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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

Observing Mode Attitude Controller for the Lunar Reconnaissance Orbiter

The Lunar Reconnaissance Orbiter (LRO) mission is the first of a series of lunar robotic spacecraft scheduled for launch in Fall 2008. LRO will spend at least one year in a low altitude polar orbit around the Moon, collecting lunar environment science and mapping data to enable future human exploration. The LRO employs a 3-axis stabilized attitude control system (ACS) whose primary control mode, the "Observing mode", provides Lunar Nadir, off-Nadir, and Inertial fine pointing for the science data collection and instrument calibration. The controller combines the capability of fine pointing with that of on-demand large angle full-sky attitude reorientation into a single ACS mode, providing simplicity of spacecraft operation as well as maximum flexibility for science data collection. A conventional suite of ACS components is employed in this mode to meet the pointing and control objectives. This paper describes the design and analysis of the primary LRO fine pointing and attitude re-orientation controller function, known as the "Observing mode" of the ACS subsystem. The control design utilizes quaternion feedback, augmented with a unique algorithm that ensures accurate Nadir tracking during large angle yaw maneuvers in the presence of high system momentum and/or maneuver rates. Results of system stability analysis and Monte Carlo simulations demonstrate that the observing mode controller can meet fine pointing and maneuver performance requirements.

Calhourn, Philip C.↗
NASA NTRS2007

Observing Mode Attitude Controller for the Lunar Reconnaissance Orbiter

The Lunar Reconnaissance Orbiter (LRO) mission is the first of a series of lunar robotic spacecraft scheduled for launch in Fall 2008. LRO will spend at least one year in a low altitude polar orbit around the Moon, collecting lunar environment science and mapping data to enable future human exploration. The LRO employs a 3-axis stabilized attitude control system (ACS) whose primary control mode, the "Observing mode", provides Lunar Nadir, off-Nadir, and Inertial fine pointing for the science data collection and instrument calibration. The controller combines the capability of fine pointing with that of on-demand large angle full-sky attitude reorientation into a single ACS mode, providing simplicity of spacecraft operation as well as maximum flexibility for science data collection. A conventional suite of ACS components is employed in this mode to meet the pointing and control objectives. This paper describes the design and analysis of the primary LRO fine pointing and attitude re-orientation controller function, known as the "Observing mode" of the ACS subsystem. The control design utilizes quaternion feedback, augmented with a unique algorithm that ensures accurate Nadir tracking during large angle yaw maneuvers in the presence of high system momentum and/or maneuver rates. Results of system stability analysis and Monte Carlo simulations demonstrate that the observing mode controller can meet fine pointing and maneuver performance requirements.

Calhoun, Philip C.↗
NASA NTRS1932

Rolling Moments Due to Rolling and Yaw for Four Wing Models in Rotation

This report presents the results of a series of autorotation and torque tests on four different rotating wing systems at various rates of roll and at several angles of yaw. The investigation covered an angle of attack range up to 90 degrees and angles of yaw of 0 degree, 5 degrees, 10 degrees, and 20 degrees. The tests were made in a 5-foot, closed-throat atmospheric wind tunnel. The object of the tests was primarily to determine the effects of various angles of yaw on the rolling moments of the rotating wings up to large angles of attack. It was found that at angles of attack above that of maximum lift the rolling moments on the wings due to yaw (or side slip) from 5 degrees to 20 degrees were roughly of the same magnitude as those due to rolling. There was a wide variation in magnitude of the rolling moment due to yaw angle. The rates and ranges of stable autorotation for the monoplane models were considerably increased by yaw, whereas for an unstaggered biplane they were little affected. The immediate cause of the rolling moment due to yaw is apparently the building up of large loads on the forward wing tip and the reduction of loads on the rearward wing tip.

Knight, Montgomery↗
NASA NTRS1975

System design of a rudder coordination system

The application of the parameter optimization computer program to the design of a rudder coordination system for the F-8 airplane is summarized. The flight condition was Mach 0.56 at 20,000 feet altitude. The system configuration selected consisted of signal paths that fed yaw rate and aileron signals to the rudder. The two signal paths were summed and then modified by a high pass filter to eliminate any steady state bias signal. The input axis of the yaw gyro was perpendicular to the aircraft zero lift line and the trim angle of attack was 7.75 degrees. The parameter optimization was used to design the complete system first, and then a root locus analysis of the individual component effects was made. The results are presented.

Whitaker, H. P.↗
NASA NTRS1973

An analytical study of the response of a constant-attitude aircraft to atmospheric turbulence

A light airplane equipped with an automatic control system which drives large wing flaps and the stabilator so as to produce a constant pitch attitude in all flight modes was analyzed for its response to a specific gust. The aircraft was also equipped with a bank-angle steering, zero sideslip automatic control system which was studied for its effectiveness in suppressing a specific lateral gust. The gusts were assumed to be comprised of 200 lateral and 400 vertical sinusoids. Each was used to excite the controlled aircraft and the time response to the sum of all sinusoids was plotted. The assumption was that the gust may be treated as stationary in space but variable in time rather than the reverse. Results indicate that such a control system can suppress vertical gusts up to the limit of control authority. Either the lateral accelerations or the yawing velocity response to lateral gusts can be suppressed with this system but not both simultaneously.

Smetana, F. O.↗
NASA NTRS2012

Entry Atmospheric Flight Control Authority Impacts on GN and C and Trajectory Performance for Orion Exploration Flight Test 1

One of the key design objectives of NASA's Orion Exploration Flight Test 1 (EFT-1) is to execute a guided entry trajectory demonstrating GN&C capability. The focus of this paper is the ight control authority of the vehicle throughout the atmospheric entry ight to the target landing site and its impacts on GN&C, parachute deployment, and integrated performance. The vehicle's attitude control authority is obtained from thrusting 12 Re- action Control System (RCS) engines, with four engines to control yaw, four engines to control pitch, and four engines to control roll. The static and dynamic stability derivatives of the vehicle are determined to assess the inherent aerodynamic stability. The aerodynamic moments at various locations in the entry trajectory are calculated and compared to the available torque provided by the RCS system. Interaction between the vehicle's RCS engine plumes and the aerodynamic conditions are considered to assess thruster effectiveness. This document presents an assessment of Orion's ight control authority and its effectiveness in controlling the vehicle during critical events in the atmospheric entry trajectory.

McNamara, Luke W.↗
NASA NTRS1982

Cockpit integration from a pilot's point of view

Extensive experience in both operational and engineering test flight was used to suggest straightforward changes to helicopter cockpit and control system design that would improve pilot performance in marginal and instrument flight conditions. Needed control system improvements considered include: (1) separation of yaw from cyclic force trim; (2) pedal force proportional to displacement rate; and (3) integration of engine controls in collective stick. Display improvements needed include: (1) natural cuing of yaw rate in attitude indicator; (2) collective position indication and radar altimeter placed within primary scan; and (3) omnidirectional display of full range airspeed data.

Green, D. L.↗
NASA NTRS1983

A system study for the application of microcomputers to research flight test techniques

The onboard simulator is a three degree of freedom aircraft behavior simulator which provides parameters used by the interception procedure. These parameters can be used for verifying closed loop performance before flight. The air to air intercept mode is a software package integrated in the simulation process that generates a target motion and performs a tracking procedure that predicts the most likely next target position, for a defined time step. This procedure also updates relative position parameters and gives adequate fire commands. A microcomputer based on an aircraft spin warning system periodically samples the assymetric thrust and yaw rate of an airplane and then issues voice synthesized warnings and /or suggests to the ilot how to respond to the situation.

Smyth, R. K.↗
NASA NTRS1984

Research in solar physics: Some techniques for analyzing data from the ultraviolet spectrometer and polarimeter

Useful information for certain aspects of the analysis of data obtained by the Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission (SMM) are contained. The meaning of the UVSPCO-ordinate system and the SMM roll, pitch, and yaw are described and the process for overlaying UVSP images is explained. The various computer programs that calculate the line of sight component of the SMM spacecraft velocity from the spacecraft to the Sun is described. The spacecraft velocity is used to correct or interpret the signal observed in USVP dopplergrams. A method of using the spacecraft velocity to calibrate UVSP dopplergrams and magnetograms, i.e., determine the width of the observed emission line is applied. The UVSP polarization analysis procedures are described and the expressions for the statistical uncertainties in various quantities obtained from UVSP measurements are given.

Henze, W., Jr.↗
NASA NTRS1991

Forebody tangential blowing for control at high angles of attack

A feasibility study to determine if the use of tangential leading edge blowing over the forebody could produce effective and practical control of the F-18 HARV aircraft at high angles of attack was conducted. A simplified model of the F-18 configuration using a vortex-lattice model was developed to obtain a better understanding of basic aerodynamic coupling effects and the influence of forebody circulation on lifting surface behavior. The effect of tangential blowing was estimated using existing wind tunnel data on normal forebody blowing and analytical studies of tangential blowing over conical forebodies. Incorporation of forebody blowing into the flight control system was investigated by adding this additional yaw control and sideforce generating actuator into the existing F-18 HARV simulation model. A control law was synthesized using LQG design methods that would schedule blowing rates as a function of vehicle sideslip, angle of attack, and roll and yaw rates.

Kroo, I.↗
NASA NTRS1992

A static investigation of the thrust vectoring system of the F/A-18 high-alpha research vehicle

A static (wind-off) test was conducted in the static test facility of the Langley 16-foot Transonic Tunnel to evaluate the vectoring capability and isolated nozzle performance of the proposed thrust vectoring system of the F/A-18 high alpha research vehicle (HARV). The thrust vectoring system consisted of three asymmetrically spaced vanes installed externally on a single test nozzle. Two nozzle configurations were tested: A maximum afterburner-power nozzle and a military-power nozzle. Vane size and vane actuation geometry were investigated, and an extensive matrix of vane deflection angles was tested. The nozzle pressure ratios ranged from two to six. The results indicate that the three vane system can successfully generate multiaxis (pitch and yaw) thrust vectoring. However, large resultant vector angles incurred large thrust losses. Resultant vector angles were always lower than the vane deflection angles. The maximum thrust vectoring angles achieved for the military-power nozzle were larger than the angles achieved for the maximum afterburner-power nozzle.

Mason, Mary L.↗
NASA NTRS1996

Thrust Vectoring on the NASA F-18 High Alpha Research Vehicle

Investigations into a multiaxis thrust-vectoring system have been conducted on an F-18 configuration. These investigations include ground-based scale-model tests, ground-based full-scale testing, and flight testing. This thrust-vectoring system has been tested on the NASA F-18 High Alpha Research Vehicle (HARV). The system provides thrust vectoring in pitch and yaw axes. Ground-based subscale test data have been gathered as background to the flight phase of the program. Tests investigated aerodynamic interaction and vane control effectiveness. The ground-based full-scale data were gathered from static engine runs with image analysis to determine relative thrust-vectoring effectiveness. Flight tests have been conducted at the NASA Dryden Flight Research Center. Parameter identification input techniques have been developed. Individual vanes were not directly controlled because of a mixer-predictor function built into the flight control laws. Combined effects of the vanes have been measured in flight and compared to combined effects of the vanes as predicted by the cold-jet test data. Very good agreement has been found in the linearized effectiveness derivatives.

Bowers, Albion H.↗
NASA NTRS1997

AXAF Coordinate Transformation at XRCF

Coordinate transformation between focal plane and detector pixel systems must be handled carefully at the X-ray Calibration Facility (XRCF) as it will be during flight. The High Resolution Mirror Assembly (HRMA) X-ray Detection System (HXDS) stage dithers, and the five-axis mount (FAM) attachment points underwent various types of motion during testing. At the XRCF when the FAM moved, the Science Instrument Module (SIM) travel direction was not necessarily aligned with the mirror axis motion, and, in addition, an arbitrary position offset had to be calibrated. Misalignment from the mirror axis was assessed by measuring its displacement from the boresight configuration of the default FAM frame, and the HXDS stage was monitored for motion from the default FAM reference point. Mirror position, prescribed in a mirror modal coordinate system, was measured in HRMA pitch and yaw axes. Prior to corrections for dithering and FAM movement, the coordinate data at XRCF also had to be corrected for possible misalignments of the mirror mount relative to XRCF and the default FAM axes due to the movement of the FAM feet. Those misalignments were processed in terms of yaw-pitch-roll Euler angles in the mirror nodal coordinate, and in the default FAM frame, respectively. An AXAF Science Center (ASC) coordinate library, pixlib, has been built to support these coordinate transformations and was used during x-ray calibration at the George C. Marshall Space Flight Center, Huntsville, AL. The design and implementation of this library will be discussed.

He, Helen↗
NASA NTRS2013

4DoF Drift Free Navigation Using Inertial Cues and Optical Flow

In this paper, we describe a novel approach in fusing optical flow with inertial cues (3D acceleration and 3D angular velocities) in order to navigate a Micro Aerial Vehicle (MAV) drift free in 4DoF and metric velocity. Our approach only requires two consecutive images with a minimum of three feature matches. It does not require any (point) map nor any type of feature history. Thus it is an inherently failsafe approach that is immune to map and feature-track failures. With these minimal requirements we show in real experiments that the system is able to navigate drift free in all angles including yaw, in one metric position axis, and in 3D metric velocity. Furthermore, it is a power-on-and-go system able to online self-calibrate the inertial biases, the visual scale and the full 6DoF extrinsic transformation parameters between camera and IMU.

reconnissance↗
NASA NTRS1976

STOLAND

The STOLAND system includes air data, navigation, guidance, flight director (including a throttle flight director on the Augmentor Wing), 3-axis autopilot and autothrottle functions. The 3-axis autopilot and autothrottle control through parallel electric servos on both aircraft and on the augmentor wing, the system also interfaces with three electrohydraulic series actuators which drive the roll control surfaces, elevator and rudder. The system incorporates automatic configuration control of the flaps and nozzles on the augmentor wing and of the flaps on the Twin Otter. Interfaces are also provided to control the wing flap chokes on the Augmentor Wing and the spoilers on the Twin Otter. The STOLAND system has all the capabilities of a conventional integrated avionics system. Aircraft stabilization is provided in pitch, roll and yaw including control wheel steering in pitch and roll. The basic modes include altitude hold and select, indicated airspeed hold and select, flight path angle hold and select, and heading hold and select. The system can couple to TACAN and VOR/DME navaids for conventional radial flying.

Grgurich, J.↗
NASA NTRSDate not supplied

Development of Data Reduction Methods for Dynamic Stability Tests in a Magnetic Suspension and Balance System

The NASA/ODU 6-inch Magnetic Suspension and Balance System (MSBS) is operational in a “free-to-yaw” configuration in a subsonic wind tunnel. The MSBS hardware has been heavily modified over recent years to utilize a transverse magnetization scheme, with mixed electromagnetic and motion tracking camera position sensors and a relatively sophisticated control system. The project aims to provide a unique test capability for dynamic stability testing of planetary entry capsules, free from support interference. Aerodynamic tests are being conducted, with a focus of validation of the data reduction methods used to extract dynamic stability parameters. The unique complication is the existence of magnetic, aerodynamic, and mass centers, where magnetic, aerodynamic, and inertia forces respectively are resolved. The paper will report on tests of a family of EEV-like geometries, where the conical half-angle varied between 45 and 60 degrees in steps of 3.75 degrees. The paper will present experimental results from the parametric family of EEV-like geometries. Simulation results will also be presented, based on a two or three degree-of-freedom Simulink model. The model allows the exploration of the effects of non-coincident centers and the sensitivity of results arising from uncertainties in location.

Entry Systems Modeling↗
NASA NTRS2006

Preliminary Study Using Forward Reaction Control System Jets During Space Shuttle Entry

Failure or degradation of the flight control system, or hull damage, can lead to loss of vehicle control during entry. Possible failure scenarios are debris impact and wing damage that could result in a large aerodynamic asymmetry which cannot be trimmed out without additional yaw control. Currently the space shuttle uses aerodynamic control surfaces and Reaction Control System jets to control attitude. The forward jets are used for orbital maneuvering only, while the aft jets are used for yaw control during entry. This paper develops a controller for using the forward reaction control system jets as an additional control during entry, and assesses its value and feasibility during failure situations. Forward-aft jet blending logic is created, and implemented on a simplified model of the space shuttle entry flight control system. The model is validated and verified on the nonlinear, six degree-of-freedom Shuttle Engineering Simulator. A rudimentary human factors study was undertaken using the forward cockpit simulator at Johnson Space Center, to assess flying qualities of the new system and pilot workload. Results presented in the paper show that the combination of forward and aft jets provides useful additional yaw control, in addition to potential fuel savings and the ability to balance the use of the fuel in the forward and aft tanks to meet availability constraints of both forward and aft fuel tanks. Piloted simulation studies indicated that using both sets of jets while flying a damaged space shuttle reduces pilot workload, and makes the vehicle more responsive.

Restrepo, Carolina↗