Results for “Model reference concept” — Page 8

NASA NTRS1978

Subsonic longitudinal and lateral-directional static aerodynamic characteristics of a general research fighter model employing a strake-wing concept

A general research fighter model was tested in the Langley 7 by 10 foot high speed tunnel at a Mach number of 0.3. Strakes with exposed semi-spans of 10 percent, 20 percent, and 30 percent of the wing reference semi-span were tested in combination with wings having leading edge sweep angles of 30, 44, and 60 degrees. The angle of attack range was from -4 degrees to approximately 48 degrees at sideslip angles of 0, -5, and 5 degrees. The data are presented without analysis in order to expedite publication.

Fox, C. H., Jr.↗

NASA NTRS1987

Implementing system simulation of C3 systems using autonomous objects

The basis of all conflict recognition in simulation is a common frame of reference. Synchronous discrete-event simulation relies on the fixed points in time as the basic frame of reference. Asynchronous discrete-event simulation relies on fixed-points in the model space as the basic frame of reference. Neither approach provides sufficient support for autonomous objects. The use of a spatial template as a frame of reference is proposed to address these insufficiencies. The concept of a spatial template is defined and an implementation approach offered. Discussed are the uses of this approach to analyze the integration of sensor data associated with Command, Control, and Communication systems.

Rogers, Ralph V.↗

NASA NTRS2018

Using Board Games as Subject Matter for Developing Expertise in Model-Based Systems Engineering

As more organizations transition from traditional document-centric systems engineering to a model-based approach, many are challenged to train their staff in new languages, tools, and methodologies, while managing the expectations of stakeholders and their expected model outcomes. In particular, challenges associated with learning a new modeling language and developing skills in the 'art' of modeling present organizations with formidable obstacles to realizing this transition. This paper hypothesizes that systems engineers may more readily learn how to correctly model with SysML, and develop intuition about the art of modeling and using patterns, if their learning references a commonly and thoroughly-understood subject, such as a board game. This paper presents a case for the use of board games as subject matter for new modelers. It demonstrates the concept with a sample model of Hasbro's popular board game, Monopoly, and discusses the limitations of this approach and potential adaptations that may broaden the applicability of the learned skills to projects. Finally, results from a small feasibility assessment and concepts for more formal study to evaluate the hypothesis are presented.

Model-Based Systems Engineering↗

NASA NTRS2018

Using Board Games as Subject Matter for Developing Expertise in Model-Based Systems Engineering

As more organizations transition from traditional document-centric systems engineering to a model-based approach, many are challenged to train their staff in new languages, tools, and methodologies, and manage the expectations of stakeholders and their expected model outcomes. In particular, challenges associated with learning a new modeling language and developing skills in the 'art' of modeling present organizations with formidable obstacles to realizing this transition. This paper hypothesizes that systems engineers may more readily learn how to correctly model with SysML, and develop intuition about the art of modeling and using patterns, if their learning references a commonly and thoroughly-understood subject matter, such as a board game. This paper presents a case for the use of board games as subject matter for new modelers, demonstrates the concept with a sample model of Hasbro's popular board game, Monopoly, and discusses the limitations of this approach and potential adaptations that may broaden the applicability of the learned skills to projects.

Systems Engineering↗

NASA NTRSDate not supplied

Design Considerations for LTV HITL Testing of Pressurized Suited Crew on a Motion-Based Platform

The upcoming NASA Lunar Terrain Vehicle (LTV) will succeed the Apollo Lunar Roving Vehicle, performing both surface exploration and logistics transfer in NASA’s return to the Moon. Human-in-the-Loop (HITL) testing will play a key role in refining the design of the LTV, ensuring its usability and ability to accommodate the astronaut population. A motion-based platform and a lunar terrain and lighting model can simulate the conditions of the lunar south pole region. It can be used by NASA to conduct HITL testing in concert with HITL testing of the drivable Ground Reference Unit (GTU) concept vehicle. The dynamic motion of the platform combined with the mobility restrictions of pressurized suits could help improve NASA understanding of vehicle-suit-astronaut interfaces. NASA human factors practitioners have proposed multiple HITL test series to use the motion-based platform in conjunction with testing of the GTU in hopes that lessons learned can be applied to help select a commercial partner to develop the Artemis LTV.

LTV↗

NASA NTRS1994

Postinstability Models in Dynamics

This paper is devoted to the concept of instability in dynamical systems with the main emphasis on orbital, Hadamard, and Reynolds instabilities. It demonstrates that the requirement about differentiability in dynamics in some cases is not consistent with the physical nature of motions, and may lead to unrealistic solutions. Special attention is paid to the fact that instability is not an invariant of motion: it depends upon frames of reference, the metric of configuration space, and classes of functions selected for mathematical models of physical phenomena. This leads to the possibility of elimination of certain types of instabilities (in particular, those which lead to chaos and turbulence) by enlarging the class of functions using the Reynolds-type transformation in combination with the stabilization principle: the additional terms (the so-called Reynolds stresses) are found from the conditions that they suppress the original instability. Based upon these ideas, a new approach to chaos and turbulence as well as a new mathematical formalism for nonlinear dynamics are discussed.

Zak, Michail↗

NASA NTRSDate not supplied

Recommendations For Developing Space Suit Integrated Food Systems and Delivering Nutrition Before, During, and After Lunar Eva

INTRODUCTION Artemis missions will include a higher tempo and frequency of extravehicular activities (EVAs) than any previous space program. Because of the physical demands expected from the crew, future space suit designs are required to incorporate nutritional support to the astronauts during lunar surface EVAs lasting longer than 4 hours. The purpose of this project was to provide recommendations to aid the development of an in-suit system that can adequately, safely, and acceptably deliver nutrition to a crewmember while confined to a space suit during EVA. METHODS Physiological, logistical, and engineering aspects of potential in-suit nutrition approaches were assessed through literature reviews, assessments of commercial off the shelf (COTS) foods, suit volumetric modeling, and feedback from subject matter experts and crewmembers. Key driving factors in the development of in-suit nutrition requirements included how much and what type of nutrition should be included, what food formulations are appropriate and safe, what are inherent limitations of space suits, what are the potential risks to the crewmember in the suit, and what practices and preferences from astronauts should be considered. Design references were conceptualized and assessed for strengths and limitations as potential in-suit nutrition systems for surface EVA. RESULTS Acute exogenous energy demands vary greatly depending on activity intensity and duration, and partial energy replenishment (i.e., 60–80 kcal∙hr-1 of EVA, or 460–680 kcal for EVAs lasting up to 8 hours) during activities could improve performance, safety, and recovery. COTS foods capable of providing these energy requirements exist; however, no COTS foods have been identified that pass NASA flight standards for microbiological safety and stability. In-suit nutrition delivery design references that were considered included in-suit concepts for a prefilled drink bag, a hydratable drink bag, and a solid food stick. In addition, a helmet feed port concept was considered for use with drink bags external to the suit. Volumetric models of the in-suit drink bag concepts, based on xEMU dimensions, indicate challenges of fitting formulations > 200 ml (equating to approximately 200 kcal). Astronaut feedback on the four concepts indicated that despite some individual preferences for inclusion of solid foods and helmet port designs, the prefilled drink bag concept was the most preferred. A prefilled drink bag can only be used if food safety and stability can be ensured, possibly requiring advancements in food delivery hardware. CONCLUSION The ability to meet the increased need for nutrition during surface EVAs through provision of nutrients in the suited configuration would benefit overall crew health, performance, and morale, and thus increase the likelihood of mission success. It is recommended that in-suit nutrition capabilities provide at least 400–600 kcal within the suit during EVAs lasting > 4 hours and that suit designs include a dedicated volume for food grade nutrition systems. The developed food system should either allow for 1) installation of prefilled (sealed sterile) liquid nutrition in the suit and provide a mechanism to break the seal at the time that consumption is desired or 2) demonstrate that the unsealed food product shelf life allows for safe consumption after at least 12 hours of EVA.

E L Dillon↗

NASA NTRSDate not supplied

Recommendations for Developing Space Suit Integrated Food Systems and Delivering Nutrition Before, During, and After Lunar EVA

INTRODUCTION Artemis missions will include a higher tempo and frequency of extravehicular activities (EVAs) than any previous space program. Because of the physical demands expected from the crew, future space suit designs are required to incorporate nutritional support to the astronauts during lunar surface EVAs lasting longer than 4 hours. The purpose of this project was to provide recommendations to aid the development of an in-suit system that can adequately, safely, and acceptably deliver nutrition to a crewmember while confined to a space suit during EVA. METHODS Physiological, logistical, and engineering aspects of potential in-suit nutrition approaches were assessed through literature reviews, assessments of commercial off the shelf (COTS) foods, suit volumetric modeling, and feedback from subject matter experts and crewmembers. Key driving factors in the development of in-suit nutrition requirements included how much and what type of nutrition should be included, what food formulations are appropriate and safe, what are inherent limitations of space suits, what are the potential risks to the crewmember in the suit, and what practices and preferences from astronauts should be considered. Design references were conceptualized and assessed for strengths and limitations as potential in-suit nutrition systems for surface EVA. RESULTS Acute exogenous energy demands vary greatly depending on activity intensity and duration, and partial energy replenishment (i.e., 60–80 kcal∙hr-1 of EVA, or 460–680 kcal for EVAs lasting up to 8 hours) during activities could improve performance, safety, and recovery. COTS foods capable of providing these energy requirements exist; however, no COTS foods have been identified that pass NASA flight standards for microbiological safety and stability. In-suit nutrition delivery design references that were considered included in-suit concepts for a prefilled drink bag, a hydratable drink bag, and a solid food stick. In addition, a helmet feed port concept was considered for use with drink bags external to the suit. Volumetric models of the in-suit drink bag concepts, based on xEMU dimensions, indicate challenges of fitting formulations > 200 ml (equating to approximately 200 kcal). Astronaut feedback on the four concepts indicated that despite some individual preferences for inclusion of solid foods and helmet port designs, the prefilled drink bag concept was the most preferred. A prefilled drink bag can only be used if food safety and stability can be ensured, possibly requiring advancements in food delivery hardware. CONCLUSION The ability to meet the increased need for nutrition during surface EVAs through provision of nutrients in the suited configuration would benefit overall crew health, performance, and morale, and thus increase the likelihood of mission success. It is recommended that in-suit nutrition capabilities provide at least 400–600 kcal within the suit during EVAs lasting > 4 hours and that suit designs include a dedicated volume for food grade nutrition systems. The developed food system should either allow for 1) installation of prefilled (sealed sterile) liquid nutrition in the suit and provide a mechanism to break the seal at the time that consumption is desired or 2) demonstrate that the unsealed food product shelf life allows for safe consumption after at least 12 hours of EVA.

space suit↗

NASA NTRS1999

Advanced Interactive Display Formats for Terminal Area Traffic Control

This research project deals with an on-line dynamic method for automated viewing parameter management in perspective displays. Perspective images are optimized such that a human observer will perceive relevant spatial geometrical features with minimal errors. In order to compute the errors at which observers reconstruct spatial features from perspective images, a visual spatial-perception model was formulated. The model was employed as the basis of an optimization scheme aimed at seeking the optimal projection parameter setting. These ideas are implemented in the context of an air traffic control (ATC) application. A concept, referred to as an active display system, was developed. This system uses heuristic rules to identify relevant geometrical features of the three-dimensional air traffic situation. Agile, on-line optimization was achieved by a specially developed and custom-tailored genetic algorithm (GA), which was to deal with the multi-modal characteristics of the objective function and exploit its time-evolving nature.

Grunwald, Arthur J.↗

NASA NTRS1999

Plug and Play Integration through Space Object Standardization

Plug and play is an industry standard promoted by Intel and Microsoft, and others that allows users to add and remove various input and output devices without making specific customizations to their systems. The idea behind concept is that using standard products eases integration of components and promotes capabilities of conforming products. The concept works because vendors comply with a standard specification. This paper reports the development of a reference architecture for the mission control domain, which is leveraging off this revolutionary concept. Standards are being developed at the application layer, which enable "plug and play" of mission software products. A Mission Control, reference architecture has been defined. For each sub-domain, the interfaces are modeled in Interface Definition Language (IDL). A subset of the IDL has been developed within both commercial off-the-shelf (COTS) and government (GOTS) products. Selected vendors have agreed to modify their products to be compatible with the defined IDL. The plug and play integration of these different products has been validated in a demonstration testbed.

Boyce, Leslye↗

NASA NTRS1999

Advanced Interactive Display Formats for Terminal Area Traffic Control

This research project deals with an on-line dynamic method for automated viewing parameter management in perspective displays. Perspective images are optimized such that a human observer will perceive relevant spatial geometrical features with minimal errors. In order to compute the errors at which observers reconstruct spatial features from perspective images, a visual spatial-perception model was formulated. The model was employed as the basis of an optimization scheme aimed at seeking the optimal projection parameter setting. These ideas are implemented in the context of an air traffic control (ATC) application. A concept, referred to as an active display system, was developed. This system uses heuristic rules to identify relevant geometrical features of the three-dimensional air traffic situation. Agile, on-line optimization was achieved by a specially developed and custom-tailored genetic algorithm (GA), which was to deal with the multi-modal characteristics of the objective function and exploit its time-evolving nature.

Grunwald, Arthur J.↗

NASA NTRS1990

Synthesis of individual rotor blade control system for gust alleviation

The utilization of rotor flapping in synthesizing an Individual Blade Control (IBC) system for gust alleviation is demonstrated. The objective is to illustrate and seek to improve Ham's IBC method. A sensor arrangement with two accelerometers mounted on the root and tip of a blade is proposed for estimating of flapping states for feedback control. Equivalent swash plate implementation of IBC is also deliberated. The study concludes by addressing the concept of general rotor states feedback, of which the IBC method is a special case. The blade flapping equation of motion is derived. Ham's original IBC method and a modified IBC scheme called Model Reference (MRIBC) are examined, followed by simulation study with ideal measurements and relative performances of the two methods. The practical aspects of IBC implementation are presented. Different configuration of sensors and their merits are considered. The realization of IBC using equivalent swash plate instead of direct actuator motion is discussed. It is shown that IBC is a particular case of rotor states feedback. The idea of general rotor states feedback is further elaborated. Finally, major conclusions are given.

Wang, Ji C.↗

NASA NTRS1990

Automated extraction of knowledge for model-based diagnostics

The concept of accessing computer aided design (CAD) design databases and extracting a process model automatically is investigated as a possible source for the generation of knowledge bases for model-based reasoning systems. The resulting system, referred to as automated knowledge generation (AKG), uses an object-oriented programming structure and constraint techniques as well as internal database of component descriptions to generate a frame-based structure that describes the model. The procedure has been designed to be general enough to be easily coupled to CAD systems that feature a database capable of providing label and connectivity data from the drawn system. The AKG system is capable of defining knowledge bases in formats required by various model-based reasoning tools.

Gonzalez, Avelino J.↗

NASA NTRS1991

Bioregenerative life support - The initial CELSS reference configuration

The next major step in the development of an operational Controlled Ecological Life-Support System (CELSS) is the creation of a human-rated ground-based demonstrator able to constitute a CELSS's proof-of-concept. The reference configuration recently devised for such a ground facility by NASA will furnish a common reference to all investigators in the field, thereby facilitating performance comparisons among candidate subsystems and clarifying system-level modeling. A detailed NASA reference CELSS flowcharting is presented.

Rummel, John D.↗

NASA NTRS2011

Performance Characterization and Simulation of Amine-Based Vacuum Swing Adsorption Units for Spacesuit Carbon Dioxide and Humidity Control

Controlling carbon dioxide (CO2) and water (H2O) concentrations in the vapor phase of a space suit is critical to ensuring an astronauts safety, comfortability, and capability to perform extra-vehicular activity (EVA) tasks. Historically, this has been accomplished using lithium hydroxide (LiOH) and metal oxides (MetOx). Lithium hydroxide is a consumable material and requires priming with water before it becomes effective at removing carbon dioxide. MetOx is regenerable through a power-intensive thermal cycle but is significantly heavier on a volume basis than LiOH. As an alternative, amine-based vacuum swing beds are under aggressive development for EVA applications which control atmospheric concentrations of both CO2 and H2O through a fully-regenerative process. The current concept, referred to as the rapid cycle amine (RCA), has resulted in numerous laboratory prototypes. Performance of these prototypes have been assessed and documented from experimental and theoretical perspectives. To support developmental efforts, a first principles model has also been established for the vacuum swing adsorption technology. The efforts documented herein summarize performance characterization and simulation results for several variable metabolic profiles subjected to the RCA. Furthermore, a variety of control methods are explored including timed swing cycles, instantaneous CO2 feedback control, and time-averaged CO2 feedback control. A variety of off-nominal tests are also explored including high/low suit temperatures, increasingly high humidity cases, and dynamic pressure cases simulating the suit pre-breathe protocol. Consequently, this work builds on efforts previous efforts to fully bound the performance of the rapid cycle amine under a variety of nominal and off-nominal conditions.

Swickrath, Michael J.↗

NASA NTRS2012

Performance Characterization and Simulation of Amine-Based Vacuum Swing Sorption Units for Spacesuit Carbon Dioxide and Humidity Control

Controlling carbon dioxide (CO2) and water (H2O) vapor concentrations in a space suit is critical to ensuring an astronauts safety, comfort, and capability to perform extra-vehicular activity (EVA) tasks. Historically, this has been accomplished using lithium hydroxide (LiOH) and metal oxide (MetOx) canisters. Lithium hydroxide is a consumable material that requires priming with water before it becomes effective at removing carbon dioxide. MetOx is regenerable through a power-intensive thermal cycle but is significantly heavier on a volume basis than LiOH. As an alternative, amine-based vacuum swing beds are under aggressive development for EVA applications. The vacuum swing units control atmospheric concentrations of both CO2 and H2O through fully-regenerative process. The current concept, referred to as the rapid cycle amine (RCA), has resulted in numerous laboratory prototypes. Performance of these prototypes have been assessed experimentally and documented in previous reports. To support developmental e orts, a first principles model has also been established for the vacuum swing sorption technology. For the first time in several decades, a major re-design of Portable Life Support System (PLSS) for the extra-vehicular mobility unit (EMU) is underway. NASA at Johnson Space Center built and tested an integrated PLSS test bed of all subsystems under a variety of simulated EVA conditions of which the RCA prototype played a significant role. The efforts documented herein summarize RCA test performance and simulation results for single and variable metabolic rate experiments in an integrated context. In addition, a variety of off-nominal tests were performed to assess the capability of the RCA to function under challenging circumstances. Tests included high water production experiments, degraded vacuum regeneration, and deliberate valve/power failure and recovery.

Swickrath, Michael J.↗

NASA NTRS2015

DAIDALUS: Detect and Avoid Alerting Logic for Unmanned Systems

This paper presents DAIDALUS (Detect and Avoid Alerting Logic for Unmanned Systems), a reference implementation of a detect and avoid concept intended to support the integration of Unmanned Aircraft Systems into civil airspace. DAIDALUS consists of self-separation and alerting algorithms that provide situational awareness to UAS remote pilots. These algorithms have been formally specified in a mathematical notation and verified for correctness in an interactive theorem prover. The software implementation has been verified against the formal models and validated against multiple stressing cases jointly developed by the US Air Force Research Laboratory, MIT Lincoln Laboratory, and NASA. The DAIDALUS reference implementation is currently under consideration for inclusion in the appendices to the Minimum Operational Performance Standards for Unmanned Aircraft Systems presently being developed by RTCA Special Committee 228.

Munoz, Cesar↗

NASA NTRS1984

Necessary and sufficient conditions for parameter convergence in adaptive control

Consideration is given to the concept of a reference signal which is sufficient to cause the parameter error in an adaptive control system to converge to zero. Simple and necessary conditions for the convergence of the parameter error are established for a model reference adaptive control (MRAC) system having a relative degree of one. The exponential stability of the MRAC under persistent excitation (PE) is also considered. Full proofs of the theoretical arguments are given in a companion paper.

Boyd, S.↗