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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

The dish-Rankine SCSTPE program (Engineering Experiment no. 1)

Activities planned for phase 2 Of the Small Community Solar Thermal Power Experiment (PFDR) program are summarized with emphasis on a dish-Rankine point focusing distributed receiver solar thermal electric system. Major design efforts include: (1) development of an advanced concept indirect-heated receiver;(2) development of hardware and software for a totally unmanned power plant control system; (3) implementation of a hybrid digital simulator which will validate plant operation prior to field testing; and (4) the acquisition of an efficient organic Rankine cycle power conversion unit. Preliminary performance analyses indicate that a mass-produced dish-Rankine PFDR system is potentially capable of producing electricity at a levelized busbar energy cost of 60 to 70 mills per KWh and with a capital cost of about $1300 per KW.

Pons, R. L.↗
NASA NTRS1980

MOD-2 wind turbine farm stability study

The dynamics of single and multiple 2.5 ME, Boeing MOD-2 wind turbine generators (WTGs) connected to utility power systems were investigated. The analysis was based on digital simulation. Both time response and frequency response methods were used. The dynamics of this type of WTG are characterized by two torsional modes, a low frequency 'shaft' mode below 1 Hz and an 'electrical' mode at 3-5 Hz. High turbine inertia and low torsional stiffness between turbine and generator are inherent features. Turbine control is based on electrical power, not turbine speed as in conventional utility turbine generators. Multi-machine dynamics differ very little from single machine dynamics.

Hinrichsen, E. N.↗
NASA NTRS1979

Dynamic modeling of brushless dc motor-power conditioner unit for electromechanical actuator application

A comprehensive digital model for the analysis of the dynamic-instantaneous performance of a power conditioner fed samarium-cobalt permanent magnet brushless DC motor is presented. The particular power conditioner-machine system at hand, for which this model was developed, is a component of an actual prototype electromechanical actuator built for NASA-JSC as a possible alternative to hydraulic actuators as part of feasibility studies for the shuttle orbiter applications. Excellent correlation between digital simulated and experimentally obtained performance data was achieved for this specific prototype. This is reported on in this paper. Details of one component of the model, its applications and the corresponding results are given in this paper.

Demerdash, N. A.↗
NASA NTRS1980

Multivarable nyquist array method with application to turbofan engine control

Extensions to the multivariable Nyquist array (MNA) method are used to design a feedback control system for the quiet clean shorthaul experimental engine. The results of this design are compared with those obtained from the deployment of an alternate control system design on a full scale nonlinear, real time digital simulation. The results clearly demonstrate the utility of the MNA synthesis procedures for highly nonlinear sophisticated design applications.

Leininger, G. G.↗
NASA NTRS1980

Alternatives for jet engine control

Alternatives to linear quadratic regulator theory in the linear case are examined along with nonlinear modelling and optimization approaches for global control. Context for the studies has been set by the DYNGEN digital simulator and by models generated for various phases of the F100 Multivariable Control Synthesis Program. With respect to the linear alternatives, the multivariable frequency domain is stressed. Progress is reported in both the direct algebraic approach to exact model matching, by means of stimulating work on the basic computational issues, and in the indirect generalized Nyquist approach. With respect to nonlinear modelling and optimization, the emphasis is twofold: the development of analytical nonlinear models of the jet engine and the use of these models in conjunction with techniques of mathematical programming in order to study global control over nonincremental portions of the flight envelope. The possibility of using tensor methods is explored.

Sain, M. K.↗
NASA NTRS1981

Application of the MNA design method to a nonlinear turbofan engine

Using nonlinear digital simulation as a representative model of the dynamic operation of the QCSEE turbofan engine, a feedback control system is designed by variable frequency design techniques. Transfer functions are generated for each of five power level settings covering the range of operation from approach power to full throttle (62.5% to 100% full power). These transfer functions are then used by an interactive control system design synthesis program to provide a closed loop feedback control using the multivariable Nyquist array and extensions to multivariable Bode diagrams and Nichols charts.

Leininger, G. G.↗
NASA NTRS1982

Combined discrete network. Continuous control modelling of operator behavior

The situation in which an operator is faced with a continuous control task plus one or more discrete information processing tasks is discussed. A modelling approach which has the capability of realistically representing both types of tasks and the resulting interactions is sought. The modelling approach utilizes discrete network models for the cognitive tasks and elements of an open-loop - closed-loop control representation for the continuous task. the approach is demonstrated through its application to a simulated Digital Avionics Information System in which subjects were required to perform retrieval and processing tasks as well as flight control. This model differs from conventional model in that system status sampling is not necessarily continuous or periodic. Rather, the pilot is assumed to read system status displays only as time permits and operate in a so-called open-loop preprogrammed fashion between sampling.

Miller, R. A.↗
NASA NTRS1982

An identification algorithm for linear stochastic systems with time delays

Linear discrete stochastic control systems containing unknown multiple time delays, plant parameters and noise variances are considered. An algorithm is established which uses the maximum-likelihood technique to identify the unknown parameters. An estimated likelihood function is evaluated based on the previous parameter estimates, which in turn generates a new descent direction vector to update the unknown parameters. The delays and plant parameters are identified in their respective parameter spaces. An example of a second-order stochastic system has been implemented by digital simulation to demonstrate the applicability of the algorithm.

Leondes, C. T.↗
NASA NTRS1983

Reliability analysis and fault-tolerant system development for a redundant strapdown inertial measurement unit

A methodology is developed and applied for quantitatively analyzing the reliability of a dual, fail-operational redundant strapdown inertial measurement unit (RSDIMU). A Markov evaluation model is defined in terms of the operational states of the RSDIMU to predict system reliability. A 27 state model is defined based upon a candidate redundancy management system which can detect and isolate a spectrum of failure magnitudes. The results of parametric studies are presented which show the effect on reliability of the gyro failure rate, both the gyro and accelerometer failure rates together, false alarms, probability of failure detection, probability of failure isolation, and probability of damage effects and mission time. A technique is developed and evaluated for generating dynamic thresholds for detecting and isolating failures of the dual, separated IMU. Special emphasis is given to the detection of multiple, nonconcurrent failures. Digital simulation time histories are presented which show the thresholds obtained and their effectiveness in detecting and isolating sensor failures.

Motyka, P.↗
NASA NTRS1983

Alternatives for jet engine control

The development of models of tensor type for a digital simulation of the quiet, clean safe engine (QCSE) gas turbine engine; the extension, to nonlinear multivariate control system design, of the concepts of total synthesis which trace their roots back to certain early investigations under this grant; the role of series descriptions as they relate to questions of scheduling in the control of gas turbine engines; the development of computer-aided design software for tensor modeling calculations; further enhancement of the softwares for linear total synthesis, mentioned above; and calculation of the first known examples using tensors for nonlinear feedback control are discussed.

Sain, M. K.↗
NASA NTRS1983

Heavy-lift airship dynamics

The basic aerodynamic and dynamic properties of an example heavy-lift airship (HLA) configuration are analyzed using a nonlinear, multibody, 6-degrees-of-freedom digital simulation. The slung-payload model is described, and a preliminary analysis of the coupled vehicle-payload dynamics is presented. Trim calculations show the importance of control mixing selection and suggest performance deficiencies in crosswind stationkeeping for the unloaded example HLA. Numerically linearized dynamics of the unloaded vehicle exhibit a divergent yaw mode and an oscillatory pitch mode whose stability characteristic is sensitive to flight speed. An analysis of the vehicle-payload dynamics shows significant coupling of the payload dynamics with those of the basic HLA. It is shown that significant improvement in the vehicle's dynamic behavior can be achieved with the incorporation of a simple flight controller having proportional, rate, and integral-error feedbacks.

Tischler, M. B.↗
NASA NTRS1983

Control of the forebody vortex orientation by asymmetric air injection. Part A: Application to enhance departure/spin recovery of fighter aircraft and Part B: Details of the flow structure

A concept developed to provide powerful directional control effectiveness for a fighter aircraft at high angles of attack is described. The concept utilizes the energy concentrated in the strong forebody vortices (which form on slender bodies of high relative incidence) by controlling the lateral orientation of the vortices with respect to the body. The objective was to utilize the side force associated with asymmetric vortices, in a controlled manner, to enhance the ability of the fighter to recover from a departure from controlled flight. The results from water tunnel and wind tunnel experiments show that a small amount of tangential blowing along the forebody near the apex can effectively alter the forebody vortex system and generate large restoring yawing moments. Six degree of freedom digital simulation results show that this concept can substantially enhance recovery characteristics of fighter aircraft with long, slender forebodies. Also, the results of experiments which were conducted on a cone model are discussed where the principal test objective was to develop an understanding of the fluid mechanics involved in the process of vortex control. Knowledge gained in these more generic tests should allow the concept to be applied to a wider range of configurations.

Skow, A. M.↗
NASA NTRS1984

Stability of a dual-spin spacecraft with spherical dampers

The present investigation is concerned with the stability characteristics of a specific dual-spin satellite configuration marked by a high degree of symmetry. The configuration includes a platform and a rotor. Both components contain arbitrarily located internal spherical dampers. The symmetry of the system configuration makes it possible to illustrate clearly the relationship between Routhian analysis, energy sink analysis, and digital simulation of the full nonlinear equations. Although the dual-spin spacecraft configuration contains energy dissipating devices on both platform and rotor, it is still possible to employ the rigorous, but relatively simple, Routh stability method. This method, unlike Floquet theory, has the potential of producing closed-form stability criteria. The energy sink method is capable of providing a closed-form stability criterion. Numerical simulation is a necessary requirement in the latter stages of design when the realistic perturbation environment must be considered.

Laskin, R. A.↗
NASA NTRS1982

An application of tensor ideas to nonlinear modeling of a turbofan jet engine

An application of tensor modelling to a digital simulation of NASA's Quiet, Clean, Shorthaul Experimental (QCSE) gas turbine engine is presented. The results show that the tensor algebra offers a universal parametrization which is helpful in conceptualization and identification for plant modelling prior to feedback or for representing scheduled controllers over an operating line.

Klingler, T. A.↗
NASA NTRS1985

DEAN: A program for dynamic engine analysis

The Dynamic Engine Analysis program, DEAN, is a FORTRAN code implemented on the IBM/370 mainframe at NASA Lewis Research Center for digital simulation of turbofan engine dynamics. DEAN is an interactive program which allows the user to simulate engine subsystems as well as a full engine systems with relative ease. The nonlinear first order ordinary differential equations which define the engine model may be solved by one of four integration schemes, a second order Runge-Kutta, a fourth order Runge-Kutta, an Adams Predictor-Corrector, or Gear's method for still systems. The numerical data generated by the model equations are displayed at specified intervals between which the user may choose to modify various parameters affecting the model equations and transient execution. Following the transient run, versatile graphics capabilities allow close examination of the data. DEAN's modeling procedure and capabilities are demonstrated by generating a model of simple compressor rig.

Sadler, G. G.↗
NASA NTRS1985

A preliminary evaluation of a failure detection filter for detecting and identifying control element failures in a transport aircraft

The application of the failure detection filter to the detection and identification of aircraft control element failures was evaluated in a linear digital simulation of the longitudinal dynamics of a B-737 Aircraft. Simulation results show that with a simple correlator and threshold detector used to process the filter residuals, the failure detection performance is seriously degraded by the effects of turbulence.

Bundick, W. T.↗
NASA NTRS1985

Optical linear algebra processors - Noise and error-source modeling

The modeling of system and component noise and error sources in optical linear algebra processors (OLAPs) are considered, with attention to the frequency-multiplexed OLAP. General expressions are obtained for the output produced as a function of various component errors and noise. A digital simulator for this model is discussed.

Casasent, D.↗
NASA NTRS1985

A preliminary evaluation of the generalized likelihood ratio for detecting and identifying control element failures in a transport aircraft

The application of the Generalized Likelihood Ratio technique to the detection and identification of aircraft control element failures has been evaluated in a linear digital simulation of the longitudinal dynamics of a B-737 aircraft. Simulation results show that the technique has potential but that the effects of wind turbulence and Kalman filter model errors are problems which must be overcome.

Bundick, W. T.↗