Influence of Reservoir Convection on Heat Extraction with Closed-Loop Geothermal Systems
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Hakes Weston-Dawkes, Raquel Sara Pilar↗
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Controller synthesis for infinite dimensional systems based on a passivity approach
The author discusses a generalization of hyperstability to systems in Hilbert space and its application to finite-dimensional stabilizing compensator design. The basic idea is to characterize tolerable perturbations in terms of the passivity of the nominal closed-loop system. Controllers achieving the required closed-loop passivity property can then be designed using H(infinity)-optimization. In particular, the author presents a design procedure for a stabilizing a finite-dimensional compensator for a given infinite-dimensional system.
Wen, John T.↗
A method for ''closing the loop'' in explicit guidance systems.
Equations implementing closed loop control in explicit guidance systems
Price, C. F.↗
Application of gas bearings to closed-system Brayton-cycle turbomachinery - Recent accomplishments and potential problem areas.
Gas lubricated bearings used in Brayton cycle closed-loop system turbomachinery in design of two-shaft power plant
TURBOMACHINE↗
Application of gas bearings to closed-system Brayton-cycle turbomachinery - Recent accomplishments and potential problem areas.
Gas lubricated bearings used in Brayton cycle closed loop system turbomachinery in design of two-shaft power plant
POWER PLANT↗
Closed-loop, approximately time-optimal control of linear systems.
Closed-loop approximately time optimal control of linear systems based on eignevector scalar product solutions to Hamilton-Jacobi equation
CLOSED LOOP SYSTEM↗
On the design of optimal input signals in system identification
The problem of designing optimal inputs in the identification of multi-input multi-output linear systems with unknown time-varying parameters is considered using a Bayesian approach. A sensitivity index gives a measure of performance for the closed-loop system inputs. The computation of the optimal closed-loop mappings is shown to be a nontrivial exercise in stochastic control with no analytic solution, but optimal open-loop and affine laws yield much more tractable problems. For time-invariant systems, the sensitivity index considered is shown to be equivalent to the trace of the (strictly positive definite) information matrix associated with the system. Numerical examples are given. A Kalman filter is used to estimate the parameters. A necessary condition for the Kalman filter not to diverge when applying linear feedback is also given.
Lopez-Toledo, A. A.↗
An onboard, closed-loop, nutation control system for a spin-stabilized spacecraft.
Automatic closed loop onboard nutation control system for unstable asymmetrical spin stabilized spacecraft, analyzing Applications Technology Satellite system and performance
Grasshoff, L. H.↗
A closed loop life support system for determining metabolic gases produced by small animals
Closed loop life support system for determining metabolic gases from rats
Binks, A. E.↗
Modeling the Scheduling of Eye Movements and Manual Responses in Performing a Sequence of Discrete Tasks
Common tasks in daily life are often accomplished by a sequence of actions that interleave information acquisition through the eyes and action execution by the hands. How are eye movements coordinated with the release of manual responses and how may their coordination be represented at the level of component mental operations? We have previously presented data from a typing-like task requiring separate choice responses to a series of five stimuli. We found a consistent pattern of results in both motor and ocular timing, and hypothesized possible relationships among underlying components. Here we report a model of that task, which demonstrates how the observed timing of eye movements to successive stimuli could be accounted for by assuming systems: an open-loop system generating saccades at a periodic rate, and a closed-loop system commanding a saccade based on stimulus processing. We relate this model to models of reading and discuss the motivation for dual control.
Wu, Shu-Chieh↗
Closed Loop Water Purification System Utilizing an Algae Membrane Photobioreactor for the International Space Station
The International Space Station (ISS) currently operates on an open-loop water purification and distribution system. This system is only 75% efficient with a 25% water loss that must be resupplied on a quarterly basis through cargo resupply missions (Pickett, M.). This system is not feasible for long-duration spaceflight missions. A closed-loop water purification system aboard the ISS can benefit water reclamation and become the water purification system for long-term space flight. The primary sub-systems integrated within the proposed closed loop system include an anaerobic digestion membrane bioreactor and an algae membrane photobioreactor. The processes mimics the abilities of natural biological systems naturally. The water that flows from the algal membrane photobioreactor is rich in nutrients providing a feed source for plants aboard the ISS or can be further processed for potable water.
photobioreactor↗
Effect of control surface mass unbalance on the stability of a closed-loop active control system
An inertial energy approach similar to the aerodynamic energy method for flutter suppression is used to investigate the effects of mass-unbalanced control surfaces on the stability of a closed-loop system. It is demonstrated that a spanwise section for sensor location can be obtained which ensures minimum sensitivity to the mode shapes of the aircraft. Leading-edge control is characterized by a compatibility between inertial stabilization and aerodynamic stabilization that trailing-edge control lacks.
Nissim, E.↗
Robustness of linear quadratic state feedback designs in the presence of system uncertainty
The paper deals with the problem of expressing the robustness (stability) property of a linear quadratic state feedback (LQSF) design quantitatively in terms of bounds on the perturbations (modeling errors or parameter variations) in the system matrices so that the closed-loop system remains stable. Nonlinear time-varying and linear time-invariant perturbations are considered. The only computation required in obtaining a measure of the robustness of an LQSF design is to determine the eigenvalues of two symmetric matrices determined when solving the algebraic Riccati equation corresponding to the LQSF design problem. Results are applied to a complex dynamic system consisting of the flare control of a STOL aircraft. The design of the flare control is formulated as an LQSF tracking problem.
Patel, R. V.↗
PC-based Digital Acoustic Control System (DACS)
The PC-based Digital Acoustic Control System (DACS), which is a closed-loop system capable of precisely controlling the spectrum in real-time mode, is discussed. The system is based on integrated facility hardware including control microphones, signal conditioners, a real-time analyzer (RTA), a shaper, high capacity power amplifiers, and acoustic horns and generators. The DACS provides both an improved spectrum simulation and realtime information of pertinent test parameters that are stored in five separate files. These files can be hard copied and/or transferred to other programs to obtain a specific format of the test data. It is demonstrated that the computer interface with digital RTA and programmable filters are most effective and efficient. This facility runs independently under the control of a computer with an IEEE-488 interface to the facility hardware.
Shah, Kamlesh C.↗
Characterization of a Recoverable Flight Control Computer System
The design and development of a Closed-Loop System to study and evaluate the performance of the Honeywell Recoverable Computer System (RCS) in electromagnetic environments (EME) is presented. The development of a Windows-based software package to handle the time-critical communication of data and commands between the RCS and flight simulation code in real-time while meeting the stringent hard deadlines is also submitted. The performance results of the RCS and characteristics of its upset recovery scheme while exercising flight control laws under ideal conditions as well as in the presence of electromagnetic fields are also discussed.
Malekpour, Mahyar↗
Dynamic testing when the response data is contaminated with noise.
Closed loop system with reference to different gyro stabilization loops present in modern space vehicle inertial measuring unit, using Prony exponential series curve fitting method as analytical tool
CLOSED LOOP SYSTEM↗
Integrated Evaluation of Closed Loop Air Revitalization System Components
NASA s vision and mission statements include an emphasis on human exploration of space, which requires environmental control and life support technologies. This Contractor Report (CR) describes the development and evaluation of an Air Revitalization System, modeling and simulation of the components, and integrated hardware testing with the goal of better understanding the inherent capabilities and limitations of this closed loop system. Major components integrated and tested included a 4-Bed Modular Sieve, Mechanical Compressor Engineering Development Unit, Temperature Swing Adsorption Compressor, and a Sabatier Engineering and Development Unit. The requisite methodolgy and technical results are contained in this CR.
Murdock, K.↗
An Optimized Integrator Windup Protection Technique Applied to a Turbofan Engine Control
This paper introduces a new technique for providing memoryless integrator windup protection which utilizes readily available optimization software tools. This integrator windup protection synthesis provides a concise methodology for creating integrator windup protection for each actuation system loop independently while assuring both controller and closed loop system stability. The individual actuation system loops' integrator windup protection can then be combined to provide integrator windup protection for the entire system. This technique is applied to an H(exp infinity) based multivariable control designed for a linear model of an advanced afterburning turbofan engine. The resulting transient characteristics are examined for the integrated system while encountering single and multiple actuation limits.
Watts, Stephen R.↗