Showing papers on "Transfer function published in 2013"

S-shaped versus V-shaped transfer functions for binary Particle Swarm Optimization

Abstract: Particle Swarm Optimization (PSO) is one of the most widely used heuristic algorithms. The simplicity and inexpensive computational cost makes this algorithm very popular and powerful in solving a wide range of problems. The binary version of this algorithm has been introduced for solving binary problems. The main part of the binary version is a transfer function which is responsible to map a continuous search space to a discrete search space. Currently there appears to be insufficient focus on the transfer function in the literature despite its apparent importance. In this study six new transfer functions divided into two families, s-shaped and v-shaped, are introduced and evaluated. Twenty-five benchmark optimization functions provided by CEC 2005 special session are employed to evaluate these transfer functions and select the best one in terms of avoiding local minima and convergence speed. In order to validate the performance of the best transfer function, a comparative study with six recent modifications of BPSO is provided as well. The results prove that the new introduced v-shaped family of transfer functions significantly improves the performance of the original binary PSO.

Advanced Structural Dynamics and Active Control of Structures

Abstract: Preface List of Symbols Chapter 1 Introduction to Structures (examples, definition, and properties) 1.1 Examples 1.1.1 A Simple Structure 1.1.2 A 2D Truss 1.1.3 A 3D Truss 1.1.4 A Beam 1.1.5 The Deep Space Network Antenna 1.1.6 The International Space Station Structure 1.2 Definition 1.3 Properties Chapter 2 Standard Models (how to describe typical structures) 2.1 Models of a Linear System 2.1.1 State-Space Representation 2.1.2 Transfer Function 2.2 Second-Order Structural Models 2.2.1 Nodal Models 2.2.2 Modal Models 2.3 State-Space Structural Models 2.3.1 Nodal Models 2.3.2 Models in Modal Coordinates 2.3.3 Modal Models Chapter 3 Special Models (how to describe less-common structures) 3.1 Models with Rigid Body Modes 3.2 Models with Accelerometers 3.2.1 State-Space Representation 3.2.2 Second-Order Representation 3.2.3 Transfer Function 3.3 Models with Actuators 3.3.1 Model with Proof-Mass Actuators 3.3.2 Model with Inertial Actuators 3.4 Models with Small Non-Proportional Damping 3.5 Generalized Model 3.5.1 State-Space Representation 3.5.2 Transfer Function 3.6 Discrete-Time Models 3.6.1 State-Space Representation 3.6.2 Transfer Function Chapter 4 Controllability and Observability (how to excite and monitor a structure) 4.1 Definition and Properties 4.1.1 Continuous-Time Systems 4.1.2 Discrete-Time Systems 4.1.3. Relationship between Continuous- and Discrete-Time Grammians 4.2 Balanced Representation 4.3 Balanced Structures with Rigid Body Modes 4.4 Input and Output Gains 4.5 Controllability and Observability of a Structural Modal Model 4.5.1 Diagonally Dominant Grammians 4.5.2 Closed-Form Grammians 4.5.3 Approximately Balanced Structure in Modal Coordinates 4.6 Controllability and Observability of a Second-Order Modal Model 4.6.1 Grammians 4.6.2 Approximately Balanced Structure in Modal Coordinates 4.7 Three Ways to Compute Hankel Singular Values 4.8 &nb

Modelling heat transfer in heterogeneous media using fractional calculus.

Abstract: This paper presents the results of modelling the heat transfer process in heterogeneous media with the assumption that part of the heat flux is dispersed in the air around the beam. The heat transfer process in a solid material (beam) can be described by an integer order partial differential equation. However, in heterogeneous media, it can be described by a sub- or hyperdiffusion equation which results in a fractional order partial differential equation. Taking into consideration that part of the heat flux is dispersed into the neighbouring environment we additionally modify the main relation between heat flux and the temperature, and we obtain in this case the heat transfer equation in a new form. This leads to the transfer function that describes the dependency between the heat flux at the beginning of the beam and the temperature at a given distance. This article also presents the experimental results of modelling real plant in the frequency domain based on the obtained transfer function.

A new control scheme for PID load frequency controller of single-area and multi-area power systems

Abstract: A new control structure with a tuning method to design a PID load frequency controller for power systems is presented. Initially, the controller is designed for single area power system, then it is extended to multi-area case. The controller parameters are obtained by expanding controller transfer function using Laurent series. Relay based identification technique is adopted to estimate power system dynamics. Robustness studies on stability and performance are provided, with respect to uncertainties in the plant parameters. The proposed scheme ensures that overall system remains asymptotically stable for all bounded uncertainties and for system oscillations. Simulation results show the feasibility of the approach and the proposed method improves the load disturbance rejection performance significantly even in the presence of the uncertainties in plant parameters.

Linear Control System Analysis and Design with MATLAB

Abstract: Part I: Introductory Material Introduction Introduction Introduction to Control Systems Definitions Historical Background Control System: A Human Being Digital Control Development Mathematical Background Engineering Control Problem Computer Literacy Outline of Text Unmanned Aircraft Vehicles Introduction Twentieth-Century UAV R&D Predator Grim Reaper (US Air Force Fact Sheet MQ-9 Reaper, Posted on January 5, 2012) RQ-4 Global Hawk (US Air Force Fact Sheet RQ-4 Global Hawk, Posted on January 19, 2012) Wind Energy Control Systems Introduction Concurrent Engineering: A Road Map for Systems Design: Energy Example QFT Controller Design CAD Toolbox Frequency Domain Analysis Introduction Steel Mill Ingot Electrocardiographic Monitoring Control Theory: Analysis and Design of Control Systems Part II: Analog Control Systems Writing System Equations Introduction Electric Circuits and Components State Concepts Transfer Function and Block Diagram Mechanical Translation Systems Analogous Circuits Mechanical Rotational Systems Effective Moment of Inertia and Damping of a Gear Train Thermal Systems Hydraulic Linear Actuator Liquid-Level System Rotating Power Amplifiers DC Servomotor AC Servomotor Lagrange's Equation Solution of Differential Equations Introduction Standard Inputs to Control Systems Steady-State Response: Sinusoidal Input Steady-State Response: Polynomial Input Transient Response: Classical Method Definition of Time Constant Example: Second-Order System (Mechanical) Example: Second-Order System (Electrical) Second-Order Transients Time-Response Specifications CAD Accuracy Checks State-Variable Equations Characteristic Values Evaluating the State Transition Matrix Complete Solution of the State Equation Laplace Transform Introduction Definition of the Laplace Transform Derivation of Laplace Transforms of Simple Functions Laplace Transform Theorems CAD Accuracy Checks Application of the Laplace Transform to Differential Equations Inverse Transformation Heaviside Partial-Fraction Expansion Theorems MATLAB(R) Partial-Fraction Example Partial-Fraction Shortcuts Graphical Interpretation of Partial-Fraction Coefficients Frequency Response from the Pole-Zero Diagram Location of Poles and Stability Laplace Transform of the Impulse Function Second-Order System with Impulse Excitation Solution of State Equation Evaluation of the Transfer-Function Matrix MATLAB(R) Script For MIMO Systems System Representation Introduction Block Diagrams Determination of the Overall Transfer Function Standard Block-Diagram Terminology Position-Control System Simulation Diagrams Signal Flow Graphs State Transition Signal Flow Graph Parallel State Diagrams from Transfer Functions Diagonalizing the A Matrix Use of State Transformation for the State-Equation Solution Transforming A Matrix with Complex Eigenvalues Transforming an A Matrix into Companion Form Using MATLAB(R) to Obtain the Companion A Matrix Control-System Characteristics Introduction Routh's Stability Criterion Mathematical and Physical Forms Feedback System Types Analysis of System Types Example: Type 2 System Steady-State Error Coefficients CAD Accuracy Checks: CADAC Use of Steady-State Error Coefficients Nonunity-Feedback System Root Locus Introduction Plotting Roots of a Characteristic Equation Qualitative Analysis of the Root Locus Procedure Outline Open-Loop Transfer Function Poles of the Control Ratio C(s)/R(s) Application of the Magnitude and Angle Conditions Geometrical Properties (Construction Rules) CAD Accuracy Checks Root Locus Example Example of Section 10.10: MATLAB(R) Root Locus Root Locus Example with an RH Plane Zero Performance Characteristics Transport Lag Synthesis Summary of Root-Locus Construction Rules for Negative Feedback Frequency Response Introduction Correlation of the Sinusoidal and Time Response Frequency-Response Curves Bode Plots (Logarithmic Plots) General Frequency-Transfer-Function Relationships Drawing the Bode Plots Example of Drawing a Bode Plot Generation of MATLAB(R) Bode Plots System Type and Gain as Related to Log Magnitude Curves CAD Accuracy Check Experimental Determination of Transfer Function Direct Polar Plots Summary: Direct Polar Plots Nyquist Stability Criterion Examples of the Nyquist Criterion Using Direct Polar Plots Nyquist Stability Criterion Applied to a System Having Dead Time Definitions of Phase Margin and Gain Margin and Their Relation to Stability Stability Characteristics of the Log Magnitude and Phase Diagram Stability from the Nichols Plot (Log Magnitude-Angle Diagram) Closed-Loop Tracking Performance Based on Frequency Response Introduction Direct Polar Plot Determination of Mm and omegam for a Simple Second-Order System Correlation of Sinusoidal and Time Responses Constant M(omega) and alpha(omega) Contours of C(Jomega)/R(Jomega) on the Complex Plane (Direct Plot) Constant 1/M and alpha Contours (Unity Feedback) in the Inverse Polar Plane Gain Adjustment of a Unity-Feedback System for a Desired Mm: Direct Polar Plot Constant M and alpha Curves on the Log Magnitude-Angle Diagram (Nichols Chart) Generation of MATLAB(R) Bode and Nyquist Plots Adjustment of Gain by Use of the Log Magnitude-Angle Diagram (Nichols Chart) Correlation of the Pole-Zero Diagram with Frequency and Time Responses Part III: Compensation: Analog Systems Root-Locus Compensation: Design Introduction to Design Transient Response: Dominant Complex Poles Additional Significant Poles Root-Locus Design Considerations Reshaping the Root Locus CAD Accuracy Checks Ideal Integral Cascade Compensation (PI Controller) Cascade Lag Compensation Design Using Passive Elements System Ideal Derivative Cascade Compensation (PD Controller) Lead Compensation Design Using Passive Elements General Lead-Compensator Design Lag-Lead Cascade Compensation Design System Comparison of Cascade Compensators PID Controller Introduction to Feedback Compensation Feedback Compensation: Design Procedures Simplified Rate Feedback Compensation: A Design Approach Design of Rate Feedback Design: Feedback of Second Derivative of Output Results of Feedback-Compensation Design Rate Feedback: Plants with Dominant Complex Poles Frequency-Response Compensation Design Introduction to Feedback Compensation Design Selection of a Cascade Compensator Cascade Lag Compensator Design Example: Cascade Lag Compensation Cascade Lead Compensator Design Example: Cascade Lead Compensation Cascade Lag-Lead Compensator Design Example: Cascade Lag-Lead Compensation Feedback Compensation Design Using Log Plots Design Example: Feedback Compensation (Log Plots) Application Guidelines: Basic Minor-Loop Feedback Compensators Part IV: Advanced Topics Control-Ratio Modeling Introduction Modeling a Desired Tracking Control Ratio Guillemin - Truxal Design Procedure Introduction to Disturbance Rejection Second-Order Disturbance-Rejection Model Disturbance-Rejection Design Principles for SISO Systems Disturbance-Rejection Design Example Disturbance-Rejection Models Design: Closed-Loop Pole-Zero Assignment (State-Variable Feedback) Introduction Controllability and Observability State Feedback for SISO Systems State-Feedback Design for SISO Systems Using the Control Canonical (Phase-Variable) Form State-Variable Feedback (Physical Variables) General Properties of State Feedback (Using Phase Variables) State-Variable Feedback: Steady-State Error Analysis Use of Steady-State Error Coefficients State-Variable Feedback: All-Pole Plant Plants with Complex Poles Compensator Containing a Zero State-Variable Feedback: Pole-Zero Plant Observers Control Systems Containing Observers Parameter Sensitivity and State-Space Trajectories Introduction Sensitivity Sensitivity Analysis Sensitivity Analysis Examples Parameter Sensitivity Examples Inaccessible States State-Space Trajectories Linearization (Jacobian Matrix) Part V: Digital Control Systems Sampled-Data Control Systems Introduction Sampling Ideal Sampling Z Transform Theorems Differentiation Process Synthesis in the z Domain (Direct Method) Inverse Z Transform Zero-Order Hold Limitations Steady-State Error Analysis for Stable Systems Root-Locus Analysis for Sampled-Data Control Systems Digital Control Systems Introduction Complementary Spectra Tustin Transformation: s- to z-Plane Transformation z-Domain to the w- and w'-Domain Transformations Digitization Technique Digitization Design Technique Pseudo-Continuous-Time Control System Design of Digital Control System Direct Compensator PCT Lead Cascade Compensation PCT Lag Compensation PCT Lag-Lead Compensation Feedback Compensation: Tracking Controlling Unwanted Disturbances Extensive Digital Feedback Compensator Example Controller Implementation Appendix A: Table of Laplace Transform Pairs Appendix B: Matrix Linear Algebra Appendix C: Introduction to MATLAB(R) and Simulink(R) Appendix D: Conversion of Units Problems Answers to Selected Problems Index

Review of inverse Laplace transform algorithms for Laplace-space numerical approaches

Abstract: A boundary element method (BEM) simulation is used to compare the efficiency of numerical inverse Laplace transform strategies, considering general requirements of Laplace-space numerical approaches. The two-dimensional BEM solution is used to solve the Laplace-transformed diffusion equation, producing a time-domain solution after a numerical Laplace transform inversion. Motivated by the needs of numerical methods posed in Laplace-transformed space, we compare five inverse Laplace transform algorithms and discuss implementation techniques to minimize the number of Laplace-space function evaluations. We investigate the ability to calculate a sequence of time domain values using the fewest Laplace-space model evaluations. We find Fourier-series based inversion algorithms work for common time behaviors, are the most robust with respect to free parameters, and allow for straightforward image function evaluation re-use across at least a log cycle of time.

Frequency-Domain Analysis of Nonlinear Active Disturbance Rejection Control via the Describing Function Method

Abstract: Active disturbance rejection control (ADRC) is a new design concept that shows promising power in dealing with the uncertainties of control systems. However, most of the previous work has been numerical time-domain development and frequency-domain analysis for the linear framework. This paper focuses on the frequency-domain analysis of the nonlinear ADRC behavior using the describing function method and characterizes the effect of the ${\rm fal}$ nonlinearity parameter on the performance of the closed-loop system. Both the describing function of the nonlinearity and the transfer function description of the system's linear portion are derived. The stability, dynamic stiffness, and tracking performance are analyzed for a second-order single-input single-output plant. The analysis results show that the nonlinearity parameter plays a crucial role in the system performance. The nonlinear ADRC has higher control efficiency than the linear ADRC but reduces the stability margin of the system. Using the fast tool servo case, simulations and hardware experiments are conducted, and the results further support the analysis.

Inclusion of Rational Models in an Electromagnetic Transients Program: Y-Parameters, Z-Parameters, S-Parameters, Transfer Functions

Abstract: Frequency-dependent effects in power system components and subnetworks can be efficiently represented via rational function-based models that characterize the component port behavior as a function of frequency. The port behavior can be defined by alternative parameter sets (e.g., admittance (Y-), impedance (Z-), or scattering (S-) parameters). The model extraction procedure approximates the port characteristics over a desired band of frequencies via a compact rational model. This paper shows a detailed procedure for interfacing such models with electromagnetic transients simulators via a Norton equivalent and convolution, for multiport Y-, Z- and S-parameter-based models. The interface of a multiport transfer function element is also shown. The procedure is applicable for models on pole-residue and state-space form. The correctness of these model implementations is demonstrated for a small electrical circuit. Application examples are shown for subnetwork modeling from computed Y-parameters and for cable modeling from measured S-parameters.

Resolving spectral information from time domain induced polarization data through 2-D inversion

Abstract: SUMMARY Field-basedtimedomain(TD)inducedpolarization(IP)surveysareusuallymodelledbytaking into account only the integral chargeability, thus disregarding spectral content. Furthermore, the effect of the transmitted waveform is commonly neglected, biasing inversion results. Given these limitations of conventional approaches, a new 2-D inversion algorithm has been developed using the full voltage decay of the IP response, together with an accurate description of the transmitter waveform and receiver transfer function. This allows reconstruction of the spectral information contained in the TD decay series. The inversion algorithm is based around a 2-D complex conductivity kernel that is computedoverarangeoffrequenciesandconvertedtotheTDthroughafastHankeltransform. Two key points in the implementation ensure that computation times are minimized. First, the speed of the Jacobian computation, time transformed from frequency domain through the same transformation adopted for the forward response is optimized. Secondly, the reduction of the number of frequencies where the forward response and Jacobian are calculated: cubic splines are used to interpolate the responses to the frequency sampling necessary in the fast Hankel transform. These features, together with parallel computation, ensure inversion times comparable with those of direct current algorithms. Thealgorithmhasbeendevelopedinalaterallyconstrainedinversionscheme,andhandles both smooth and layered inversions; the latter being helpful in sedimentary environments, where quasi-layered models often represent the actual geology more accurately than smooth minimum-structure models. In the layered inversion approach, a general method to derive the thickness derivative from the complex conductivity Jacobian is also proposed. One synthetic example of layered inversion and one field example of smooth inversion show the capability of the algorithm and illustrates a complete uncertainty analysis of the model parameters. With this new algorithm, in situ TD IP measurements give access to the spectral content of the polarization processes, opening up new applications in environmental and hydrogeophysical investigations.

Sensitivity Analysis of Load-Damping Characteristic in Power System Frequency Regulation

Abstract: The smart grid initiative leads to growing interests in demand responses and the load models, especially the frequency-sensitive loads such as motors. The reason is that high-penetration controllable load may have substantial impact on system frequency response (SFR). However, the effect of the frequency-related load-damping coefficient is still not completely understood. This paper investigates the effect of frequency-sensitive load on system frequency using typical SFR model. Theoretic analyses based on transfer functions show that the frequency deviation under a different load-damping coefficient is relatively small and bounded when the power system is essentially stable; while the frequency deviation can be accelerated when a power system is unstable after disturbance. For the stable case, the largest frequency dip under a perturbation and the corresponding critical time can be derived by inverse Laplace transformation using a full model considering load-damping coefficient. Further, the error in evaluating the load-frequency coefficient gives the largest impact to frequency deviation right at the time when the largest frequency dip occurs. Multiple-machine cases and automatic generation control (AGC) are also included in the analyses with verifications by simulation studies. The conclusion can be useful for system operators for decision-making of load control or interruption.

Small-Signal Modeling of Open-Loop PWM Z-Source Converter by Circuit-Averaging Technique

Abstract: This paper presents the ac small-signal modeling of the power stage of pulsewidth-modulated Z-source converter in continuous conduction mode by the circuit-averaging technique. The small-signal models used to derive the open-loop power-stage input voltage-to-capacitor voltage, input voltage-to-inductor current, control-to-capacitor voltage, and control-to-inductor current transfer functions are derived. Open-loop power-stage transfer functions corresponding to the capacitor voltage loop and inductor current loop are derived. The transfer functions derived take into account the equivalent series resistances of the inductors and capacitors. Experimental validation of the derived small-signal models is presented for a laboratory prototype. The theoretical predictions are in good agreement with the experimental results.

Determination of the transfer function for optical surface topography measuring instruments—a review

Abstract: A significant number of areal surface topography measuring instruments, largely based on optical techniques, are commercially available. However,implementation of optical instrumentation into production is currently difficult dueto the lack of understanding of the complex interaction between the light and the component surface. Studying the optical transfer function of the instrument can help address this issue. Herea review is given of techniques for the measurement of optical transfer functions. Starting from the basis of a spatially coherent, monochromatic confocal scanning imaging system, the theory of optical transfer functions in three-dimensional (3D) imaging is presented. Further generalizations are reviewed allowing the extension of the theory to the description of conventional and interferometric 3D imaging systems. Polychromatic transfer functions and surface topography measurements are also discussed. Following presentation of theoretical results, experimental methods to measure the optical transfer function of each class of system are presented, with a focus on suitable methods for the establishment of calibration standards in 3D imaging and surface topography measurements.

Synthesis of Cross-Coupled Reduced-Order Dispersive Delay Structures (DDSs) With Arbitrary Group Delay and Controlled Magnitude

Abstract: For the first time, a systematic synthesis method for cross-coupled dispersive delay structures (DDSs) with controlled magnitude for analog signal processing applications is proposed. In this method, the transfer function is synthesized using a polynomial expansion approach, which allows to separately control the magnitude and group-delay response of the DDS. The synthesized transfer function also features a reduced order-namely, half-compared to that of previously reported synthesis techniques for linear-phase filters. Once it has been constructed, the transfer function is transferred into coupling matrices that can be implemented in arbitrary cross-coupled-resonator technologies. Several design examples are provided for different prescribed group-delay responses. An experimental waveguide prototype is demonstrated. The agreement between the measured and prescribed responses illustrates the proposed synthesis method.

Research on frequency-band characteristics and parameters configuration of linear active disturbance rejection control for second-order systems

Abstract: Starting with frequency domain analysis, the tracking ability of linear extended state observer(LESO) and the characteristics of linear active disturbance rejection control(LADRC), such as the stability, rejection quality for external disturbance, robustness for control input gain uncertainty and model uncertainty, as well as noise sensitivity characteristics, are analyzed based on the close-loop transfer function and frequency response. Then, the relationship between the dynamic characteristics and the controller parameters is discussed and the method of parameter selection is proposed. Finally, the method is applied to a weapon control system, and its effectiveness is validated. In addition, issues such as overshoot phenomenon, actuator saturation and the design of pre-filter are addressed, establishing both the conceptual and practical foundation for engineering design.

An optical FPGA: reconfigurable simultaneous multi-output spectral pulse-shaping for linear optical processing

Abstract: We demonstrate a pulse-shaping technique that allows for spectrally resolved splitting of an input signal to multiple output ports. This ability enables reconfigurable creation of splitters with complex wavelength-dependent splitting ratios, giving similar flexibility to a Field Programmable Gate Array (FPGA) in electronics. Our technique can be used to create reprogrammable optical (interferometric) circuits, by emulating their multi-port spectral transfer functions instead of the traditional method of creating an interferometer by splitting and recombining the light with an added delay. We demonstrate the capabilities of this technique by creating a Mach-Zehnder interferometer, an all-optical discrete Fourier transform filter, two nested Mach-Zehnder interferometers and a complex splitter with a triangular-shaped response.

A Methodology for Mutual Coupling Estimation and Compensation in Antennas

Abstract: A simple methodology is presented for the estimation and compensation of mutual coupling in antenna systems of arbitrary geometries, including antenna arrays in the vicinity of scatterers. The methodology includes both theoretical and experimental schemes, while also, does not resort to assumptions often encountered in previous mutual coupling estimation approaches. In particular, our methodology uses a matrix representation for the antenna system and is based on a new concept, the antenna current Green's function which uses the recently proven inverse reciprocity theorem, or more intuitively, a relation of the transfer function for the transmitting mode of the antenna system to the corresponding transfer function for the receiving mode. Validation is performed by comparing calculated predictions to measurements and simulations of a practical antenna system as well as a two- and four-element array. An algorithm using matrix interpolation, that aims at exploiting the antenna transfer function, is also developed and experimentally demonstrated for practical array calibrations and coupling compensation techniques in array signal processing. The developed procedures are non-specific and can also be applied to a diversity of antenna systems and other complex scattering problems.

Coherence scanning interferometry: linear theory of surface measurement

Abstract: The characterization of imaging methods as three-dimensional (3D) linear filtering operations provides a useful way to compare the 3D performance of optical surface topography measuring instruments, such as coherence scanning interferometry, confocal and structured light microscopy. In this way, the imaging system is defined in terms of the point spread function in the space domain or equivalently by the transfer function in the spatial frequency domain. The derivation of these characteristics usually involves making the Born approximation, which is strictly only applicable to weakly scattering objects; however, for the case of surface scattering, the system is linear if multiple scattering is assumed to be negligible and the Kirchhoff approximation is assumed. A difference between the filter characteristics derived in each case is found. However this paper discusses these differences and explains the equivalence of the two approaches when applied to a weakly scattering object.

Projection-Based Fast Learning Fully Complex-Valued Relaxation Neural Network

Abstract: This paper presents a fully complex-valued relaxation network (FCRN) with its projection-based learning algorithm. The FCRN is a single hidden layer network with a Gaussian-like sech activation function in the hidden layer and an exponential activation function in the output layer. For a given number of hidden neurons, the input weights are assigned randomly and the output weights are estimated by minimizing a nonlinear logarithmic function (called as an energy function) which explicitly contains both the magnitude and phase errors. A projection-based learning algorithm determines the optimal output weights corresponding to the minima of the energy function by converting the nonlinear programming problem into that of solving a set of simultaneous linear algebraic equations. The resultant FCRN approximates the desired output more accurately with a lower computational effort. The classification ability of FCRN is evaluated using a set of real-valued benchmark classification problems from the University of California, Irvine machine learning repository. Here, a circular transformation is used to transform the real-valued input features to the complex domain. Next, the FCRN is used to solve three practical problems: a quadrature amplitude modulation channel equalization, an adaptive beamforming, and a mammogram classification. Performance results from this paper clearly indicate the superior classification/approximation performance of the FCRN.

Artificial Neural Network–Based System Identification for a Single-Shaft Gas Turbine

Abstract: —During recent decades, artificial intelligence has been employed as a powerful tool for identification of complex industrial systems with nonlinear dynamics, such as gas turbines (GT). In this study, a methodology based on artificial neural network (ANN) techniques was developed for offline system identification of a low-power gas turbine. The processed data was obtained from a SIMULINK model of a gas turbine in MATLAB environment. A comprehensive computer program code was generated and run in MATLAB environment for creating and training different ANN models with two-layer feed-forward multi-layer perceptron (MLP) structure. The code consisted of various training functions, different number of neurons as well as a variety of transfer (activation) functions for hidden and output layers of the network. It was shown that the optimal model for a two-layer network with MLP structure, consisted of 20 neurons in its hidden layer and used trainlm as its training function, as well as tansig and logsid as its transfer functions for the hidden and output layers. It was also observed that trainlm has a superior performance in terms of minimum MSE, compared with each of the other training functions. The resulting model could predict performance of the system with high accuracy. The methodology provides a comprehensive view of the performance of over 18720 ANN models for system identification of single shaft GT. One can use the optimal ANN model from this study when training from real data obtained from this type of GT. This is particularly useful when real data is only available over a limited operational range.

Process variation in silicon photonic devices

Abstract: An array of passive silicon-on-insulator optical devices is laid out in repeating patterns on four foundry-fabricated wafers. The physical and optical characterization of these microrings, racetrack resonators, and directional couplers are found to exhibit significant variation in optical response. A device-heating experiment carried out on a number of different devices demonstrates that thermal effects are independent of the device’s location on the wafer. An analysis of the variation of the optical responses of the room-temperature devices is used to determine the process variation. We find that if we form successive arrays of the values of a quantity of interest (the peak wavelength of a transfer function) at a single device at some point on the wafer, and then increase the size of the array by including the values of the devices at ever greater distances from the original, then the variance of the values of the successive arrays increases linearly with the linear extent of the sample. That is, the process variation exhibits “random walk” pattern with spatial extent. We express the process variation in units of variance per length and find that our measured values agree with others in the literature; that is, the process variation is approximately 1 nm2/cm.

Analysis and Design of Average Current Mode Control Using a Describing-Function-Based Equivalent Circuit Model

Abstract: This paper proposes a small-signal model for average current mode control based on an equivalent circuit. The model uses a three-terminal equivalent circuit model based on a linearized describing function method to include the feedback effect of the sideband frequency components of the inductor current. The model extends the results obtained in peak current mode control to average current mode control. The proposed small-signal model is accurate up to half switching frequency, predicting the subharmonic instability. The proposed model is verified using SIMPLIS simulation and hardware experiments, which show good agreement with the measurement results. Based on the proposed model, new feedback design guidelines are presented. The proposed design guidelines are compared with several conventional, widely used design criteria. By designing the external ramp following the proposed design guidelines, the quality factor of the double poles at half of the switching frequency in the control-to-output transfer function can be precisely controlled. This helps the feedback loop design to achieve wide control bandwidth and proper damping.

Analytical Transfer Functions Relating Power and Ground Voltage Fluctuations to Jitter at a Single-Ended Full-Swing Buffer

Abstract: The transfer functions relating supply voltage fluctuations to jitter are analytically derived in closed form expressions for a single-ended buffer. The analytic transfer functions are derived from a linear differential equation obtained from asymptotic linear inverter I-V curves. The transfer functions are validated by comparison with HSPICE simulations. The estimated jitter is compared with the simulated jitter using eye diagrams with single-frequency and multitone supply voltage fluctuations.

Analysis of the operation of gradient echo memories using a quantum input?output model

Abstract: The gradient echo memory (GEM) technique is a promising candidate for real devices due to its demonstrated performance, but to date high performance experiments can only be described numerically. In this paper we derive a model for GEM as a cascade of infinite interconnected harmonic oscillators. We take a quantum input–output approach to analyse this system, describing the read and write processes of GEM each as a linear-time-invariant process. We provide an analytical solution to the problem in terms of transfer functions which describe the memory behaviour for arbitrary inputs and operating regimes. This allows us to go beyond previous works and analyse the storage quality in the regimes of high optical depth and memory-bandwidth comparable to input bandwidth, exactly the regime of high-efficiency experiments.

Robust Stability Analysis for Feedback Interconnections of Time-Varying Linear Systems

Abstract: Feedback interconnections of causal linear systems are studied in a continuous-time setting. The developments include a linear time-varying (LTV) generalization of Vinnicombe's nu-gap metric and an integral-quadratic-constraint-based robust L2-stability theorem for uncertain feedback interconnections of potentially open-loop unstable systems. These main results are established in terms of Toeplitz--Wiener--Hopf and Hankel operators, and the Fredholm index, for a class of causal linear systems with the following attributes: (i) a system graph (i.e., subspace of L2 input-output pairs) admits normalized strong right (i.e., image) and left (i.e., kernel) representations, and (ii) the corresponding Hankel operators are compact. These properties are first verified for stabilizable and detectable LTV state-space models to initially motivate the abstract formulation, and subsequently verified for frequency-domain multiplication by constantly proper Callier--Desoer transfer functions in analysis that confirms consistency of the developments with the time-invariant theory. To conclude, the aforementioned robust stability theorem is applied in an illustrative example concerning the feedback interconnection of distributed-parameter systems over a network with time-varying gains. (Less)

Methods related to real-time cancer diagnostics at endoscopy utilizing fiber-optic raman spectroscopy

Abstract: A method of achieving instrument independent measurements for quantitative analysis of fiber-optic Raman spectroscope system, the system comprising a laser source, a spectroscope and a fiber optic probe to transmit light from the laser source to a target and return scattered light to the spectroscope, the method comprising transmitting light from the laser source to a standard target having a known spectrum, recording a calibration spectrum of the scattered light from the standard target, comparing the known spectrum and the calibration system and generating a probe and/or probe-system transfer function, and storing the transfer function. Further provided is a method of performing real-time diagnostic Raman spectroscopy optionally in combination with the other disclosed methods.

Formalization of Laplace Transform Using the Multivariable Calculus Theory of HOL-Light

Abstract: Algebraic techniques based on Laplace transform are widely used for solving differential equations and evaluating transfer of signals while analyzing physical aspects of many safety-critical systems. To facilitate formal analysis of these systems, we present the formalization of Laplace transform using the multivariable calculus theories of HOL-Light. In particular, we use integral, differential, transcendental and topological theories of multivariable calculus to formally define Laplace transform in higher-order logic and reason about the correctness of Laplace transform properties, such as existence, linearity, frequency shifting and differentiation and integration in time domain. In order to demonstrate the practical effectiveness of this formalization, we use it to formally verify the transfer function of Linear Transfer Converter (LTC) circuit, which is a commonly used electrical circuit.