Results for “Flight Control System” — Page 45

NASA NTRS1980

Reliability validation of systems for life-critical applications

A framework is proposed which addresses traditional reliability validation approaches consisting of life testing techniques which are inapplicable for digital flight control systems. A specific validation methodology is identified based on logical proofs, analytical modeling, and experimental testing. Research activities required to support continued development of validation technology are identified, and the validation procedure is driven by the reliability model obtained from the system description. The analytical reliability model is shown to be a proper abstraction of the system under consideration, and a proof of correctness of system design and system scheduler performance is proposed.

Trivedi, K. S.↗

NASA NTRS1958

X-15 hydraulic-system development

Despite the exacting requirements and conditions of the X-15 including much higher temperature, high horsepower, and extreme vibration and duty cycles, the hydraulic flight control systems compare favorably, weightwise, with preceding models. Although some items, such as the pumps, are heavier, the total system, excluding actuators, weighs approximately 195 pounds as compared with 196 pounds for the F-107A airplane. Use of the new piggy-back pump, with its low flow during most of the operating time, also permitted a reduction in fluid capacity of the hydraulic reservoirs and the total systems, even though the volume of some of the actuators is quite large. This effected a considerable saving in fluid weight. Complete ground-support equipment is available and this equipment, as well as the airplane systems, contains means for complete 5- to 15- micron filtration under controlled temperature conditions. By use of advanced engineering techniques and extensive laboratory testing, it has been possible to provide a sound, lightweight hydraulic system for this advanced, high-performance airplane. (author)

Culleton, R J↗

NASA NTRSDate not supplied

Control Architecture for a Concept Aircraft with a Series/Parallel Partial Hybrid Powertrain and Distributed Electric Propulsion

Traditional aircraft propulsion control approaches are insufficient for electrified aircraft powertrains due to their increased complexity compared to current systems. New control approaches are required to manage the increased interdependency and complexity of these electrified powertrains. Additionally, electrification enables aircraft to have multiple distributed thrust producing fans that the flight control system can leverage for enhanced maneuverability, further increasing the control complexity. This paper describes the control architecture for a concept vehicle with these characteristics, the SUbsonic Single Aft eNgine (SUSAN) Electrofan. SUSAN is a series/parallel partial hybrid electric single-aisle transport aircraft that leverages its electrified powertrain to provide fuel burn and emissions benefits when compared to the state-of-the-art. Achieving these benefits requires an appropriately designed control architecture that coordinates the various powertrain and flight control subsystems. As such, the SUSAN aircraft is designed with a high level of automation, allowing it to properly manage coupled subsystems and react rapidly to failures and anomalies. This paper presents a summary of the SUSAN powertrain design and discusses several of the novel control approaches used to manage the complex electrified powertrain.

Control↗

NASA NTRSDate not supplied

Control Architecture for a Concept Aircraft with a Series/Parallel Partial Hybrid Powertrain and Distributed Electric Propulsion

Traditional aircraft propulsion control approaches are insufficient for electrified aircraft powertrains due to their increased complexity compared to current systems. New control approaches are required to manage the increased interdependency and complexity of these electrified powertrains. Additionally, electrification enables aircraft to have multiple distributed thrust producing fans that the flight control system can leverage for enhanced maneuverability, further increasing the control complexity. This paper describes the control architecture for a concept vehicle with these characteristics, the SUbsonic Single Aft eNgine (SUSAN) Electrofan. SUSAN is a series/parallel partial hybrid electric single-aisle transport aircraft that leverages its electrified powertrain to provide fuel burn and emissions benefits when compared to the state-of-the-art. Achieving these benefits requires an appropriately designed control architecture that coordinates the various powertrain and flight control subsystems. As such, the SUSAN aircraft is designed with a high level of automation, allowing it to properly manage coupled subsystems and react rapidly to failures and anomalies. This paper presents a summary of the SUSAN powertrain design and discusses several of the novel control approaches used to manage the complex electrified powertrain.

Control↗

NASA NTRS2023

Control Architecture for a Concept Aircraft with a Series/Parallel Partial Hybrid Powertrain and Distributed Electric Propulsion

Traditional aircraft propulsion control approaches are insufficient for electrified aircraft powertrains due to their increased complexity compared to current systems. New control approaches are required to manage the increased interdependency and complexity of these electrified powertrains. Additionally, electrification enables aircraft to have multiple distributed thrust producing fans that the flight control system can leverage for enhanced maneuverability, further increasing the control complexity. This paper describes the control architecture for a concept vehicle with these characteristics, the SUbsonic Single Aft eNgine (SUSAN) Electrofan. SUSAN is a series/parallel partial hybrid electric single-aisle transport aircraft that leverages its electrified powertrain to provide fuel burn and emissions benefits when compared to the state-of-the-art. Achieving these benefits requires an appropriately designed control architecture that coordinates the various powertrain and flight control subsystems. As such, the SUSAN aircraft is designed with a high level of automation, allowing it to properly manage coupled subsystems and react rapidly to failures and anomalies. This paper presents a summary of the SUSAN powertrain design and discusses several of the novel control approaches used to manage the complex electrified powertrain.

Control↗

NASA NTRS1985

A method to stabilize linear systems using eigenvalue gradient information

Formal optimization methods and eigenvalue gradient information are used to develop a stabilizing control law for a closed loop linear system that is initially unstable. The method was originally formulated by using direct, constrained optimization methods with the constraints being the real parts of the eigenvalues. However, because of problems in trying to achieve stabilizing control laws, the problem was reformulated to be solved differently. The method described uses the Davidon-Fletcher-Powell minimization technique to solve an indirect, constrained minimization problem in which the performance index is the Kreisselmeier-Steinhauser function of the real parts of all the eigenvalues. The method is applied successfully to solve two different problems: the determination of a fourth-order control law stabilizes a single-input single-output active flutter suppression system and the determination of a second-order control law for a multi-input multi-output lateral-directional flight control system. Various sets of design variables and initial starting points were chosen to show the robustness of the method.

Wieseman, C. D.↗

NASA NTRS1986

Evaluation of reliability modeling tools for advanced fault tolerant systems

The Computer Aided Reliability Estimation (CARE III) and Automated Reliability Interactice Estimation System (ARIES 82) reliability tools for application to advanced fault tolerance aerospace systems were evaluated. To determine reliability modeling requirements, the evaluation focused on the Draper Laboratories' Advanced Information Processing System (AIPS) architecture as an example architecture for fault tolerance aerospace systems. Advantages and limitations were identified for each reliability evaluation tool. The CARE III program was designed primarily for analyzing ultrareliable flight control systems. The ARIES 82 program's primary use was to support university research and teaching. Both CARE III and ARIES 82 were not suited for determining the reliability of complex nodal networks of the type used to interconnect processing sites in the AIPS architecture. It was concluded that ARIES was not suitable for modeling advanced fault tolerant systems. It was further concluded that subject to some limitations (the difficulty in modeling systems with unpowered spare modules, systems where equipment maintenance must be considered, systems where failure depends on the sequence in which faults occurred, and systems where multiple faults greater than a double near coincident faults must be considered), CARE III is best suited for evaluating the reliability of advanced tolerant systems for air transport.

Baker, Robert↗

NASA NTRS1994

Parameter identification for X-31A at high angles of attack

The U.S./German experimental aircraft X-31A was designed and constructed to demonstrate enhanced fighter maneuverability. Post-stall maneuvering is enabled by applying new technologies such as high angle of attack aerodynamics and flight control system integrated thrust vectoring. Two demonstrator aircraft have been built by the main contractors, Rockwell International and Deutsche Aerospace (formerly MBB). Flight testing started in October 1990 and before the end of 1992 both aircraft had accomplished a significant number of flights covering the entire AoA regime from about -5 to 70 deg. Throughout the envelope expansion, DLR Institute of Flight Mechanics conducted parameter identification (PID) to determine the aerodynamic parameters of the aircraft from flight test data and to compare the results to the predictions from the aerodynamic dataset (ADS). The application of system identification to high AoA / post-stall flight data raises some major problems, which are discussed in this paper. Results from both longitudinal and lateral-directional motion will be presented.

S Weiss↗

NASA NTRS1996

Free-flight investigation of forebody blowing for stability and control

A free-flight wind-tunnel investigation was conducted on a generic fighter model with forebody pneumatic vortex control for high angle-of-attack directional control. This is believed to be the first flight demonstration of a forebody blowing concept integrated into a closed-loop flight control system for stability augmentation and control. The investigation showed that the static wind tunnel estimates of the yaw control available generally agreed with flight results. The control scheme for the blowing nozzles consisted of an on/off control with a deadband. Controlled flight was obtained for the model using forebody blowing for directional control to beyond 45 deg. angle of attack.

Brandon, Jay M.↗

NASA NTRS2002

Eigenstructure Assignment for Fault Tolerant Flight Control Design

In recent years, fault tolerant flight control systems have gained an increased interest for high performance military aircraft as well as civil aircraft. Fault tolerant control systems can be described as either active or passive. An active fault tolerant control system has to either reconfigure or adapt the controller in response to a failure. One approach is to reconfigure the controller based upon detection and identification of the failure. Another approach is to use direct adaptive control to adjust the controller without explicitly identifying the failure. In contrast, a passive fault tolerant control system uses a fixed controller which achieves acceptable performance for a presumed set of failures. We have obtained a passive fault tolerant flight control law for the F/A-18 aircraft which achieves acceptable handling qualities for a class of control surface failures. The class of failures includes the symmetric failure of any one control surface being stuck at its trim value. A comparison was made of an eigenstructure assignment gain designed for the unfailed aircraft with a fault tolerant multiobjective optimization gain. We have shown that time responses for the unfailed aircraft using the eigenstructure assignment gain and the fault tolerant gain are identical. Furthermore, the fault tolerant gain achieves MIL-F-8785C specifications for all failure conditions.

Sobel, Kenneth↗

NASA NTRS1976

Simulation test results for lift/cruise fan research and technology aircraft

A flight simulation program was conducted on the flight simulator for advanced aircraft (FSAA). The flight simulation was a part of a contracted effort to provide a lift/cruise fan V/STOL aircraft mathematical model for flight simulation. The simulated aircraft is a configuration of the Lift/Cruise Fan V/STOL research technology aircraft (RTA). The aircraft was powered by three gas generators driving three fans. One lift fan was installed in the nose of the aircraft, and two lift/cruise fans at the wing root. The thrust of these fans was modulated to provide pitch and roll control, and vectored to provide yaw, side force control, and longitudinal translation. Two versions of the RTA were defined. One was powered by the GE J97/LF460 propulsion system which was gas-coupled for power transfer between fans for control. The other version was powered by DDA XT701 gas generators driving 62 inch variable pitch fans. The flight control system in both versions of the RTA was the same.

Bland, M. P.↗

NASA NTRS1977

Space Shuttle Orbiter Approach and Landing Test Evaluation Report. Captive-Active Flight Test Summary

Captive-active tests consisted of three mated carrier aircraft/Orbiter flights with an active manned Orbiter. The objectives of this series of flights were to (1) verify the separation profile, (2) verify the integrated structure, aerodynamics, and flight control system, (3) verify Orbiter integrated system operations, and (4) refine and finalize carrier aircraft, Orbiter crew, and ground procedures in preparation for free flight tests. A summary description of the flights is presented with assessments of flight test requirements, and of the performance operations, and of significant flight anomalies is included.

Source record↗

NASA NTRS1979

Math modeling and computer mechanization for real time simulation of rotary-wing aircraft

Mathematical modeling and computer mechanization for real time simulation of rotary wing aircraft is discussed. Error analysis in the digital simulation of dynamic systems, such as rotary wing aircraft is described. The method for digital simulation of nonlinearities with discontinuities, such as exist in typical flight control systems and rotor blade hinges, is discussed.

Howe, R. M.↗

NASA NTRS1986

RT_BUILD: An expert programmer for implementing and simulating Ada real-time control software

The RT BUILD is an expert control system programmer that creates real-time Ada code from block-diagram descriptions of control systems. Since RT BUILD embodies substantial knowledge about the implementation of real-time control systems, it can perform many, if not most of the functions normally performed by human real-time programmers. Though much basic research was done in automatic programming, RT BUILD appears to be the first application of this research to an important problem in flight control system development. In particular, RT BUILD was designed to directly increase productivity and reliability for control implementations of large complex systems.

Lehman, Larry L.↗

NASA NTRS2019

"Sensor Web Evolution - Webs of Webs for NASA Science - Focus on small Uninhabited Aerial Systems (sUAS)"

This paper will describe the evolution of information collection, derivation and delivery mechanisms in webs of NASA sensor webs, with a focus on recent advancements in small Uninhabited Aerial Systems (sUAS). I will discuss the movement to "Fog Computing", also known as Edge Computing. Fog Computing facilitates the distribution of common operations and networking between edge devices and cloud computing facilities, optimizing the production of actionable intelligence. Initially, sUASs utilized onboard data collection as standard, with minimal data downloaded directly. Information products were derived in conventional computational environments, generally desk top computers, and information products made available to the Science Community in weeks or months. With the increased availability, and increasingly lower costs, of beyond line of sight (BLOS) satellite based communication, transmission rates and data volumes increased, and processing migrated to Cloud based services. Contemporary sUASs are moving some of that information product derivation to on vehicle services, and are creating a distributed Cloud/Fog environment. I will describe the technological advances that have made this possible, including low power multi-core Central Processing Units (CPU), and, more recently, the availability of high end Graphical Processing Units (GPU) that consume only a few watts. Intelligent system software, leveraging these hardware advances, finally allows for information product generation on-board, rather than simple data collection. Additionally, intelligent flight control systems now support mutual vehicle to vehicle collaboration, allowing sUASs to create ad-hoc sensor webs on demand, as required. Also discussed will be the lessons learned by the Authors' development of data systems for NASA's large High Altitude Long Endurance (HALE) UASs like Predator and Global Hawk, and how those lessons are being applied to sUAS development. This paper will focus on application, rather a deep dive into the technology, and will highlight improving data management through these new technologies.

Sensor Web↗

NASA NTRSDate not supplied

UASs in the VOG/Edge/FOG Sensor Web Environment

This paper will describe the evolution of information collection, derivation and delivery mechanisms in sensor webs utilizing Uninhabited Aerial Systems (UAS).We will discuss the movement to "Fog Computing", also known as Edge Computing. Fog Computing facilitates the distribution of common operations and networking between edge devices and cloud computing facilities, optimizing the production of actionable intelligence. Initially, UASs utilized onboard data collection as standard, with minimal data downloaded directly. Information products were derived in conventional computational environments, generally desk top computers, and information products made available to the Science Community in weeks or months. With the increased availability, and increasingly lower costs, of beyond line of sight (BLOS) satellite based communication, transmission rates and data volumes increased, and processing migrated to Cloud based services. Contemporary UASs are moving some of that information product derivation to on vehicle services, and are creating a distributed Cloud/Fog environment. The Author will describe the technological advances that have made this possible, including low power multi-core Central Processing Units (CPU), and, more recently, the availability of high end Graphical Processing Units (GPU) that consume only a few watts. Intelligent system software, leveraging these hardware advances, finally allows for information product generation on-board, rather than simple data collection. Additionally, intelligent flight control systems now support mutual vehicle to vehicle collaboration, allowing UASs to create ad-hoc sensor webs on demand, as required. Also discussed will be the lessons learned by the Authors' development of data systems for NASA's large High Altitude Long Endurance (HALE) UASs like Predator and Global Hawk, and how those lessons are being applied to other UAS development This paper will focus on applications, rather a deep dive into the technology, and will highlight improving data management through these new technologies.

UAS↗

NASA NTRS2008

Aerodynamic Effects and Modeling of Damage to Transport Aircraft

A wind tunnel investigation was conducted to measure the aerodynamic effects of damage to lifting and stability/control surfaces of a commercial transport aircraft configuration. The modeling of such effects is necessary for the development of flight control systems to recover aircraft from adverse, damage-related loss-of-control events, as well as for the estimation of aerodynamic characteristics from flight data under such conditions. Damage in the form of partial or total loss of area was applied to the wing, horizontal tail, and vertical tail. Aerodynamic stability and control implications of damage to each surface are presented, to aid in the identification of potential boundaries in recoverable stability or control degradation. The aerodynamic modeling issues raised by the wind tunnel results are discussed, particularly the additional modeling requirements necessitated by asymmetries due to damage, and the potential benefits of such expanded modeling.

Shah, Gautam H.↗

NASA NTRS1983

Design, implementation and flight testing of PIF autopilots for general aviation aircraft

The designs of Proportional-Integrated-Filter (PIF) auto-pilots for a General Aviation (NAVION) aircraft are presented. The PIF autopilot uses the sampled-data regulator and command generator tracking to determine roll select, pitch select, heading select, altitude select and localizer/glideslope capture and hold autopilot modes. The PIF control law uses typical General Aviation sensors for state feedback, command error integration for command tracking, digital complementary filtering and analog prefiltering for sensor noise suppression, a control filter for computation delay accommodation and the incremental form to eliminate trim values in implementation. Theoretical developments described in detail, were needed to combine the sampled-data regulator with command generator tracking for use as a digital flight control system. The digital PIF autopilots are evaluated using closed-loop eigenvalues and linear simulations. The implementation of the PIF autopilots in a digital flight computer using a high order language (FORTRAN) is briefly described. The successful flight test results for each PIF autopilot mode is presented.

Broussard, J. R.↗