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At least 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Dynamics and Control of Attitude, Power, and Momentum for a Spacecraft Using Flywheels and Control Moment Gyroscopes

Several laws are designed for simultaneous control of the orientation of an Earth-pointing spacecraft, the energy stored by counter-rotating flywheels, and the angular momentum of the flywheels and control moment gyroscopes used together as an integrated set of actuators for attitude control. General, nonlinear equations of motion are presented in vector-dyadic form, and used to obtain approximate expressions which are then linearized in preparation for design of control laws that include feedback of flywheel kinetic energy error as a means of compensating for damping exerted by rotor bearings. Two flywheel steering laws are developed such that torque commanded by an attitude control law is achieved while energy is stored or discharged at the required rate. Using the International Space Station as an example, numerical simulations are performed to demonstrate control about a torque equilibrium attitude, and illustrate the benefits of kinetic energy error feedback. Control laws for attitude hold are also developed, and used to show the amount of propellant that can be saved when flywheels assist the CMGs. Nonlinear control laws for large-angle slew maneuvers perform well, but excessive momentum is required to reorient a vehicle like the International Space Station.

Roithmayr, Carlos M.↗
NASA NTRS2001

STS-105/Discovery/ISS 7A.1: Pre-Launch Activities, Launch, Orbit Activities and Landing

The crew of Space Shuttle Discovery on STS-105 is introduced at their pre-launch meal and at suit-up. The crew members include Commander Scott Horowitz, Pilot Rick Sturckow, and Mission Specialists Patrick Forrester and Daniel Barry, together with the Expedition 3 crew of the International Space Station (ISS). The Expedition 3 crew includes Commander Frank Culbertson, Soyuz Commander Vladimir Dezhurov, and Flight Engineer Mikhail Tyurin. When the astronauts depart for the launch pad in the Astrovan, their convoy is shown from above. Upon reaching the launch pad, they conduct a walk around of the shuttle, display signs for family members while being inspected in the White Room, and are strapped into their seats onboard Disciovery. The video includes footage of Discovery in the Orbiter Processing Facility, and some of the pre-launch procedures at the Launch Control Center are shown. The angles of launch replays include: TV-1, Beach Tracker, VAB, Pad A, Tower 1, UCS-15, Grandstand, OTV-70, Onboard, IGOR, and UCS-23. The moment of docking between Discovery and the ISS is shown from inside Discovery's cabin. While in orbit, the crew conducted extravehicular activities (EVAs) to attach an experiments container, and install handrails on the Destiny module of the ISS. The video shows the docking and unloading of the Leonardo Multipurpose Logistics Module (MPLM) onto the ISS. The deployment of a satellite from Discovery with the coast of the Gulf of Mexico in the background is shown. Cape Canaveral is also shown from space. Landing replays include VAB, Tower 1, mid-field, South End SLF, North End SLF, Tower 2, Playalinda DOAMS, UCS-23, and Pilot Point of View (PPOV). NASA Administrator Dan Goldin meets the crew upon landing and participates in their walk around of Discovery. The video concludes with a short speech by commander Horowitz.

Source record↗
NASA NTRS1953

Wind-Tunnel Investigation at Low Speed of the Pitching Stability Derivatives of a 1/9-Scale Powered Model of the Convair XFY-1 Vertically Rising Airplane, TED No. NACA DE 373

An experimental investigation has been conducted in the Langley stability tunnel at low speed to determine the pitching stability derivatives of a 1/9-scale powered model of the Convair XFY-1 vertically rising airplane. Effects of thrust coefficient, control deflections, and propeller blade angle were investigated. The tests were made through an angle-of-attack range from about -4deg to 29deg, and the thrust coefficient range was from 0 to 0.7. In order to expedite distribution of these data, no analysis of the data has been prepared for this paper.

Queijo, M. J.↗
NASA NTRS2007

Servomotor and Controller Having Large Dynamic Range

A recently developed micro-commanding rotational-position-control system offers advantages of less mechanical complexity, less susceptibility to mechanical resonances, less power demand, less bulk, less weight, and lower cost, relative to prior rotational-position-control systems based on stepping motors and gear drives. This system includes a digital-signal- processor (DSP)-based electronic controller, plus a shaft-angle resolver and a servomotor mounted on the same shaft. Heretofore, micro-stepping has usually been associated with stepping motors, but in this system, the servomotor is micro-commanded in response to rotational-position feedback from the shaft-angle resolver. The shaft-angle resolver is of a four-speed type chosen because it affords four times the resolution of a single-speed resolver. A key innovative aspect of this system is its position-feedback signal- conditioning circuits, which condition the resolver output signal for multiple ranges of rotational speed. In the preferred version of the system, two rotational- speed ranges are included, but any number of ranges could be added to expand the speed range or increase resolution in particular ranges. In the preferred version, the resolver output is conditioned with two resolver-to-digital converters (RDCs). One RDC is used for speeds from 0.00012 to 2.5 rpm; the other RDC is used for speeds of 2.5 to 6,000 rpm. For the lower speed range, the number of discrete steps of RDC output per revolution was set at 262,144 (4 quadrants at 16 bits per quadrant). For the higher speed range, the number of discrete steps per revolution was set at 4,096 (4 quadrants at 10 bits per quadrant).

Alhorn, Dean C.↗
NASA NTRS1957

Investigation at High Subsonic Speeds of the Static Longitudinal and Lateral Stability Characteristics of Two Canard Airplane Configurations

The present investigation was conducted in the Langley high-speed 7-by 10-foot tunnel to determine the static longitudinal and lateral stability characteristics at high subsonic speeds of two canard airplane configurations previously tested at supersonic speeds. The Mach number range of this investigation extended from 0.60 to 0.94 and a maximum angle-of-attack range of -2dewg to 24deg was obtained at the lowest test Mach number. Two wing plan forms of equal area were studied in the present tests; one was a 60deg delta wing and the other was a trapezoid wing having an aspect ratio of 3, taper ratio of 0.143, and an unswept 80-percent-chord line. The canard control had a trapezoidal plan form and its area was approximately 11.5 percent of the wing area. The model also had a low-aspect-ratio highly swept vertical tail and twin ventral fins. The longitudinal control characteristics of the models were consistent with past experience at low speed on canard configurations in that stalling of the canard surface occurred at moderate and high control deflections for moderate values of angle of attack. This stalling could impose appreciable limitations on the maximum trim-lift coefficient attainable. The control effectiveness and maximum value of trim-lift was significantly increased by addition of a body flap having a conical shape and located slightly behind the canard surface on the bottom of the body. Addition of the canard surface at 0deg deflection had relatively little effect on overall directional stability of the delta-wing configuration; however, deflection of the canard surface from 0deg to 10deg had a large favorable effect on directional stability at high angles of attack for both the trapezoid- and delta-wing configurations.

Sleeman, William C., Jr.↗
NASA NTRS1992

An improved lateral control wheel steering law for the Transport Systems Research Vehicle (TSRV)

A lateral control wheel steering law with improved performance was developed for the Transport Systems Research Vehicle (TSRV) simulation and used in the Microwave Landing System research project. The control law converted rotational hand controller inputs into roll rate commands, manipulated ailerons, spoilers, and the rudder to achieve the desired roll rates. The system included automatic turn coordination, track angle hold, and autopilot/autoland modes. The resulting control law produced faster roll rates (15 degrees/sec), quicker response to command reversals, and safer bank angle limits, while using a more concise program code.

Ragsdale, W. A.↗
NASA NTRS1972

Roll-modulated lifting entry optimization.

Equations of lifting entry are considered for fixed-angle-of-attack vehicular motion with path control for roll modulation of lift. Attention is directed to relocation and its consequences for the fixed-angle-of-attack atmospheric entry problem. Two reduced-order methods for working with the resulting system of equations are briefly examined. The methods are deemed to warrant further study.

Kelley, H. J.↗
NASA NTRS2002

Reusable Launch Vehicle Attitude Control Using a Time-Varying Sliding Mode Control Technique

In this paper we present a time-varying sliding mode control (TVSMC) technique for reusable launch vehicle (RLV) attitude control in ascent and entry flight phases. In ascent flight the guidance commands Euler roll, pitch and yaw angles, and in entry flight it commands the aerodynamic angles of bank, attack and sideslip. The controller employs a body rate inner loop and the attitude outer loop, which are separated in time-scale by the singular perturbation principle. The novelty of the TVSMC is that both the sliding surface and the boundary layer dynamics can be varied in real time using the PD-eigenvalue assignment technique. This salient feature is used to cope with control command saturation and integrator windup in the presence of severe disturbance or control effector failure, which enhances the robustness and fault tolerance of the controller. The TV-SMC ascent and descent designs are currently being tested with high fidelity, 6-DOF dispersion simulations. The test results will be presented in the final version of this paper.

Shtessel, Yuri B.↗
NASA NTRS2002

Improved Re-Configurable Sliding Mode Controller for Reusable Launch Vehicle of Second Generation Addressing Aerodynamic Surface Failures and Thrust Deficiencies

In this report we present a time-varying sliding mode control (TV-SMC) technique for reusable launch vehicle (RLV) attitude control in ascent and entry flight phases. In ascent flight the guidance commands Euler roll, pitch and yaw angles, and in entry flight it commands the aerodynamic angles of bank, attack and sideslip. The controller employs a body rate inner loop and the attitude outer loop, which are separated in time-scale by the singular perturbation principle. The novelty of the TVSMC is that both the sliding surface and the boundary layer dynamics can be varied in real time using the PD-eigenvalue assignment technique. This salient feature is used to cope with control command saturation and integrator windup in the presence of severe disturbance or control effector failure, which enhances the robustness and fault tolerance of the controller. The TV-SMC is developed and tuned up for the X-33 sub-orbital technology demonstration vehicle in launch and re-entry modes. A variety of nominal, dispersion and failure scenarios have tested via high fidelity 6DOF simulations using MAVERIC/SLIM simulation software.

Shtessel, Yuri B.↗
NASA NTRS2019

Navigation performance of the 2018 InSight Mars Lander mission

The NASA InSight spacecraft was launched successfully from Vandenberg Air Force Base on an Atlas V 401 launch vehicle on May 5, 2018 and landed on November 26, 2018. Accurate targeting to the atmospheric entry point by the Navigation team achieved by carefully controlling the final entry flight path angle to -12.0 degrees with a tolerance of +/- 0.21 degrees. This paper will describe how the InSight Navigation team met this difficult task in the presence of frequent unbalanced thrusting for attitude control. The continuous correction for this unplanned ∆V far exceeded pre-launch expectations and proved a challenge to predict accurately.

Wallace, Mark↗
NASA NTRS1958

Aerodynamic Characteristics at a Mach Number of 6.8 of Two Hypersonic Missile Configurations, One with Low-Aspect-Ratio Cruciform Fins and Trailing-Edge Flaps and One with a Flared Afterbody and All-Movable Controls

An investigation has been made to determine the aerodynamic characteristics in pitch at a Mach number of 6.8 of hypersonic missile configurations with cruciform trailing-edge flaps and with all-movable control surfaces. The flaps were tested on a configuration having low-aspect-ratio cruciform fins with an apex angle of 5 degrees; the all-movable controls were mounted at the 46.7-percent body station on a configuration having a 10 degrees flared afterbody. The tests were made through an angle-of-attack range of -2 degrees to 20 degrees at zero sideslip in the Langley 11-inch hypersonic tunnel. The results indicated that the all-movable controls on the flared-afterbody model should be capable of producing much larger values of trim lift and of normal acceleration than the trailing-edge-flap configuration. The flared-afterbody configuration had considerably higher drag than the cruciform-fin model but only slightly lower values of lift-drag ratio.

Bernot, P. T.↗
NASA NTRS1958

Aerodynamic Characteristics at a Mach Number of 6.8 of Two Hypersonic Missile Configurations, One with Low-Aspect-Ratio Cruciform Fins and Trailing-Edge Flaps and One with a Flared Afterbody and All-Movable Controls

An investigation has been made to determine the aerodynamic characteristics in pitch at a Mach number of 6.8 of hypersonic missile configurations with cruciform trailing-edge flaps and with all-movable control surfaces. The flaps were tested on a configuration having low-aspect-ratio cruciform fins with an apex angle of 5 deg the all-movable controls were mounted at the 46.7-percent body station on a configuration having a 10 deg flared afterbody. The tests were made through an angle-of-attack range of -2 deg to 20 deg at zero sideslip in the Langley 11-inch hypersonic tunnel. The results indicated that the all-movable controls on the flared afterbody model should be capable of producing much larger values of trim lift and of normal acceleration than the trailing-edge -flap configuration. The flared -after body configuration had considerably higher drag than the cruciform-fin model but only slightly lower values of lift drag ratio.

Robinson, Ross B↗
NASA NTRS2008

Cluster/Peace Electrons Velocity Distribution Function: Modeling the Strahl in the Solar Wind

We present a study of kinetic properties of the strahl electron velocity distribution functions (VDF's) in the solar wind. These are used to investigate the pitch-angle scattering and stability of the population to interactions with electromagnetic (whistler) fluctuations. The study is based on high time resolution data from the Cluster/PEACE electron spectrometer. Our study focuses on the mechanisms that control and regulate the pitch-angle and stability of strahl electrons in the solar wind; mechanisms that are not yet well understood. Various parameters are investigated such as the electron heat-flux and temperature anisotropy. The goal is to check whether the strahl electrons are constrained by some instability (e.g., the whistler instability), or are maintained by other types of processes. The electron heat-flux and temperature anisotropy are determined by fitting the VDF's to a spectral spherical harmonic model from which the moments are derived directly from the model coefficients.

Figueroa-Vinas, Adolfo↗
NASA NTRS2009

Modeling the Strahl in the Solar Wind Using CLUSTER/PEACE Electron Distribution Functions

We present a study of kinetic properties of the strahl electron velocity distribution functions (VDF's) in the solar wind. These are used to investigate the pitch-angle scattering and stability of the population to interactions with electromagnetic (whistler) fluctuations. The study is based on high time resolution data from the Cluster/PEACE electron spectrometer. Our study focuses on the mechanisms that control and regulate the pitch-angle and stability of strahl electrons in the solar wind; mechanisms that are not yet well understood. Various parameters are investigated such as the strahl-electron density, temperature anisotropy, and electron heat-flux. The goal is to check whether the strahl electrons are constrained by some instability (e.g., the whistler instability), or are maintained by other types of processes. The electron heat-flux and temperature anisotropy are determined by modeling the 3D-VDFs to a spectral spherical harmonic model from which the moments are obtained directly from the spectral coefficients.

Vinas, Adolfo F.↗
NASA NTRS1993

Actuator and aerodynamic modeling for high-angle-of-attack aeroservoelasticity

Accurate prediction of airframe/actuation coupling is required by the imposing demands of modern flight control systems. In particular, for agility enhancement at high angle of attack and low dynamic pressure, structural integration characteristics such as hinge moments, effective actuator stiffness, and airframe/control surface damping can have a significant effect on stability predictions. Actuator responses are customarily represented with low-order transfer functions matched to actuator test data, and control surface stiffness is often modeled as a linear spring. The inclusion of the physical properties of actuation and its installation on the airframe is therefore addressed in this paper using detailed actuator models which consider the physical, electrical, and mechanical elements of actuation. The aeroservoelastic analysis procedure is described in which the actuators are modeled as detailed high-order transfer functions and as approximate low-order transfer functions. The impacts of unsteady aerodynamic modeling on aeroservoelastic stability are also investigated in this paper by varying the order of approximation, or number of aerodynamic lag states, in the analysis. Test data from a thrust-vectoring configuration of an F/A-18 aircraft are compared to predictions to determine the effects on accuracy as a function of modeling complexity.

Brenner, Martin J.↗
NASA NTRS1993

Actuator and aerodynamic modeling for high-angle-of-attack aeroservoelasticity

Accurate prediction of airframe/actuation coupling is required by the imposing demands of modern flight control systems. In particular, for agility enhancement at high angle of attack and low dynamic pressure, structural integration characteristics such as hinge moments, effective actuator stiffness, and airframe/control surface damping can have a significant effect on stability predictions. Actuator responses are customarily represented with low-order transfer functions matched to actuator test data, and control surface stiffness is often modeled as a linear spring. The inclusion of the physical properties of actuation and its installation on the airframe is therefore addressed using detailed actuator models which consider the physical, electrical, and mechanical elements of actuation. The aeroservoelastic analysis procedure is described in which the actuators are modeled as detailed high-order transfer functions and as approximate low-order transfer functions. The impacts of unsteady aerodynamic modeling on aeroservoelastic stability are also investigated by varying the order of approximation, or number of aerodynamic lag states, in the analysis. Test data from a thrust-vectoring configuration of an F/A-l8 aircraft are compared to predictions to determine the effects on accuracy as a function of modeling complexity.

Brenner, Martin J.↗
NASA NTRS1992

Nonlinear feedback control of highly manoeuvrable aircraft

This paper describes the application of nonlinear quadratic regulator (NLQR) theory to the design of control laws for a typical high-performance aircraft. The NLQR controller design is performed using truncated solutions of the Hamilton-Jacobi-Bellman equation of optimal control theory. The performance of the NLQR controller is compared with the performance of a conventional P + I gain scheduled controller designed by applying standard frequency response techniques to the equations of motion of the aircraft linearized at various angles of attack. Both techniques result in control laws which are very similar in structure to one another and which yield similar performance. The results of applying both control laws to a high-g vertical turn are illustrated by nonlinear simulation.

Garrard, William L.↗
NASA NTRS1978

Effects of errors on decoupled control systems

Various error sources in a decoupled control system are considered in connection with longitudinal control on a simulated externally blown jet-flap STOL aircraft. The system employed the throttle, horizontal tail, and flaps to decouple the forward velocity, pitch angle, and flight-path angle. The errors considered were: (1) imperfect knowledge of airplane aerodynamic and control characteristics; (2) imperfect measurements of airplane state variables; (3) change in flight conditions, and (4) lag in the airplane controls and in engine response. The effects of the various errors on the decoupling process were generally minor. Significant coupling in flight-path angle was caused by control lag during speed-command maneuvers. However, this coupling could be eliminated by including the control lag in the design of the decoupled system. Other error sources affected primarily the commanded response quantity.

Hamer, H. A.↗