Control of a continuum electromechanical instability.
Continuum mechanical and electromechanical systems instability control by means of active distributed coupling structures
SYSTEMS ANALYSIS↗
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Results for “distributed controls”
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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High performance architecture for robot control
Practical aspects of the design and implementation of a modular, high performance, parallel computer control system for telerobots are discussed. Topics of consideration include system architecture, operator interface, and control execution. In a laboratory environment, a telerobotics test control configuration is used to obtain measurements on communications and control loop timing for use in an effective full scale operational system design. The feasibility of the selected architectural approach has been successfully demonstrated. The modularity of the software and hardware enables ease of transport for use in the operational system. The distributed partioning of the control algorithms and the performance measurements acquired during control system implementation are discussed.
Byler, E.↗
Dynamic model and cooperative control of a serially linked manipulator system
The use of a redundant manipulator to execute multiple tasks specified at different points on the manipulator is demonstrated. This is accomplished by decomposing a redundant arm at an intermediate arm location called the 'elbow' into two nonredundant local arms referred as the 'basearm' and the 'forearm'. This decomposition transforms a redundant arm into a serially linked dual-arm system, where the cooperation between the basearm and the forearm is carried out through the task distribution and the elbow control. The kinematics of a decomposed redundant manipulator are discussed, and a Cartesian space dynamic model and dynamic equation of a decomposed redundant manipulator are presented. The capability of generating Cartesian force, the local efficiency of generating Cartesian acceleration, and dynamic task distribution are discussed.
Lee, Sukhan↗
A framework for real-time distributed expert systems: On-orbit spacecraft fault diagnosis, monitoring and control
Control of on-orbit operation of a spacecraft requires retention and application of special purpose, often unique, knowledge of equipment and procedures. Real-time distributed expert systems (RTDES) permit a modular approach to a complex application such as on-orbit spacecraft support. One aspect of a human-machine system that lends itself to the application of RTDES is the function of satellite/mission controllers - the next logical step toward the creation of truly autonomous spacecraft systems. This system application is described.
Mullikin, Richard L.↗
Fundamental problems of injector design
The principal control of the combustion within a liquid-propellant rocket thrust chamber is provided by the injector. Only when precise control of the injection process is attained can optimum performance, dynamic stability, heat transfer compatibility and reproducibility be provided. Control must be designed into each step of the injection process with sufficient isolation provided to insure stability. In the design of the injector manifolding, the main desire is to provide mass and mixture ratio regulation across the injector face. The design of the injector orifices must be such that this mass and mixture ratio control is retained through the orifices and imparted to the droplet sprays that are produced. Furthermore, the orifice design must control the size and distribution of the droplets generated so that combustion will be completed within the chamber. Mechanical damping devices are often required to protect the early mixing zone from transverse velocities and associated displacement effects in the chamber. Only when each phase of the injection process is carefully controlled can the design aims be reached.
David T Harrje↗
Rock sampling
A method for sampling rock and other brittle materials and for controlling resultant particle sizes is described. The method involves cutting grooves in the rock surface to provide a grouping of parallel ridges and subsequently machining the ridges to provide a powder specimen. The machining step may comprise milling, drilling, lathe cutting or the like; but a planing step is advantageous. Control of the particle size distribution is effected primarily by changing the height and width of these ridges. This control exceeds that obtainable by conventional grinding.
Blum, P.↗
Cost comparison of competing local distribution systems for communication satellite traffic
The boundaries of market areas which favor various means for distributing communications satellite traffic are considered. The distribution methods considered are: control Earth station with cable access, rooftop Earth stations, Earth station with radio access, and various combinations of these methods. The least cost system for a hypothetical region described by number of users and the average cable access mileage is discussed. The region is characterized by a function which expresses the distribution of users. The results indicate that the least cost distribution is central Earth station with cable access for medium to high density areas of a region combined with rooftop Earth stations or (for higher volumes) radio access for remote users.
Dopfel, F. E.↗
Telerobotic research for in-space structural assembly and servicing
The paper reviews Langley's Telerobotic Technology Program and the recent and planned research in automated space assembly. Research areas include multiple manipulator coordination and control, automatic modes, evaluation of control modalities for teleoperated tasks, active sensing for world modeling and control, and architectures for distributed telerobotic systems. Studies of master/slave teleoperators performing representative space tasks showed that current teleoperator systems can be used to accomplish remote space operations. These studies also identified that research is required to improve the systems to reduce operator workload and task completion time. Closed-loop noncontact and contact sensor based control for automatic acquisition, positioning, and active compliance have been developed. A control structure for multiple manipulator coordination and control with manual, shared, and automatic modes performing space type tasks is being evaluated.
Meintel, Alfred J., Jr.↗
Comparison of analytical and experimental subsonic steady and unsteady pressure distributions for a high-aspect-ratio-supercritical wing model with oscillating control surfaces
The results of a comparative study using the unsteady aerodynamic lifting surface theory, known as the Doublet Lattice method, and experimental subsonic steady- and unsteady-pressure measurements, are presented for a high-aspect-ratio supercritical wing model. Comparisons of pressure distributions due to wing angle of attack and control-surface deflections were made. In general, good correlation existed between experimental and theoretical data over most of the wing planform. The more significant deviations found between experimental and theoretical data were in the vicinity of control surfaces for both static and oscillatory control-surface deflections.
Mccain, W. E.↗
System Engineering on the Use for Ares I,V - the Simpler, the Better
The Ares I and Ares V Vehicles will utilize the J-2X rocket engine developed for NASA by the Pratt & Whitney Rocketdyne Company. The J-2X is an improved higher power version of the original J-2 engine used during the Apollo program. With higher power and updated requirements for safety and performance, the J-2X becomes a new engine using state-of-the-art design methodology, materials and manufacturing processes. The implementation of Systems Engineering (SE) principles enables the rapid J-2X development program to remain aligned with the ARES I and V vehicle programs, Meeting the aggressive development schedule is a challenge. Coordinating the best expertise thai NASA and PWR have to offer requires effectively utilizing resources at multiple sites. This presents formidable communication challenges. SE allows honest and open discussions of issues and problems. This simple idea is often overlooked in large and complex SE programs. Regular and effective meetings linking SE objectives to component designs are used to voice differences of opinions with customer and contractor in attendance so that the best mutual decisions can be made on the shortest possible schedule. Regular technical interchange meetings on secure program wide computer networks and CM processes are effective,in the "Controlled Change" process that exemplifies good SE. Good communication is a key effective SE implementation. The System of Systems approach is the vision of the Orion program which facilitates the establishment of dynamic SE processes at all levels including the engine. SE enables requirements evolution by facilitating organizational and process agility. Flow down and distribution of requirements is controlled by Allocation Reports which breakdown numerical design objectives (weight, reliability, etc.) into quanta goals for each component area. Linked databases of design and verification requirements helps eliminate redundancy and potential mistakes inherent m separated systems. Another tool, the Architecture Design Description, is being used to control J-2X system architecture and effectively communicate configuration changes to those involved in the design process. But the proof is in successful program accomplishment. The SE is the methodology being used to meet the challenge of completing J-2X engine certification 2 years ahead of any engine program ever developed at PWR. The Ares I SE system of systems has delivered according to expectations thus far. All major design reviews (SRR. PDR, CDR) have been successfully conducted to satisfy overall program objectives using SE as the basis for accomplishment. The paper describes SE tools and techniques utilized to achieve this success.
Kelly, William↗
Algebraic grid generation for coolant passages of turbine blades with serpentine channels and pin fins
In order to study numerically details of the flow and heat transfer within coolant passages of turbine blades, a method must first be developed to generate grid systems within the very complicated geometries involved. In this study, a grid generation package was developed that is capable of generating the required grid systems. The package developed is based on an algebraic grid generation technique that permits the user considerable control over how grid points are to be distributed in a very explicit way. These controls include orthogonality of grid lines next to boundary surfaces and ability to cluster about arbitrary points, lines, and surfaces. This paper describes that grid generation package and shows how it can be used to generate grid systems within complicated-shaped coolant passages via an example.
Shih, T. I.-P.↗
Frequency and timing system for the consolidated DSN and STDN tracking network
The consolidation on the existing Deep Space Network (DSN) and colocated Goddard Spaceflight Tracking and Data Network (STDN) stations into a multiple antenna array is discussed. Each site includes a signal processing center (SPC) centered in an array of four or five antennas each located within approximately 300 to 800 meters of the SPC. A central frequency and timing system (FTS) located in the SPC contains reference frequency, timing and time code generation, and distribution equipment for both the SPC and each antenna with its associated front end antenna control building. The reference frequency distribution and clock equipment are driven by a hydrogen maser as the prime frequency standard with cesium beam frequency standard as the secondary.
Coffin, R. C.↗
Thermal control for the 1990's
Current thermal distribution systems on large spacecraft, such as the Space Shuttle and Spacelab, use pumped fluid loops that circulate the coolant between a series of user stations and a single rejection point, involving complex plumbing and controls with a significant power penalty and limited reliability. In order to provide heat transport at near-isothermal conditions in future large spacecraft, two-phase flow systems will be implemented by taking advantage of the heat of vaporization and condensation of common working fluids at minimal expenditure of power and temperature variation. Such systems are considered for the cases of the thermal requirements of nearly 100 potential astrophysics and astronomy instruments. Data on temperature requirements, power dissipations, environmental fluxes, heat addition or rejection, and general description, are used to form conceptual designs for the thermal utility.
Ollendorf, S.↗
A development framework for distributed artificial intelligence
The authors describe distributed artificial intelligence (DAI) applications in which multiple organizations of agents solve multiple domain problems. They then describe work in progress on a DAI system development environment, called SOCIAL, which consists of three primary language-based components. The Knowledge Object Language defines models of knowledge representation and reasoning. The metaCourier language supplies the underlying functionality for interprocess communication and control access across heterogeneous computing environments. The metaAgents language defines models for agent organization coordination, control, and resource management. Application agents and agent organizations will be constructed by combining metaAgents and metaCourier building blocks with task-specific functionality such as diagnostic or planning reasoning. This architecture hides implementation details of communications, control, and integration in distributed processing environments, enabling application developers to concentrate on the design and functionality of the intelligent agents and agent networks themselves.
Adler, Richard M.↗
SCDM in a Distributed Environment
The Software Configuration Management (SCM) of the Space Launch Initiative (SLI) Advanced Engineering Environment (AEE) products is performed in a distributed environment-meaning the activities performed during the project lifecycle are across numerous NASA Centers, facilities, organizations, colleges and industry. SCM is the glue that holds the project and products together-especially in a distributed environment. It identifies, controls, accounts, and verified the details of the products; the schedule of activities; the assigned responsibilities; and the required resources, including staff, tools, and computer facilities. Data/document management (DM) captures and conveys the SCM and project efforts. SCM and DM are integrally linked; hence, Software Configuration and Data Management (SCDM). This paper discusses one team's challenges in implementing SCDM in a distributed environment. The distributed nature of the project introduces new opportunities for moving SCDM to the next level of usefulness in today's high-tech development arena. The lessons learned from the implementation of distributed SCDM in support of the SLI AEE Project provide valuable information for future implementations of SCM and DM.
Crowley, Sandra L.↗
Simultaneous structure/control optimization of large flexible spacecraft
This paper presents an approach to the simultaneous optimal design of a structure and control system for large flexible spacecrafts based on realistic objective function and constraints. The weight or total cost of structure and control system is minimized subject to constraints on the magnitude of response to a given disturbance involving both rigid-body and elastic modes. A nested optimization technique is developed to solve the combined problem. As an example, simple beam-like spacecraft under a steady-state white-noise disturbance force is investigated and some results of optimization are presented. In the numerical examples, the stiffness distribution, the location of controller and the control gains are optimized. Direct feedback control and linear quadratic optimal control laws are used with both inertial and non-inertial disturbing force. It is shown that the total cost is sensitive to the overall structural stiffness so that a simultaneous optimization of the structure and control system is indeed useful.
Onoda, Junjiro↗
NASA Exhibits
A series of NASA presentations for the Supercomputing 2001 conference are summarized. The topics include: (1) Mars Surveyor Landing Sites "Collaboratory"; (2) Parallel and Distributed CFD for Unsteady Flows with Moving Overset Grids; (3) IP Multicast for Seamless Support of Remote Science; (4) Consolidated Supercomputing Management Office; (5) Growler: A Component-Based Framework for Distributed/Collaborative Scientific Visualization and Computational Steering; (6) Data Mining on the Information Power Grid (IPG); (7) Debugging on the IPG; (8) Debakey Heart Assist Device: (9) Unsteady Turbopump for Reusable Launch Vehicle; (10) Exploratory Computing Environments Component Framework; (11) OVERSET Computational Fluid Dynamics Tools; (12) Control and Observation in Distributed Environments; (13) Multi-Level Parallelism Scaling on NASA's Origin 1024 CPU System; (14) Computing, Information, & Communications Technology; (15) NAS Grid Benchmarks; (16) IPG: A Large-Scale Distributed Computing and Data Management System; and (17) ILab: Parameter Study Creation and Submission on the IPG.
Deardorff, Glenn↗
Robust Coordination for Large Sets of Simple Rovers
The ability to coordinate sets of rovers in an unknown environment is critical to the long-term success of many of NASA;s exploration missions. Such coordination policies must have the ability to adapt in unmodeled or partially modeled domains and must be robust against environmental noise and rover failures. In addition such coordination policies must accommodate a large number of rovers, without excessive and burdensome hand-tuning. In this paper we present a distributed coordination method that addresses these issues in the domain of controlling a set of simple rovers. The application of these methods allows reliable and efficient robotic exploration in dangerous, dynamic, and previously unexplored domains. Most control policies for space missions are directly programmed by engineers or created through the use of planning tools, and are appropriate for single rover missions or missions requiring the coordination of a small number of rovers. Such methods typically require significant amounts of domain knowledge, and are difficult to scale to large numbers of rovers. The method described in this article aims to address cases where a large number of rovers need to coordinate to solve a complex time dependent problem in a noisy environment. In this approach, each rover decomposes a global utility, representing the overall goal of the system, into rover-specific utilities that properly assign credit to the rover s actions. Each rover then has the responsibility to create a control policy that maximizes its own rover-specific utility. We show a method of creating rover-utilities that are "aligned" with the global utility, such that when the rovers maximize their own utility, they also maximize the global utility. In addition we show that our method creates rover-utilities that allow the rovers to create their control policies quickly and reliably. Our distributed learning method allows large sets rovers be used unmodeled domains, while providing robustness against rover failures and changing environments. In experimental simulations we show that our method scales well with large numbers of rovers in addition to being robust against noisy sensor inputs and noisy servo control. The results show that our method is able to scale to large numbers of rovers and achieves up to 400% performance improvement over standard machine learning methods.
Tumer, Kagan↗