Human transfer functions in multi-axis and multi-loop control systems
Human transfer functions in multiaxis and multiloop control systems
CLOSED LOOP SYSTEM↗
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Stochastic models for multi-valued, multi- dimensional relations Semiannual status report, Jun. 16, 1966 - Jan. 15, 1967
Covered space, Riemann geometry extension, and partition function research on stochastic models for multivalued, multidimensional relations
RIEMANN SPACE↗
Stochastic models for multi-valved, multi-dimensional relations semiannual status report, 16 jan. - 15 sep. 1967
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Bhargava, T. N.↗
Study on multi-satellite, multi-measurement of the structure of the earth's bow shock
The pulsation model of the earth's bow shock proposed a nonuniform shock having both perpendicular (abrupt, monotonic) and oblique (oscillatory, multigradient) properties simultaneously, depending on local orientation of the shock surface to the interplanetary field B sub sw in parallel planes defined by B sub sw and solar wind velocity. Multiple, concurrent, satellite observations of the shock and solar wind conditions were used. Twenty-six potentially useful intervals of concurrent Explorer 33 and 35 data acquisition were examined, of which six were selected for closer study. In addition, two years of OGO-5 and HEOS 1 magnetometer data were examined for possible conjunctions to these spacecraft having applicable data. One case of clear nonuniformity and several of field-dependent structure were documented. A computational aid, called pulsation index, was developed.
Source record↗
Multi-input, multi-output regulator design for constant disturbances and non-zero set points with application to automatic landing in a crosswind
Undesirable steady offsets result when a stationary, linear regulator using state feedback is subjected to constant disturbances and/or non-zero setspoints. To eliminate these offsets, the disturbances and non-zero setpoints can be fed forward to the control. Only when the number of outputs is less than or equal to the number of control inputs can the outputs be maintained at arbitrary non-zero setpoints. The state and the disturbance may be estimated using a constant gain Kalman filter or by modeling the constant disturbances as exponentially correlated processes with long correlation times.
Holley, W. E.↗
Characteristics of internal- and jet-noise radiation from a multi-lobe, multi-tube suppressor nozzle tested statically and under flight simulation
Nozzle transmission coefficient (NTC) for a 12-lobe, 24-tube suppressor nozzle and a reference round convergent nozzle of equal area are obtained by an impulse test technique. This technique utilizes a high voltage spark discharge as a noise source within the test duct. Effects of nozzle geometry, jet Mach number, jet temperature and flight velocity on the radiation characteristics of the two nozzles are presented. Likewise, the jet mixing noise measured in the absence of internal noise for both nozzles at static and also simulated flight conditions are discussed.
Ahuja, K. K.↗
Multi-input, multi-output system control for experimental aircraft
Two techniques, direct eigenspace assignment (DEA) and explicit model following (EMF), are used initially to synthesize control laws for the longitudinal dynamics model of a Short Takeoff and Landing (STOL) vehicle in the landing configuration. The vehicle model and the flight control design are presented. The two synthesis techniques are briefly discussed and the handling qualities specifications mapped into the algorithm formulations. The control laws resulting from exercising the algorithms are evaluated in terms of achieved performance and robustness. Since the synthesized control laws involve full state feedback, methodologies were implemented for the control laws using output feedback without adversely affecting performance and robustness. Finally, the salient features of the two design techniques are summarized and the areas that require further investigation are suggested.
Schmidt, D. K.↗
Multi-input multi-output system control for experimental aircraft
Results from the synthesis of control laws for an advanced short takeoff aircraft in a low-speed approach flight condition are given. Two of four candidate synthesis techniques are reported: direct eigenspace assignment and explicit model following via a linear quadratic regulator (LQR) formulation. A fundamental objective of this work is to obtain low-order feedback compensators, synthesized via the above techniques, and the judicious use of state estimation, thus allowing the use of a reasonable number of sensors for feedback.
Schmidt, David K.↗
Operation of a multi-year, multi-agency project
Organizational and technological aspects of the operation by NASA and ESA of the IUE satellite observatory since its launch in 1978 are discussed. Topics addressed include the division of responsibilities among the ground stations, the IUE orbit and its evolution, the IUE spacecraft, normal operations (proposal selection and observation planning, shift handover, and spacecraft operations), and a typical observation (target identification and acquisition, telescope focus, spectrograph modes, camera operations, calibration, and data reduction). Consideration is given to constraints on IUE operation due to the sun-earth-moon configuration (eclipses), spacecraft power, radiation, temperature, and momentum-wheel speed; problems encountered with gyros, onboard computers, the fine sun sensor, and cameras; and the reliable high-efficiency overall performance of the IUE. Diagrams, drawings, and graphs are provided.
Faelker, Juergen↗
Characterizing forest stands with multi-incidence angle and multi-polarized SAR data
The potential for using HH-polarized L-band SAR data obtained at different incidence angles from satellite altitudes to identify and map different forest cover types and stand density classes is studied. Reasonably accurate results are obtained if the speckle characteristics of the data are suppressed by low-pass spatial filters and a contextual classification algorithm. Multipolarized L-band SAR data obtained from aircraft altitudes over the same test site are also analyzed to assess the relationships between polarization and forest stand characteristics. It is found that incidence angle controls, to a very large extent, the characteristics of the data and the type of information that can be obtained from L-band, HH-polarized satellite SAR data. Cross-polarization of L-band SAR data enhances and differentiates various forest stand characteristics which cannot be defined using only the like-polarized data, and vice-versa.
Hoffer, R. M.↗
Multi-point measurements of ULF wave phases using a multi-channel energetic ion detector
The oscillation of differential fluxes of energetic ions modulated by a ULF wave often shows a phase shift between measurements in back-to-back detectors with look directions perpendicular to the ambient magnetic field. In a plasma of a single ion species, the phase difference is caused by displacement of the effective measurement positions by one ion gyroradius to each side of the detector. As the wave phase is periodic, the observed phase shift can correspond to a family of possible wavelengths. Simultaneous measurements of the flux modulations in different energy channels, which are equivalent to measurements of the wave phase at different positions, may make it possible to single out a unique wavelength consistent with all the measurements. Using the medium-energy-particle experiments ISEE-1 and 2, each of which may serve as a back-to-back detector, the above method was applied to a compressional Pc 5 wave observed near the equatorial plane at L between about 7 and 11. The transverse propagation properties of the wave were determined unambiguously.
Lin, N.↗
Multi-reactor configurations for multi-megawatt spacecraft power supplies
Several conceptual designs for a multimegawatt space nuclear power supply system were developed on the basis of hardware and technology from the existing multihundred kilowatt-class SP-100 reactor program. It is shown that net power outputs in the multimegawatt range can be achieved by using a modular multireactor configuration of several SP-100-derived nuclear power supplies. A variety of geometries were examined for their applicability to the multireactor configuration, showing that modular multireactor systems have the advantage of an increased redundancy in the power system, as compared with a single-reactor system, allowing higher reliabilities than those achievable with single-reactor systems. Results are presented on the Mars Cargo Mission analysis, showing that modularity allows the option of redeployment of power systems in Mars and facilitates refurbishment and turnaround of NEP transfer vehicles.
George, Jeffrey A.↗
Color composite processing of multi-wavelength, multi-polarization airborne radar imagery
Multiwavelength, multipolarization radar image data can be processed to allow the clear depiction of most information in color composite displays. The first principal component, depicted as variations in image intensity, captures the dominant variation in the data and reduces noise without degradation of spatial detail. Other principal components, depicted primarily as variations in image chromaticity, are derived from spatially filtered data so that image colors can be attributed to significant wavelength and polarization contrasts, and not to speckle. Processing paths can be designed to emphasize wavelength contrasts, polarization contrasts, or overall discrimination of surface features.
Crippen, Robert E.↗
Free and forced response of nearly periodic multi-span beams and multi-bay trusses
The influence of several effects on mode localization in free-free multispan beams is investigated. Finite-element methods are used to study localization as a function of Timoshenko beam effects, imperfection strength, coupling strength, and imperfection type. The multispan beam study is conducted with random realizations of a forty-span free-free beam. In addition, free and forced response of free-free trusses and frames is investigated. Results indicate that, for the trusses and frames considered, the dynamic behavior can be approximated by continuum modeling approaches for only the lowest few global modes. Also, for reasonable values of modal damping, localized modes play a subtle role in the overall structural response.
Lust, S. D.↗
Multi-frequency, multi-polarization SAR and radiometer sea ice classification
Microwave remotely sensed data were acquired simultaneously in March 1988 over Beaufort, Chukchi, and Bering Sea ice using the JPL multifrequency, polarimetric synthetic aperture radar (SAR), and multifrequency dual-polarization GSFC radiometer. The experiment was conducted as a series of coordinated underflights of the DMSP SSM/I satellite radiometer to validate ice products derived from its radiance values. Concurrent flights by an NRL P-3 aircraft enabled overlapping high-resolution, single-frequency images to be acquired over the same surfaces using a Ka-band scanning microwave radiometer. Precise coregistration to an accuracy of 100 m, +/- 25 m enables comparison of temporally and spatially coincident active and passive microwave datasets. Three-channel polarimetric SAR data are compared with dual-polarized radiometer data at several SSM/I frequencies, showing backscatter signatures to be highly correlated with radiometric temperatures. Further comparisons are used to evaluate ice concentration retrievals and to show how multiparameter datasets can be used to resolve ambiguities present in identifying certain sea ice forms with a single microwave instrument.
Drinkwater, Mark R.↗
Techniques in processing multi-frequency multi-polarization spaceborne SAR data
This paper presents the algorithm design of the SIR-C ground data processor, with emphasis on the unique elements involved in the production of registered multifrequency polarimetric data products. A quick-look processing algorithm used for generation of low-resolution browse image products and estimation of echo signal parameters is also presented. Specifically the discussion covers: (1) azimuth reference function generation to produce registered polarimetric imagery; (2) geometric rectification to accommondate cross-track and along-track Doppler drifts; (3) multilook filtering designed to generate output imagery with a uniform resolution; and (4) efficient coding to compress the polarimetric image data for distribution.
Curlander, John C.↗
Multi-frequency multi-polarization processing for spaceborne SAR
The Shuttle Imaging Radar-C (SIR-C) is the third in a series of space shuttle based synthetic aperture radars (SAR) sponsored by the National Aeronautics and Space Administration (NASA). The SIR-C ground data processing system is to process the playbacked SAR signal data into a variety of data products for distribution to the science community. An overview of the end-to-end ground data processing system with emphasis on the unique characteristics involved in the system design is presented. Included in the discussion are science requirements, radar system specifications, input data format specifications, system operations design, data products design, processing algorithm design, hardware architecture design, and software design.
Curlander, John C.↗
Hybrid suboptimal control of multi-rate multi-loop sampled-data systems
A hybrid state-space controller is developed for suboptimal digital control of multirate multiloop multivariable continuous-time systems. First, an LQR is designed for a continuous-time subsystem which has a large bandwidth and is connnected in the inner loop of the overall system. The designed LQR would optimally place the eigenvalues of a closed-loop subsystem in the common region of an open sector bounded by sector angles + or - pi/2k for k = 2 or 3 from the negative real axis and the left-hand side of a vertical line on the negative real axis in the s-plane. Then, the developed continuous-time state-feedback gain is converted into an equivalent fast-rate discrete-time state-feedback gain via a digital redesign technique (Tsai et al. 1989, Shieh et al. 1990) reviewed here. A real state reconstructor is redeveloped utilizing the fast-rate input-output data of the system of interest. The design procedure of multiloop multivariable systems using multirate samplers is shown, and a terminal homing missile system example is used to demonstrate the effectiveness of the proposed method.
Shieh, Leang S.↗