Parametric system identification on logarithmic frequency response data

MODEL SIMPLIFICATION AND DIGITAL DESIGN OF MULTIVARIABLE SAMPLED-DATA CONTROL SYSTEMS VIA A DOMINANT-DATA MATCHING METHOD

The Line-of-Sight stabilization and tracking control based on gyro stabilized platform is required to isolate Line of sight from the movement and vibration of carrier and ensure pointing and tracking for target in electro-optical tracking system.This work describes the design of a high performance controller for an electromechanical target tracking system with an optical sensor for sighting.The control law has been obtained using a linear model of the electro mechanical system.The modelling of the system has been carried out using the experimental frequency response data.The PID adesigning of control system methodology has been used to design the controller and study the comparative analysis using both controller and optimized tuned performance is also seeing by using the designing the PID controller in different loop analysis and study responses of system by using step response and frequency response analysis by using the bode diagram so as to stabilize the line of sight stabilization and tracking control system.The mixed sensitivity optimisation problem has been posed and weighting functions are selected by using the gradient and dissent method having more numbers of iterations so that they not only encapsulate all the design goals but also accommodate the modelling uncertainties.A stabilising controller with excellent robustness properties has been obtained.Investigator has used MATLAB for the designing of controller and simulated the system for a required criterion of the system.

Magnetic bearings are becoming increasingly popular in ventricular assist devices. In most cases, blood fills a portion of the gap between the magnetic actuators and rotor. Understanding the effects of the operating fluid on magnetic suspension is necessary, particularly when the device geometry features a relatively large gap (typically defined as greater than 150 um and as large as 2 mm in some pumps). A large gap reduces cell damage and allows unrestricted flow, it but increases the distance and amount of material through which magnetic fields must pass. These net effects of the operating fluid on the magnetic suspension can be characterized in terms of a contribution to the overall damping and stiffness of the system. This contribution may be caused by traditional tribological properties (density and viscosity) as well as the magnetic properties of the medium. This research isolates the effects of fluid diamagnetism on a magnetically levitated blood pump. Experimental transient and frequency responses of the system operating at 3000 to 6000 rpm are presented while pumping different liquid media: Blood, water, and fluids with similar densities and viscosities to each, but different magnetic susceptibilities. In order to calculate the stiffness and damping coefficients, a mathematical model of the system is iteratively updated to match experimental transient response. The resulting coefficients are validated in the frequency domain by means of simulations, which agree with experimental frequency response data. The relationship between diamagnetism, damping and stiffness coefficients of the test fluids with known magnetic susceptibility is also used to obtain a quantitative estimate of the magnetic susceptibility of blood.

In the present work, model transformer windings were used to obtain Sweep frequency Response Analyzer measurement data for various experimentally simulated faults. Transfer function and its corresponding parameters were computed for different types of transformer faults by subspace based identification method. An attempt was made to use these parameters for training Artificial Neural Network. The result of study on application of Artificial Neural Network algorithm for diagnosing and identifying the transformer winding faults from the Frequency Response Analysis data is presented. It was observed that, predicted fault closely follows the created fault suggesting the effectiveness of Artificial Neural Network technique for distinguishing between the normal and failed state quite satisfactorily.

Tapered transmission line resonators can be used to achieve specific frequency responses and enhance the performance of microwave devices and impedance transformers. To develop a mathematical model (transfer function) of such a wideband resonator will facilitate the construction of an equivalent circuit and the synthesis of resonators of this type. This study discusses the system modeling of tapered transmission line (TTL) resonators using the singularity expansion method (SEM). The transfer function is analytically established for two types of wideband TTL resonators: exponential tapered transmission lines (ETTL) and linear tapered transmission lines (LTTL). The analytical transfer function is derived for the general tapered ratio (k/β). The physical poles of the structures are identified using the pole-energy matrix pencil (MP) approach. The transfer function expression is then utilized to develop an accurate equivalent lumped-element circuit for the TTL resonator. This study’s simplified approach for estimating the transfer function and associated poles and zeros from the S-parameters is the main contribution, whereas it is known that the transfer function becomes complicated for wideband frequency response. A direct synthesis approach is presented to develop two-stage and four-stage ultra-wideband (UWB) bandpass filters. The agreement between the frequency response data and the derived transfer function of the system model of the synthesized TTL filters demonstrates the reliability of the presented method. The proposed system modeling and synthesis methodology can be applied to more sophisticated filter TTL architectures.

In this paper, we explore certain tradeoffs in haptic rendering performance with different device architectures, specifically examining admittance and series elastic actuator (SEA) architectures. We apply performance analysis techniques that decompose the driving point impedance frequency response into effective stiffness, inertia, and damping and discuss device behaviors as rendering reverts to hardware dynamics with increasing frequency. SEA has previously been discussed in terms of stiffness limitations due to stability; here we discuss a frequency limit for haptic rendering with both architectures, and discuss differing high-frequency behaviors to consider when selecting a device architecture. Theoretical conclusions are accompanied by experimental frequency response data and a perceptual experiment using a reconfigurable haptic device.

Recently, neuro-transfer function (neuro-TF) has become a recognized method for electromagnetic (EM) parametric modeling. The existing neuro-TF methods use the vector fitting technique to perform transfer function (TF) parameter extraction, commonly encountering nonsmoothness and discontinuity issues for the extracted TF parameters with respect to geometrical parameters. This letter proposes an advanced autoencoder TF parameter extraction technique for neuro-TF parametric modeling of microwave components. In the proposed technique, the autoencoder is introduced to extract a set of TF parameters as TF parameters from the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$</tex-math> </inline-formula> -parameters with the encoder part and generate a decoder function as the TF in the original neuro-TF model. The TF parameters extracted using the proposed technique behave much smoother than the TF parameters extracted using traditional vector fitting. Meanwhile, the proposed technique avoids the discontinuity problem caused by vector fitting in the standard neuro-TF method. Parametric modeling using the smooth TF parameters can thus have higher accuracy than modeling with nonsmooth TF parameters. The proposed technique is demonstrated by two examples of EM parametric modeling of microwave components.

This paper presents various types of windings in a power transformer, their FEM methods, frequency response analysis etc. Frequency response analysis (FRA) standards are used in all places. In frequency response, one reference spectrum is first done and after fault is done, spectrum is compared with reference one. A 3-D model of a transformer is considered to show the field distribution, inductance and capacitance matrices, force analysis etc. The forces developed in a transformer winding has also been explained and transient case has been studied.

A test method to detect winding deformation by using pseudorandom binary M-Sequence excitation signals is proposed. This broadband excitation signal and the corresponding response from the winding are combined to obtain the analytic expression of the winding's transfer function by using a Recursive Least Square method. The coefficients, poles, and zeros of the transfer function can be used to describe the winding status, and any mechanical changes in the winding over time can be therefore detected. The steps and algorithms involved in using the M-Sequence method are presented, and a comparative simulation between the M-Sequence method and Frequency Response Analysis (FRA) is carried out using an equivalent circuit for the winding. Results of the simulation confirm that the response sensitivity of the M-Sequence method is as good as FRA in a common frequency band, and is actually more sensitive for slight winding deformations of series capacitance. The correlation factor of the transfer function coefficients, used as example, can also diagnose slight deformation. Additionally, significant differences exist in the map of the poles and/or zeros before and after deformation. The study confirms the feasibility of using the M-Sequence method for detection of winding deformation in transformers. Transfer function can have a wider application than frequency response curves, then analysis and judgment based on the transfer function may offer more analysis tools. The theory and simulation study of the new method provide supports for subsequent development of its corresponding detecting system as well as experimental research.

A procedure is developed for obtaining the transfer function of a linear system from the frequency-response data in terms of its poles and zeros. The method is based upon the fact that the transfer function is an analytic function of the complex variable s at all points in the s plane except the isolated points which are the poles of the function. Hence if the function is specified along the jω axis, it is possible to extend the function in the left-half or right-half s plane by means of conformai mapping techniques. The curvilinear squares in the G(s) plane corresponding to a grid of constant σ and constant ω lines in the s plane can be constructed with fair accuracy after a little practice. The particular values of σ and ω, for which the lines pass through the origin of the s plane, can thus be determined by locating the zeros of the transfer function. The poles are similarly obtained by working with the inverse function. Since there are several values of s satisfying G(s) = 0, the mapping from the s plane to the G(s) plane is not entirely a one-to-one mapping, and several regions in the s plane are mapped on to the same region in the G(s) plane. A method is suggested to overcome this difficulty and to obtain, step-by-step, all the zeros and poles of the transfer function corresponding to the given frequency-response locus. The method is illustrated by means of three numerical examples.

Direct Numerical Design of Reduced Order Controllers from Experimental Data

Frequency response analysis (FRA) is considered as an accurate, fast, effective and sensitive method for detection of mechanical defects within power transformers, providing worthy information on active part structure. FRA measurement has been industrialized and employed since the last decade while FRA spectrum interpretation is still under development. The interaction of distributed resistances, series and shunt capacitances as well as self- and mutual-inductances in transformer winding leads to FRA spectrum oscillations. In fact, each and every parameter has its own impact on this spectrum. This study has concentrated on shunt capacitance influences on frequency response spectrum oscillations in Bode diagram. Shunt capacitance impacts on low-, mid- and high-frequency bands of FRA spectrum are discussed. A practical study on a single phase air-core glassy model transformer is carried out to explore the influence of shunt capacitances of HV and LV windings with respect to the transformer tank on FRA spectrum. In addition, a single phase 11/0.25 kV, 25 kVA core type distribution transformer is also tested to evaluate the shunt capacitance impacts on FRA fluctuations.

Frequency response analysis (FRA) has gained attention as a reliable diagnostic tool, to assess the mechanical integrity of power transformers, due to standardised FRA measurement methods. However, the assessment of FRA results is still a challenge as it demands skilful personnel for diagnosis. Since there is no definitive and reliable code available for FRA interpretation. In this study, the three‐dimensional (3D) finite integration technique is used to simulate the physical geometrical dimensions of a three‐phase transformer which emulate the behaviour of real transformer and frequency response measurements. This novel method eliminates the need for lumped parameter circuit models, as it provides the ability to extract the FRA signatures directly from the 3D winding model. Axial displacement of different levels is simulated in several connection schemes. It was found that variation of the inter‐winding capacitance due to the axial displacement possesses a linear relationship with the degree of axial displacement fault. This provides the possibility for the quantitative determination of winding axial displacement fault using FRA. A simple mathematical relation is derived for calculating the variation of inter‐winding capacitance and a geometrical factor is introduced to generalise the method. Finally, lookup charts are introduced to diagnose axial displacement fault in different transformers.

1. The horizontal and vertical vestibuloocular reflex (HVOR and VVOR, respectively) was studied in four chronically instrumented pigeons. Eye movements were measured using the magnetic search-coil technique and were produced by rotation in the dark. During the rotation paradigms, the pigeons were either pharmacologically aroused (using amphetamine) or drug free (normal). The pigeon HVOR and VVOR were tested using step and sinusoidal rotational stimulation. The range of frequencies (0.03-6.0 Hz) and the magnitude of the sinusoidal stimuli were chosen to match those used in a previous study of the responses of semicircular canal primary afferents (SCPAs) in unanesthetized (i.e., normal) pigeons. 2. The gain of the HVOR and VVOR in both normal and aroused pigeons was independent of stimulus magnitude (6-30 degrees/s) over the frequency range tested. In aroused pigeons, the frequency independent gain (G) of the HVOR (G = 0.6) and VVOR (G = 0.9) was roughly twice that for normal pigeons. Pigeon VOR phase under all combinations of orientation and arousal level was independent of stimulus magnitude except at the lowest frequency tested (0.03 Hz). At this frequency, phase lead decreased as stimulus magnitude increased for the HVOR and VVOR in both normal and aroused pigeons. 3. The step and sinusoidal gains were greater for the VVOR than for the HVOR under the same level of arousal. Neither the gain nor the dominant time constant of the VOR (tau vor) differed for rotation direction (clockwise or counterclockwise) for the HVOR or VVOR in normal or aroused pigeons. 4. The mean value of tau vor was 4.0 +/- 0.5 (SE) s as estimated from frequency response data and 4.3 +/- 0.4 s as estimated from step response data for the HVOR and VVOR in both normal and aroused pigeons. In comparison, the mean value of the dominant or cupular time constant (tau c) of normal pigeon SCPAs was approximately 10 s as estimated from frequency response data. These results indicate that tau vor is shorter than tau c in the pigeon. 5. At higher frequencies, the pigeon HVOR and VVOR exhibit an increasing phase lag unaccompanied by a gain change--characteristics produced by a pure time delay. The value of this time delay was about 7 ms for both the HVOR and VVOR in both normal and aroused pigeons. The HVOR and VVOR in normal and aroused pigeons lacked the higher frequency lead characteristics present in the frequency responses of most pigeon SCPAs.

Frequency Response Analysis (FRA) is a test method used for assessment of mechanical condition of transformer active parts. Its biggest problem is the interpretation of test results, namely the relationship between scale of differences between compared curves and the decision for further operation of the given transformer. Very often visible differences between two FRA curves do not mean that there is a deformation in the winding. The cause of the curve shift may come from other elements of the transformer that influence inductive or capacitive parameters. This paper takes under consideration the influence of both capacitance and inductance changes on transformer frequency response (FR). The analysis is performed with the computer model of a transformer and also some experimental results are presented, showing the influence of capacitance and inductance changes on the FR of real transformers. The results of research showed that this influence may lead to misleading effects on the shape of FR characteristics. The paper presents an analysis that can be used in the assessment of FRA measurement, especially in the case of uncertain data comparison results.