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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

A unified perspective on robot control - The energy Lyapunov function approach

A unified framework for the stability analysis of robot tracking control is presented. By using an energy-motivated Lyapunov function candidate, the closed-loop stability is shown for a large family of control laws sharing a common structure of proportional and derivative feedback and a model-based feedforward. The feedforward can be zero, partial or complete linearized dynamics, partial or complete nonlinear dynamics, or linearized or nonlinear dynamics with parameter adaptation. As result, the dichotomous approaches to the robot control problem based on the open-loop linearization and nonlinear Lyapunov analysis are both included in this treatment. Furthermore, quantitative estimates of the trade-offs between different schemes in terms of the tracking performance, steady state error, domain of convergence, realtime computation load and required a prior model information are derived.

Wen, John T.↗
NASA NTRS2016

Unpredictable Variable Prenatal Stress Programs Expression of Genes Involved in Appetite Control and Energy Expenditure

Exposure to stress in the womb shapes neurobiological and physiological outcomes of offspring in later life, including body weight regulation and metabolic profiles. Our previous work utilizing a centrifugation-induced hyper-gravity demonstrated significantly increased (8-15%) body mass in male, but not female, rats exposed throughout gestation to chronic 2-g from conception to birth. We reported a similar outcome in adult offspring exposed throughout gestation to Unpredictable Variable Prenatal Stress (UVPS). Here we examine gene expression changes and the plasma of animals treated with our UVPS model to identify a potential role for prenatal stress in this hypergravity programming effect. Specifically we focused on appetite control and energy expenditure pathways in prenatally stressed adult (90-day-old) male Sprague-Dawley rats.

Prenatal Stress↗
NASA NTRS2007

Voltage Controller Saves Energy, Prolongs Life of Motors

In 1985, Power Efficiency Corporation of Las Vegas licensed NASA voltage controller technology from Marshall Space Flight Center. In the following years, Power Efficiency made patented improvements to the technology and marketed the resulting products throughout the world as the Performance Controller and the Power Efficiency energy-saving soft start. Soft start gradually introduces power to an electric motor, thus eliminating the harsh, violent mechanical stresses of having the device go from a dormant state to one of full activity; prevents it from running too hot; and increases the motor's lifetime. The product can pay for itself through the reduction in electricity consumed (according to Power Efficiency, within 3 years), depending on the duty cycle of the motor and the prevailing power rates. In many instances, the purchaser is eligible for special utility rebates for the environmental protection it provides. Common applications of Power Efficiency's soft start include mixers, grinders, granulators, conveyors, crushers, stamping presses, injection molders, elevators with MG sets, and escalators. The device has been retrofitted onto equipment at major department store chains, hotels, airports, universities, and for various manufacturers

Source record↗
NASA NTRS1978

Controlled cellular energy conversion in brown adipose tissue thermogenesis

Brown adipose tissue serves as a model system for nonshivering thermogenesis (NST) since a) it has as a primary physiological function the conversion of chemical energy to heat; and b) preliminary data from other tissues involved in NST (e.g., muscle) indicate that parallel mechanisms may be involved. Now that biochemical pathways have been proposed for brown fat thermogenesis, cellular models consistent with a thermodynamic representation can be formulated. Stated concisely, the thermogenic mechanism in a brown fat cell can be considered as an energy converter involving a sequence of cellular events controlled by signals over the autonomic nervous system. A thermodynamic description for NST is developed in terms of a nonisothermal system under steady-state conditions using network thermodynamics. Pathways simulated include mitochondrial ATP synthesis, a Na+/K+ membrane pump, and ionic diffusion through the adipocyte membrane.

Horowitz, J. M.↗
NASA NTRS1985

Accelerators for critical experiments involving single-particle upset in solid-state microcircuits

Charged-particle interactions in microelectronic circuit chips (integrated circuits) present a particularly insidious problem for solid-state electronic systems due to the generation of soft errors or single-particle event upset (SEU) by either cosmic rays or other radiation sources. Particle accelerators are used to provide both light and heavy ions in order to assess the propensity of integrated circuit chips for SEU. Critical aspects of this assessment involve the ability to analytically model SEU for the prediction of error rates in known radiation environments. In order to accurately model SEU, the measurement and prediction of energy deposition in the form of an electron-hole plasma generated along an ion track is of paramount importance. This requires the use of accelerators which allow for ease in both energy control (change of energy) and change of ion species. This and other aspects of ion-beam control and diagnostics (e.g., uniformity and flux) are of critical concern for the experimental verification of theoretical SEU models.

Zoutendyk, J. A.↗
NASA NTRS1977

Magnetic bearing momentum wheels with magnetic gimballing capability for 3-axis active attitude control and energy storage

Magnetic bearings used for the suspension of momentum wheels provide conclusive advantages: the low friction torques and the absence of abrasion allow the realization of lightweight high speed wheels with high angular momentum and energy storage capacity and virtually unlimited lifetime. The use of actively controlled bearings provides a magnetic gimballing capability by applying the external signals to the two servo loops controlling the rotational degrees of freedom. Thus, an attitude control system can be realized by using only one rotating mass for 3-axis active satellite stabilization.

Sindlinger, R. S.↗
NASA NTRS1985

Tetrahedron array of reaction wheels for attitude control and energy storage

A spacecraft subsystem, working in conjunction with a solar array, which provides 3-axis attitude control as well as some power system functions is described. Four flywheels, driven by variable-field d.c. motors and arranged in a tetrahedron configuration, are employed. In sunlight, the system provides voltage regulation while the wheels are accelerated to some maximum speed. In the dark, the motors become flywheel-driven generators which provide regulated power to other spacecraft electrical loads. A microprocessor is used to compute field current levels for each of the 4 motor/generators, based on measurements of the system voltage level, the flywheel speeds, and the attitude control torques desired.

Flatley, T. W.↗
NASA NTRS1982

A dynamic measure of controllability and observability for the placement of actuators and sensors on large space structures

The degree of controllability of a large space structure is found by a four step procedure: (1) finding the minimum control energy for driving the system from a given initial state to the origin in the prescribed time; (2) finding the region of initial state which can be driven to the origin with constrained control energy and time using optimal control strategy; (3) scaling the axes so that a unit displacement in every direction is equally important to control; and (4) finding the linear measurement of the weighted "volume" of the ellipsoid in the equicontrol space. For observability, the error covariance must be reduced toward zero using measurements optimally, and the criterion must be standardized by the magnitude of tolerable errors. The results obtained using these methods are applied to the vibration modes of a free-free beam.

Vandervelde, W. E.↗
NASA NTRS1988

A new class of energy based control laws for revolute robot arms - Tracking control, robustness enhancement and adaptive control

A class of joint-level control laws for all-revolute robot arms is introduced. The analysis is similar to the recently proposed energy Liapunov function approach except that the closed-loop potential function is shaped in accordance with the underlying joint space topology. By using energy Liapunov functions with the modified potential energy, a much simpler analysis can be used to show closed-loop global asymptotic stability and local exponential stability. When Coulomb and viscous friction and model parameter errors are present, a sliding-mode-like modification of the control law is proposed to add a robustness-enhancing outer loop. Adaptive control is also addressed within the same framework. A linear-in-the-parameters formulation is adopted, and globally asymptotically stable adaptive control laws are derived by replacing the model parameters in the nonadaptive control laws by their estimates.

Wen, John T.↗
NASA NTRS1972

Modular Space Station Phase B Extension Preliminary Systems Design Report. Volume VI: Trades and Analyses

This document contains trades and analyses conducted during the Modular Space Station Phase B System Definition. Requirements and concepts considered and the tradeoff analysis leading to the preferred concept are presented. Integrated analyses are presented for subsystems and thermal control. Specific trades and analyses are presented for water management, atmosphere control, energy storage, radiators, navigation, control moment gyros, and system maintenance. The analyses of manipulator concepts and requirements, and supplemental analyses of information management issues are summarized. Subsystem reliability analyses include a detailed discussion of the critical failure analysis.

Jones, A. L.↗
NASA NTRS1973

Transient analysis of energy Transfer Control (ECT) and compressor bleed concepts of remote lift fan control

The transient performance of two concepts for control of vertical takeoff aircraft remote lift fans is analyzed and discussed. Both concepts employ flow transfer between pairs of lift fans located in separate parts of the aircraft in order to obtain attitude control moments for hover and low-speed flight. The results presented are from a digital computer, dynamic analysis of the YJ97/LF460 remote drive turbofan. The transient responses of the two systems are presented for step demands in lift and moment.

Sellers, J. F.↗
NASA NTRS1973

Steady state analysis of Energy Transfer Control (ETC) and compressor bleed concepts of remote lift fan control

Two new concepts of control for VTOL aircraft remote lift fans are analyzed and discussed. Both concepts employ flow transfer among lift fans located in separate parts of the aircraft in order to obtain attitude control moments in hover and low-speed flight. The results presented are from a digital computer analysis of the YJ97/LF460 remote drive turbofan, although qualitative conclusions should apply to any remote fan system. The basic operating principles of the two systems are described, and their steady-state moment generating capabilities are discussed. Lift-recovery strategies for component failures are also analyzed.

Sellers, J. F.↗
NASA NTRS1977

A design handbook for phase change thermal control and energy storage devices

Comprehensive survey is given of the thermal aspects of phase change material devices. Fundamental mechanisms of heat transfer within the phase change device are discussed. Performance in zero-g and one-g fields are examined as it relates to such a device. Computer models for phase change materials, with metal fillers, undergoing conductive and convective processes are detailed. Using these models, extensive parametric data are presented for a hypothetical configuration with a rectangular phase change housing, using straight fins as the filler, and paraffin as the phase change material. These data are generated over a range of realistic sizes, material properties, and thermal boundary conditions. A number of illustrative examples are given to demonstrate use of the parametric data. Also, a complete listing of phase change material property data are reproduced herein as an aid to the reader.

Humphries, W. R.↗
NASA NTRS1989

Model reduction and control of flexible structures using Krylov subspaces

Krylov vectors and the concept of parameter-matching are combined to develop a model reduction algorithm for a damped structural dynamics system. The reduced-order model obtained matches a certain number of low-frequency moments of the full-order system. The major application of the present method is to the control of flexible structures. It is shown that, in the control of flexible structures, there generally exist three types of control energy spillover, namely, the control spillover, the observation spillover, and dynamic spillover. The formulation based on Krylov subspaces can eliminate the control and the observation spillover, while leaving only the dynamic spillover to be considered. Two examples are used to illustrate the efficacy of the Krylov method.

Craig, Roy R., Jr.↗
NASA NTRS1991

Controlling hazardous energy sources (lockout/tagout)

The minimum requirements as established by the Occupational Safety and Health Administration (OSHA) standard 29 CFR 1910.147 are discussed for preventing the unexpected operation of equipment or release of energy which could cause injury to personnel, damage to equipment, harm to the environment, or loss or compromise of test data. Safety requirements both for government and contractor personnel are explained for potentially hazardous energy sources during work operations at LeRC (Cleveland and Plum Brook Stations). Basic rules are presented to ensure protection against harmful exposures, and baseline implementation requirements are discussed from which detailed lockout/tagout procedures can be developed for individual equipment items. Examples of energy sources covered by this document include electrical, pneumatic, mechanical, chemical, cryogenic, thermal, spring tension/compression suspended or moving loads, and other potentially hazardous sources. Activities covered by this standard include, but are not limited to, construction, maintenance, installation, calibration, inspection, cleaning, or repair.

Dominguez, Manuel B.↗