Application of Optimal Input Synthesis to Aircraft Parameter Identification

1976 ◽  
Vol 98 (2) ◽  
pp. 139-145 ◽  
Author(s):  
N. K. Gupta ◽  
R. K. Mehra ◽  
W. E. Hall
Keyword(s):  
Steady State ◽  
Frequency Domain ◽  
Time Domain ◽  
Stability And Control ◽  
Input Design ◽  
Short Period ◽  
Control Derivatives ◽  
The Stability ◽  
The Time Domain ◽  
And Control

This paper considers an application of the Frequency Domain Input Synthesis procedure reference [12] for identifying the stability and control derivatives of an aircraft. In previous studies, the input design has mostly been carried out in the time-domain. However, by using a frequency-domain approach, one can handle criteria that are not easily handled by the time-domain approaches. Numerical results are presented for optimal elevator deflections to estimate the longitudinal stability and control derivatives subject to root-mean square constraints on the input. The applicability of the steady state optimal inputs to finite duration flight testing is investigated. It is shown that the steady state approximation of frequency-domain synthesis is good for data lengths greater than two time cycles for the short period mode of the aircraft longitudinal motions. For data lengths shorter than this, the phase relationships between different frequency components becomes important. The frequency domain inputs are shown to be much better than the conventional doublet inputs.

scholarly journals OPTIMAL DESIGN OF MICROGRID IN AN AUTONOMOUS MODE USING ANTCOLONY OPTIMIZATION

2013 ◽  
pp. 14-18
Author(s):  
N. CHITRA ◽  
TAMIZHARASI. G ◽  
A. SENTHIL KUMAR
Keyword(s):  
Time Domain ◽  
Power Sharing ◽  
Time Domain Simulation ◽  
Stability And Control ◽  
Control Effectiveness ◽  
Damping Characteristics ◽  
Autonomous Mode ◽  
The Stability ◽  
And Control ◽  
Nonlinear Time Domain

The dynamic nature of the distribution network challenges the stability and control effectiveness of the microgrid in autonomous mode. In this paper, nonlinear model of microgrid operating in autonomous mode has been presented. The controller parameters and power sharing coefficients are optimized in case of autonomous mode. The control problem has been formulated as an optimization problem where Ant colony optimization is employed to search for optimal settings of the optimized parameters. In addition, nonlinear time-domain-based objective function has been proposed to minimize the error in the measured power and to enhance the damping characteristics, respectively. Finally, the nonlinear time-domain simulation has been carried out to assess the effectiveness of the proposed controllers under different disturbances and loading conditions. The results show satisfactory performance with efficient damping characteristics of the microgrid considered in this study.

scholarly journals DEFINITION THE STABILITY AND CONTROL DERIVATIVES IN THE LONGITUDINAL CHANNEL OF SMALL SUBSONIC UAV

2013 ◽  
pp. 55-68
Author(s):  
О. В. Збруцький ◽  
Р. В. Карнаушенко ◽  
О. П. Мариношенко
Keyword(s):  
Angular Velocity ◽  
Speed Of Sound ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Kinematic Parameters ◽  
Stability And Control ◽  
Control Derivatives ◽  
The Stability ◽  
And Control ◽  
Longitudinal Channel

The problems of determining the stability and control derivatives of small subsonic UAV in the longitudinal channel are solved.An approach to the stability and control derivatives determination based on the analysis results of wind tunnel investigation and analyzes conducted .To the longitudinal movement usually referred traffic aircraft where it is in the plane of symmetry of one and the same vertical plane. Thus the aerodynamic lateral force, rolling moment and yaw angles of heel and slip and angular velocity of roll and glide zero. To investigate the longitudinal motion of the aircraft (movement in the longitudinal channel) important issue is to determine the components of the aerodynamic forces and moments as a function of the kinematic parameters of the flight, the so-called aerodynamic derivatives.Given that the object is a lightweight UAV that has subsonic range of operating speeds, significantly less than the speed of sound, it should be noted that the derivative of the coefficient of lift coefficient and drag coefficient for longitudinal moment of flight speed can be taken to be zero at subsonic speed range. This is due to the fact that these values are almost constant with airspeed , lower the speed of sound . Change the value of these parameters with growth rate appears only when approaching the speed of sound, due to changes in the position of the center of pressure and the additional impedance. Also, when calculating stability derivatives are generally neglected by changing the drag because the drag value of derivatives are small and commensurate with the error of the calculation methods.Derivatives of lift coefficient by the following kinematic parameters: angle of attack, the angular velocity of rotation around the transverse axis , rate of change of angle of attack and angle of elevator deflection are defined.Obtained results make it possible to analyze the movement of the UAV in the longitudinal channel and determinate the coefficients of a mathematical model of the UAV. Also possible  to determinate the stability and controllability of the UAV during automatic control systems design.

scholarly journals Time-resolving the COVID-19 outbreak using frequency domain analysis

2020 ◽  
Author(s):  
Keno L. Krewer ◽  
Mischa Bonn
Keyword(s):  
Steady State ◽  
Severe Acute Respiratory Syndrome ◽  
Spectral Density ◽  
Frequency Domain ◽  
Time Domain ◽  
Case Fatality ◽  
Frequency Domain Analysis ◽  
Time Domain Data ◽  
Current Outbreak ◽  
The Time Domain

AbstractDifficulties assessing and predicting the current outbreak of the severe acute respiratory syndrome coronavirus 2 can be traced, in part, to the limitations of a static description of a dynamic system. Fourier transforming the time-domain data of infections and fatalities into the frequency domain makes the dynamics easily accessible. Defining a quantity like the “case fatality” as a spectral density allows a more sensible comparison between different countries and demographics during an ongoing outbreak. Such a case fatality informs not only how many of the confirmed cases end up as fatalities, but also when. For COVID-19, knowing this time and using the entire case fatality spectrum allows determining that an outbreak had entered a steady-state (most likely its end) about 14 days before this is obvious from time-domain data. The lag between confirmations and deaths also helps to estimate the effectiveness of contact management: The larger the lag, the less time the average confirmed person had to infect people before quarantine.

scholarly journals Multi-Axis Inputs for Identification of a Reconfigurable Fixed-Wing UAV

Aerospace ◽  
2020 ◽  
Vol 7 (8) ◽  
pp. 113
Author(s):  
Piotr Lichota
Keyword(s):  
System Identification ◽  
Optimality Criterion ◽  
Likelihood Principle ◽  
Stability And Control ◽  
Input Design ◽  
Relative Standard ◽  
Control Derivatives ◽  
Flight Controls ◽  
Aircraft System ◽  
And Control

Designing a reconfiguration system for an aircraft requires a good mathematical model of the object. An accurate model describing the aircraft dynamics can be obtained from system identification. In this case, special maneuvers for parameter estimation must be designed, as the reconfiguration algorithm may require to use flight controls separately, even if they usually work in pairs. The simultaneous multi-axis multi-step input design for reconfigurable fixed-wing aircraft system identification is presented in this paper. D-optimality criterion and genetic algorithm were used to design the flight controls deflections. The aircraft model was excited with those inputs and its outputs were recorded. These data were used to estimate stability and control derivatives by using the maximum likelihood principle. Visual match between registered and identified outputs as well as relative standard deviations were used to validate the outcomes. The system was also excited with simultaneous multisine inputs and its stability and control derivatives were estimated with the same approach as earlier in order to assess the multi-step design.

scholarly journals Regular design equations for the discrete reduced-order Kalman filter

2012 ◽  
Vol 22 (2) ◽  
pp. 175-189
Author(s):  
Peter Hippe
Keyword(s):  
Kalman Filter ◽  
Frequency Domain ◽  
Time Domain ◽  
Filter Design ◽  
Minimum Variance ◽  
Reduced Order ◽  
Regular Design ◽  
The Stability ◽  
The Time Domain ◽  
Standard Software

Regular design equations for the discrete reduced-order Kalman filter In the presence of white Gaussian noises at the input and the output of a system Kalman filters provide a minimum-variance state estimate. When part of the measurements can be regarded as noise-free, the order of the filter is reduced. The filter design can be carried out both in the time domain and in the frequency domain. In the case of full-order filters all measurements are corrupted by noise and therefore the design equations are regular. In the presence of noise-free measurements, however, they are not regular so that standard software cannot readily be applied in a time-domain design. In the frequency domain the spectral factorization of the non-regular polynomial matrix equation causes no problems. However, the known proof of optimality of the factorization result requires a regular measurement covariance matrix. This paper presents regular (reduced-order) design equations for the reduced-order discrete-time Kalman filter in the time and in the frequency domains so that standard software is applicable. They also allow to formulate the conditions for the stability of the filter and to prove the optimality of the existing solutions.

Dynamics and Stability of Plunge Milling Operations

2006 ◽  
Vol 129 (1) ◽  
pp. 32-40 ◽  
Author(s):  
Jeong Hoon Ko ◽  
Yusuf Altintas
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Cutting Forces ◽  
Milling Process ◽  
Body Motion ◽  
Plunge Milling ◽  
Milling Operations ◽  
Tool Setting ◽  
The Stability ◽  
The Time Domain

Plunge milling operations are used to remove excess material rapidly in roughing operations. The cutter is fed in the direction of the spindle axis which has the highest structural rigidity. This paper presents a comprehensive model of plunge milling process by considering rigid body motion of the cutter, and three translational and torsional vibrations of the structure. The time domain simulation model allows prediction of cutting forces, torque, and vibrations while considering tool setting errors and time varying process parameters. The stability law is formulated as a four-dimensional eigenvalue problem, and the stability lobes are predicted directly with analytical solution in frequency domain. Time domain prediction of cutting forces and vibrations, as well as the frequency domain and chatter stability solution are verified with a series of plunge milling experiments.

scholarly journals Vertical tail sizing of propeller-driven aircraft considering the asymmetric blade effect

2021 ◽  
pp. 095441002110294
Author(s):  
Mohsen Rostami ◽  
Joon Chung ◽  
Daniel Neufeld
Keyword(s):  
Significant Contribution ◽  
Incident Angle ◽  
Empirical Methods ◽  
Handling Qualities ◽  
Stability And Control ◽  
Directional Stability ◽  
Control Derivatives ◽  
The Stability ◽  
Semi Empirical ◽  
And Control

An engineering approach is presented to analyse the asymmetric blade thrust effect with the help of analytical and semi-empirical methods. It is shown that the contribution of the asymmetric blade thrust effect in the lateral-directional stability of multi-engine propeller-driven aircraft is significant particularly in critical flight conditions with one engine out of service. Also, in some cases where the engines are rotating in one direction, the asymmetric blade effect has substantial effects on the handling qualities of the aircraft even in normal flight conditions. Overall, due to the significant contribution of this phenomenon in the lateral-directional stability of propeller-driven airplanes, it is important to consider it in the design of the vertical stabilizer and rudder. The resulting analytical method has been used to determine the vertical tail incident angle and desired rudder deflection in accordance with the most critical flight condition for two different cases and validated to ensure the accuracy of the result. In this work, the aerodynamic coefficients as well as the stability and control derivatives have been predicted using analytical and semi-empirical methods validated for light aircraft.

scholarly journals Aerodynamic Parameters Estimation Using Radial Basis Function Neural Partial Differentiation Method

2018 ◽  
Vol 68 (3) ◽  
pp. 241 ◽  
Author(s):  
Jitu Sanwale ◽  
Dhan Jeet Singh
Keyword(s):  
Neural Network ◽  
Radial Basis Function ◽  
Basis Function ◽  
Flight Data ◽  
Stability And Control ◽  
Partial Differentiation ◽  
Radial Basis ◽  
Control Derivatives ◽  
The Stability ◽  
And Control

Aerodynamic parameter estimation involves modelling of force and moment coefficients and computation of stability and control derivatives from recorded flight data. This problem is extensively studied in the past using classical approaches such as output error, filter error and equation error methods. An alternative approach to these model based methods is the machine learning such as artificial neural network. In this paper, radial basis function neural network (RBF NN) is used to model the lateral-directional force and moment coefficients. The RBF NN is trained using k-means clustering algorithm for finding the centers of radial basis function and extended Kalman filter for obtaining the weights in the output layer. Then, a new method is proposed to obtain the stability and control derivatives. The first order partial differentiation is performed analytically on the radial basis function neural network approximated output. The stability and control derivatives are computed at each training data point, thus reducing the post training time and computational efforts compared to hitherto delta method and its variants. The efficacy of the identified model and proposed neural derivative method is demonstrated using real time flight data of ATTAS aircraft. The results from the proposed approach compare well with those from the other.

scholarly journals The Analysis of Controllability and Stability of an Approximate Model of Heat Transfer in an Autoclave

2018 ◽  
Vol 28 (3) ◽  
pp. 416-428 ◽  
Author(s):  
Sergey A. Mokrushin ◽  
Valeri S. Khoroshavin ◽  
Sergey I. Ohapkin ◽  
Alexander V. Zotov ◽  
Victor S. Grudinin
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Transfer Functions ◽  
Structural Transformations ◽  
Space Representation ◽  
Proportional Integral ◽  
State Space Representation ◽  
The Matrix ◽  
The Stability ◽  
The Time Domain

Introduction.Ensuring the safety of country food industry in terms of the duration of storage and the quality of products is impossible without sterilizing products in autoclaves. The effectiveness of the sterilization processes depends on the degree of their automation. In the last twenty years, the improvement of automatic and automated control systems was primarily based on the development of technical means for automation without theoretical justification of decision-making. The proposed work is aimed at identifying the links between the parameters and connections of the sterilization process and the choice of structural and parametric features of the control system. Materials and Methods. A qualitative analysis is carried out based on the modern theory of automatic control for an approximative model of the thermal process of steam heating in an autoclave, taking into account the laws of heat transfer and the sufficiency of using a twodimensional model depending upon the structural and functional features of the model, which have regard to the parameters and relationships of the process, namely, the Kalman’s controllability properties of the model in the time domain in the state-space representation (the transition from the transfer function with zeros in the numerator to the normal differential system differential equations is also described). There were also analized the stability properties of the model in the frequency domain by means of transfer functions and structural transformations and the relationship of parameters in the form of inequalities with the subsequent choice of proportional-integral-differential configuration components for a real autoclave using the matrix of expert estimates. Results. It is shown that to make a qualitatively study of the issues of controllability and stability of the approximative model of the thermal process of water heating by steam in an autoclave, depending on the process parameters, it is necessary to represent the model the time domain (in the state-space representation) and in the frequency domain (in the form of transfer functions). The analysis of the controllability of the process is based on three approaches: the first (formalized) approach is based on the representation of the model in the form of a normal system of ordinary differential equations in the Cauchy form with the development of a method of decreasing the order of the higher derivatives of coordinates and introducing additional control signals taking into account the control derivatives; the second (unformalized) is based on the exclusion of management derivatives through structural transformation; the third (direct) approach uses the first-order heat balance and heat conduction equations derived from physical considerations. Under the conditions of Kalman’s controllability, dependencies between the parameters of the process and the degree of its controllability have been obtained.The analysis of the stability of the process is based on studying the poles of the transfer functions in the frequency domain and the characteristic roots of the equations of state in the time domain. On the basis of structural transformations, a closed canister heating loop with water with inertia, depending on the autoclave charging parameters, is isolated. Transient processes in this circuit take an amplifying, aperiodic or integral character, which affects the nature of the transient processes of the control system as a whole. The formalized choice of the components of the proportional-integral-differential regulation law is carried out depending on the frequency of application of the degree of loading and the need for the components of the proportional-integral-differential regulator using the matrix of expert estimates. Conclusions. The results of the research will serve as the material for the development of a real model of the autoclaving process, taking into account the static and dynamic characteristics of measuring, conversion and actuating elements, investigating the influence and compensation of inertia and nonlinearities of real elements, followed by the development of an automated system for controlling the sterilization process in autoclaves. The results of the work can be used to study general and applied problems of optimal control in both food and other industries, for example, in the production of building materials and the production of rubber products.

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