Variable sweep-rate frequency response and vibration testing
Variable sweep rate frequency response and vibration testing for test time reduction, using closed loop controller for sweep rate modulation
Lorenzo, C. F.↗
SEARCH · Search NASA
Results for “closed loop 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.
A closed loop cryogenic environment pressure regulating system
Nonlinear closed loop control system to regulate the pressure in a cryogenic environment is described. System employs four position contactor with two control bands to react to the signals. Diagrams of element transfer function and required equipment are included.
Huguley, J. C.↗
Terminal shock position and restart control of a Mach 2.7, two-dimensional, twin duct mixed compression inlet
Experimental results of terminal shock and restart control system tests of a two-dimensional, twin-duct mixed compression inlet are presented. High-response (110-Hz bandwidth) overboard bypass doors were used, both as the variable to control shock position and as the means of disturbing the inlet airflow. An inherent instability in inlet shock position resulted in noisy feedback signals and thus restricted the terminal shock position control performance that was achieved. Proportional-plus-integral type controllers using either throat exit static pressure or shock position sensor feedback gave adequate low-frequency control. The inlet restart control system kept the terminal shock control loop closed throughout the unstart-restart transient. The capability to restart the inlet was non limited by the inlet instability.
Cole, G. L.↗
A hollow cathode neutralizer for a 30-cm diameter bombardment thruster
Recent improvements in overall thruster performance have imposed new constraints on neutralizer performance. The use of compensated grid extraction system requires a reevaluation of neutralizer position. A series of tests were conducted to determine what effect neutralizer cathode geometry has on performance. The parameters investigated included orifice diameter and length, and cathode diameter. Similar tests investigated open and enclosed keeper geometries. Neutralizer position tests with compensated grids suggested positions approximately 10 cm from the accelerator and radially out of the beam envelope should result in satisfactory performance and long life. Operation at keeper current of 1.5 am resulted in lower total neutralizer power, the elimination of tip heater power, and suitable closed loop control of the neutralizer vaporizer.
Bechtel, R. T.↗
Zone generator for Large Space Telescope technology
A concept is presented for monitoring the optical adjustment and performance of a Large Space Telescope which consists of a 1.2m diameter turntable with a laser stylus to operate at speeds up to 30 rpm. The focus of the laser stylus is under closed loop control. A technique for scribing zones of suitable depth, width, and uniformity applicable to large telescope mirrors is also reported.
Erickson, K. E.↗
Stepping optical path difference in an interferometer
Stepping method permits higher amplitude modulation of secondary mirror of Fourier interferometer. Amplitude of mirror motion is limited only by available voltage drive on error-correcting actuator. Closed-loop controller provides servo error voltage linearly proportional to offset from proper null position. Bidirectional counter serves to count number of reference laser fringes offset from null position.
Schindler, R. A.↗
Shuttle/tethered satellite system conceptual design study
A closed-loop control system was added to the tether reel which improves control over the tethered satellite. In addition to increasing the stability of the tethered satellite along local vertical, this control system is used for deployment and retrieval of tethered satellites. This conceptual design study describes a tether system for suspending a science payload at an altitude of 120 km from space shuttle orbiter flying at an altitude of 200 km. In addition to the hardware conceptual designs, various aspects concerning Orbiter accommodations are discussed.
Source record↗
Demand-type gas supply system for rocket borne thin-window proportional counters
A simple closed loop control system has been developed to maintain the gas pressure in thin-window proportional counters during rocket flights. This system permits convenient external control of detector pressure and system flushing rate. The control system is activated at launch with the sealing of a reference volume at the existing system pressure. Inflight control to plus or minus 2 torr at a working pressure of 760 torr has been achieved on six rocket flights.
Acton, L. W.↗
Shuttle/tethered satellite system
A tethered satellite system has been conceived as a device to extend the capability of the Space Shuttle to perform scientific/applications investigations and operational activities. The concept envisions a multiple-use tethered system with closed-loop control, capable of supporting a payload or satellite suspended from the Shuttle cargo bay, toward or away from the earth, at distances up to 100 kilometers from the Shuttle. This paper discusses the background and results of early analyses and feasibility studies, and presents a design and operational description of the system. Also presented are a discussion of potential applications of the Tethered Satellite System, and plans for an operational verification flight in 1982.
Rupp, C. C.↗
A preference-ordered discrete-gaming approach to air-combat analysis
An approach to one-on-one air-combat analysis is described which employs discrete gaming of a parameterized model featuring choice between several closed-loop control policies. A preference-ordering formulation due to Falco is applied to rational choice between outcomes: win, loss, mutual capture, purposeful disengagement, draw. Approximate optimization is provided by an active-cell scheme similar to Falco's obtained by a 'backing up' process similar to that of Kopp. The approach is designed primarily for short-duration duels between craft with large-envelope weaponry. Some illustrative computations are presented for an example modeled using constant-speed vehicles and very rough estimation of energy shifts.
Kelley, H. J.↗
Correlation tracking for a Planetary Pointing and Tracking System
The Planetary Pointing and Tracking System (PPTS) is being developed to provide precision pointing for science platforms on future autonomous planetary spacecraft. The PPTS design approach using a CCD optical sensor for closed-loop control with respect to the target body, a gyro for inertial stabilization, and brushless dc torque motors for smooth and continuous platform articulation is essential for high resolution planetary imaging and automated science execution. An integral part of PPTS is the correlation tracker which has the potential to revolutionize autonomous guidance.
Assefi, T.↗
A laboratory facility for electric vehicle propulsion system testing
The road load simulator facility located at the NASA Lewis Research Center enables a propulsion system or any of its components to be evaluated under a realistic vehicle inertia and road loads. The load is applied to the system under test according to the road load equation: F(net)=K1F1+K2F2V+K3 sq V+K4(dv/dt)+K5 sin theta. The coefficient of each term in the equation can be varied over a wide range with vehicle inertial representative of vehicles up to 7500 pounds simulated by means of flywheels. The required torque is applied by the flywheels, a hydroviscous absorber and clutch, and a drive motor integrated by a closed loop control system to produce a smooth, continuous load up to 150 horsepower.
Sargent, N. B.↗
Developments at M.I.T. related to magnetic model suspension and balance systems for large scale facilities
The paper deals with magnetic model suspension and balance systems for wind tunnel use. Particular attention is given to the extension of the electromagnetic position sensor (EPS) system producing roll position signals and the ac roll drive system producing closed loop control of rolling moment.
Haldeman, C. W.↗
Shuttle/tethered satellite system
A tethered satellite system was conceived as a device to extend the capability of the Space Shuttle to perform scientific/applications investigations and operational activities. The concept envisions a multiple-use tethered system with closed-loop control, capable of supporting a payload or satellite suspended from the Shuttle cargo bay, toward or away from the Earth, at distances up to 100 kilometers from the Shuttle. The background and results of early analyses and feasibility studies are discussed and a design and operational description of the system are presented. Also presented are a discussion of potential applications of the Tethered Satellite System, and plans for an operational verification flight in 1982.
Rupp, C. C.↗
Toward autonomous spacecraft
Ways in which autonomous behavior of spacecraft can be extended to treat situations wherein a closed loop control by a human may not be appropriate or even possible are explored. Predictive models that minimize mean least squared error and arbitrary cost functions are discussed. A methodology for extracting cyclic components for an arbitrary environment with respect to usual and arbitrary criteria is developed. An approach to prediction and control based on evolutionary programming is outlined. A computer program capable of predicting time series is presented. A design of a control system for a robotic dense with partially unknown physical properties is presented.
Fogel, L. J.↗
Software and system level tests of a test flight mercury ion thruster subsystem
A U.S. Air Force technology spacecraft flight is scheduled to carry an Ion Auxiliary Propulsion System (IAPS) as part of its experimental payload. This paper presents the results of the successful flight-software qualification and system-level tests which were performed on IAPS. The software tests were performed with an operating engineering model ion thruster and power processing unit, and failure/off-normal recovery modes, operation with and without temperature telemetry from the thruster vaporizers, and with closed-loop control or fixed setpoint operation of the thruster vaporizers. The system-level tests cover a wide range of thermal and operating conditions with the entire system exposed to a simulated space environment.
Robson, R. R.↗
Tethered Satellite System Project Overview
The Skyhook concept is reviewed and the use of a tethered satellite system (TSS) to enable scientific investigations from the shuttle using a closed loop control system is examined. The tethered satellite system has capabilities for deployment toward or away from Earth, for multiple round trip missions, and for deployment at distances up to 100 KN from the orbiter. The deployer, which consists of an entendable boom, a reel for the tether, and the tether itself, permits deployment and retrieval at a safe distance, allows alignment of the force vector of the tether through the center of gravity of the shuttle, and gives some initial gravity gradient separation to aid in deployment and ultimate retrieval of the tethered satellite. Charts show TSS activities in terms of systems studies, key guidelines, Italian and U.S. responsibilities, user activities, and major science and applications accommodation features. Scientific objectives for TSS-1 and TSS-2 verification missions and the current status of the project are also given.
Laue, J. H.↗
Nonintrusive shaft speed sensor
Reusable rocket engines such as the Space Shuttle Main Engines (SSME), the Orbital Transfer Vehicles (OTV), etc., have throttling capabilities that require real-time, closed-loop control systems of engine propellant flows, combustion temperatures and pressures, and turbopump rotary speeds. In the case of the SSME, there are four turbopumps that require real-time measurement and control of their rotary speeds. Variable-reluctance magnetic speed sensors were designed, fabricated, and tested for all four turbopumps, resulting in the successful implementation and operation of three of these speed sensors during each of the 12 Shuttle flights.
Barkhoudarian, S.↗