Performance degradation of multiple-input multiple-output (MIMO) control systems having limited actuators is often handled by augmenting the controller with an antiwindup mechanism, which attempts to maintain system performance when limits are encountered. The goals of this paper are: (1) To develop a method to analyze antiwindup systems to determine precisely what stability and performance degradation is incurred under limited conditions. It is shown that by reformulating limited actuator...

Topics: NASA Technical Reports Server (NTRS), AIRCRAFT CONTROL, CONTROL STABILITY, CONTROL SYSTEMS DESIGN,...

The Mini-Mast testbed was one of the first large scale Controls-Structure-Interaction (CSI) systems used to evaluate state-of-the-art methodology in flexible structure control. Now that all the testing at Langley Research Center has been completed, a look back is warranted to evaluate the program. This paper describes some of the experiences and technology development studies by NASA, university, and industry investigators. Lessons learned are presented from three categories: the testbed...

Topics: NASA Technical Reports Server (NTRS), CONTROL THEORY, FLEXIBLE BODIES, LARGE SPACE STRUCTURES, MIMO...

This final technical report covers a three and one-half year period preceding February 28, 1993 during which support was provided under NASA Grant NAG-1-1065. Following a general description of the system identification problem and a brief survey of methods to attack it, the basic ideas behind the approach taken in this research effort are presented. The results obtained are described with reference to the published work, including the five semiannual progress reports previously submitted and...

Topics: NASA Technical Reports Server (NTRS), AEROSPACE SYSTEMS, NONLINEAR SYSTEMS, PARAMETER...

NASA is designing an Advanced Extravehicular Mobility Unit (AEMU)to support future manned missions beyond low-Earth orbit (LEO). A key component of the AEMU is the communications assembly that allows for the wireless transfer of voice, video, and suit telemetry. The Extravehicular Mobility Unit (EMU) currently used on the International Space Station (ISS) contains a radio system with a single omni-directional resonant cavity antenna operating slightly above 400 MHz capable of transmitting and...

Topics: NASA Technical Reports Server (NTRS), ANTENNA DESIGN, OMNIDIRECTIONAL ANTENNAS, EXTRAVEHICULAR...

Orthogonal harmonic multisine excitations were utilized in a wind tunnel test and in simulation of the SemiSpan Supersonic Transport model to assess aeroservoelastic characteristics. Fundamental issues associated with analyzing sinusoidal signals were examined, including spectral leakage, excitation truncation, and uncertainties on frequency response functions and mean-square coherence. Simulation allowed for evaluation of these issues relative to a truth model, while wind tunnel data...

Topics: NASA Technical Reports Server (NTRS), EXCITATION, SUPERSONIC TRANSPORTS, SYSTEM IDENTIFICATION,...

Advanced noise control methodologies to reduce sound emission from aircraft engines take advantage of the modal structure of the noise in the duct. This noise is caused by the interaction of rotor wakes with downstream obstructions such as exit guide vanes. Mode synthesis has been accomplished in circular ducts and current active noise control work has made use of this capability to cancel fan noise. The goal of the current effort is to examine the fundamental process of higher order mode...

Topics: NASA Technical Reports Server (NTRS), MODES, CURVATURE, NOISE (SOUND), AIRCRAFT ENGINES,...

This paper presents a semi-analytic method for computing frequency dependent means, variances, and failure probabilities for arbitrarily large-order closed-loop dynamical systems possessing a single uncertain parameter or with multiple highly correlated uncertain parameters. The approach will be shown to not suffer from the same computational challenges associated with computing failure probabilities using conventional FORM/SORM techniques. The approach is demonstrated by computing the...

Topics: NASA Technical Reports Server (NTRS), CONTROL SYSTEMS DESIGN, PROBABILITY THEORY, DYNAMICAL...

Systems and methods of adaptive control for uncertain nonlinear multi-input multi-output systems in the presence of significant unmatched uncertainty with assured performance are provided. The need for gain-scheduling is eliminated through the use of bandwidth-limited (low-pass) filtering in the control channel, which appropriately attenuates the high frequencies typically appearing in fast adaptation situations and preserves the robustness margins in the presence of fast adaptation.

Topics: NASA Technical Reports Server (NTRS), ADAPTIVE CONTROL, NONLINEARITY, MIMO (CONTROL SYSTEMS),...

The computational requirements for obtaining the results summarized in the preceding section were very modest and were easily accomplished using computer-aided control system design software. Of special significance is the ability of the PDT to indicate a loop closure sequence for MIMO QFT designs that employ sequential loop closure. Although discussed as part of a 2 x 2 design, the PDT is obviously applicable to designs with a greater number of inputs and system responses.

Topics: NASA Technical Reports Server (NTRS), COMPUTER AIDED DESIGN, CONTROL SYSTEMS DESIGN, FEEDBACK, MIMO...

The goal of this paper is to demonstrate the use of fuzzy logic controllers in modifying the figure of a piezoceramic bimorph mirror. Non-contact electron actuation technology is used to actively control a bimorph mirror comprised two PZT-5H wafers by varying the electron flux and electron voltages. Due to electron blooming generated by the electron flux, it is difficult to develop an accurate control model for the bimorph mirror through theoretical analysis alone. The non-contact shape control...

Topics: NASA Technical Reports Server (NTRS), PIEZOELECTRIC CERAMICS, FUZZY SYSTEMS, MATHEMATICAL MODELS,...

A discrete-time adaptive control law for stabilization, command following, and disturbance rejection that is effective for systems that are unstable, MIMO, and/or nonminimum phase. The adaptive control algorithm includes guidelines concerning the modeling information needed for implementation. This information includes the relative degree, the first nonzero Markov parameter, and the nonminimum-phase zeros. Except when the plant has nonminimum-phase zeros whose absolute value is less than the...

Topics: NASA Technical Reports Server (NTRS), CONTROL THEORY, ADAPTIVE CONTROL, COSTS, MIMO (CONTROL...

Two methods for control system reconfiguration have been investigated. The first method is a robust servomechanism control approach (optimal tracking problem) that is a generalization of the classical proportional-plus-integral control to multiple input-multiple output systems. The second method is a control-allocation approach based on a quadratic programming formulation. A globally convergent fixed-point iteration algorithm has been developed to make onboard implementation of this method...

Topics: NASA Technical Reports Server (NTRS), CONTROL SYSTEMS DESIGN, MIMO (CONTROL SYSTEMS), X-33 REUSABLE...

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296

Sep 20, 2010
09/10

by
Armstrong, Wilbur; Doane, George C., III; Dean, Garvi

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The high frequency code has been made an interactive code using FORTRAN 5.0. The option to plot n-tau curves was added using the graphics routines of FORTRAN 5.0 and GRAFMATIC. The user is now able to run with input values non-dimensional (as in the original code) or dimensional. Input data may be modified from the keyboard. The low and intermediate frequency codes have been run through a set of variations. This will help the user to understand how the stability of a configuration will change...

Topics: AIRCRAFT CONTROL, FLIGHT SAFETY, LATERAL CONTROL, FLIGHT CONTROL, FLIGHT STABILITY TESTS, MIMO...

336
336

May 22, 2011
05/11

by
Stuckey, James M

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The following are discussed: CPR-488/141-B problem (CPR XUS); CPR XUS foam popcorning (wind tunnel test); BX-250/141-B spray problem; NCFI 24-57 (NCFI-141B); PDL 4034/141B pour foam; primer for ET; and potential TMCPP toxic problem.

Topics: CONTROL SYSTEMS DESIGN, FLEXIBLE SPACECRAFT, LARGE SPACE STRUCTURES, OPTIMAL CONTROL, CONTROL...

180
180

May 23, 2011
05/11

by
Fotedar, L. K.; Krishen, K

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This paper summarizes the results of a radiation transfer study conducted on houseplants using controlled environmental conditions. These conditions included: (1) air and soil temperature; (2) incident and reflected radiation; and (3) soil moisture. The reflectance, transmittance, and emittance measurements were conducted in six spectral bands: microwave, red, yellow, green, violet and infrared, over a period of three years. Measurements were taken on both healthy and diseased plants. The data...

Topics: MATHEMATICAL MODELS, TRANSFER FUNCTIONS, LINEAR SYSTEMS, MATRICES (MATHEMATICS), MATRIX METHODS,...

132
132

May 23, 2011
05/11

by
Deere, Karen A.; Asbury, Scott C

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A translating throat single expansion-ramp nozzle (SERN) concept was designed to improve the off-design performance of a SERN with a large, fixed expansion ratio. The concept of translating the nozzle throat provides the SERN with a variable expansion ratio. An experimental and computational study was conducted to predict and verify the internal performance of this concept. Three nozzles with expansion ratios designed for low, intermediate, and high Mach number operating conditions were tested...

Topics: ROTARY WING AIRCRAFT, CONTROL SYSTEMS DESIGN, FLIGHT CONTROL, MIMO (CONTROL SYSTEMS), DYNAMIC...

The process is described of analysis, design, digital implementation, and subsonic testing of an active control flutter suppression system for a full span, free-to-roll wind tunnel model of an advanced fighter concept. The design technique uses a frequency domain representation of the plant and used optimization techniques to generate a robust multi input/multi output controller. During testing in a fixed-in-roll configuration, simultaneous suppression of both symmetric and antisymmetric...

Topics: NASA Technical Reports Server (NTRS), ACTIVE CONTROL, CONTROLLERS, MIMO (CONTROL SYSTEMS),...

This interim report continues with the research effort on advanced adaptive controls for space robotics systems. In particular, previous results developed by the principle investigator and his research team centered around fuzzy logic control (FLC) in which the lack of knowledge of the robotic system as well as the uncertainties of the environment are compensated for by a rule base structure which interacts with varying degrees of belief of control action using system measurements. An on-line...

Topics: NASA Technical Reports Server (NTRS), ADAPTIVE CONTROL, AEROSPACE SYSTEMS, CONTROL SYSTEMS DESIGN,...

Manned orbiters will require active vibration isolation for acceleration-sensitive microgravity science experiments. Since umbilicals are highly desirable or even indispensable for many experiments, and since their presence greatly affects the complexity of the isolation problem, they should be considered in control synthesis. In this paper a general framework is presented for applying extended H2 synthesis methods to the three-dimensional microgravity isolation problem. The methodology...

Topics: NASA Technical Reports Server (NTRS), CONTROL SYSTEMS DESIGN, LINEAR QUADRATIC REGULATOR,...

Two methods for control system reconfiguration have been investigated. The first method is a robust servomechanism control approach (optimal tracking problem) that is a generalization of the classical proportional-plus-integral control to multiple input-multiple output systems. The second method is a control-allocation approach based on a quadratic programming formulation. A globally convergent fixed-point iteration algorithm has been developed to make onboard implementation of this method...

Topics: NASA Technical Reports Server (NTRS), FLIGHT CONTROL, SERVOMECHANISMS, PROPORTIONAL CONTROL, MIMO...

This invention is a ground flutter testing system without a wind tunnel, called Dry Wind Tunnel (DWT) System. The DWT system consists of a Ground Vibration Test (GVT) hardware system, a multiple input multiple output (MIMO) force controller software, and a real-time unsteady aerodynamic force generation software, that is developed from an aerodynamic reduced order model (ROM). The ground flutter test using the DWT System operates on a real structural model, therefore no scaled-down structural...

Topics: NASA Technical Reports Server (NTRS), WIND TUNNELS, FLUTTER, VIBRATION TESTS, GROUND TESTS, MIMO...

The paper presents performance and robustness analysis of the modified reference model MRAC (model reference adaptive control) or M-MRAC in short, which differs from the conventional MRAC systems by feeding back the tracking error to the reference model. The tracking error feedback gain in concert with the adaptation rate provides an additional capability to regulate not only the transient performance of the tracking error, but also the transient performance of the control signal. This differs...

Topics: NASA Technical Reports Server (NTRS), MODEL REFERENCE ADAPTIVE CONTROL, LINEAR SYSTEMS, ERROR...

Singular value analysis can give conservative stability margin results. Applying structure to the uncertainty can reduce this conservatism. This paper presents flight-determined stability margins for the X-29A lateral-directional, multiloop control system. These margins are compared with the predicted unscaled singular values and scaled structured singular values. The algorithm was further evaluated with flight data by changing the roll-rate-to-aileron command-feedback gain by +/- 20 percent....

Topics: NASA Technical Reports Server (NTRS), AIRCRAFT CONTROL, FLIGHT CONTROL, FLIGHT STABILITY TESTS,...

In low earth orbit (LEO) satellite applications spacecraft power is provided by photovoltaic cells and batteries. To overcome battery shortcomings the University of Maryland, working in cooperation with NASA/GSFC and NASA/LeRC, has developed a magnetically suspended flywheel for energy storage applications. The system is referred to as an Open Core Composite Flywheel (OCCF) energy storage system. Successful application of flywheel energy storage requires integration of several technologies,...

Topics: NASA Technical Reports Server (NTRS), H-INFINITY CONTROL, MAGNETIC ENERGY STORAGE, FLYWHEELS,...

This report summarizes the results of a three year effort by Blue Line Engineering Co. to advance the state of segmented mirror systems in several separate but related areas. The initial set of tasks were designed to address the issues of system level architecture, digital processing system, cluster level support structures, and advanced mirror fabrication concepts. Later in the project new tasks were added to provide support to the existing segmented mirror testbed at Marshall Space Flight...

Topics: NASA Technical Reports Server (NTRS), SEGMENTED MIRRORS, FABRICATION, ARCHITECTURE (COMPUTERS),...

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115

Jun 2, 2011
06/11

by
Erickson, Edwin F.; Kaufman, Michael; Colgan, Sea

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The Near infrared Camera and Multi-Object Spectrometer (NICMOS) was installed on the Hubble Space Telescope during a space shuttle servicing mission in February 1997. Using NICMOS, early release observations of the nearest region to Earth where massive stars are being formed-the belt of the constellation Orion-were obtained. These images reveal intricate structures in both the near-infrared continuum and in emissions from molecular hydrogen. Numerous H2-emitting knots have been resolved.

Topics: SLIDING, MIMO (CONTROL SYSTEMS), ENERGY DISSIPATION, MATHEMATICAL MODELS, CONTROL SYSTEMS DESIGN,...

464
464

May 23, 2011
05/11

by
Suder, Kenneth L

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A detailed experimental investigation to understand and quantify the development of loss and blockage in the flow field of a transonic, axial flow compressor rotor has been undertaken. Detailed laser anemometer measurements were acquired upstream, within, and downstream of a transonic, axial compressor rotor operating at design and off-design conditions. The rotor was operated at 100, 85, 80, and 60 of design speed which provided inlet relative Mach numbers at the blade tip of 1.48, 1.26, 1.18,...

Topics: FLIGHT CONDITIONS, ROBUSTNESS (MATHEMATICS), YAW, DEGREES OF FREEDOM, FLY BY WIRE CONTROL,...

The research being performed under NASA Grant NAG1-1361 involves a more clear understanding and definition of the constraints involved in the pole-zero placement or assignment process for multiple input, multiple output systems. Complete state feedback to more than a single controller under conditions of complete controllability and observability is redundant if pole placement alone is the design objective. The additional feedback gains, above and beyond those required for pole placement can be...

Topics: NASA Technical Reports Server (NTRS), CONTROL SYSTEMS DESIGN, CONTROLLERS, FEEDBACK CONTROL, MIMO...

A general design methodology to integrate active control with passive damping was demonstrated on the NASA LaRC CSI Evolutionary Model (CEM), a ground testbed for future large, flexible spacecraft. Vibration suppression controllers designed for Line-of Sight (LOS) minimization were successfully implemented on the CEM. A frequency-shaped H2 methodology was developed, allowing the designer to specify the roll-off of the MIMO compensator. A closed loop bandwidth of 4 Hz, including the six rigid...

Topics: NASA Technical Reports Server (NTRS), ACTIVE CONTROL, FEEDBACK CONTROL, FLEXIBLE SPACECRAFT, MIMO...

646
646

Sep 20, 2010
09/10

by
Sloan, Alan D

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A deterministic fractal is an image which has low information content and no inherent scale. Because of their low information content, deterministic fractals can be described with small data sets. They can be displayed at high resolution since they are not bound by an inherent scale. A remarkable consequence follows. Fractal images can be encoded at very high compression ratios. This fern, for example is encoded in less than 50 bytes and yet can be displayed at resolutions with increasing...

Topics: AMPLIFICATION, KALMAN FILTERS, LINEAR FILTERS, MIMO (CONTROL SYSTEMS), SCALARS, MATRICES...

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201

Jun 2, 2011
06/11

by
Wong, Gregory L.; Swenson, Harry N

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The Dynamic Planner was designed, implemented and integrated in to the Center/Tracon (Terminal Radar Approach Control) Automation System (CTAS) to assist Traffic Management Coordination (TMCs) in their task of planning and scheduling arrival traffic when the traffic is approximately 35 to 200 nautical miles from the destination airport. The TMC may input to the DP a series of current and future scheduling constraints that reflect the operational and environmental conditions of the airspace....

Topics: STOCHASTIC PROCESSES, STABILITY, HIGH FREQUENCIES, DETERMINANTS, FEEDBACK CONTROL, CONTROL SYSTEMS...

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209

Jun 9, 2011
06/11

by
Maghami, Peiman G.; Sparks, Dean W., Jr.; Lim, Kyong B

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New synthesis techniques for the design of fault accommodating controllers for flexible systems are developed. Three robust control design strategies, static dissipative, dynamic dissipative and mu-synthesis, are used in the approach. The approach provides techniques for designing controllers that maximize, in some sense, the tolerance of the closed-loop system against faults in actuators and sensors, while guaranteeing performance robustness at a specified performance level, measured in terms...

Topics: ACOUSTICS, PRESSURIZING, ALUMINUM, VIBRATION TESTS, MATHEMATICAL MODELS, TEST STANDS, DATA...

This paper presents development of multi-input multi-output (MIMO) Generalized Pre-dictive Control (GPC) law and its application to reconfigurable control design in the event of actuator saturation. A Controlled Auto-Regressive Integrating Moving Average (CARIMA) model is used to describe the plant dynamics. The control law is derived using input-output description of the system and is also related to the state-space form of the model. The stability of the GPC control law without...

Topics: NASA Technical Reports Server (NTRS), MIMO (CONTROL SYSTEMS), MATHEMATICAL MODELS, SISO (CONTROL...

Viewgraphs on optical interferometer testbed presented at the MIT Space Research Engineering Center 3rd Annual Symposium are included. Topics covered include: space-based optical interferometer; optical metrology; sensors and actuators; real time control hardware; controlled structures technology (CST) design methodology; identification for MIMO control; FEM/ID correlation for the naked truss; disturbance modeling; disturbance source implementation; structure design: passive damping; low...

Topics: NASA Technical Reports Server (NTRS), INTERFEROMETERS, MIMO (CONTROL SYSTEMS), OPTICAL MEASURING...

Two methods are examined for limit and integrator wind-up protection for multi-input, multi-output linear controllers subject to actuator constraints. The methods begin with an existing linear controller that satisfies the specifications for the nominal, small perturbation, linear model of the plant. The controllers are formulated to include an additional contribution to the state derivative calculations. The first method to be examined is the multi-variable version of the single-input,...

Topics: NASA Technical Reports Server (NTRS), ACTUATORS, CONTROL SYSTEMS DESIGN, CONTROLLERS, INTEGRATORS,...

A method for adaptive identification of reduced-order models for continuous stable SISO and MIMO plants is presented. The method recursively finds a model whose transfer function (matrix) matches that of the plant on a set of frequencies chosen by the designer. The algorithm utilizes the Moving Discrete Fourier Transform (MDFT) to continuously monitor the frequency-domain profile of the system input and output signals. The MDFT is an efficient method of monitoring discrete points in the...

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, CONTROL STABILITY, INTERPOLATION, MIMO (CONTROL...

The eigensystem realization algorithm (ERA) is a multiple-input, multiple-output, time domain technique for structural modal identification and minimum-order system realization. Modal identification is the process of calculating structural eigenvalues and eigenvectors (natural vibration frequencies, damping, mode shapes, and modal masses) from experimental data. System realization is the process of constructing state-space dynamic models for modern control design. This user's guide documents...

Topics: NASA Technical Reports Server (NTRS), CONTROL SYSTEMS DESIGN, DYNAMIC MODELS, DYNAMIC STRUCTURAL...

352
352

May 23, 2011
05/11

by
Tiller, Michael M

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In engineering, simulation software is often used as a convenient means for carrying out experiments to evaluate physical systems. The benefit of using simulations as 'numerical' experiments is that the experimental conditions can be easily modified and repeated at much lower cost than the comparable physical experiment. The goal of these experiments is to 'improve' the process or result of the experiment. In most cases, the computational experiments employ the same trial and error approach as...

Topics: COMPUTER AIDED DESIGN, CONTROL SYSTEMS DESIGN, FEEDBACK, MIMO (CONTROL SYSTEMS), APPROXIMATION,...

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337

Jun 2, 2011
06/11

by
Kilic, Bahattin; Madenci, Erdogan; Ambur, Damodar R

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Adhesively bonded lap joints involve dissimilar material junctions and sharp changes in geometry, possibly leading to premature failure. Although the finite element method is well suited to model the bonded lap joints, traditional finite elements are incapable of correctly resolving the stress state at junctions of dissimilar materials because of the unbounded nature of the stresses. In order to facilitate the use of bonded lap joints in future structures, this study presents a finite element...

Topics: CONTROL SYSTEMS DESIGN, MIMO (CONTROL SYSTEMS), SISO (CONTROL SYSTEMS), DISTRIBUTION FUNCTIONS,...

The linear-quadratic-gaussian (LQG) compensator was developed to facilitate the design of control laws for multi-input, multi-output (MIMO) systems. The compensator is computed by solving two algebraic equations for which standard closed-loop solutions exist. Unfortunately, the minimal dimension of an LQG compensator is almost always equal to the dimension of the plant and can thus often violate practical implementation constraints on controller order. This deficiency is especially highlighted...

Topics: NASA Technical Reports Server (NTRS), CONTROL SYSTEMS DESIGN, CONTROL THEORY, CONTROLLERS, DIGITAL...

Control law design for rotorcraft fly-by-wire systems normally attempts to decouple angular responses using fixed-gain crossfeeds. This approach can lead to poor decoupling over the frequency range of pilot inputs and increase the load on the feedback loops. In order to improve the decoupling performance, dynamic crossfeeds may be adopted. Moreover, because of the large changes that occur in rotorcraft dynamics due to small changes about the nominal design condition, especially for...

Topics: NASA Technical Reports Server (NTRS), FLIGHT CONDITIONS, FLY BY WIRE CONTROL, HOVERING, MIMO...

The Aeroelasticity Branch at NASA Langley Research Center has a long and substantive history of tiltrotor aeroelastic research. That research has included a broad range of experimental investigations in the Langley Transonic Dynamics Tunnel (TDT) using a variety of scale models and the development of essential analyses. Since 1994, the tiltrotor research program has been using a 1/5-scale, semispan aeroelastic model of the V-22 designed and built by Bell Helicopter Textron Inc. (BHTI) in 1981....

Topics: NASA Technical Reports Server (NTRS), CONTROL SYSTEMS DESIGN, ACTIVE CONTROL, HELICOPTERS,...

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242

May 23, 2011
05/11

by
Goodman, Jeremy; Kulsrud, Russell M

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The PI further explored an m = 1 internal-wave instability of accretion disks that he had previously discovered. In brief, tidal distortions of the disk destabilize internal waves -- nearly incompressible disturbances whose wavelength is comparable to the disk thickness or smaller. These waves require either a radial gradient in specific angular momentum, or a vertical gradient in entropy or molecular weight; both gradients should be of a sign that normally makes for stable oscillations, but...

Topics: CROSS COUPLING, DECOUPLING, CONTROL THEORY, CONTROLLABILITY, MANUAL CONTROL, HOVERING, ROTARY WING...

Rotorcraft flight control systems present design challenges which often exceed those associated with fixed-wing aircraft. First, large variations in the response characteristics of the rotorcraft result from the wide range of airspeeds of typical operation (hover to over 100 kts). Second, the assumption of vehicle rigidity often employed in the design of fixed-wing flight control systems is rarely justified in rotorcraft where rotor degrees of freedom can have a significant impact on the system...

Topics: NASA Technical Reports Server (NTRS), ROTARY WING AIRCRAFT, CONTROL SYSTEMS DESIGN, FLIGHT CONTROL,...

A mixing chamber used in rocket engine combustion testing at NASA Stennis Space Center is modeled by a second order nonlinear MIMO system. The mixer is used to condition the thermodynamic properties of cryogenic liquid propellant by controlled injection of the same substance in the gaseous phase. The three inputs of the mixer are the positions of the valves regulating the liquid and gas flows at the inlets, and the position of the exit valve regulating the flow of conditioned propellant. The...

Topics: NASA Technical Reports Server (NTRS), NONLINEAR SYSTEMS, MIMO (CONTROL SYSTEMS), LIQUID PROPELLANT...

This work investigates the effects of actuator saturation in multi-input, multi-output (MIMO) control systems. The adverse system behavior introduced by the saturation nonlinearity is viewed here as resulting from two mechanisms: controller windup - a problem caused by the discrepancy between the limited actuator commands and the corresponding control signals, and directionality - the problem of how to use nonlimited actuators when a limited condition exists. The tracking mode and Hanus methods...

Topics: NASA Technical Reports Server (NTRS), ACTUATORS, CONTROL STABILITY, CONTROL SYSTEMS DESIGN, CONTROL...

Techniques for the design of control systems for manually controlled, high-performance aircraft must provide the following: (1) multi-input, multi-output (MIMO) solutions, (2) acceptable handling qualities including no tendencies for pilot-induced oscillations, (3) a tractable approach for compensator design, (4) performance and stability robustness in the presence of significant plant uncertainty, and (5) performance and stability robustness in the presence actuator saturation (particularly...

Topics: NASA Technical Reports Server (NTRS), ROBUSTNESS (MATHEMATICS), FLIGHT CONTROL, ACTUATORS, CONTROL...

A technique is developed which demonstrates how to interpret a large fully-populated filter gain matrix as a set of scalar gains. The inverse problem is also solved, namely, how to develop a large-order filter gain matrix from a specified set of scalar gains. Examples are given to illustrate the method.

Topics: NASA Technical Reports Server (NTRS), AMPLIFICATION, KALMAN FILTERS, LINEAR FILTERS, MIMO (CONTROL...

A frequency-domain procedure for the design of sliding mode controllers for multi-input, multi-output (MIMO) systems is presented. The methodology accommodates the effects of parasitic dynamics such as those introduced by unmodeled actuators through the introduction of multiple asymptotic observers and model reference hedging. The design procedure includes a frequency domain approach to specify the sliding manifold, the observer eigenvalues, and the hedge model. The procedure is applied to the...

Topics: NASA Technical Reports Server (NTRS), MIMO (CONTROL SYSTEMS), CONTROL EQUIPMENT, CONTROL SYSTEMS...

Numerical simulations to assess the effectiveness of Generalized Predictive Control (GPC) for active control of dynamic systems having rigid-body modes are presented. GPC is a linear, time-invariant, multi-input/multi-output predictive control method that uses an ARX model to characterize the system and to design the controller. Although the method can accommodate both embedded (implicit) and explicit feedforward paths for incorporation of disturbance effects, only the case of embedded...

Topics: NASA Technical Reports Server (NTRS), ACTIVE CONTROL, MATHEMATICAL MODELS, RIGID STRUCTURES,...