scholarly journals A single-step identification strategy for the coupled TITO process using fractional calculus

2021 ◽  
pp. 014233122199273
Author(s):  
Kajal Kothari ◽  
Utkal Mehta ◽  
Ravneel Prasad
Keyword(s):  
Transfer Functions ◽  
Mimo System ◽  
Operational Matrix ◽  
Experimental Studies ◽  
Algebraic Approach ◽  
Coupled System ◽  
Single Step ◽  
Accurate Estimation ◽  
Complete Control ◽  
Identification Strategy

The reliable performance of a complete control system depends on accurate model information being used to represent each subsystem. The identification and modelling of multivariable systems are complex and challenging due to cross-coupling. Such a system may require multiple steps and decentralized testing to obtain full system models effectively. In this paper, a direct identification strategy is proposed for the coupled two-input two-output (TITO) system with measurable input–output signals. A well-known closed-loop relay test is utilized to generate a set of inputs–outputs data from a single run. Based on the collected data, four individual fractional-order transfer functions, two for main paths and two for cross-paths, are estimated from single-run test signals. The orthogonal series-based algebraic approach is adopted, namely the Haar wavelet operational matrix, to handle the fractional derivatives of the signal in a simple manner. A single-step strategy yields faster identification with accurate estimation. The simulation and experimental studies depict the efficiency and applicability of the proposed identification technique. The demonstrated results on the twin rotor multiple-input multiple-output (MIMO) system (TRMS) clearly reveal that the presented idea works well with the highly coupled system even in the presence of measurement noise.

scholarly journals Experiment and Analysis of Active Vibration Suppression via an Absorber with a Tunable Delay

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yixia Sun
Keyword(s):  
Vibration Suppression ◽  
Transfer Functions ◽  
Experimental Studies ◽  
Coupled System ◽  
Gain Coefficient ◽  
Feedback Gain ◽  
Primary System ◽  
Active Vibration ◽  
The Stability ◽  
Proper Values

A time-delayed absorber is utilized to suppress the vibration of a primary system excited by a simple harmonic force. The inherent and intentional time delays in the feedback control loop are taken into consideration. The value of the former is fixed, while the value of the latter is tunable in the controller. To begin with, the mechanical model of the system is established and the acceleration transfer functions of the system are derived. Consequently, the stability analysis of the coupled system is carried out. Finally, the experimental studies on the performance of the time-delayed absorber are conducted. Both experimental and theoretical results show that the time-delayed absorber with proper values of feedback gain coefficient and intentional time delay greatly suppresses the vibration of the primary system. The numerical results validate the correctness of the experimental and theoretical ones.

scholarly journals Collective Losses of Low Power Cage Induction Motors—A New Approach

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1749
Author(s):  
Elzbieta Szychta ◽  
Leszek Szychta
Keyword(s):  
Control System ◽  
Experimental Studies ◽  
Complex Problem ◽  
Accurate Estimation ◽  
New Approach ◽  
Water Pumping ◽  
Efficiency Control ◽  
Interacting Systems ◽  
Cage Induction Motor ◽  
Selection Of

Energy efficiency of systems of water pumping is a complex problem since efficiency of two distinct interacting systems needs to be combined: water and power supply. This paper introduces a non-intrusive method of calculating the so-called “collective losses” of a cage induction motor. The term “collective losses”, which the authors define, allows for accurate estimation of motor efficiency. Control system of a pump determines operating point of a pumping station, and thus its efficiency. General estimated performance characteristics of a motor, components of a control system, are assumed to serve selection of a range of pumping speed variations. Rotational speed has a direct effect on motor load torque, pump power and head, and thus on motor performance. Hellwig’s statistical method was used to specify characteristics of estimated collective losses on the basis of experimental studies of 21 motors rated at up to 2.2 kW. The results of simulations and experiments are used to verify validity and efficiency of the suggested method. The method is non-intrusive, simple to use, and requires minimum data.

An Evaluation of Stability Indices Using Sensitivity Functions for Active Magnetic Bearing Supported High-Speed Rotor

2006 ◽  
Vol 129 (2) ◽  
pp. 230-238 ◽  
Author(s):  
Naohiko Takahashi ◽  
Hiroyuki Fujiwara ◽  
Osami Matsushita ◽  
Makoto Ito ◽  
Yasuo Fukushima
Keyword(s):  
High Speed ◽  
Transfer Functions ◽  
Mimo System ◽  
Magnetic Bearing ◽  
Singular Value ◽  
Active Magnetic Bearing ◽  
Sensitivity Functions ◽  
Phase Lags ◽  
The Stability ◽  
Stability Indices

In active magnetic bearing (AMB) systems, stability is the most important factor for reliable operation. Rotor positions in radial direction are regulated by four-axis control in AMB, i.e., a radial system is to be treated as a multi-input multioutput (MIMO) system. One of the general indices representing the stability of a MIMO system is “maximum singular value” of a sensitivity function matrix, which needs full matrix elements for calculation. On the other hand, ISO 14839-3 employs “maximum gain” of the diagonal elements. In this concept, each control axis is considered as an independent single-input single-output (SISO) system and thus the stability indices can be determined with just four sensitivity functions. This paper discusses the stability indices using sensitivity functions as SISO systems with parallel/conical mode treatment and/or side-by-side treatment, and as a MIMO system with using maximum singular value; the paper also highlights the differences among these approaches. In addition, a conversion from usual x∕y axis form to forward/backward form is proposed, and the stability is evaluated in its converted form. For experimental demonstration, a test rig diverted from a high-speed compressor was used. The transfer functions were measured by exciting the control circuits with swept signals at rotor standstill and at its 30,000 revolutions/min rotational speed. For stability limit evaluation, the control loop gains were increased in one case, and in another case phase lags were inserted in the controller to lead the system close to unstable intentionally. In this experiment, the side-by-side assessment, which conforms to the ISO standard, indicates the least sensitive results, but the difference from the other assessments are not so great as to lead to inadequate evaluations. Converting the transfer functions to the forward/backward form decouples the mixed peaks due to gyroscopic effect in bode plot at rotation and gives much closer assessment to maximum singular value assessment. If large phase lags are inserted into the controller, the second bending mode is destabilized, but the sensitivity functions do not catch this instability. The ISO standard can be used practically in determining the stability of the AMB system, nevertheless it must be borne in mind that the sensitivity functions do not always highlight the instability in bending modes.

Viscous Damping Modelling of Floating Bridge Pontoons With Heaving Skirt and its Impact on Bridge Girder Bending Moments

2017 ◽  
Author(s):  
Xu Xiang ◽  
Erik Svangstu ◽  
Øyvind Nedrebø ◽  
Bernt Jakobsen ◽  
Mathias Egeland Eidem ◽  
...  
Keyword(s):  
Relevant Literature ◽  
Experimental Studies ◽  
Iteration Process ◽  
Damping Coefficient ◽  
Accurate Estimation ◽  
Bending Moments ◽  
Bottom Part ◽  
Floating Bridge ◽  
Damping Effects ◽  
Offshore Industry

The current floating bridge concepts of Norwegian Public Roads Administration (Statens vegvesen, NPRA) use a flange shape part at the bottom part of the pontoons. The flange is in principle similar to the damping plates used in the offshore industry for SPAR type of structures. The project group initiated the flange part based on the requirement of extra added mass for tuning the bridge system Eigen-modes. Thus, the important modes can be shifted out of the main wave energy zone. The current study will focus on the damping effects of such structure. The damping effects on weak axis bending moment prediction is studied. The modelling of such damping is first proposed according to relevant literature based on both numerical and experimental studies. Since the reference studies were mainly focused on cylindrical structures, it is difficult to obtain an accurate estimation of the damping coefficient for the current bridge pontoon design, which contains a rectangular part between two half-cylindrical parts. In addition, the estimation of pontoon motions needs the input of damping coefficient, which means that the evaluation of damping coefficient is an iteration process. In order to include the uncertainties, a conservative value was adopted to represent the damping effect. The comparison of accounting for the damping effects or not has been given for all the bridge pontoons. The results show that the damping effects are important at the peaks of the responses; in addition, the reduction of the predicted maximum bending moments can be expected around 10–15 percent along different positions of the bridge. However, a further investigation also shows that viscous excitation would increase the bending moments slightly. The comparison also indicates the value of further investigating the effects by CFD or model test methods.

scholarly journals STUDY OF GRAIN DRYING IN THE AUTOMATED GRAIN DRYING UNIT

2018 ◽  
Vol 12 (4) ◽  
pp. 29-34
Author(s):  
S. A. Pavlov ◽  
T. F. Frolova
Keyword(s):  
Moisture Content ◽  
Coming Out ◽  
Transfer Functions ◽  
Heating Temperature ◽  
Initial Moisture Content ◽  
Experimental Studies ◽  
Research Purpose ◽  
Complex Object ◽  
Grain Moisture ◽  
Grain Drying

Mine and column grain dryers are a fairly complex object of control in the production line. The process of grain drying is characterized  by a large number of parameters, quantitatively and qualitatively characterizing the dryer operation. First of all, this includes the criteria of maximum performance and minimum deviations of the moisture content of the dried grain from the standard values. These criteria, as studies show, are interconnected with each other: an increase in the performance П of the dryer leads to an increase in the moisture content of the grain coming out of it, and, conversely, an attempt to reduce the moisture content of grain causes the need to reduce the performance П. (Research purpose) The research purpose is to develop the expression for the transfer functions of the of grain flow control depending on perturbations of the initial moisture content and the maximum grain temperature, as well as to conduct experimental studies. (Materials and methods) The authors have developed simplified mathematical models of moisture perturbation compensation of grain coming in for drying and its heating temperature in a drying chamber by changing the dryer performance on the basis of theoretical-and-experimental studies. (Results and discussion). The authors  have obtained  expressions to control the process performance when the current humidity and temperature change through the dryer performance parameters as a function of grain moisture flow and heat used to grain heating up to an acceptable temperature. Farm tests of developed transition management functions have been implemented for dryer SZT-16 controlled by PLC S7-1200 Siemens and operating in an automatic mode. Tests have been conducted on the “Babachev” farm, Karachev district of the Bryansk region in the process of drying food wheat grain. (Conclusion) It has been confirmed that the dryer performance is determined not only by the rated capacity but also by the deviation of the current moisture content of grain from the specified values and by the ratio of the amount of heat used for evaporating and heating. The dryer performance at constant initial humidity is determined by its rated performance, the maximum specified difference of grain temperatures, as well as the ratio of the amounts of heat used for evaporating and heating.

Blood Flow Modeling to Improve Cardiovascular Diagnostics: Application of A GTF to Predict Central Aortic Pressure using a 1-D Model

2018 ◽  
Vol 7 (4.26) ◽  
pp. 146
Author(s):  
A. T. Butt ◽  
Y. A. Abakr ◽  
K. B. Mustapha
Keyword(s):  
Transfer Function ◽  
Transfer Functions ◽  
Experimental Studies ◽  
Aortic Pressure ◽  
Iliac Arteries ◽  
Central Aortic Pressure ◽  
Blood Flow Modeling ◽  
Feasible Alternative ◽  
Generalized Transfer Function ◽  
Mean Square Errors

This study aims to demonstrate that a comprehensive one-dimensional model of the arterial network can be used in conjunction with the generalized transfer function (GTF) technique to estimate central aortic pressure using pressure waveforms obtained from peripheral sites. The peripheral and central pressure waveforms for a healthy subject are used to estimate transfer functions, which are then used to reconstruct central aortic pressure waveforms for a second model that simulates arterial stiffening. The similarities between the simulated aortic waveform and the waveforms estimated using the transfer function are and   from the brachial, carotid and iliac arteries, respectively. The root-mean-square errors (RMSE) for the reconstructed waveforms from the brachial, carotid and iliac arteries are and  mmHg, respectively. The results from this study illustrate that the proposed method provides a feasible alternative to higher dimensional models as well as experimental studies and can greatly enhance the accuracy of central aortic pressure estimation.     

scholarly journals Experimental and Numerical Studies on Vibration Modes and Transcranial Attenuation Characteristics in Unilateral Bone Conduction Hearing

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Jia Li ◽  
Liujie Ren ◽  
Tongge Wu ◽  
Dongming Yin ◽  
Peidong Dai ◽  
...  
Keyword(s):  
Frequency Response ◽  
Inner Ear ◽  
Sound Localization ◽  
Transfer Functions ◽  
Bone Conduction ◽  
Experimental Studies ◽  
Hearing Threshold ◽  
Fe Model ◽  
Vibration Modes ◽  
Attenuation Characteristics

Bone conduction (BC) hearing devices have been used to improve hearing in patients with unilateral conductive hearing loss; however, the clinical results of improvement in the sound localization ability are still controversial. Transcranial transmission in BC may be an important factor affecting sound localization abilities. Transcranial or interaural attenuation, derived from energy attenuation during the BC process, is determined by the different transfer functions of multiple pathways and affected by the whole-head vibration modes. The purpose of this study is to analyze the frequency dependence of BC vibration modes of the whole head, the contribution of middle and inner ear pathways to BC hearing, and the relationship between transcranial attenuation results by dynamics measurement and hearing thresholds. Experimental studies of vibration modes and transcranial attenuation characteristics in BC are performed using scanning laser Doppler vibrometry (LDV) measurements on human cadaver heads. Differences in vibration modes between the excitation and contralateral sides are observed. Additionally, a multiscale human whole-head FE model, including the skull, bony outer ear, ossicular chains, and bony inner ear structures, is proposed to study the mechanism of BC in the human hearing system. After verifying the rationality of the FE model using mechanical impedance and frequency response data, the transcranial attenuation on the temporal bone surfaces and the middle ear structure is calculated in the FE model. Moreover, the vibration characteristics of bilateral ossicular chains and the cochlear bony wall are observed in the whole-head FM model to study their contributions to BC hearing. By analyzing the experimental and numerical results of the vibration modes and the frequency response of the whole head incorporating the ossicular chain and cochlear bony wall, the intrinsic relationship between the results of transcranial attenuation by 1D LDV, 3D LDV, and hearing threshold measurements is further investigated.

scholarly journals A Multivariable Controller for an Automotive Gas Turbine

1979 ◽  
Author(s):  
D. E. Winterbone ◽  
N. Munro ◽  
D. J. Nuske
Keyword(s):  
Control System ◽  
Gas Turbine ◽  
Transfer Functions ◽  
Poor Response ◽  
Test Bed ◽  
Complete Control ◽  
Loop Control ◽  
Non Linear ◽  
Basic Objective ◽  
Careful Manipulation

A complete control system design study is described, starting with a non-linear mathematical model and finishing with the control hardware. The basic objective of the study was to design a controller which reduced the characteristically poor response of the two-shaft automotive gas turbine. This was achieved by identifying the reasons for the acceleration delay and then designing the controller to compensate for them. The gas turbine was simulated by means of a quasi-steady non-linear thermodynamic model implemented on a digital computer. Careful manipulation of the equations enabled the model to run in real-time. This model was linearized at various operating points and the transfer functions obtained were compared with those measured on the plant. The control system was designed using Rosenbrock’s multivariable inverse Nyquist array technique. These compensators were grafted onto the original single loop control box and fitted to the engine. The results obtained on the engine test bed are compared with those using the original controller. A very large reduction in response lag is obtained with the multivariable control system.

CFD Simulation of Roll Damping Characteristics of a Ship Mid-Section With Bilge Keel

2016 ◽  
Author(s):  
Mohsin A. R. Irkal ◽  
S. Nallayarasu ◽  
S. K. Bhattacharyya
Keyword(s):  
Fluid Dynamics ◽  
Cfd Simulation ◽  
Experimental Studies ◽  
Ship Hull ◽  
Estimation Methods ◽  
Accurate Estimation ◽  
Roll Motion ◽  
Roll Damping ◽  
Damping Characteristics ◽  
Bilge Keel

The prediction of nonlinear roll motion of ships depends highly on the accurate estimation of roll damping. The nonlinear nature of roll damping arises from the viscous flow and the associated phenomenon of flow separation around the ship hull. Roll damping changes noticeably with a slight change in the ship hull geometry and appendages. The estimation methods employed in industry are highly empirical in nature. These empirical methods were derived from combinations of model tests conducted in wave flumes and basins, and some selected formulae used in fluid dynamics. These methods have limitations and the roll damping prediction show large variation with change in the ship parameters. The advances made in Computational Fluid Dynamics (CFD) in recent times, and validation of the CFD results using experimental studies, can help in predicting roll motion and damping more accurately. The present work uses CFD as a tool to estimate roll damping of a ship mid-section with bilge keel with validation using published experimental results.

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