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At least 739 records · Page 41

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NASA NTRS1991

Application and flight test of linearizing transformations using measurement feedback to the nonlinear control problem

The design of nonlinear controllers has relied on the use of detailed aerodynamic and engine models that must be associated with the control law in the flight system implementation. Many of these controllers were applied to vehicle flight path control problems and have attempted to combine both inner- and outer-loop control functions in a single controller. An approach to the nonlinear trajectory control problem is presented. This approach uses linearizing transformations with measurement feedback to eliminate the need for detailed aircraft models in outer-loop control applications. By applying this approach and separating the inner-loop and outer-loop functions two things were achieved: (1) the need for incorporating detailed aerodynamic models in the controller is obviated; and (2) the controller is more easily incorporated into existing aircraft flight control systems. An implementation of the controller is discussed, and this controller is tested on a six degree-of-freedom F-15 simulation and in flight on an F-15 aircraft. Simulation data are presented which validates this approach over a large portion of the F-15 flight envelope. Proof of this concept is provided by flight-test data that closely matches simulation results. Flight-test data are also presented.

Antoniewicz, Robert F.↗

NASA NTRS1991

A comparison of acceleration control and pulse control in simulated spacecraft docking maneuvers

Results are reported from a study designed to compare acceleration control with pulse control in simulated spacecraft docking maneuvers. Nine commercial airline pilots served as test subjects and the simulated remote dockings of an orbital maneuvering vehicle (OMV) to a space station were initiated from 50, 100, and 150 meters along the station's minus velocity vector. The trials were grouped into blocks of 18 consisting of six repetitions of the three ranges. It was found that mission duration was lower with pulse mode, while fuel consumption was lower with acceleration mode. It is suggested that this result is most likely specific to the thruster values that are being used.

Brody, Adam R.↗

NASA NTRS2005

Verifying Correct Functionality of Avionics Subsystems

This project focuses on the testing of the telecommunications interface subsystem of the Multi-Mission System Architecture Platform to ensure proper functionality. The Multi-Mission System Architecture Platform is a set of basic tools designed to be used in future spacecraft. The responsibilities of the telecommunications interface include communication between the spacecraft and ground teams as well as acting as the bus controller for the system. The tests completed include bit wise read\write tests to each register, testing of status bits, and verifying various bus controller activities. Testing is accomplished through the use of software-based simulations run on an electronic design of the system. The tests are written in Verilog Hardware Definition Language and they simulate specific states and conditions in telecommunication interfaces. Upon successful completion, the output is examined to verify that the system responded appropriately.

Meuer, Ben t.↗

NASA NTRS2017

Design and Development of a 200-kW Turbo-Electric Distributed Propulsion Testbed

There a few NASA funded electric and hybrid electric projects from different NASA Centers, including the NASA Armstrong Flight Research Center (AFRC) (Edwards, California). Each project identifies a specific technology gap that is currently inhibiting the growth and proliferation of relevant technologies in commercial aviation. This paper describes the design and development of a turbo-electric distributed propulsion (TeDP) hardware-in-the-loop (HIL) simulation bench, which is a test bed for discovering turbo-electric control, distributed electric control, power management control, and integration competencies while providing risk mitigation for future turbo-electric flying demonstrators.

propulsion↗

NASA NTRS2017

Commercial Crew Vehicle Ascent Abort Simulation and Analysis

SpaceX and Boeing have been selected to develop and operate crew vehicles to transport astronauts to and from the International Space Station. Their design work is to be analyzed to ensure that they are meeting all of the safety and operational requirements put forth by NASA. Throughout my time here, I worked familiarized myself with the SpaceX Dragon Abort system, as well as the NASA Human-Systems Integration Requirements (HSIR). This included understanding the different abort scenarios, and how each one could potentially impact the astronaut crew. In addition, I familiarized myself with the simulation developed my NASA to test and analyze the Guidance Navigation and Control (GN&C) systems developed by SpaceX and Boeing.

Gnam, Christopher↗

NASA NTRS1984

A flight-test and simulation evaluation of the longitudinal final approach and landing performance of an automatic system for a light wing loading STOL aircraft equipped with wing spoilers

As part of a comprehensive flight-test investigation of short takeoff and landing (STOL) operating systems for the terminal systems for the terminal area, an automatic landing system has been developed and evaluated for a light wing-loading turboprop-powered aircraft. An advanced digital avionics system performed display, navigation, guidance, and control functions for the test aircraft. Control signals were generated in order to command powered actuators for all conventional controls and for a set of symmetrically driven wing spoilers. This report describes effects of the spoiler control on longitudinal autoland (automatic landing) performance. Flight-test results, with and without spoiler control, are presented and compared with available (basically, conventional takeoff and landing) performance criteria. These comparisons are augmented by results from a comprehensive simulation of the controlled aircraft that included representations of the microwave landing system navigation errors that were encountered in flight as well as expected variations in atmospheric turbulence and wind shear. Flight-test results show that the addition of spoiler control improves the touchdown performance of the automatic landing system. Spoilers improve longitudinal touchdown and landing pitch-attitude performance, particularly in tailwind conditions. Furthermore, simulation results indicate that performance would probably be satisfactory for a wider range of atmospheric disturbances than those encountered in flight. Flight results also indicate that the addition of spoiler control during the final approach does not result in any measurable change in glidepath track performance, and results in a very small deterioration in airspeed tracking. This difference contrasts with simulations results, which indicate some improvement in glidepath tracking and no appreciable change in airspeed tracking. The modeling problem in the simulation that contributed to this discrepancy with flight was not resolved.

Brown, S. C.↗

NASA NTRS2003

Microgravity Emissions Laboratory Testing of the Light Microscopy Module Control Box Fan

The Microgravity Emissions Laboratory (MEL) was developed at the NASA Glenn Research Center for the characterization, simulation, and verification of the International Space Station (ISS) microgravity environment. This Glenn lab was developed in support of the Fluids and Combustion Facility (FCF). The MEL is a six-degrees-of-freedom inertial measurement system that can characterize the inertial response forces (emissions) of components, subrack payloads, or rack-level payloads down to 10 7g. The inertial force output data generated from the steady-state or transient operations of the test article are used with finite element analysis, statistical energy analysis, and other analysis tools to predict the on-orbit environment at specific science or rack interface locations. Customers of the MEL have used benefits in isolation performance testing in defining available attenuation during the engineering hardware design phase of their experiment s development. The Light Microscopy Module (LMM) Control Box (LCB) fan was tested in the MEL in June and July of 2002. The LMM is planned as a remotely controllable on-orbit microscope subrack facility that will be accommodated in an FCF Fluids Integrated Rack on the ISS. The disturbances measured in the MEL test resulted from operation of the air-circulation fan within the LCB. The objectives of the testing were (1) to identify an isolator to be added to the LCB fan assembly to reduce fan-speed harmonics and (2) to identify the fan-disturbance forcing functions for use in rack-response analysis of the LMM and Fluids Integrated Rack facility. This report describes the MEL, the testing process, and the results from ground-based MEL LCB fan testing.

McNelis, Anne M.↗

NASA NTRS2020

U.S. Coast Guard Boat Recovery Simulation at the NASA Ames Vertical Motion Simulator

The U.S. Coast Guard routinely uses the Over-The-Horizon (OTH-IV), a cutter deployed, rigid-hulled inflatable boat for rescue and law enforcement operations. The term "cutter" refers to a Coast Guard vessel 65 feet in length or greater with accommodations for crew to live aboard and the ability to deploy smaller boats including the OTH-IV. A deployment method employed by some cutter class vessels is a davit crane system and specialized hook mechanism to connect the smaller boat. The launch and recovery operation requires several crewmembers, where one is tasked with releasing and connecting the hook to the small boat. Manipulating the hook can pose a risk to the crewmember depending on sea conditions combined with fatigue level or task expertise. Equipment and crewmembers are tested extensively due to the inherent risk of the task, but the sea conditions cannot be controlled. To address the sea condition variable, the U.S. Coast Guard and NASA leveraged the Vertical Motion Simulator (VMS) as a platform to test new equipment or train crewmembers in varying sea conditions. With 6 degrees of freedom and a vertical displacement of +/- 22ft, the VMS is capable of simulating conditions up to sea-state 5. The proof of concept experiment took place in September 2018 and demonstrated that the VMS can accurately simulate varying sea-states, collect performance data, and design a reliable and safe system for participants. The U.S. Coast Guard provided boat displacement data from the Large Amplitude Motion Program (LAMP). The program generates multi-directional waves with a cosine squared spreading function which produced a time history response of displacement data (surge, sway, heave, roll, pitch, yaw) of the OTH-IV's center of gravity (C.G). The displacement data was differentiated into acceleration evaluated at the crewmember's position at the front (bow) of the boat. Those accelerations were transformed to the VMS coordinate system and used as command inputs to the motion system's washout filters. The VMS uses Interchangeable Cabs (ICab) to perform flight simulations on a variety of aircraft or spacecraft configurations. An ICab typically contains seats, restraints, pilot controls, instrument panel, and out-the-window projectors all enclosed in a familiar cockpit configuration. To replicate the launch and recovery of a small boat, all the conventional features of a flight simulator and canopy were removed to be replaced with a to-scale OTH-IV bow mockup. The bow section was constructed from aluminum, and a connection point known as the davit ring. Additionally, a hook replica was suspended by a cable from the ceiling as if it were hanging from a davit crane aboard a cutter vessel. The last step was providing an auxiliary control to close the distance between suspended hook and the davit ring on the bow mockup. Without control the boat would simulate the wave motion, but with no guarantee that the crewmember will be in reach of the hook. Since the wave motion was repeatable, an additional acceleration command sent to the washout filters to move the simulator in the surge, sway, and heave directions, independently. The commands were rate limited such that the additional movement was not detectable with respect to the wave motion. The results showed that for each wave profile, a unique set of acceleration commands provided opportunities for crewmembers to gain control of the hook and connect it to the davit ring.

Riccobono, Nicholas S.↗

NASA NTRS2002

ISS Material Science Research Rack HWIL Interface Simulation

In this paper, the first Material Science Research Rack (MSRR-1) hardware-in-the-loop (HWIL) interface simulation is described. Dynamic Concepts developed this HWIL simulation system with funding and management provided by the Flight Software group (ED14) of NASA-MSFC's Avionics Department. The HWIL system has been used both as a flight software development environment and as a software qualification tool. To fulfill these roles, the HWIL simulator accurately models the system dynamics of many MSRR-1 subsystems and emulates most of the internal interface signals. The modeled subsystems include the Experiment Modules, the Thermal Environment Control System, the Vacuum Access System, the Solid State Power Controller Module, and the Active Rack Isolation Systems. The emulated signals reside on three separate MIL-STD-1553B digital communication buses, the ISS Medium Rate Data Link, and several analog controller and sensor signals. To enhance the range of testing, it was necessary to simulate several off-nominal conditions that may occur in the interfacing subsystems.

Williams, Philip J.↗

NASA NTRS1975

A new arc heater shroud test technique for thermo-structural testing of full-scale, nose-tip skirt materials

An arc heater shroud test technique was developed for thermostructural testing of full-scale, missile nose tip-skirt assemblies. Reentry trajectory simulation is provided by changing the arc heater operation in a prescribed manner through manual and automatic controls. Excellent test repeatability allows screening of materials by direct comparison of test results. Continuous recordings of model surface temperature, pressure, heat flux, and model internal temperatures are made at several locations during the test.

Williams, R. R.↗

NASA NTRSDate not supplied

Correlated Electromagnetic Levitation Actuator: A Reaction Sphere Based Attitude Control System

To address problems experienced by current reaction wheels and control moment gyroscopebased attitude control systems (ACS), researchers at NASA’s Marshall Space Flight Center have begun developing a reaction sphere actuator based on correlated electromagnetic levitation that will be immune to destructive bearing friction, momentum saturation, and gimbal lock. The Correlated Electromagnetic Levitation Actuator (CELA) advances the state of the art of reaction sphere ACSs by employing the concept of correlated magnetics. It is a frictionless, direct-drive reaction sphere that harnesses a unique technology with an array of applications across multiple disciplines. Correlated electromagnets function in a manner that is analogous to a matched filter; the convolution of two signals is peaked at the index representing the greatest match. For CELA, the signals are the patterns of magnetic flux density as a function of position. The magnitude of the convolution equates to an attractive or repulsive force, and these forces can be azimuthal or radial. The development of CELA is based in four distinct disciplines: Advanced Manufacturing, Prototype Development, Electromagnetic Modeling, and Controls. We are developing novel manufacturing techniques required to build arrays of permanent and electromagnet dipoles on curved surfaces. To print the permanent magnetic array, we have developed a probe with pyramidal magnets that will reside on a robotic arm to induce localized magnetic fields on a surface. The probe also includes the ability to erase dipole patterns from a permanent magnet by heating the surface to its Curie temperature. A number of test articles and prototypes have been developed using additive manufacturing methods. These prototypes have included hemispherical motors to test the drive algorithm, and a levitation test bed that demonstrates a magnetic bearing method based on attractive magnetic forces and ratiometric Hall effect sensors. We developed an array of electromagnetic dipoles on a printed circuit board (PCB) with individual H-bridges controlling each coil. This device created various flux density patterns and we measured their magnetic fields using a custom Hall effect 3-D probe and a LabVIEW virtual instrument. These data will serve as a benchmark for characterizing the accuracy of future models. Current work is focused on modeling the magnetic fields of our prototype arrays using COMSOL Finite Element Analysis and verifying the model against our test data. Accurate modeling will allow us to quickly test new patterns of electromagnets and their macro behavior. Eventually, the magnetic field models will be implemented in our controls simulations to facilitate precise control of the reaction sphere. Initial model results agree with field measurements to within 1 G (5% of measured flux density). Currently, we are testing different material properties of the electromagnets and their magnetic fields and thermal effects. These results will be used to refine the design of the electromagnetic dipoles. Our control efforts have centered on developing commutation, levitation, and field pattern shaping hardware in the form of breadboards and PCBs with software running on a local microcontroller. In addition, our partners developed MATLAB Simulink models to demonstrate a PID controller thatmitigates disturbance forces resulting from the interaction of drive and levitation magnetics. Finally, we have designed a three-axis test stand that will be used in future work to demonstrate CELA’s orientation control capability.

controls↗

NASA NTRSDate not supplied

Correlated Electromagnetic Levitation Actuator: A Reaction Sphere-Based Attitude Control System

To address problems experienced by current reaction wheels and control moment gyroscopebased attitude control systems (ACS), researchers at National Aeronautics and Space Administration’s (NASA’s) Marshall Space Flight Center (MSFC) have begun developing a reaction sphere actuator based on correlated electromagnetic levitation that will be immune to destructive bearing friction, momentum saturation, and gimbal lock. The Correlated Electromagnetic Levitation Actuator (CELA) advances the state of the art of reaction sphere ACSs by employing the concept of correlated magnetics. It is a frictionless, direct-drive reaction sphere that harnesses a unique technology with an array of applications across multiple disciplines. Correlated electromagnets function in a manner that is analogous to a matched filter; the convolution of two signals is peaked at the index representing the greatest match. For CELA, the signals are the patterns of magnetic flux density as a function of position. The magnitude of the convolution equates to an attractive or repulsive force, and these forces can be azimuthal or radial. The development of CELA is based in four distinct disciplines: Advanced Manufacturing, Prototype Development, Electromagnetic Modeling, and Controls. We are developing novel manufacturing techniques required to build arrays of permanent and electromagnet dipoles on curved surfaces. To print the permanent magnetic array, we have developed a probe with pyramidal magnets that will reside on a robotic arm to induce localized magnetic fields on a surface. We have also used high temperature ovens to erase dipole patterns from a permanent magnet by heating the surface to its Curie temperature. A number of test articles and prototypes have been developed using additive manufacturing methods. These prototypes have included hemispherical motors to test the drive algorithm, and a levitation test bed that demonstrates a magnetic bearing method based on attractive magnetic forces and ratiometric Hall effect sensors. We developed an array of electromagnetic dipoles on a printed circuit board (PCB) with individual H-bridges controlling each coil. This device created various flux density patterns and we measured their magnetic fields using a custom Hall effect 3-D probe and a LabVIEW virtual instrument. These data will serve as a benchmark for characterizing the accuracy of future models. Current work is focused on modeling the magnetic fields of our prototype arrays using COMSOL finite element analysis (FEA) and verifying the model against our test data. Accurate modeling will allow us to quickly test new patterns of electromagnets and their macro behavior. Eventually, the magnetic field models will be implemented in our controls simulations to facilitate precise control of the reaction sphere. Initial model results agree with field measurements to within 1 G (5% of measured flux density). Currently, we are testing different material properties of the electromagnets and their magnetic fields and thermal effects. These results will be used to refine the design of the electromagnetic dipoles. Our control efforts have centered on developing commutation, levitation, and field pattern shaping hardware in the form of breadboards and PCBs with software running on a local microcontroller. In addition, our partners developed MATLAB Simulink models to demonstrate a PID controller that mitigates disturbance forces resulting from the interaction of drive and levitation magnetics. Finally, we have designed a three-axis test stand that will be used in future work to demonstrate CELA’s orientation control capability.

reaction sphere↗

NASA NTRS1988

An application of high authority/low authority control and positivity

Control Dynamics Company (CDy), in conjunction with NASA Marshall Space Flight Center (MSFC), has supported the U.S. Air Force Wright Aeronautical Laboratory (AFWAL) in conducting an investigation of the implementation of several DOD controls techniques. These techniques are to provide vibration suppression and precise attitude control for flexible space structures. AFWAL issued a contract to Control Dynamics to perform this work under the Active Control Technique Evaluation for Spacecraft (ACES) Program. The High Authority Control/Low Authority Control (HAC/LAC) and Positivity controls techniques, which were cultivated under the DARPA Active Control of Space Structures (ACOSS) Program, were applied to a structural model of the NASA/MSFC Ground Test Facility ACES configuration. The control systems design were accomplished and linear post-analyses of the closed-loop systems are provided. The control system designs take into account effects of sampling and delay in the control computer. Nonlinear simulation runs were used to verify the control system designs and implementations in the facility control computers. Finally, test results are given to verify operations of the control systems in the test facility.

Seltzer, S. M.↗

NASA NTRS1973

Flight test results from the CV990 simulated space shuttle during unpowered automatic approaches and landings

Unpowered automatic approaches and landings with a CV990 aircraft were conducted to study navigation, guidance, and control problems associated with terminal area approach and landing for the space shuttle. The flight tests were designed to study from 11,300 m to touchdown the performance of a navigation and guidance concept which utilized blended radio/inertial navigation using VOR, DME, and ILS as the ground navigation aids. In excess of fifty automatic approaches and landings were conducted. Preliminary results indicate that this concept may provide sufficient accuracy to accomplish automatic landing of the shuttle orbiter without air-breathing engines on a conventional size runway.

Edwards, F. G.↗

NASA NTRS1980

Comparison of several inflow control devices for flight simulation of fan tone noise using a JT15D-1 engine

To enable accurate simulation of in-flight fan tone noise during ground static tests, four devices intended to reduce inflow disturbances and turbulence were tested with a JT15D-1 turbofan engine. These inflow control devices (ICD's) consisted of honeycomb/screen structures mounted over the engine inlet. The ICD's ranged from 1.6 to 4 fan diameters in size, and differed in shape and fabrication method. All the ICD's significantly reduced the BPF tone in the far-field directivity patterns, but the smallest ICD's apparently introduced propagating modes which could be recognized by additional lobes in the speeds; at supersonic fan tip speed the smallest ICD's had some measurable loss, but the largest had no loss. Data from a typical transducer show that the unsteady inflow distortion modes (turbulence) were eliminated or significantly reduced when either of the ICD's was installed. However, some steady inflow distortion modes remained.

Mcardle, J. G.↗

NASA NTRSDate not supplied

OVERFLOW Analysis of Supersonic Retropropulsion Testing on a Blunt Mars Entry Vehicle Concept

Supersonic retropropulsion (SRP) flow over a Hypersonic Inflatable Aerodynamic Decelerator (HIAD) blunt-body vehicle was simulated using the Overflow Computational Fluid Dynamics (CFD) solver. Two nozzle configurations were tested (1E and 1F) as a subset of the seven total configurations in the Descent System Study (DSS) testing campaign. A generalized, Adaptive Mesh Refinement (AMR) shock capturing and plume refinement technique was developed and calibrated for producing automatic and unique grid systems optimized for any given testing condition. Solution independence from grid resolution was determined by successively increasing grid refinement until asymptotic convergence of the mean aerodynamic loads was observed. Overflow Reynolds-averaged Navier-Stokes (RANS) solutions produced realistic SRP flow phenomena, including Mach disk normal shocks contained in high-thrust plumes and bow shock triple-points. Solutions for the 1E nozzle configuration were steady. Conversely, a subset of the 1F test conditions were unsteady and exhibited periodic, non-sinusoidal expansions and contractions of the streamwise-oriented plume, resulting in unsteady aerodynamic loads on the vehicle. Initial investigations into the effect of turbulence modeling fidelity demonstrated significant differences between the aerodynamic loads simulated with RANS and Detached Eddy Simulation (DES). Multiple flow mechanisms were identified as root causes of these differences, including bow shock shape augmentation and reduced entrainment due to reduced turbulence in the DES simulations. Initial comparisons of pitching moment control authority and aerodynamic drag performance between the tested nozzle configurations demonstrated that the 1E configuration may be more advantageous for the Mars Entry, Descent, and Landing (EDL) task.

Supersonic Retropropulsion↗

NASA NTRSDate not supplied

OVERFLOW Analysis of Supersonic Retropropulsion Testing on a Blunt Mars Entry Vehicle Concept

Supersonic Retropropulsion↗

NASA NTRS1974

Reaction control system plume flow field interaction effects on the Space Shuttle orbiter

This paper presents an analysis of data obtained from wind tunnel tests of the aerodynamic interference induced by the reaction control system jets on Space Shuttle orbiter configurations. The test data was obtained using cold gas simulation techniques with nozzles scaled to match jet exit momentum ratio as the primary parameter at Mach numbers from 2.5 to 10. Significant induced effects have been found that degrade the performance of the pitch and roll reaction controls and that induce cross-coupling effects for yaw reaction control. Analysis of the induced data shows good correlation with jet exit momentum ratio.

Rausch, J. R.↗