92 research outputs found
An improved design of a fully automated multiple output micropotentiometer
This paper describes in details a new design of a fully automated multiple output micropotentiometer (?pot). A prototype has been built at the National Institute for Standards (NIS), Egypt to establish this highly improved AC voltage source in the millivolt range. The new device offers three different outputs covering a wide frequency range from only one outlet. This valuably supports the precise sourcing ranges of low AC voltage at NIS. The design and the operation theory of this prototype have been discussed in details. An automatic calibration technique has been introduced through specially designed software using the LabVIEW program to enhance the calibration technique and to reduce the uncertainty contributions. Relative small AC-DC differences of our prototype in the three output ranges are fairly verified. The expanded uncertainties of the calibration results for the three output ranges have been faithfully estimated. However, further work is needed to achieve the optimum performance of this new device
The ampere and the electrical units in the quantum era
By fixing two fundamental constants from quantum mechanics, the Planck
constant and the elementary charge , the revised Syst\`eme International
(SI) of units endorses explicitly quantum mechanics. This evolution also
highlights the importance of this theory which underpins the most accurate
realization of the units. From 20 May 2019, the new definitions of the kilogram
and of the ampere, based on fixed values of and respectively, will
particularly impact the electrical metrology. The Josephson effect (JE) and the
quantum Hall effect (QHE), used to maintain voltage and resistance standards
with unprecedented reproducibility since 1990, will henceforth provide
realizations of the volt and the ohm without the uncertainties inherited from
the older electromechanical definitions. More broadly, the revised SI will
sustain the exploitation of quantum effects to realize electrical units, to the
benefit of end-users. Here, we review the state-of-the-art of these standards
and discuss further applications and perspectives.Comment: 78 pages, 35 figure
Position estimation and performance prediction for permanent-magnet motor drives
PhD ThesisThis thesis presents a theoretical and experimental development of a novel position
estimator, a simulation model, and an analytical solution for brushless PM motor drive. The
operation of the drive, the position estimation model of the test motor, development of
hardware, and basic operation of inverter are discussed. Starting with the well-known
continuous-time model of brushless PM motor, a sampled-data model is developed that is
suitable for th6, application of real-time position estimator.
An analytical methodo f calculating the steady-stateb ehaviouro f the brushlessP M motor for
1200in verter operation is presentedT. he analysisa ssumesth at the machinea ir gap is free of
saliency effects, and has sinusoidal back EMF. The analytical solution is derived for 60"
electrical of the whole period. By experimental results, it is shown that the method of
analysis is adequate to predict Ihe motor's performance for typical operating points
including phase advance and phase delay operation. C)
I
A computer simulation model for prediction of the performance of brushless PM moto rs is
presented. The model is formulated entirely in the natural abc frame of reference, which
allows direct comparison of the simulation and corresponding experimental results. The
equations and diagrams are put into a convenient form for the simulation and future
developments and library modules. The simulation model and corresponding experimental
data of the brushless PM motor drive is given.
The thesis describes a modem solution to real-time rotor position estimation, which has been
subject to intense research activity for the last 15 years. The implemented new algorithm for
shaft position sensorless operation of PM motors is based on the flux linkage and line
current estimation. The position estimation algorithm has also been verified by both off-line
and on-line experiments (accomplished by a DSP, TMS320C30), and a wide range of
steady-statea nd transient results have been 0gi0v en including starting from rest. The position
estimation method effectively moves the position measurement point in the drive from the
mechanical side to the motor's terminals. As well as eliminating the mechanical shaft
position sensor, the investigated method can be used for high performance torque control of
brushless PM motors. The thesis demonstrates that, in contrast to many other "sensorless"
schemes, the new position estimation method is able to work effectively over the full
operating range of the drive, and is applicable to a wide range of motor/converter types.
Since the hardware is straightforward, only the new position estimation algorithm
differentiates a system. Therefore, if a DSP control system is already implemented in the
drive, the position estimator can be implemented at low cost.Istanbul Technical University and Higher Education Counci
Advanced scanners and imaging systems for earth observations
Assessments of present and future sensors and sensor related technology are reported along with a description of user needs and applications. Five areas are outlined: (1) electromechanical scanners, (2) self-scanned solid state sensors, (3) electron beam imagers, (4) sensor related technology, and (5) user applications. Recommendations, charts, system designs, technical approaches, and bibliographies are included for each area
A Multi-Band Far-Infrared Survey with a Balloon-Borne Telescope
Nine additional radiation sources, above a 3-sigma confidence level of 1300 Jy, were identified at 100 microns by far infrared photometry of the galactic plane using a 0.4 meter aperture, liquid helium cooled, multichannel far infrared balloon-borne telescope. The instrument is described, including its electronics, pointing and suspension systems, and ground support equipment. Testing procedures and flight staging are discussed along with the reduction and analysis of the data acquired. The history of infrared astronomy is reviewed. General infrared techniques and the concerns of balloon astronomers are explored
Viking '75 spacecraft design and test summary. Volume 1: Lander design
The Viking Mars program is summarized. The design of the Viking lander spacecraft is described
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