The Derivation and Use of Aerodynamic Transfer Functions of Airframes

1955 ◽  
Vol 59 (539) ◽  
pp. 743-761 ◽  
Author(s):  
F. R. J. Spearman
Keyword(s):  
Transfer Functions ◽  
Block Diagram ◽  
Cross Coupling ◽  
Aerodynamic Characteristics ◽  
Open Loop ◽  
Control Surface ◽  
Electrical Networks ◽  
Servo Mechanism ◽  
Amplifier Design ◽  
Set Up

SummaryThe aerodynamic characteristics of airframes are expressed as aerodynamic transfer functions, giving the relationships between input and output for each of the three separate planes of motion, roll, pitch, and yaw. By assuming no cross-coupling between planes and linear aerodynamics, and by making certain other assumptions, which apply particularly to conventional airframes with fixed wings and rear controls, relatively simple approximate algebraic transfer functions giving the relationships between the control surface deflection (the input) and any airframe motion (the output), are obtained.The open loop aerodynamic transfer functions thus obtained are used as part of the auto-pilot block diagram, in which the performance of other components, such as actuators, instruments and electrical networks, are also expressed in transfer function form. The aerodynamic transfer functions are useful in auto-pilot evolution and synthesis in that they aid selection of the airframe motions to be measured, modified, and fed back to close the auto-pilot loop.For mathematical assessment of closed loop performance and stability, open loop transient and frequency responses are used, and curves of airframe responses are plotted in linear, logarithmic and polar form by standard methods from the aerodynamic transfer functions. Some methods of using these curves, which follow the general lines adopted in servo-mechanism and electronic amplifier design, are explained briefly.Analogue computers are frequently used when the computations to be made are so complicated as to need the use of a computing machine. The aerodynamic transfer functions then form one block of the simulator set-up, and on larger computers the more exact form, including any non-linearities and cross-coupling effects, can be used.

scholarly journals Dynamic Modeling and Coupling Characteristic Analysis of Two-Axis Rate Gyro Seeker

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Shixiang Liu ◽  
Tianyu Lu ◽  
Teng Shang ◽  
Qunli Xia
Keyword(s):  
Block Diagram ◽  
Cross Coupling ◽  
Coupled System ◽  
Open Loop ◽  
Servo Control ◽  
Control Mode ◽  
Characteristic Analysis ◽  
Rate Gyro ◽  
Coupling Characteristics ◽  
Stabilized Platform

A dynamic model of a two-axis rate gyro-stabilized platform-based seeker with cross-coupling, mass imbalance, and disturbance torque is developed on the basis of the working principle of seeker two-loop steady tracking theory; coordinate transformations are used to analyze the effects of seeker servo control mode on missile guidance and control systems. Frequency domain is used to identify the servo motor transfer function. Furthermore, a block diagram of the two-gimbal-coupled system is developed, and the coupling characteristics of gimbal angle are analyzed with different missile body inputs. Simulation results show that the analysis conforms with the actual movement rule of seeker gimbal and optical axis, and cross-coupling exists between the two gimbals. The lag compensation network can increase the open loop gain and increase the capacity for disturbance rate rejection. Simulations validate the theory and technology support for developing the seeker servo control model in engineering.

scholarly journals АНАЛИТИЧЕСКОЕ КОНСТРУИРОВАНИЕ РАЗОМКНУТЫХ СИСТЕМ СТОХАСТИЧЕСКОГО УПРАВЛЕНИЯ МНОГОМЕРНЫМ НЕЛИНЕЙНЫМ ОБЪЕКТОМ

2017 ◽  
Vol 8 (3) ◽  
Author(s):  
Л. Н. Блохин ◽  
С. И. Осадчий ◽  
В. А. Зозуля
Keyword(s):  
Control System ◽  
Transfer Functions ◽  
Block Diagram ◽  
Control Object ◽  
Metrological Certification ◽  
Open Loop ◽  
Problem Solution ◽  
Loop Control ◽  
Control Signals ◽  
Random Components

This article is devoted to the development of a new method of synthesis a regulators’ transfer functions matrix of an optimal multivariable open-loop control system. The regulator is designed to maximize an accuracy of a nonlinear multivariable control object transition from one steady state to another. It is assumed that disturbances act on the control object and sensors measuring data has inertia and noise. Both disturbances and noises are an additive combination of regular and random components. Random components belong to a class of interconnected stationary processes with rational spectral density matrices. A substantiated method differs from the known one by the fact that during formulation and solution of the problem somebody uses a new block diagram of the control system, which takes into account the results of metrological certification of a sensor dynamics. Synthesis of the regulator is carried out in the frequency domain by the Wiener-Kolmogorov method. A new algorithm, which is obtained as a result of synthesis problem solution, allows you to find the matrix of regulator transfer functions , which provides a minimum of corresponding quadratic quality criteria’s. The first of them is equal to the sum of certain way weighted squared deviations regular repetition errors of the object path and control signals. The second criterion is equal to the sum of the weighted variance of the random error components and the control signals. To execute the proposed algorithm it is necessary to perform the operations of Wiener factorization and separation of rational matrices. The corresponding functions are contained in the freely distributed software package SciLab.

A simple way for producing holographic filters suitable for image improvement

1978 ◽  
Vol 36 (1) ◽  
pp. 226-227
Author(s):  
K.-H. Herrmann ◽  
E. Reuber ◽  
P. Schiske
Keyword(s):  
Transfer Functions ◽  
Diffraction Order ◽  
Lateral Position ◽  
Simple Method ◽  
Spatial Frequencies ◽  
Resolution Electron ◽  
Wiener Filters ◽  
Image Improvement ◽  
Optical Reconstruction ◽  
Set Up

Aposteriori deblurring of high resolution electron micrographs of weak phase objects can be performed by holographic filters [1,2] which are arranged in the Fourier domain of a light-optical reconstruction set-up. According to the diffraction efficiency and the lateral position of the grating structure, the filters permit adjustment of the amplitudes and phases of the spatial frequencies in the image which is obtained in the first diffraction order.In the case of bright field imaging with axial illumination, the Contrast Transfer Functions (CTF) are oscillating, but real. For different imageforming conditions and several signal-to-noise ratios an extensive set of Wiener-filters should be available. A simple method of producing such filters by only photographic and mechanical means will be described here.A transparent master grating with 6.25 lines/mm and 160 mm diameter was produced by a high precision computer plotter. It is photographed through a rotating mask, plotted by a standard plotter.

RESPONSE OF A HIGH-SPEED WAVE-PIERCING CATAMARAN TO AN ACTIVE RIDE CONTROL SYSTEM

2021 ◽  
Vol 158 (A4) ◽  
Author(s):  
J AlaviMehr ◽  
M R Davis ◽  
J Lavroff ◽  
D S Holloway ◽  
G A Thomas
Keyword(s):  
Control System ◽  
Control Systems ◽  
High Speed ◽  
Control Surface ◽  
Control Algorithms ◽  
Active Centre ◽  
Ride Control ◽  
Control Step ◽  
Set Up ◽  
Ride Control System

Ride control systems on high-seed vessels are an important design features for improving passenger comfort and reducing motion sickness and dynamic structural loads. To investigate the performance of ride control systems a 2.5m catamaran model based on the 112m INCAT catamaran was tested with an active centre bow mounted T-Foil and two active stern mounted trim tabs. The model was set-up for towing tank tests in calm water to measure the motions response to ride control step inputs. Heave and pitch response were measured when the model was excited by deflections of the T-Foil and the stern tab separately. Appropriate combinations of the control surface deflections were then determined to produce pure heave and pure pitch response. This forms the basis for setting the gains of the ride control system to implement different control algorithms in terms of the heave and pitch motions in encountered waves. A two degree of freedom rigid body analysis was undertaken to theoretically evaluate the experimental results and showed close agreement with the tank test responses. This work gives an insight into the motions control response and forms the basis for future investigations of optimal control algorithms.

Application of a Compensation Inspection Method in Geodynamic Monitoring

2015 ◽  
Vol 799-800 ◽  
pp. 989-993 ◽  
Author(s):  
Artem Bykov ◽  
Igor' Kurilov ◽  
Oleg Kuzichkin
Keyword(s):  
Transfer Functions ◽  
Block Diagram ◽  
Piecewise Linear ◽  
Linear Functions ◽  
Measuring System ◽  
System Of Equations ◽  
Piecewise Linear Functions ◽  
Geoelectric Section ◽  
Inspection Method ◽  
Geodynamic Monitoring

The paper proves the application of a compensation testing method for geodynamic monitoring when using multi-pole electrical systems. The transfer functions of a geoelectric section are presented as a system of equations, whose coefficients are determined at the initial setup of the measuring system. The block diagram of the compensation method application for geodynamic monitoring based on a multi-pole electrical system is given. Approximation in terms of continuous piecewise-linear functions will be used to distinguish the geodynamic offset vector of the geoelectric section. A system of equations for defining the geodynamic offset vector through the approximation vector by continuous piecewise-linear functions on a recorded geoelectric signal error is considered.

RFID Loop Tags for Merchandise Identification Onboard Ships

2014 ◽  
Vol 1036 ◽  
pp. 969-974
Author(s):  
Daniela Deacu
Keyword(s):  
Radio Frequency Identification ◽  
Block Diagram ◽  
Simulated Data ◽  
Open Loop ◽  
Closed Loops ◽  
Passive Tags ◽  
Received Power ◽  
Resonance Frequencies ◽  
Frequency Identification ◽  
Good Agreement

Radio frequency identification (RFID) is one of the most actual techniques employed to control the circuit of merchandises, as an alternative to the classical barecode. RFID tags should be cheap and easy to reproduct on a multitude of dielectric supports. There are several types of RFID systems, depending on whether tag and/or reader are active or passive. For cost reasons, merchandise identification should use active reader and passive tag, as the latter might be manufactured on a cheap FR4 support or printed directly on paper, by using a conductive ink. Passive tags can be shaped as straight dipoles, meandered dipoles, or loops. When a small area is required, loops are more appropriated. Codes are made different one from another by using on the same tag antennas with different resonance frequencies. Another advantage of loops is that they can be placed one inside other, so the occupied area is even smaller compared to other multi-resonant tags. Firstly, a single loop is analyzed, in order to model the resonant behaviour, correlated to the loop geometry and size. Open and closed loops are studied; the lowest resonance frequency for a given loop length is achieved for the open loop. In that case, the loop is resonating as a dipole. Next, a tag with three concentric loops is investigated. Separately, a small loop is used on the tag, in order to couple the received power in a resistor. When the tag is close to the reader, the latter is triggered if power is absorbed simultaneously on the three expected frequencies. The proposed tag was simulated and manufactured. Results show a good agreement between measured and simulated data. Finally, a block diagram for the reader was proposed.

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