Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “external control”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Wireless Temperature-Monitoring System

A relatively inexpensive instrumentation system that includes units that are connected to thermocouples and that are parts of a radio-communication network has been developed to enable monitoring of temperatures at multiple locations. Because there is no need to string wires or cables for communication, the system is well suited for monitoring temperatures at remote locations and for applications in which frequent changes of monitored or monitoring locations are needed. The system can also be adapted to monitoring of slowly varying physical quantities, other than temperature, that can be transduced by solid-state electronic sensors. electronic sensors. The system comprises any number of transmitting units and a single receiving unit. Each transmitting unit includes connections for as many as four external thermocouples, a signal-conditioning module, a control module, and a radio-communication module. The signal-conditioning module acts as an interface between the thermocouples and the rest of the transmitting unit and includes a built-in solid ambient temperature sensor that is in addition to the external thermocouples. The control module is a system-on-chip embedded processor that includes analog-to-digital converters, serial and parallel data ports, and an interface for local connection to an analog meter that is used during installation to verify correct operation. The radio-communication module contains a commercial spread-spectrum transceiver that operates in the 900-MHz industrial, scientific, and medical (ISM) frequency band. This transceiver transmits data to the receiving unit at a rate of 19,200 baud. The receiving unit includes a transceiver like that of a transmitting unit, plus a control module that contains a system-on-chip processor that includes serial data port for output to a computer that runs monitoring and/or control software, a parallel data port for output to a printer, and a seven-segment light-emitting-diode display. Each transmitting unit is battery-powered and can operate for at least seven days continuously while reporting temperatures every half hour. The receiving unit is powered by a wall-mounted transformer source. The receiving unit responds to each transmitting unit and reports the readings of each of the four thermocouples and of the ambient-temperature sensor of the transmitting unit. The end-to-end accuracy of the system is plus or minus 0.2 C over the temperature range from 0 to 100 C. The radio-communication range between the receiving and transmitting units is approximately equal to 0.5 mile (approximately equal to 0.8 km).

Solano, Wanda↗
NASA NTRS2003

Wireless Temperature-Monitoring System

A relatively inexpensive instrumentation system that includes units that are connected to thermocouples and that are parts of a radio-communication network has been developed to enable monitoring of temperatures at multiple locations. Because there is no need to string wires or cables for communication, the system is well suited for monitoring temperatures at remote locations and for applications in which frequent changes of monitored or monitoring locations are needed. The system can also be adapted to monitoring of slowly varying physical quantities, other than temperature, that can be transduced by solid-state electronic sensors. The system comprises any number of transmitting units and a single receiving unit (see figure). Each transmitting unit includes connections for as many as four external thermocouples, a signal-conditioning module, a control module, and a radio-communication module. The signal- conditioning module acts as an interface between the thermocouples and the rest of the transmitting unit and includes a built-in solid ambient-temperature sensor that is in addition to the external thermocouples. The control module is a "system-on-chip" embedded processor that includes analog-to-digital converters, serial and parallel data ports, and an interface for local connection to an analog meter that is used during installation to verify correct operation. The radio-communication module contains a commercial spread-spectrum transceiver that operates in the 900-MHz industrial, scientific, and medical (ISM) frequency band. This transceiver transmits data to the receiving unit at a rate of 19,200 baud. The receiving unit includes a transceiver like that of a transmitting unit, plus a control module that contains a system-on-chip processor that includes serial data port for output to a computer that runs monitoring and/or control software, a parallel data port for output to a printer, and a seven-segment light-emitting-diode display.

Solano, Wanda↗
DOE OSTI2022

Role of Sr doping and external strain on relieving bottleneck of oxygen diffusion in La 2- x Sr x CuO 4-δ

In many complex oxides, the oxygen vacancy formation is a promising route to modify the material properties such as a superconductivity and an oxygen diffusivity. Cation substitutions and external strain have been utilized to control the concentration and diffusion of oxygen vacancies, but the mechanisms behind the controls are not fully understood. Using first-principles calculations, we find how Sr doping and external strain greatly enhances the diffusivity of oxygen vacancies in La 2-x Sr x CuO 4-δ (LSCO) in the atomic level. In hole-doped case (2x > δ), the formation energy of an apical vacancy in the LaO layer is larger than its equatorial counterpart by 0.2 eV that the bottleneck of diffusion process is for oxygen vacancies to escape equatorial sites. Such an energy difference can be reduced and even reversed by either small strain (< 1.5%) or short-range attraction between Sr and oxygen vacancy, and in turn, the oxygen diffusivity is greatly enhanced. For fully compensated hole case (2x ≦ δ), the formation energy of an apical vacancy becomes too high that most oxygen vacancies cannot move but would be trapped at equatorial sites. From our electronic structure analysis, we found that the contrasting change in the formation energy by Sr doping and external strain is originated from the different localization natures of electron carrier from both types of oxygen vacancies.

25 ENERGY STORAGE↗
NASA NTRS1977

Load control system

The load control system developed for the shuttle external structural tests is described. The system consists of a load programming/display module, and a load control module along with the following hydraulic system components: servo valves, dump valves, hydraulic system components, and servo valve manifold blocks. One load programming/display subsystem can support multiple load control subsystem modules.

Grosse, J. C.↗
NASA NTRS2002

Vertical Field of View Reference Point Study for Flight Path Control and Hazard Avoidance

Researchers within the eXternal Visibility System (XVS) element of the High-Speed Research (HSR) program developed and evaluated display concepts that will provide the flight crew of the proposed High-Speed Civil Transport (HSCT) with integrated imagery and symbology to permit path control and hazard avoidance functions while maintaining required situation awareness. The challenge of the XVS program is to develop concepts that would permit a no-nose-droop configuration of an HSCT and expanded low visibility HSCT operational capabilities. This study was one of a series of experiments exploring the 'design space' restrictions for physical placement of an XVS display. The primary experimental issues here was 'conformality' of the forward display vertical position with respect to the side window in simulated flight. 'Conformality' refers to the case such that the horizon and objects appear in the same relative positions when viewed through the forward windows or display and the side windows. This study quantified the effects of visual conformality on pilot flight path control and hazard avoidance performance. Here, conformality related to the positioning and relationship of the artificial horizon line and associated symbology presented on the forward display and the horizon and associated ground, horizon, and sky textures as they would appear in the real view through a window presented in the side window display. No significant performance consequences were found for the non-conformal conditions.

Comstock, J. Raymond, Jr.↗
NASA NTRS1981

The application of fracture control to a weld specification

An approach used on the external tank (ET) portion of the Space Shuttle Program which employs fracture control to establish defect acceptance criteria in a welding specification is discussed. Weld acceptance criteria developed for the ET fabricated from 2219 aluminum are demonstrated using as an example one of the actual ET welds. A table of weld grades as a function of acceptable defect length is presented. The design drawing specifies the weld grade for a particular weld; then the inspector uses the grade to determine the defect length for radiographic and penetrant acceptance of the weld. By allowing each weld to be judged by its own defect requirement instead of using the tightest requirement, the number of weld repairs has been minimized, resulting in lower cost with no compromise in performance.

Bolstad, D. A.↗
NASA NTRS1981

Solar heating and cooling system installed at RKL Controls Company, Lumberton, New Jersey

The final results of the design and operation of a computer controlled solar heated and cooled 40,000 square foot manufacturing building, sales office, and computer control center/display room are summarized. The system description, test data, major problems and resolutions, performance, operation and maintenance manual, equipment manufacturers' literature, and as-built drawings are presented. The solar system is composed of 6,000 square feet of flat plate collectors, external above ground storage subsystem, controls, absorption chiller, heat recovery, and a cooling tower.

Source record↗
NASA NTRS2008

Aquarius's Instrument Science Data System (ISDS) Automated to Acquire, Process, Trend Data and Produce Radiometric System Assessment Reports

The Aquarius Radiometer, a subsystem of the Aquarius Instrument required a data acquisition ground system to support calibration and radiometer performance assessment. To support calibration and compose performance assessments, we developed an automated system which uploaded raw data to a ftp server and saved raw and processed data to a database. This paper details the overall functionalities of the Aquarius Instrument Science Data System (ISDS) and the individual electrical ground support equipment (EGSE) which produced data files that were infused into the ISDS. Real time EGSEs include an ICDS Simulator, Calibration GSE, Labview controlled power supply, and a chamber data acquisition system. ICDS Simulator serves as a test conductor primary workstation, collecting radiometer housekeeping (HK) and science data and passing commands and HK telemetry collection request to the radiometer. Calibration GSE (Radiometer Active Test Source) provides source choice from multiple targets for the radiometer external calibration. Power Supply GSE, controlled by labview, provides real time voltage and current monitoring of the radiometer. And finally the chamber data acquisition system produces data reflecting chamber vacuum pressure, thermistor temperatures, AVG and watts. Each GSE system produce text based data files every two to six minutes and automatically copies the data files to the Central Archiver PC. The Archiver PC stores the data files, schedules automated uploads of these files to an external FTP server, and accepts request to copy all data files to the ISDS for offline data processing and analysis. Aquarius Radiometer ISDS contains PHP and MATLab programs to parse, process and save all data to a MySQL database. Analysis tools (MATLab programs) in the ISDS system are capable of displaying radiometer science, telemetry and auxiliary data in near real time as well as performing data analysis and producing automated performance assessment reports of the Aquarius Radiometer.

Source record↗
NASA NTRS1975

Multimode attitude and orbit control for the Atmosphere Explorer spacecraft

The orbit profile for the Atmosphere Explorer requires a velocity adjust capability of 2000 ft/sec/sec and individual maneuvers of up to 24 ft/sec in magnitude. This requirement is met by a monopropellant hydrazine propulsion subsystem which also provides, by virtue of the tank arrangement, a means of adjusting the spacecraft center of mass in orbit, thereby minimizing external disturbance torques. The attitude control subsystem is of the momentum bias type. A large internal flywheel furnishes gyroscopic stiffness and permits rapid changes in operating mode (despun to spinning mode) by controlled interchange of momentum between the flywheel and the spacecraft main body.

Stewart, B.↗
NASA NTRS1991

Controlling panel flutter using adaptive materials

The effectiveness of using adaptive materials to control panel flutter is examined. Adaptive materials are those whose strain or mechanical properties can be controlled by the application of an external stimulus. Two such material types are piezoelectric (ceramics or polymers) and shape memory alloys. These materials experience controllable strain when subjected to applied voltage and heat, respectively. The present study investigates the use of both material types to modify the flutter characteristics of a simply supported panel in supersonic flow. Piezoelectric materials respond quickly to applied voltages and can be used with feedback control for active vibration suppression. The adaptive process of the shape memory alloy used in this study (geometry and stiffness change) is a relatively low frequency phenomenon; therefore, it is considered for passive (on/off) control schemes only. Nondimensional parameters for these adaptive materials are used with linear panel models, yielding results which allow for a better understanding of their capabilities in controlling aeroelastic responses.

Scott, R. C.↗
NASA NTRS1998

Sliding Mode Thermal Control System for Space Station Furnace Facility

The decoupled control of the nonlinear, multiinput-multioutput, and highly coupled space station furnace facility (SSFF) thermal control system is addressed. Sliding mode control theory, a subset of variable-structure control theory, is employed to increase the performance, robustness, and reliability of the SSFF's currently designed control system. This paper presents the nonlinear thermal control system description and develops the sliding mode controllers that cause the interconnected subsystems to operate in their local sliding modes, resulting in control system invariance to plant uncertainties and external and interaction disturbances. The desired decoupled flow-rate tracking is achieved by optimization of the local linear sliding mode equations. The controllers are implemented digitally and extensive simulation results are presented to show the flow-rate tracking robustness and invariance to plant uncertainties, nonlinearities, external disturbances, and variations of the system pressure supplied to the controlled subsystems.

Jackson Mark E.↗
NASA NTRS1993

Shuttle primary reaction control system engine exhaust plume contamination effects

Space Shuttle proximity operations constitute an important part of the SSF induced external environment. The impingement of primary reaction control system (PRCS) engine plumes on SSF functional surfaces during docking or berthing and separation leads to concerns about molecular contamination and high speed particle impact. The Shuttle Plume Impingement flight Experiment (SPIE) was designed to provide a direct measure of both the molecular contamination and particle impact rates produced by Shuttle PRCS engines in the LEO environment. The measured permanent deposition produced by PRCS engine firings was less than that assumed in current SSF programatic assessments. Only two to three possible high velocity particle impact pits were observed on the RMS end effector hardware.

Koontz, Steve↗
NASA NTRS1994

Force override rate control for robotic manipulators

The work reported deals with the problem of operating a robot manipulator under a rate control mode while the end effector is not in contact with the external environment, and then switching to a force control mode when contact is made. The paper details how the modal changeover may be accomplished in a manner transparent to the operator, and will allow operator applied forces to be reflected at the robot end effector. A one degree of freedom demonstration system is used to illustrate the concept, which is then applied to a PUMA manipulator. Sample code for the implementation of the control is provided, experimental results show that the optimum setting for the gain is a function of the compliance of the end effector, and the compliance of the external constraint.

Driels, Morris↗
DOE OSTI2025

Effects of an External Magnetic Field on Keyhole Mode Laser Melting of 316 Stainless Steel

Keyhole-mode laser melting is an efficient method for joining or cutting large, thick components, but controlling keyhole depth and fluctuations has remained challenging. Applying an external magnetic field can control melt pool flows and indirectly influence keyhole morphology and dynamics. The induced Lorentz force, comprising Seebeck and damping components, plays a crucial role in the melt pool dynamics, depending on temperature gradient, flow rates, and magnetic field orientation and magnitude. This research investigates the effects of an external magnetic field on keyhole behavior during laser spot melting of 316 stainless steel using synchronized high-speed synchrotron X-ray and thermal imaging. Findings revealed that a longitudinal magnetic field (120 mT) increased keyhole depth but exacerbated lateral fluctuations, resulted in a 20% increase in the melt pool temperature gradient and a 27% decrease in cooling rate. Conversely, a transverse magnetic field (760 mT) reduced keyhole depth and improved porosity formation. The findings suggest that a decrease in keyhole depth correlates with a decrease in fluctuations, and vice versa. These insights enhance understanding of external magnetic fields’ impact on laser melting, with implications for improving part quality.

Alamdari, Aslan Bafahm [The Ohio State Univ., Colu↗
DOE OSTI2026

Spin Texture Control and Magnetic Gap Engineering in a Ferromagnetic Insulator–Topological Insulator Sandwiched Heterostructure

Quantum materials that combine magnetism with topological order are emerging as key platforms for next-generation spintronics and low-energy electronics. They enable the realization of emergent quantum phenomena, such as the quantum anomalous Hall effect and axion insulator states. The ferromagnetic insulator (FMI)/topological insulator (TI)/FMI sandwich structure of a single-septuple layer (1SL) MnBi 2 Te 4 /four-quintuple layer (4QL) Bi 2 Te 3 /1SL MnBi 2 Te 4 holds great potential to achieve such desirable quantum phenomena at an elevated temperature, owing to its large Dirac point band gap and high Curie temperature. Here, for this work, spin- and angle-resolved photoemission spectroscopy (spin-ARPES) is employed to directly verify that the band gap arises from broken time-reversal symmetry via proximity-driven magnetization. This study demonstrates direct control of the spin state via external magnetic fields and unambiguously confirms the exchange interaction as the gap-opening mechanism. The robust magnetic gap and controllable spin texture make this heterostructure a suitable candidate for spintronic applications and magnetic topological quantum phases.

exchange gap↗
NASA NTRS2004

Variable Speed CMG Control of a Dual-Spin Stabilized Unconventional VTOL Air Vehicle

This paper describes an approach based on using both bias momentum and multiple control moment gyros for controlling the attitude of statically unstable thrust-levitated vehicles in hover or slow translation. The stabilization approach described in this paper uses these internal angular momentum transfer devices for stability, augmented by thrust vectoring for trim and other outer loop control functions, including CMG stabilization/ desaturation under persistent external disturbances. Simulation results show the feasibility of (1) improved vehicle performance beyond bias momentum assisted vector thrusting control, and (2) using control moment gyros to significantly reduce the external torque required from the vector thrusting machinery.

Lim, Kyong B.↗
DOE OSTI2023

Integrated Optimization of Powertrain Energy Management and Vehicle Motion Control for Autonomous Hybrid Electric Vehicles

Hybrid Electric Vehicles (HEVs) and autonomous vehicles have been widely studied recently for on-road transportation. In the study of autonomous HEVs, the control of the vehicle's external dynamics and powertrain dynamics are often treated separately. Optimizing these two problems together can significantly improve fuel economy. In this paper, an autonomous HEV following a leader is considered. First, the augmented model to integrate the abovementioned dynamics is presented. Second, the optimization problem is defined to find the optimum fuel consumption of the follower in pursuit of a leader in a drive cycle. A customized control strategy based on Approximate Dynamic Programming (ADP) is then explored in which the optimal cost-to-go at each time step is approximated using neural networks. Also, the accuracy of the optimization solution is enhanced by applying the concept of the reachable sets. At last, three case studies show that the examined integrated control strategy outperforms the one with the separated optimization method by an additional 7.4%, 4.6%, and 11.8% improvement in fuel consumption, respectively.

33 ADVANCED PROPULSION SYSTEMS↗