that arrives within the beamwidth of the direct path signal, is studied. Three-dimensional beamspace domain maximum likelihood (3D-BDML) is a computationally simple ML bearing estimation algorithm applicable in this scenario which operates in a 3-D beamspace. A variation of 3D-BDML incorporating the multipath geometry as a priori information is presented. In symmetric 3D-BDML the pointing angle of the center beam is equal to the bisector angle between the direct path ray and the image ray, which may be estimated a priori given only the radar height and the target range. The effect of the inclusion of a priori information on the performance of 3D-BDML is analyzed in terms of the dependence on the relative phase difference between the direct and specular path signals, the sensitivity to error in the bisector angle estimate, and the results of operation when no specular multipath component is present in the data. In addition, computationally simple schemes for coherently incorporating multifrequency data into 3D-BDML are investigated     

High performance magnetostrictive actuators

The application of magnetostriction in the design of a hybrid, electromechanical/hydraulic high-performance linear (large force and stroke) and/or rotational (large moment and angle) actuator is considered. The design concept combines the high power density of actuation possible with magnetostriction (approaching 0.1 HP/cm³ of the magnetostrictive material assuming 3 kHz excitation frequency) and the design flexibility of hydraulics. The objective of the research described was to validate the concept theoretically and to study alternatives and improvements. The system, as currently envisioned, offers very small packaging volume (approximately an order of magnitude smaller than conventional electromechanical systems), flexible packaging (relative location of the major system components is not critical), and easy control (precise control of actuation speed, quick reverse time, and inherent position lockup). The major technical problems associated with the design are outlined, and results of a computer simulation of a prototype actuator are presented     

Sequential ridge regression

A sequential algorithm which closely approximates ridge regression is introduced, and it is pointed out that the desired sequential ridge estimator can be obtained by properly choosing the free parameters of a startup technique for ordinary sequential least squares estimation. The derivation of this result is trivial; however, since no matrix inversions are needed for its implementation, this algorithm is of practical importance     

A target cueing and tracking system (TCATS) for smart videoprocessing

A smart system that uses state-of-the-art image processing techniques to detect and track targets moving in video or infrared imagery is presented. It is a general-purpose system that was developed to be independent of the application and the user interface. TCATS has successfully demonstrated a high detection capability and the ability to ignore exterior environmental conditions, such as cloud shadows moving through the scene, snow, blowing dust, rain and moderate camera motion. TCATS can handle many targets and retain the identity of each object from one frame to the next. Special rugged hardware has been developed to reduce the size, cost, and power consumption and to increase the processing rate, reliability, and environmental operating capability of the system. TCATS can be incorporated into an existing video assessment system without a major cost outlay intruder. The TCATS algorithms, custom-developed hardware, and preliminary field test results are described     

Global communication using a constellation of low Earth meridianorbits

The concept of meridian orbits is briefly reviewed. It is shown that, if a satellite in the meridian orbit makes an odd number (>1) of revolutions per day, then the satellite passes over the same set of meridians twice a day. Satellites in such orbits pass over the same portion of the sky twice a day and every day. This enables a user to adopt a programmed mode of tracking, thereby avoiding a computational facility for orbit prediction, look angle generation, and auto tracking. A constellation of 38 or more satellites placed in a 1200-km altitude circular orbit is favorable for global communications due to various factors. It is shown that appropriate phasing in right ascension of the ascending node and mean anomaly results in a constellation wherein each satellite appears over the user's horizon one satellite after another. Visibility and coverage plots are provided to verify the continuous coverage     

Direct integration methods in dynamic problems of structural mechanics

A method of direct integration with respect to time is proposed to solve dynamic problems of structural mechanics and comparison with the well-known methods is presented.