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At least 55 records · Page 3

The analysis of delays in simulator digital computing systems. Volume 1: Formulation of an analysis approach using a central example simulator model

The effects of spurious delays in real time digital computing systems are examined. Various sources of spurious delays are defined and analyzed using an extant simulator system as an example. A specific analysis procedure is set forth and four cases are viewed in terms of their time and frequency domain characteristics. Numerical solutions are obtained for three single rate one- and two-computer examples, and the analysis problem is formulated for a two-rate, two-computer example.

Heffley, R. K.↗

Digital simulation of hybrid loop operation in RFI backgrounds.

A digital computer model for Monte-Carlo simulation of an imperfect second-order hybrid phase-locked loop (PLL) operating in radio-frequency interference (RFI) and Gaussian noise backgrounds has been developed. Characterization of hybrid loop performance in terms of cycle slipping statistics and phase error variance, through computer simulation, indicates that the hybrid loop has desirable performance characteristics in RFI backgrounds over the conventional PLL or the costas loop.

Ziemer, R. E.↗

A comparison of digitally simulated holographic images with actual holographic images

In making digitally generated holograms the digital computer and its associated plotting equipment degrade the quality of the hologram. It is necessary then to study the computer generated hologram in terms of these degradations. A computer simulated optical processor allows the results to be observed via computer simulated images. This research reports a method for optimizing the computer image reconstruction and compares these images with optically produced holographic images. The versatility of the simulated optical processor is illustrated by several spatial filtering and hologram reconstructions.

Calhoun, M. D.↗

Function generation subprograms for use in digital simulations

Function generation subprograms were developed for handling functions of one variable and two types of functions of two variables. These subprograms can be used in any digital or hybrid simulation requiring function generation. Use of these programs can often lower overall program execution time.

Hart, C. E.↗

Common modeling system for digital simulation

The Joint Modeling and Simulation System is a tri-service investigation into a common modeling framework for the development digital models. The basis for the success of this framework is an X-window-based, open systems architecture, object-based/oriented methodology, standard interface approach to digital model construction, configuration, execution, and post processing. For years Department of Defense (DOD) agencies have produced various weapon systems/technologies and typically digital representations of the systems/technologies. These digital representations (models) have also been developed for other reasons such as studies and analysis, Cost Effectiveness Analysis (COEA) tradeoffs, etc. Unfortunately, there have been no Modeling and Simulation (M&S) standards, guidelines, or efforts towards commonality in DOD M&S. The typical scenario is an organization hires a contractor to build hardware and in doing so an digital model may be constructed. Until recently, this model was not even obtained by the organization. Even if it was procured, it was on a unique platform, in a unique language, with unique interfaces, and, with the result being UNIQUE maintenance required. Additionally, the constructors of the model expended more effort in writing the 'infrastructure' of the model/simulation (e.g. user interface, database/database management system, data journalizing/archiving, graphical presentations, environment characteristics, other components in the simulation, etc.) than in producing the model of the desired system. Other side effects include: duplication of efforts; varying assumptions; lack of credibility/validation; and decentralization in policy and execution. J-MASS provides the infrastructure, standards, toolset, and architecture to permit M&S developers and analysts to concentrate on the their area of interest.

Painter, Rick↗

Digital simulation of an aerospace vehicle.

Aerospace Vehicle Simulation /AVS/ Program simulating continuous and discrete dynamics of aerospace vehicles and ground support equipment on digital computer

Mitchell, J. R.↗

Determination of the implementation of the 3-axis attitude motion simulator digital position controller

The digital position controller implemented in the control computer of the 3-axis attitude motion simulator is mathematically reconstructed and documented, since the information supplied with the executable code of this controller was insufficient to make substantial modifications to it. Also developed were methodologies to introduce changes in the controller which do not require rewriting the software. Finally, recommendations are made on possible improvement to the control system performance.

Magana, Mario E.↗

Digital simulation of the SIR-C sensor electronics

In this paper software for simulation of the response of the SIR-C sensor to a point target is described. Synthetic SAR data is generated by passing successive chirps through a simulation of the transmitter electronics, propagation path and receiver electronics. This result is then processed with a digital correlator to yield the point target response of the system. This allows an accurate assessment of the effect of the radar design on the final image product.

Klein, Jeffrey D.↗

Digital simulation of a 30-cm diameter ion thruster control system

A hybrid model of a 30-cm diameter ion thruster and transistorized power processor was formulated and implemented on a digital computer. The control loops as presented are stable for normal values of loop gain when propellant line delay times are zero. Small oscillations are present in the loops when representative thruster delay times are included in the model. Discharge supply characteristics can affect the control loop oscillations. Recovery from runaway can be aggravated by delay time and, to a greater extent, by discharge supply characteristics.

Kudo, I.↗

Improved technique for digital simulation of bending and slosh phenomena

Mathematical model representation of bending and slosh phenomena in the Saturn vehicle results in linear second order differential equations. Improved technique was developed to provide a real-time digital solution of the equations. The technique may also be applied to nonreal time digital simultations, resulting in savings of digital computer time.

Stauffer, N. E.↗

Analog-digital simulation of transient-induced logic errors and upset susceptibility of an advanced control system

A simulation study is described which predicts the susceptibility of an advanced control system to electrical transients resulting in logic errors, latched errors, error propagation, and digital upset. The system is based on a custom-designed microprocessor and it incorporates fault-tolerant techniques. The system under test and the method to perform the transient injection experiment are described. Results for 2100 transient injections are analyzed and classified according to charge level, type of error, and location of injection.

Carreno, Victor A.↗

Aid For Simulating Digital Flight Control Systems

DIVERS translator is computer program to convert descriptions of digital flight-control systems (DFCS) into computer program. Language developed to represent design charts of DFCS. Translator converts DIVERS source code into easily transportable language, while minimizing probability that results are affected by interpretation of programmer. Final translated program used as standard of comparison to verify operation of actual flight-control systems. Applicable to simulation of other control systems; for example, electrical circuits and logic processes. Written in C.

Hartman, Richard M.↗