Obtaining multi-loop pursuit-control pilot models from computer simulation

2008 ◽  
Vol 222 (2) ◽  
pp. 189-199 ◽  
Author(s):  
R A Hess
Keyword(s):  
Computer Simulation ◽  
Time Domain ◽  
Flight Control ◽  
Linear Models ◽  
Degree Of Freedom ◽  
Pilot Model ◽  
Pursuit Control ◽  
The Time Domain ◽  
Frequency Domain Techniques ◽  
Six Degree Of Freedom

A method for generating simplified pursuit-control pilot models for computer simulation of multi-axis flight control tasks has been developed. The method involves a sequential loop closure synthesis procedure for creating the pilot model and includes handling qualities estimation. The original model formulation previously reported in the literature used frequency-domain techniques, primarily Bode diagrams to select model gains. The present research demonstrates how similar results can be obtained in the time-domain. This latter approach is particularly useful when complex, non-linear aircraft models are being used. The time-domain approach is exercised in a six-degree of freedom rotorcraft control simulation and in a six-degree of freedom tailless fighter simulation, both involving linear models.

Research on the Dynamic Characteristic of the Bogie in Dynamic Track Stabilizer under the Excitation of the Track Irregularities

2012 ◽  
Vol 178-181 ◽  
pp. 1438-1441
Author(s):  
Li Hua Wang ◽  
Guang Wei Liu ◽  
An Ning Huang ◽  
Ya Yu Huang
Keyword(s):  
Spectral Density ◽  
Dynamic Characteristic ◽  
Time Domain ◽  
Large Scale ◽  
Degree Of Freedom ◽  
Speed Up ◽  
Critical Components ◽  
The Time Domain ◽  
Six Degree Of Freedom ◽  
Track Irregularities

With the large-scale speed-up of the railway, the dynamic track stabilizer will play an important role on the track overhauling and railroading of new line in our country. Bogie is one of the major critical components of the dynamic track stabilizer; its vibrating characteristic will affect the vibrating characteristic of the dynamic track stabilizer directly. The method of numerical simulate was used, based on the spectral density of the track irregularities, the time domain loads of the track irregularities were gained. Then the vibrating characteristics of the dynamic track stabilizer bogie under the excitation of the track irregularities were analyzed on the bases of the ANSYS/LS-DYNA. And the lateral, dilation, ups and downs, nod, swing and anti-rolling vibrating characteristics of the bogie on the six degree of freedom were obtained. The analysis results of this paper will provide foundation for the research on the stationarity and security of the dynamic track stabilizer.

Time‐domain estimation of MT Impedance tensor

Geophysics ◽  
1994 ◽  
Vol 59 (5) ◽  
pp. 712-721 ◽  
Author(s):  
Umberto Spagnolini
Keyword(s):  
Time Domain ◽  
Bayes Estimation ◽  
Impedance Tensor ◽  
Data Sets ◽  
Least Mean Square ◽  
Step Size ◽  
Juan De Fuca ◽  
The Time Domain ◽  
Reference Processing ◽  
Frequency Domain Techniques

The spectral analysis of magnetotelluric (MT) data for impedance tensor estimation requires the stationarity of measured magnetic (H) and electric (E) fields. However, it is well known that noise biases timedomain tensor estimates obtained via an iterative search by a descent algorithm to determine the least‐mean‐square residual between measured and estimated E data obtained from H data. To limit the noise that slows down, or even prevents convergence, the steepest descent step size is based upon the statistics of the residual (Bayes’ estimation). With respect to uncorrelated noise, the time‐domain technique is more robust than frequency‐domain techniques. Furthermore, the technique requires only short‐time stationarity. The time‐domain technique is applied to data sets (Lincoln Line sites) from the EMSLAB Juan de Fuca project (Electromagnetic Sounding of the Lithosphere and Asthenosphere Beneath the Juan de Fuca Plate), as well as to data from a southern Italian site. The results of EMSLAB data analysis are comparable to those obtained by robust remote reference processing where larger data sets were used.

A Numerical Method for Representing Retardation Functions With Complex Exponentials

2017 ◽  
Author(s):  
Fushun Liu ◽  
Lei Jin ◽  
Jiefeng Chen ◽  
Wei Li
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Degrees Of Freedom ◽  
Added Mass ◽  
Memory Effects ◽  
Floating Structure ◽  
Frequency Dependent ◽  
Laplace Domain ◽  
The Time Domain ◽  
Frequency Domain Techniques

Numerical time- or frequency-domain techniques can be used to analyze motion responses of a floating structure in waves. Time-domain simulations of a linear transient or nonlinear system usually involve a convolution terms and are computationally demanding, and frequency-domain models are usually limited to steady-state responses. Recent research efforts have focused on improving model efficiency by approximating and replacing the convolution term in the time domain simulation. Contrary to existed techniques, this paper will utilize and extend a more novel method to the frequency response estimation of floating structures. This approach represents the convolution terms, which are associated with fluid memory effects, with a series of poles and corresponding residues in Laplace domain, based on the estimated frequency-dependent added mass and damping of the structure. The advantage of this approach is that the frequency-dependent motion equations in the time domain can then be transformed into Laplace domain without requiring Laplace-domain expressions of the added mass and damping. Two examples are employed to investigate the approach: The first is an analytical added mass and damping, which satisfies all the properties of convolution terms in time and frequency domains simultaneously. This demonstrates the accuracy of the new form of the retardation functions; secondly, a numerical six degrees of freedom model is employed to study its application to estimate the response of a floating structure. The key conclusions are: (1) the proposed pole-residue form can be used to consider the fluid memory effects; and (2) responses are in good agreement with traditional frequency-domain techniques.

Suspension Dynamics by Computer Simulation

1968 ◽  
Vol 90 (4) ◽  
pp. 708-715
Author(s):  
W. B. Diboll ◽  
H. S. Bieniecki
Keyword(s):  
Computer Simulation ◽  
Digital Computer ◽  
Total Mass ◽  
Analytical Study ◽  
Center Of Gravity ◽  
Degree Of Freedom ◽  
Design Parameters ◽  
Spring Stiffness ◽  
Suspension Dynamics ◽  
Six Degree Of Freedom

An analytical study of the effect of changing the design parameters of a two mass, six-degree-of-freedom suspension system was made. Rail cars with coil and air springs were analyzed by analog and digital computer. Spring stiffness, spring spacing, damping rates, height of center of gravity, and total mass were varied. The effect on frequency and response were determined.

A New Method for Optimizing Friction Damping in Randomly Excited Systems

1989 ◽  
Author(s):  
T. M. Cameron ◽  
J. H. Griffin
Keyword(s):  
Time Domain ◽  
Turbine Blades ◽  
Single Mode ◽  
Random Excitation ◽  
Degree Of Freedom ◽  
System Response ◽  
Friction Damping ◽  
Single Mode Approximation ◽  
The One ◽  
The Time Domain

A method is developed that can be used to calculate the stationary response of randomly excited nonlinear systems. The method iterates to obtain the fast Fourier transform of the system response, returning to the time domain at each iteration to take advantage of the ease in evaluating nonlinearities there. The updated estimates of the nonlinear terms are transformed back into the frequency domain in order to continue iterating on the frequency spectrum of the staionary response. This approach is used to calculate the response of a one degree of freedom system with friction damping that is subjected to random excitation. The one degree of freedom system provides a single mode approximation of systems (e.g. turbine blades) with friction damping. This study investigates various strategies that can be used to optimize the friction load so as to minimize the response of the system.

scholarly journals Reduction of False Alarm Probability in the Measuring Node of the Hydroacoustic Monitoring System

2020 ◽  
pp. 568-577
Author(s):  
Pavel A. Starodubtsev ◽  
Evgeny A. Storozhok ◽  
Roman N. Alifanov
Keyword(s):  
Computer Simulation ◽  
False Alarm ◽  
Monitoring System ◽  
Time Domain ◽  
False Alarm Probability ◽  
Signal Source ◽  
Amplifier Output ◽  
Primary Identification ◽  
The Time Domain ◽  
Measuring Unit

The probability of a false alarm in the measuring unit of the hydroacoustic monitoring system can be reduced if the primary identification of the signal source is carried out. For this purpose, it is necessary to provide for the presence of noise portraits of targets in the database node. The signals from the pre-amplifier output of the measuring unit are compared with the signals stored in the database by calculating the standard deviation. The signal with the minimum deviation and its corresponding source are determined. Comparison of signals can be made by calculating the correlation function. This article presents the results of computer simulation of the primary classification unit of the measuring unit in the MATLAB&SIMULINK system. The compared signals are represented in the time domain

Robust Nonlinear Finite-State Inflow Model for Lifting Rotor Coupled With Blade Flapping

2017 ◽  
Author(s):  
Jianzhe Huang ◽  
David Peters
Keyword(s):  
Real Time ◽  
Time Domain ◽  
Flight Control ◽  
Closed Form Solution ◽  
Form Solution ◽  
Blade Element Theory ◽  
Finite State ◽  
Flight Controls ◽  
The Time Domain ◽  
Induced Velocity

Real-time inflow model for lifting rotor is required for pilot-in-the-loop simulation and flight control design. The recent developed blended inflow model have advanced the state-of-the-art with closed-form solution for all three components of the flow everywhere in the field, including below the plane of the rotor disk both in-wake and out-of-wake. The nonlinearity will be introduced in such blended model to make it more flexible not only for helicopter in cruise condition, but also for helicopter in low speed flight or hover. The dynamic loading for such inflow model will be computed in real-time based on blade element theory. Then the flap motions of blades of lifting rotor will be coupled, and the induced velocity will be solved numerically in the time domain through the simpletic scheme. A Harrington rotor will be studied as an example. The induced velocity in the time domain for such a rotor will be calculated with a specific flight controls.

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