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Results for “ROTOR GYROSCOPE”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

The role of cryogenics in the gyroscope experiment

The design of apparatus being built to measure the general relativistic precession of gyroscopes in earth orbit is discussed, with emphasis on the role of cryogenics. Operation with a superconducting rotor is crucial in that it provides the only known way of attaining the required angular resolution of 0.001 arc-sec. Operation at low temperatures also provides the star tracker, to which the gyros are referenced, with excellent null stability. The boil-off gas from the large helium dewar is used to operate the vehicle in a drag-free mode which is expected to improve the gyro performance by a factor of ten. The dewar system is compatible with a wide range of experiments requiring temperatures as low as 2K in space.

Lipa, J. A.↗
NASA NTRS1983

The influence of gyroscopic forces on the dynamic behavior and flutter of rotating blades

The structural dynamics of a cantilever turbomachine blade mounted on a spinning and precessing rotor are investigated. Both stability and forced vibration are considered with a blade model that increases in complexity (and verisimilitude) from a spring-restrained point mass, to a uniform cantilever, to a twisted uniform cantilever turbomachine blade mounted on a spinning and precessing rotor are investigated. Both stability and forced vibration are considered with a blade model that increases in complexity (and verisimilitude) from a spring-restrained point mass, to a uniform cantilever, to a twisted uniform cantilever, to a tapered twisted cantilever of arbitrary cross-section. In every instance the formulation is from first principles using a finite element based on beam theory. Both ramp-type and periodic-type precessional angular displacements are considered. In concluding, forced vibrating and flutter are studied using the final and most sophisticated structural model. The analysis of stability is presented and a number of numerical examples are worked out.

Sisto, F.↗
NASA NTRS1980

Electrical torques on the electrostatic gyro in the gyro relativity experiment

A comprehensive discussion and calculation of electrical torques on an electrostatic gyro as they relate to the gyroscope experiment to test general relativity is presented. Drift rates were computed for some typical state of the art rotors, including higher harmonics in the rotor shape. The effect of orbital averaging of gravity gradient forces, roll averaging of torques, and the effect of spin averaging on the effective shape of the rotor were considered. The electrical torques are reduced sufficiently in a low g environment to permit a measurement of the relativistic drifts predicted by general relativity.

Eby, P.↗
NASA NTRS1988

A feedback linearization approach to spacecraft control using momentum exchange devices

Recent developments in the area of nonlinear control theory have shown how coordiante changes in the state and input spaces can be used with nonlinear feedback to transform certain nonlinear ordinary differential equations into equivalent linear equations. These feedback linearization techniques are applied to resolve two problems arising in the control of spacecraft equipped with control moment gyroscopes (CMGs). The first application involves the computation of rate commands for the gimbals that rotate the individual gyroscopes to produce commanded torques on the spacecraft. The second application is to the long-term management of stored momentum in the system of control moment gyroscopes using environmental torques acting on the vehicle. An approach to distributing control effort among a group of redundant actuators is described that uses feedback linearization techniques to parameterize sets of controls which influence a specified subsystem in a desired way. The approach is adapted for use in spacecraft control with double-gimballed gyroscopes to produce an algorithm that avoids problematic gimbal configurations by approximating sets of gimbal rates that drive CMG rotors into desirable configurations. The momentum management problem is stated as a trajectory optimization problem with a nonlinear dynamical constraint. Feedback linearization and collocation are used to transform this problem into an unconstrainted nonlinear program. The approach to trajectory optimization is fast and robust. A number of examples are presented showing applications to the proposed NASA space station.

Dzielski, John Edward↗
NASA NTRS1988

An approach to CMG steering using feedback linearization

This paper presents an approach for controlling spacecraft equipped with control moment gyroscopes. A technique from feedback linearization theory is used to transform the original nonlinear problem to an equivalent linear form without approximating assumptions. In this form, the spacecraft dynamics appear linearly, and are decoupled from redundancy in the system of gyroscopes. A general approach to distributing control effort among the available actuators is described which includes provisions for redistribution of rotors, explicit bounds in gimbal rates, and guaranteed operation at or near singular configurations. A particular algorithm is developed for systems of double-gimbal devices, and demonstrated in two examples for which existing approaches fail to give adequate performance.

Dzielski, John↗
NASA NTRS1991

Approach to control moment gyroscope steering using feedback linearization

This paper presents an approach for controlling spacecraft equipped with control moment gyroscopes. A technique from feedback linearization theory is used to transform the original nonlinear problem to an equivalent linear form without approximating assumptions. In this form, the spacecraft dynamics appear linearly, and are decoupled from redundancy in the system of gyroscopes. A general approach to distributing control effort among the available actuators is described which includes provisions for redistribution of rotors, explicit bounds in gimbal rates, and guaranteed operation at or near singular configurations. A particular algorithm is developed for systems of double-gimbal devices, and demonstrated in two examples for which existing approaches fail to give adequate performance.

Dzielski, John↗
NASA NTRS1982

Rotor vibration caused by external excitation and rub

For turbomachinery with low natural frequencies, considerations have been recently required for rotor vibrations caused by external forces except unbalance one, such as foundation motion, seismic wave, rub and so forth. Such a forced vibration is investigated analytically and experimentally in the present paper. Vibrations in a rotor-bearing system under a harmonic excitation are analyzed by the modal technique in the case of a linear system including gyroscopic effect. For a nonlinear system a new and powerful quasi-modal technique is developed and applied to the vibration caused by rub.

Matsushita, O.↗
NASA NTRS1997

An Inlet Distortion Assessment During Aircraft Departures at High Angle of Attack for an F/A-18A Aircraft

The F404-GE-400-powered F/A-18A High Alpha Research Vehicle (HARV) was used to examine the quality of inlet airflow during departed flight maneuvers, that is, during flight outside the normal maneuvering envelope where control surfaces have little or no effectiveness. Six nose-left and six nose-right departures were initiated at Mach numbers between 0.3 and 0.4 at an altitude of 35 kft. The entry yaw rates were approximately 40 to 90 deg/sec. Engine surges were encountered during three of the nose-left and one of the nose-right departures. Time-variant inlet-total-pressure distortion levels at the engine face did not significantly exceed those at maximum angle-of-attack and sideslip maneuvers during controlled flight. Surges caused by inlet distortion levels resulted from a combination of high levels of inlet distortion and rapid changes in aircraft position. These rapid changes indicate a combination of engine support and gyroscopic loads being applied to the engine structure that impact the aerodynamic stability of the compressor through changes in the rotor-to-case clearances. This document presents the slides from an oral presentation.

Steenken, William G.↗
NASA NTRS1999

Factors Affecting Inlet-Engine Compatibility During Aircraft Departures at High Angle of Attack for an F/A -18A Aircraft

The F404-GE-400 engine powered F/A- 18A High Alpha Research Vehicle (HARV) was used to examine the quality of inlet airflow during departed flight maneuvers, that is, during flight outside the normal maneuvering envelope where control surfaces have little or no effectiveness. A series of six nose-left and six nose-right departures were initiated at Mach numbers between 0.3 and 0.4 at an altitude of 35 kft. The yaw rates at departure recovery were in the range of 40 to 90 degrees per second. Engine surges were encountered during three of the nose-left and one of the nose-right departures. Time-variant inlet-total-pressure distortion levels at the engine face were determined to not significantly exceed those measured at maximum angle-of-attack and - sideslip maneuvers during controlled flight. Surges as a result of inlet distortion levels were anticipated to initiate in the fan. Analysis revealed that the surges initiated in the compressor and were the result of a combination of high levels of inlet distortion and rapid changes in aircraft motion. These rapid changes in aircraft motion are indicative of a combination of engine mount and gyroscopic loads being applied to the engine structure that impact the aerodynamic stability of the compressor through changes in the rotor-to-case clearances.

Steenken, W. G.↗
NASA NTRS1970

Hydrodynamic squeeze-film bearings for gyroscopes

Experimental tests are conducted on squeeze-film bearings by applying electricity to piezoelectric ceramics, causing vibrations at thousands or millions of Hz that are amplified and transmitted to the bearing. Rotor operation through 24,000 rpm without whirl instability proved bearing ability to support rotor weight without hydrodynamic action.

Chiang, T.↗
NASA NTRS1987

Emergency Control for a Circulation-Control Helicopter Rotor

Digital system gives pilot partial command when primary system fails. Emergency system provides digital control of rigid circulation-control rotor for experimental X-wing aircraft. In addition to centering collective-pitch control, new command provides limited roll control via collective pitch and gyroscopic decoupling in pitch and aerodynamic decoupling.

Fischer, William C.↗
NASA NTRS1975

Perform a gyro test of general relativity in a satellite and develop associated control technology

The progress accomplished in the Stanford Gyro Relativity program during the period November 1974 to October 1975 was described. Gyro developments were continued in the main laboratory dewar, concentrating on the operation of a three axis gyro readout and on improvements to the methods of canceling trapped fields in the rotor; these efforts culminated in the first successful observation of the London moment in the spinning gyro rotor in March 1975. Following a review meeting at that time, a new goal was formulated for the next 12 to 18 months, namely to operate a gyroscope in the new ultra-low field facility with readout resolution approaching 1 arc-second. The following other tasks were also completed: (1) sputtering work, (2) magnetometry, (3) construction and installation of the North Star simulator, (4) analysis of torques on the gyro, especially in inclined orbits, (5) equivalence principle accelerometer, and (6) analysis of a twin-satellite test of relativity.

Fairbank, W. M.↗
NASA NTRS2009

Improved Model of a Mercury Ring Damper

A short document discusses the general problem of mathematical modeling of the three-dimensional rotational dynamics of rigid bodies and of the use of Euler parameters to eliminate the singularities occasioned by the use of Euler angles in such modeling. The document goes on to characterize a Hamiltonian model, developed by the authors, that utilizes the Euler parameters and, hence, is suitable for use in computational simulations that involve arbitrary rotational motion. In this formulation unlike in prior Euler-parameter-based formulations, there are no algebraic constraints. This formulation includes a general potential energy function, incorporates a minimum set of momentum variables, and takes an explicit state-space form convenient for numerical implementation. Practical application of this formulation has been demonstrated by the development of a new and simplified model of the rotational motion of a rigid rotor to which is attached a partially filled mercury ring damper. Models like this one are used in guidance and control of spin-stabilized spacecraft and gyroscope-stabilized seekers in guided missiles.

Fahrenthold, Eric P.↗
NASA NTRS1991

Dynamic modelling and analysis of a magnetically suspended flexible rotor

A 12-state lumped-element model is presented for a flexible rotor supported by two attractive force electromagnetic journal bearings. The rotor is modeled as a rigid disk with radial mass unbalance mounted on a flexible, massless shaft with internal damping (Jeffcott rotor). The disk is offset axially from the midspan of the shaft. Bearing dynamics in each radial direction are modeled as a parallel combination of a negative (unstable) spring and a linear current-to-force actuator. The model includes translation and rotation of the rigid mass and the first and second bending models of the flexible shaft, and it simultaneously includes internal shaft damping, gyroscopic effects, and the unstable nature of the attractive force magnetic bearings. The model is used to analyze the dependence of the system transmission zeros and open-loop poles on system parameters. The dominant open-loop poles occur in stable/unstable pairs with bandwidth dependent on the ratios of bearing (unstable) stiffnesses to rotor mass and damping dependent on the shaft spin rate. The zeros occur in complex conjugate pairs with bandwidth dependent on the ratios of shaft stiffness to rotor mass and damping dependent on the shaft spin rate. Some of the transmission zeros are non-minimum phase when the spin rate exceeds the shaft critical speed. The transmission zeros and open-loop poles impact the design of magnetic bearing control systems. The minimum loop cross-over frequency of the closed-loop system is the speed of the unstable open-loop poles. For the supercritical shaft spin rates, the presence of non-minimum phase zeros limits the distribution rejection achievable at frequencies near or above the shaft critical speed. Since non-minimum phase transmission zeros can only be changed by changing the system inputs and/or outputs, closed-loop performance is limited for supercritical spin rates unless additional force or torque actuators are added.

Mccallum, Duncan C.↗
NASA NTRS1979

Performance advantages of dynamically tuned gyroscopes in high accuracy spacecraft pointing and stabilization applications

The paper compares and describes the advantages of dry tuned gyros over floated gyros for space applications. Attention is given to describing the Teledyne SDG-5 gyro and the second-generation NASA Standard Dry Rotor Inertial Reference Unit (DRIRU II). Certain tests which were conducted to evaluate the SDG-5 and DRIRU II for specific mission requirements are outlined, and their results are compared with published test results on other gyro types. Performance advantages are highlighted.

Irvine, R.↗
NASA NTRS1985

Superconducting gyroscope research

Four basic areas of research and development of superconducting gyroscopes are studied. Chapter 1 studies the analysis of a SQUID readout for a superconducting gyroscope. Chapter 2 studies the dependence of spin-up torque on channel and gas properties. Chapter 3 studies the theory of super fluid plug operation. And chapter 4 studies the gyro rotor and housing manufacture.

Hendricks, J. B.↗
NASA NTRS1999

International Space Station Attitude Control and Energy Storage Experiment: Effects of Flywheel Torque

The Attitude Control and Energy Storage Experiment is currently under development for the International Space Station; two counter-rotating flywheels will be levitated with magnetic bearings and placed in vacuum housings. The primary objective of the experiment is to store and discharge energy, in combination with existing batteries, into the electrical power system. The secondary objective is to use the flywheels to exert torque on the Station; a simple torque profile has been designed so that the Station's Control Moment Gyroscopes will be assisted in maintaining torque equilibrium attitude. Two energy storage contingencies could result in the inadvertent application of torque by the flywheels to the Station: an emergency shutdown of one flywheel rotor while the other remains spinning, and energy storage with only one rotor instead of the counterrotating pair. Analysis of these two contingencies shows that attitude control and the microgravity environment will not be adversely affected.

Roithmayr, Carlos M.↗
NASA NTRS1961

Some Recent Studies in Structural Dynamics of Rotor Aircraft

This paper presents a summary of four recent studies relating to the structural-dynamics problems of rotor-powered aircraft. The first study concerns the measurement by means of dynamic models of the forces and moments at the hubs of various rotor configurations. The results of this study show that the periodic components of the forces and moments are highly dependent on both the rotor configuration and the flight condition. The second study treats the problem of resonance amplifications of rotor-blade stress and shows that by using multiple flapping hinges or flex-joints it is possible to control the natural frequencies of the rotor blade so that conditions of resonance between the frequencies of the aerodynamic input forces and the natural frequencies of the lower blade modes are avoided for all rotor speeds. Two studies of the stability of rotor aircraft axe also discussed. One of these involves the mechanical instability or ground resonance of rotorcraft wherein the rotor support in each of two mutually perpendicular directions in the rotor plane is represented as a multiple-degree-of-freedom system in contrast to the system having a "single" degree of freedom normally used in helicopter analysis. The consideration of the rotor support system as a two-degree-of-freedom system predicts additional unstable ranges of rotor speed not predicted by former analyses. The other instability treated is propeller whirl for which the significant motions are the pitching and yawing motions of the propeller disk which are coupled together by gyroscopic forces. The effect of the significant variables on the instability is presented and shows that the speed at which the instability occurs can be increased by increasing the relative stiffness of the propeller in the pitch and yaw directions or by increasing the effective structural damping of the nacelle.

George W Brooks↗