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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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Description and Flight Test Results of the NASA F-8 Digital Fly-by-Wire Control System

A NASA program to develop digital fly-by-wire (DFBW) technology for aircraft applications is discussed. Phase I of the program demonstrated the feasibility of using a digital fly-by-wire system for aircraft control through developing and flight testing a single channel system, which used Apollo hardware, in an F-8C airplane. The objective of Phase II of the program is to establish a technology base for designing practical DFBW systems. It will involve developing and flight testing a triplex digital fly-by-wire system using state-of-the-art airborne computers, system hardware, software, and redundancy concepts. The papers included in this report describe the Phase I system and its development and present results from the flight program. Man-rated flight software and the effects of lightning on digital flight control systems are also discussed.

Source record↗
NASA NTRS1978

Development and test of an inlet and duct to provide airflow for a wing boundary layer control system

The boundary layer control (BLC) system of the quiet short-haul research airplane (QSRA) requires significant amounts of pressurized airflow for successful operation. An inlet and duct were successfully developed which removed airflow from the engine fan duct for the BLC system at or above the required total pressure of 99% of the average fan duct total pressure. The design was constrained by the tight space limitations of the QSRA nacelle. Potential flow with boundary layer analysis techniques were used as an aid to select the inlet and duct geometries. Airflow and total pressure profile data were obtained during development tests.

Gunnarson, D. W.↗
NASA NTRS1994

SCOS 2: ESA's new generation of mission control system

New mission-control infrastructure is currently being developed by ESOC, which will constitute the second generation of the Spacecraft Control Operations system (SCOS 2). The financial, functional and strategic requirements lying behind the new development are explained. The SCOS 2 approach is described. The technological implications of these approaches is described: in particular it is explained how this leads to the use of object oriented techniques to provide the required 'building block' approach. The paper summarizes the way in which the financial, functional and strategic requirements have been met through this combination of solutions. Finally, the paper outlines the development process to date, noting how risk reduction was achieved in the approach to new technologies and summarizes the current status future plans.

Jones, M.↗
NASA NTRS1987

Simulation evaluation of the control system command monitoring concept for the NASA V/STOL research aircraft (VSRA)

A control-system monitoring concept is described that has the potential of rapidly detecting computer command failures (hardware or software) in fly-by-wire control systems. The concept has been successfully tested on the NASA Vertical/Short Takeoff and Landing Research Aircraft (VSRA) in the Ames Research Center's Vertical Motion Simulator. The test was particularly stringent, since the VSRA is required to operate in a hazardous environment. The fidelity of the aircraft model used in the simulation was verified by flying both the simulated and actual aircraft in a precision hover task using specially designed targets.

Schroeder, J. A.↗
NASA NTRS1974

An experimental study of a hybrid adaptive control system

A Liapunov type model reference adaptive control system with five adjustable gains is implemented using a PDP-11 digital computer and an EAI 380 analog computer. The plant controlled is a laboratory type dc servo system. It is made to follow closely a second order linear model. The experimental results demonstrate the feasibility of implementing this rather complex design using only a minicomputer and a reasonable number of operational amplifiers. Also, it points out that satisfactory performance can be achieved even when certain assumptions necessary for the theory are not satisfied.

Lizewski, E. F.↗
NASA NTRS1974

A spacecraft integrated power/attitude control system

A study to determine the viability and application of a system capable of performing the dual function of power storage/generation and attitude control has been conducted. Results from the study indicate that an integrated power/attitude control system (IPACS) can satisfy future mission requirements while providing significant savings in weight, volume, and cost over conventional systems. A failure-mode configuration of an IPACS was applied to a shuttle-launched RAM free-flyer and simulated using make-do hardware linked to a hybrid computer. Data from the simulation runs indicate that control interactions resulting from heavy power demands have minimal effect on system control effectiveness. The system was shown to be capable of meeting the stringent pointing requirements of 1 arc-second while operating under the influence of an orbital disturbance environment and during periods of momentum variations imposed by energy transfer requirements.

Keckler, C. R.↗
NASA NTRS1971

Attitude control systems for load relief of Saturn-class launch vehicles

The effectiveness of attitude control laws that are designed to reduce bending moment loads and improve the controllability of large Saturn class boosters is discussed. These laws are referred to as load relief control systems. The two factors are assessed by simulations of varying degrees of complexity, from 2-D rigid body to 6-D with flexible body. A load relief control system, nicknamed AGE, is selected as the most effective of the various proposed schemes. This system is compared with other load relief laws and with simple attitude control. Most nominal vehicles use attitude control laws since their goal is to stay on the flight path without regard to the induced loads.

Sharp, J.↗
NASA NTRS1981

Practical robustness measures in multivariable control system analysis

The robustness of the stability of multivariable linear time invariant feedback control systems with respect to model uncertainty is considered using frequency domain criteria. Available robustness tests are unified under a common framework based on the nature and structure of model errors. These results are derived using a multivariable version of Nyquist's stability theorem in which the minimum singular value of the return difference transfer matrix is shown to be the multivariable generalization of the distance to the critical point on a single input, single output Nyquist diagram. Using the return difference transfer matrix, a very general robustness theorem is presented from which all of the robustness tests dealing with specific model errors may be derived. The robustness tests that explicitly utilized model error structure are able to guarantee feedback system stability in the face of model errors of larger magnitude than those robustness tests that do not. The robustness of linear quadratic Gaussian control systems are analyzed.

Lehtomaki, N. A.↗
NASA NTRS1981

A decoupled control system for improved flight performance in wind shear

A fixed-base simulation study has been made to compare the approach and landing performance of a decoupled longitudinal control system and the velocity-vector control-wheel steering (VCWS) system that currently exists on the NASA Terminal Configured Vehicle (TCV). The decoupled control system employed constant prefilter and feedback gains to provide steady-state decoupling of flight-path angle, pitch angle, and forward velocity using symmetric spoilers, throttle, and elevator as active control elements. In severe wind shear, of the Kennedy-type, the decoupled control system improved both approach performance and touchdown performance even when the spoiler deflection was limited to 16 deg. On a 10-point rating scale, three research pilots rated the approach and landing task with decoupled controls as much as 3 to 4 increments better than the use of the VCWS system in severe winds

Miller, G. K., Jr.↗
NASA NTRS1987

Hubble space telescope pointing control system simulation

A time domain simulation of the Hubble Space Telescope (HST) pointing control system is described. The simulation was developed to aid in the evaluation of moving target pointing algorithms and to serve as an analysis tool. The HST pointing control system is briefly described, and the time domain simulation is discussed. A typical simulation result for moving target tracking is presented.

Strohbehn, K.↗
NASA NTRS2018

Spaceport Command and Control System: Network Engineering

The Spaceport Command and Control System (SCCS) project's goal is to facilitate the checkout and launch of NASA's next generation SLS vehicle in order to enable human exploration through deep space. SCCS is made up of complex software that will control and monitor the Space Launch System rocket and Orion spacecraft. Once it is fully developed, SCCS will be a large improvement to previous software since it takes advantage of modern computers and information making it faster and more reliable than the software used previously on the Shuttle program. The software will be tailored to the specific needs of the Space Launch System (SLS) and Orion spacecraft. These three projects will be brought together for the launch of Exploration Mission-1.

Mackh, Katherine↗
NASA NTRS1983

Parameter testing for lattice filter based adaptive modal control systems

For Large Space Structures (LSS), an adaptive control system is highly desirable. The present investigation is concerned with an 'indirect' adaptive control scheme wherein the system order, mode shapes, and modal amplitudes are estimated on-line using an identification scheme based on recursive, least-squares, lattice filters. Using the identified model parameters, a modal control law based on a pole-placement scheme with the objective of vibration suppression is employed. A method is presented for closed loop adaptive control of a flexible free-free beam. The adaptive control scheme consists of a two stage identification scheme working in series and a modal pole placement control scheme. The main conclusion from the current study is that the identified parameters cannot be directly used for controller design purposes.

Sundararajan, N.↗
NASA NTRS2002

An attitude control system for the SIM Test Bed 3 (STB3)

In this paper, the details of the design, construction and performance of the attitude control system are presented. The attitude control system has been used to meet certain SIM requirements. An example of this performance test is also included.

spaceborne↗
NASA NTRS1981

Hierarchical specification of the SIFT fault tolerant flight control system

The specification and mechanical verification of the Software Implemented Fault Tolerance (SIFT) flight control system is described. The methodology employed in the verification effort is discussed, and a description of the hierarchical models of the SIFT system is given. To meet the objective of NASA for the reliability of safety critical flight control systems, the SIFT computer must achieve a reliability well beyond the levels at which reliability can be actually measured. The methodology employed to demonstrate rigorously that the SIFT computer meets as reliability requirements is described. The hierarchy of design specifications from very abstract descriptions of system function down to the actual implementation is explained. The most abstract design specifications can be used to verify that the system functions correctly and with the desired reliability since almost all details of the realization were abstracted out. A succession of lower level models refine these specifications to the level of the actual implementation, and can be used to demonstrate that the implementation has the properties claimed of the abstract design specifications.

Melliar-Smith, P. M.↗
NASA NTRS1961

Analytical Investigation of an Adaptive Flight-Control System Using a Sinusoidal Test Signal

An analytical study was made of an adaptive flight-control system which measures vehicle response to small-amplitude control-surface deflections produced by a sinusoidal test signal. Changes in the response to this signal are related to environmental changes,, and the system is continuously altered to maintain this response equal to a preselected value. The system is suitable for use in high-performance aircraft and missiles and requires only the addition of a signal generator and a logic circuit consisting of a filter-rectifier network and a comparator-integrator network to a basic command-control system. Thus, it presents a relatively simple approach to the problem. The effects on system performance of variation in flight condition, system-gain level, test-signal frequency, and sensor location are included in the analysis. Longitudinal control of a high-performance research aircraft over flight conditions ranging from landing approach to a Mach number of 5.8 at an altitude of 150,000 feet, and longitudinal control of a four-stage solid-fuel missile including the first bending mode over the atmospheric portion of a launch trajectory constituted the basis for the analytical study. Results of an analog-computer study using time-varying coefficients are presented to compare the control obtained with the adaptive system with-that obtained with a fixed-gain system during the atmospheric portion of a missile launch trajectory. The system has demonstrated an ability to maintain satisfactory vehicle control-system stability over wide ranges of environmental change.

Harris, Jack E.↗
NASA NTRS1981

Flight test of a full authority Digital Electronic Engine Control system in an F-15 aircraft

The Digital Electronic Engine Control (DEEC) system considered is a relatively low cost digital full authority control system containing selectively redundant components and fault detection logic with capability for accommodating faults to various levels of operational capability. The DEEC digital control system is built around a 16-bit, 1.2 microsecond cycle time, CMOS microprocessor, microcomputer system with approximately 14 K of available memory. Attention is given to the control mode, component bench testing, closed loop bench testing, a failure mode and effects analysis, sea-level engine testing, simulated altitude engine testing, flight testing, the data system, cockpit, and real time display.

Barrett, W. J.↗
NASA NTRS1980

Analysis of space shuttle orbiter entry dynamics from Mach 10 to Mach 2.5 with the November 1976 flight control system

A six-degree-of-freedom simulation analysis was performed for the space shuttle orbiter entry from Mach 10 to Mach 2.5 with realistic off-nominal conditions using the flight control system referred to as the November 1976 Integrated Digital Autopilot. The off-nominal conditions included: (1) aerodynamic uncertainties in extrapolating from wind tunnel of flight characteristics, (2) error in deriving angle of attack from onboard instrumentation, (3) failure of two of the four reaction control-system thrusters on each side (design specification), and (4) lateral center-of-gravity offset. Many combinations of these off-nominal conditions resulted in a loss of the orbiter. Control-system modifications were identified to prevent this possibility.

Powell, R. W.↗