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Large scale systems are defined as systems requiring more than one decision maker to control the system. Decentralized control and decomposition are discussed for large scale dynamic systems. Information and many-person decision problems are analyzed.
A shake test was performed on the Large Scale Dynamic Rig in the 40- by 80-Foot Wind Tunnel in support of the McDonnell Douglas Advanced Rotor Technology (MDART) Test Program. The shake test identifies the hub modes and the dynamic calibration matrix of the rotor balance. For hub mode identification, three configurations were tested: wind tunnel scale unlocked with dampers engaged and disengaged, and wind tunnel scale locked. Test data were analyzed with a multi-degree-of-freedom time domain algorithm to identify the modal properties of the hub modes. The damping of the low frequency hub modes (ground resonance modes) increases significantly with the wind tunnel dampers engaged. For dynamic calibration of the rotor balance, the shake test was performed only with the wind tunnel dampers engaged. The dynamic calibration matrix, computed from the shake test data using a least squares error method, is used to correct the five-per-rev vibratory balance readings. The corrections are large for the side force, moderate for the axial force and inplane hub moments, and small for the normal force.
The purpose of this paper is to outline the derivation and limitations of a dynamic scaling law for Earth based testing of this type of Mars terminal descent system.
Classes of large scale dynamic systems were discussed in the context of modern control theory. Specific examples discussed were in the technical fields of aeronautics, water resources and electric power.
Full scale dynamic test programs of large booster vehicles - monograph
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The classes of large-scale dynamic systems are discussed in terms of modeling with emphasis on air transportation system modeling.
Understanding the large-scale dynamics of the magnetospheric boundary is an important step towards achieving the ISTP mission's broad objective of assessing the global transport of plasma and energy through the geospace environment. Our approach is based on three-dimensional global magnetohydrodynamic (MHD) simulations of the solar wind-magnetosphere- ionosphere system, and consists of using interplanetary magnetic field (IMF) and plasma parameters measured by solar wind monitors upstream of the bow shock as input to the simulations for predicting the large-scale dynamics of the magnetospheric boundary. The validity of these predictions is tested by comparing local data streams with time series measured by downstream spacecraft crossing the magnetospheric boundary. In this paper, we review results from several case studies which confirm that our MHD model reproduces very well the large-scale motion of the magnetospheric boundary. The first case illustrates the complexity of the magnetic field topology that can occur at the dayside magnetospheric boundary for periods of northward IMF with strong Bx and By components. The second comparison reviewed combines dynamic and topological aspects in an investigation of the evolution of the distant tail at 200 R(sub E) from the Earth.
Dynamic problems of aerospace vehicles, using aeroelastically scaled dynamic models
Goals: Water budget-related dynamical phase space; Connect large-scale dynamical conditions to atmospheric water budget (including precipitation); Connect atmospheric water budget to cloud type distributions.
Research on the F/A-18E/F configuration was conducted using a 22%-dynamically-scaled drop model to study flight dynamics in the subsonic regime. Several topics were investigated including longitudinal response, departure/spin resistance, developed spins and recoveries, and the failing leaf mode. Comparisons to full-scale flight test results were made and show the drop model strongly correlates to the airplane even under very dynamic conditions. The capability to use the drop model to expand on the information gained from full-scale flight testing is also discussed. Finally, a preliminary analysis of an unusual inclined spinning motion, dubbed the "cartwheel", is presented here for the first time.
Dynamically scaled, free-flying models are used by the National Aeronautics and Space Administration (NASA) to study the stalling and spinning characteristics of civil and military airplane configurations. Such tests have been conducted for many different designs, and it has been possible to correlate the results predicted by the model tests with flight test results obtained in the investigations. The present paper describes four of the dynamic model testing techniques used at the NASA Langley Research Center, including the scaling laws used in the construction of models and in the interpretation of results. Predictions of stall/spin behavior based on model results have generally been very accurate, and the model tests are regarded as an invaluable precursor to full-scale flight tests. However, aerodynamic scale effects between some models and full-scale airplanes due to differences in test values of Reynolds number have resulted in erroneous predictions for a few configurations. A discussion of these effects is provided, together with the approach used to modify the model so that its behavior more closely matches that of the airplane. Finally, two typical applications of the techniques to the X-29A research airplane and several general aviation research airplanes are presented to illustrate the type of information provided by the tests.
Dynamically scaled, free-flying models are used by the National Aeronautics and Space Administration (NASA) to study the stalling and spinning characteristics of civil and military airplane configurations. Such tests have been conducted for many different designs, and it has been possible to correlate the results predicted by the model tests with flight test results obtained in the investigations. The present paper describes four of the dynamic model testing techniques used at the NASA Langley Research Center, including the scaling laws used in the construction of models and in the interpretation of results. Predictions of stall/spin behavior based on model results have generally been very accurate, and the model tests are regarded as an invaluable precursor to full-scale flight tests. However, aerodynamic scale effects between some models and full-scale airplanes due to differences in test values of Reynolds number have resulted in erroneous predictions for a few configurations. A discussion of these effects is provided, together with the approach used to modify the model so that its behavior more closely matches that of the airplane. Finally, two typical applications of the techniques to the X-29A research airplane and several general aviation research airplanes are presented to illustrate the type of information provided by the tests.
Full scale dynamic landing impact investigation of prototype lunar module landing gear
We consider the class of large-scale dynamical systems consisting of identical subsystems, but with complex connectivity. It is shown that the irreducibility of this large system is directly related to the irreducibility of a simple system, which is obtained by a replacement of the subsystems by integrators.
Some notions of decentralization and coordination in the control of large-scale dynamic systems are discussed. Decentralization and coordination have always been important concepts in the study of large systems. Roughly speaking decentralization is the process of dividing a large problem into subproblems so that it can be handled more easily. Coordination is the manipulation of the subproblem so that the original problem is solved. The various types of decentralization and coordination that have been used to control dynamic systems are discussed. The emphasis was to distinguish between on-line and off-line operations to understand the results available by indicating the aspects of the problem which are decentralized.
The quality of TOPEX/POSEIDON determinations of the global scale dynamic ocean topography have been assessed by determining mean topography solutions for successive 10-day repeat cycles and by examining the temporal changes in the sea surface topography to identify known features. The assessment is based on the analysis of TOPEX altimeter data cycles 1 through 36. Important errors in the tide model used to correct the altimeter data have been identified. The errors were reduced significantly by use of a new tide model derived with the TOPEX/POSEIDON measurements. Maps of the global 1-year mean topography, produced using four of the most accurate of the marine geoid, show that the largest error in the dynamic ocean topography show expected features, such as the known annual hemispherical sea surface rise and fall and the seasonal variability due to monsoon influence in the Indian Ocean. Changes in the sequence of 10-day topography maps show the development and propagation of an equatorial Kelvin wave in the Pacific beginning in December 1992 with a propagation velocity of approximately 3 m/s. The observations are consistent with observed changes in the equatorial trade winds, and with tide gauge and other in situ observations of the strengthening of the El Nino. Comparison of TOPEX-determine sea surface height at points near oceanic tide gauges shows agreement at the 4 cm root-mean-square (RMS) level over the tropical Pacific. The results show that the TOPEX altimeter data set can be used to map the ocean surface with a temporal resolution of 10 days and an accuracy which is insonsistent with traditional in situ methods for the determination of sea level variations.
Techniques of predicting and/or controlling the dynamic behavior of large scale systems are discussed in terms of decentralized decision making. Topics discussed include: (1) control of large scale systems by dynamic team with delayed information sharing; (2) dynamic resource allocation problems by a team (hierarchical structure with a coordinator); and (3) some problems related to the construction of a model of reduced dimension.