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9th International Symposium on Advanced Topics in Electrical Engineering (ATEE)

作者： Petrescu, Lucian Cazacu, Emil Petrescu, Catalina Univ Politehn Bucuresti Dept Elect Engn Bucharest 060042 Romania

ISBN: (纸本)9781479975143

Hysteresis phenomenon is currently met in magnetic materials characterization. From many years this hysteresis had been modeled with different approaches. The aim of this paper is to present a comparison between few sigmoid functions used more often in other research areas. The functions were updated according to the requirements of the magnetic hysteresis and there comparisons for three different magnetic materials were performed. In the last part, hysteresis losses are evaluated using relative errors between experimental loop area and modeled loop area.

关键词： magnetic hysteresis sigmoid functions hysteresis losses evaluation

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Approximating piecewise nonlinearities in dynamic systems with sigmoid functions: advantages and limitations

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NONLINEAR DYNAMICS 2023年第9期111卷 8545-8569页

作者： Martinelli, Cristiano Coraddu, Andrea Cammarano, Andrea Univ Strathclyde Dept Naval Architecture Ocean & Marine Engn 100 Montrose St Glasgow G4 0LZ Scotland Delft Univ Technol Dept Maritime & Transport Technol Mekelweg 2 NL-2628 CD Delft Netherlands Univ Glasgow James Watt Sch Engn James Watt South Bldg Glasgow G12 8QQ Scotland

In the industry field, the increasingly stringent requirements of lightweight structures are exposing the ultimately nonlinear nature of mechanical systems. This is extremely true for systems with moving parts and loose fixtures which show piecewise stiffness behaviours. Nevertheless, the numerical solution of systems with ideal piecewise mathematical characteristics is associated with time-consuming procedures and a high computational burden. Smoothing functions can conveniently simplify the mathematical form of such systems, but little research has been carried out to evaluate their effect on the mechanical response of multi-degree-of-freedom systems. To investigate this problem, a slightly damped mechanical two-degree-of-freedom system with soft piecewise constraints is studied via numerical continuation and numerical integration procedures. sigmoid functions are adopted to approximate the constraints, and the effect of such approximation is explored by comparing the results of the approximate system with the ones of the ideal piecewise counter-part. The numerical results show that the sigmoid functions can correctly catch the very complex dynamics of the proposed system when both the above-mentioned techniques are adopted. Moreover, a reduction in the computational burden, as well as an increase in numerical robustness, is observed in the approximate case.

关键词： Nonlinear dynamics Non-smooth systems Piecewise stiffness sigmoid functions Period doubling isolated solutions Numerical continuation Basins of attraction

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Interface capturing schemes based on sigmoid functions

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COMPUTERS & FLUIDS 2024年 280卷

作者： Zhang, Ke Shen, Yiqing Univ Chinese Acad Sci Sch Engn Sci Beijing 100049 Peoples R China

The non-polynomial THINC (tangent of hyperbola for interface capturing) scheme has been reported to show both numerical simplicity and high fidelity for resolving contact interfaces. In this paper, two types of smooth sigmoid functions are employed to construct the non-polynomial reconstructions for capturing interfaces (similarly, called SFINC schemes, sigmoid functions for interface capturing). One type is that the exact jump location (a parameter introduced in the reconstruction) can be analytically calculated, and another type cannot. The algebraic function and the Gudermannian function belong to the first and the second types, respectively, and are investigated in this paper. An approximate method for calculating the jump location of the Gudermannian function is proposed. The method avoids the iteration process of determining the jump location, and hence is efficient and practical in applications. The numerical validations and comparisons of SFINC schemes are presented to show their performance for simulating complex compressible flow fields.

关键词： THINC sigmoid functions Non-polynomial reconstructions SFINC Gudermannian function

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Characterization of a class of sigmoid functions with applications to neural networks

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NEURAL NETWORKS 1996年第5期9卷 819-835页

作者： Menon, A Mehrotra, K Mohan, CK Ranka, S SYRACUSE UNIV SCH COMP & INFORMAT SCICTR SCI & TECHNOL 2120SYRACUSENY 13244

We study two classes of sigmoids: the simple sigmoids, defined to be odd, asymptotically bounded, completely monotone functions in one variable, and the hyperbolic sigmoids, a proper subset of simple sigmoids and a natural generalization of the hyperbolic tangent. We obtain a complete characterization for the inverses of hyperbolic sigmoids using Euler's incomplete beta functions, and describe composition rules that illustrate how such functions may be synthesized from others. These results are applied to two problems. First we show that with respect to simple sigmoids the continuous Cohen-Grossberg-Hopfield model can be reduced to the (associated) Legendre differential equations. Second, we show that the effect of using simple sigmoids as node transfer functions in a one-hidden layer feedforward network with one summing output may be interpreted as representing the output function as a Fourier series sine transform evaluated at the hidden layer node inputs, thus extending and complementing earlier results in this area. Copyright (C) 1996 Elsevier Science Ltd

关键词： sigmoid functions hypergeometric series legendre equation Cohen-Grossberg-Hopfield model additive model Fourier transform

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New methodologies for SVC modeling in the power flow problem based on sigmoid functions

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ELECTRICAL ENGINEERING 2024年第1期106卷 971-981页

作者： Barbosa, Joao Pedro Peters Passos Filho, Joao Alberto Univ Fed Juiz de Fora Dept Elect Energy Rua Jose Lourenco Kelmer BR-36036900 Juiz De Fora MG Brazil

This paper presents new methodologies for modeling static VAr compensators (SVCs) in the power flow problem. The proposed formulations utilize sigmoid functions to model the control equations that describe the steady-state behavior of SVCs. The first methodology introduces reactive power injection as a new state variable, while the second methodology utilizes the thyristor firing angle. These steady-state SVC methodologies were applied to the power flow problem using the full Newton formulation, which incorporates the control equations into the system of nonlinear equations. One of the main contributions of these proposed methodologies is that they eliminate the need for alternating adjustments concerning the operational limits of the SVC during the iterative power flow process. The implementation of a power flow program was tested on both small-scale tutorial systems and the medium-scale IEEE Nordic system. The presented results validate and demonstrate the effectiveness of the proposed methodology.

关键词： Static VAr compensator Power flow Control devices sigmoid functions

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Modelling Technique utilizing Modified sigmoid functions for Describing Power Transistor Device Capacitances Applied on GaN HEMT and Silicon MOSFET 31

Modelling Technique utilizing Modified Sigmoid Functions for...

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31st Annual IEEE Applied Power Electronics Specialists Conference and Exposition (APEC)

作者： Yeo, H. L. Tseng, K. J. Nanyang Technol Univ Sch Elect & Elect Engn Singapore Singapore

ISBN: (纸本)9781467395502

In power transistor models, it is very important that device capacitances are modelled accurately so that switching losses, EMI filter requirements and gate timing requirements of the converter can be accurately determined. In this paper, a modelling technique utilizing modified sigmoid functions to describe the device capacitances is applied on a GaN HEMT and a silicon MOSFET to develop their corresponding SPICE models. Comparison of switching energies of the transistors under slow-switching conditions suggest that the technique is suitable for modelling both types of transistors. The developed model for the GaN HEMT is also shown to simulate faster than the manufacturer's model under fast switching conditions.

关键词： GaN HEMT Silicon MOSFET Modelling and Simulation sigmoid functions

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Rendering of Virtual Fixtures for MIS Using Generalized sigmoid functions

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14th Conference on Medicine Meets Virtual Reality

作者： Ren, Jing Patel, Rajni V. McIsaac, Kenneth A. John P Robarts Res Inst Imaging Res Labs London ON N6A 5K8 Canada

ISBN: (纸本)9781586035839

To avoid undesired collisions and improve the level of safety and precision, artificial potential field (APF) can be employed to generate virtual forces around protected tissue and to provide surgeons with real-time force refection through haptic feedback. In this paper, we propose a potential field-based force model using the generalized sigmoid function, and show that it can represent a large class of shapes. The proposed approach has several advantages such as computational efficiency, easily adjustable level of force reflection, and force continuity.

关键词： Artificial potential fields haptic feedback sigmoid functions

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sigmoid-like functions and root finding methods

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APPLIED MATHEMATICS AND COMPUTATION 2008年第2期204卷 784-793页

作者： Petkovic, Miodrag S. Yun, Beong In Univ Nis Dept Math Fac Elect Engn Nish 18000 Serbia Kunsan Natl Univ Sch Math Informat & Stat Kunsan 573701 South Korea

An efficient method for finding an initial approximation to a real root of nonlinear equation f(x) = 0 is proposed. The presented approach is based on numerical integration of the transform functions tanh m(f(x)), arctan m(f(x)) (m > 0) and sgn (f(x)) of sigmoidal type. Combining numerical integration method and rapidly convergent iterative methods, we construct a hybrid method of great efficiency. The introduced sigmoid-like functions are also convenient for the detection of a cluster of zeros or a multiple zero lying in a given interval. The presented numerical examples demonstrate the feasibility and efficiency of the proposed procedures. (C) 2008 Elsevier Inc. All rights reserved.

关键词： Nonlinear equations sigmoid functions Initial approximations Root solvers Numerical integration Hybrid methods Cluster of zeros

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The Binary Equilibrium Optimization Algorithm with sigmoid Transfer functions 2020

The Binary Equilibrium Optimization Algorithm with Sigmoid T...

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12th International Conference on Machine Learning and Computing (ICMLC)

作者： Gao, Zheng-Ming Zhao, Juan Li, Su-Ruo Jingchu Univ Technol Sch Comp Engn Jingmen Peoples R China Jingchu Univ Technol Sch Elect & Informat Enginnering Jingmen Peoples R China

ISBN: (纸本)9781450376426

The binary version of bio-inspired approaches is used frequently in modern digital world. We therefore propose a new kind of binary version of the equilibrium optimization algorithm which was just raised before. Causing the universal usage for sigmoid function, we carried out the simulation experiments on the values of beta parameter for sigmoid function. Results show that the value of beta should be large in the interval of 2 to 5 for most unimodal and multimodal, and even bottom flat-like benchmark functions. Unfortunately, some of the multimodal and bottom flat-like benchmark functions need smaller value of beta. Even more, some of them such as Salomon function lack the discipline for beta parameter. Conclusions could be made that specific experiment should be carried out for given problems before real application.

关键词： The equilibrium optimization algorithm binary approaches transfer functions sigmoid functions

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Modelling Technique utilizing Modified sigmoid functions for Describing Power Transistor Device Capacitances Applied on GaN HEMT and Silicon MOSFET

Modelling Technique utilizing Modified Sigmoid Functions for...

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Annual IEEE Applied Power Electronics Conference and Exposition

作者： H. L. Yeo K. J. Tseng School of Electrical and Electronic Engineering Nanyang Technological University Singapore

ISBN: (纸本)9781467395519

关键词： GaN HEMT Silicon MOSFET Modelling and Simulation sigmoid functions

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