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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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Laser frequency stabilization methods are based on a frequency discriminant which generates an unambiguous deviation signal used for automatic stabilization. Closed-loop control stabilizes cavity length at a null point. Some systems have a stabilized ring laser using a piezoelectric dither and others use a Doppler gain tube.
Computer program determines the response of a composite linear structure to sinusoidal base motion of a restrained structure or sinusoidal forces of a free structure. This program is applied to problems of testing practices and closed-loop stability of autopilot controlled space vehicles. It is written for the IBM 7094 in FORTRAN 4 language.
The motion sensors of the vestibular system are studied to determine their role in human dynamic space orientation and manual vehicle control. The investigation yielded control models for the sensors, descriptions of the subsystems for eye stabilization, and demonstrations of the effects of motion cues on closed loop manual control. Experiments on the abilities of subjects to perceive a variety of linear motions provided data on the dynamic characteristics of the otoliths, the linear motion sensors. Angular acceleration threshold measurements supplemented knowledge of the semicircular canals, the angular motion sensors. Mathematical models are presented to describe the known control characteristics of the vestibular sensors, relating subjective perception of motion to objective motion of a vehicle. The vestibular system, the neck rotation proprioceptors and the visual system form part of the control system which maintains the eye stationary relative to a target or a reference. The contribution of each of these systems was identified through experiments involving head and body rotations about a vertical axis. Compensatory eye movements in response to neck rotation were demonstrated and their dynamic characteristics described by a lag-lead model. The eye motions attributable to neck rotations and vestibular stimulation obey superposition when both systems are active. Human operator compensatory tracking is investigated in simple vehicle orientation control system with stable and unstable controlled elements. Control of vehicle orientation to a reference is simulated in three modes: visual, motion and combined. Motion cues sensed by the vestibular system through tactile sensation enable the operator to generate more lead compensation than in fixed base simulation with only visual input. The tracking performance of the human in an unstable control system near the limits of controllability is shown to depend heavily upon the rate information provided by the vestibular sensors.
Open and closed-loop actuation and electronic control mechanism for advanced scan platform
Closed-loop compensatory tracking for measuring operator delay time in control action
Closed-loop control systems including human operator for manned spacecraft
Four approximations to closed loop steering function in application to spacecraft guidance
Design, fabrication, and testing of inverter module for closed loop advanced control signal processor - thin film circuit, and conformal coating and encapsulation
Sequential suboptimal adaptive control of nonlinear systems, considering generation of optimum closed-loop control for startup dynamics of nuclear reactor
Closed loop LaCoste and Romberg gravimeter servo system operating at sensitivity approach thermal fluctuation limits
Linear optimal control technique for flexible- booster control system design, showing drift minimum model with matrix transformations for closed-loop dynamics
Drift- and offset-control circuit compensates the inherent temperature drift and offset of a closed-loop feedback amplifier. It overcomes the disadvantages of conventional chopping circuits used to minimize drift in low-level, direct-coupled amplifiers.
Sensor automatically and accurately measures the two-dimensional deflection angles of a laser beam to provide closed-loop servomechanism control of laser beam directivity.
Closed loop, manual, time optimal, bang bang control of high order systems using concept of switching surface
Closed loop capacitive pressure transducer with extended frequency response for very low pressure measurements
Performance testing of NERVA XE-1 control drum actuator to determine its ability to function in closed loop positioning system
Performance comparison of electromechanical and electroluminescent displays in closed loop manual tracking task and reading accuracy tests
Closed loop facility designed to study MHD generator using argon-cesium working fluid