On hyperbolic laws of capacitor discharge through self‐timed digital loads

A new model to predict the dynamic behavior of a self‐timed autonomous digital system powered by a capacitor is derived. The model demonstrates the hyperbolic shape of the discharging process on the capacitor. It allows a symbolic analysis of the discharging process for complex digital loads comprised of series (stack) and parallel configurations of digital circuits. For example, for a stack configuration, important non‐trivial relationships between the hyperbolic discharging rates have been derived based on the knowledge of the velocity saturation index (alpha) of the semiconductor devices used in the digital part. For a realistic (modern complementary metal oxide semiconductor (CMOS) devices) value of alpha = 1.5, the discharging process for a stack of two identical circuits proceeds nearly three times slower than that of any of the stand‐alone circuits. This shows a potential way of extending the lifetime of the energy sources by means of stacking self‐timed circuits. Although the analysis is based on configurations consisting of ring oscillators in CMOS technology, the analysis method can be extended to other types of self‐timed systems and other semiconductor technologies in which the instantaneous switching activity of the digital load is determined by the instantaneous voltage levels provided by the capacitive power transfer mechanism. The analytical derivations have been validated by simulations and experiments carried out with real hardware. © 2014 The Authors. International Journal of Circuit Theory and Applications published by John Wiley & Sons, Ltd.     

An efficient piecewise‐linear DC analysis method for general non‐linear circuits

The convergence problems of conventional DC analysis can be partly avoided by using piecewise‐linear analysis. This paper proposes a piecewise‐linear DC analysis method that can efficiently handle arbitrary couplings between non‐linear circuit elements. Piecewise‐linear modelling of the non‐linear circuit elements is automatically performed during simulation, using simplicial subdivisions. The number of linear regions, and thereby iterations, is considerably reduced by combining the common parts of separate simplicial subdivisions. Due to these reasons and since the method is formulated with the commonly used modified nodal approach, it has been possible to implement the method in the general‐purpose circuit simulator APLAC. The correct operation of the method is demonstrated with three examples. Copyright © 1999 John Wiley & Sons, Ltd.     

An interval algorithm for finding all solutions of non‐linear resistive circuits

In this letter, an efficient algorithm is proposed for finding all solutions of non‐linear (not piecewise‐linear) resistive circuits. This algorithm is based on interval analysis, the dual simplex method, and the contraction methods. By numerical examples, it is shown that the proposed algorithm could find all solutions of systems of 500–700 non‐linear circuit equations in acceptable computation time. Copyright © 2004 John Wiley & Sons, Ltd.     

Exact sampled‐data analysis of quasi‐resonant converters with finite filter inductance and capacitance

Previous models of quasi‐resonant converters generally use averaging and assume infinite filter inductance and capacitance to reduce circuit complexity, but at the expense of accuracy. In this paper, exact sampled‐data modelling is used. A general block diagram model applicable to various topologies of quasi‐resonant converters is proposed. Large‐signal analysis, steady‐state analysis and small‐signal analysis are all studied. They agree closely with the experimental results in the literature. Compared with the averaging approach, the sampled‐data approach is more systematic and accurate. Copyright © 2001 John Wiley & Sons, Ltd.     

Sampled‐data poles,zeros, and modeling for current‐mode control

Exact and approximate sampled‐data models in closed forms are derived for switching DC–DC converters under peak/valley current‐mode control. The corresponding sampled‐data poles and zeros in closed forms are also derived. The location and stability conditions of the poles and zeros, boundary conditions of subharmonic instability, and nulling of the audio‐susceptibility are also derived. It is proved that the stable operating range of the source voltage is linearly proportional to the ramp slope. The sampled‐data models agree with previous experiment results and accurately predict the subharmonic instability. The different view from the sampled‐data model about the number and stability (minimum phase) of pole and zero does not necessarily invalidate the traditional continuous‐time averaged model. However, this different view gives better prediction about converter dynamics and is useful for the analog or digital controller design for DC–DC converters. Copyright © 2011 John Wiley & Sons, Ltd.     

Fault modeling on complex field using least‐square circle fitting for linear analog circuits

A new fault modeling method using least‐square circle fitting (LSCF ) for linear analog circuits is proposed in this paper. In this method, Monte Carlo simulation is used to obtain the output voltage values when the parameter of one faulty component is changed while those of the other components vary within their tolerance limits. All the output response voltage values for every faulty circuit statue are decomposed into real and imaginary parts on a complex field. Then, LSCF method is adopted to match these data, yielding a corresponding circular curve on complex plane, which also can be expressed with a circular function. Its center coordinates and radius are established as the fault features. During measurements, by calculating the distance from one real output to each circular center coordinate and comparing the distance with each circular radius, a faulty component can be diagnosed. The effectiveness of the proposed approach is verified by experiments. The results show that (i) the proposed fault modeling can accurately locate the fault component, and (ii) it can also simply be a fault dictionary. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Model reference adaptive control system design for linear time‐varying systems with unstructured and bounded varying functions

In recent years, many methods of model reference adaptive control system (MRACS) for a linear time‐varying (LTV) plant have been proposed. These methods assumed that the structure of plant parameters is known in advance. However, it is difficult to get a priori information of plant parameters. In this paper, an MRACS design for an LTV system based on high‐order estimator (HOE) is proposed. By applying dynamic certainty equivalence (DyCE) to LTV plants, a new MRAC law of LTV system is derived without knowing the structure of the plant parameters. The MRACS law is generated by using high‐order derivatives of an estimated parameter, so that robust HOE with a normalization signal and σ modification for the system introduced. Our proposed method can attain better performance than conventional methods, such as estimation with variable forgetting factor (VF) and the gradient projection method (GPM). The robust HOE establishes the boundedness of all of the estimated parameters under the condition that the estimated parameter and the first derivative of the parameter are bounded. It is shown that all signals in the adaptive loop are bounded and the output error converges to a closed set. The proposed method is compared to the familiar schemes, the gradient projection method and the estimation based on forgetting factor through numerical simulations, and the effectiveness of our proposed method is shown. © 2000 Scripta Technica, Electr Eng Jpn, 130(4): 87–98, 2000     

Exact and explicit expressions for the small‐signal dynamics and frequency response of switching converters

In this paper, exact and explicit expressions for the dynamics and small‐signal responses of piecewise linear switching converters are derived. The results are very useful for the exact simulation and analysis of converter circuits. These expressions can also be used to develop simplified (approximate) models of converters for practical design purposes. An example is given to show that the well‐known state‐space averaging model is in fact the first‐order approximation of our exact model. Copyright © 2004 John Wiley & Sons, Ltd.     

A method for analysing the transient and the steady‐state oscillations in third‐order oscillators with shifting bias

We provide an asymptotic method for systematically analysing the transient and the steady‐state oscillations in third‐order oscillators with shifting bias. The method allows us to construct the general solution of the weakly non‐linear differential equation describing these oscillators through an iteration procedure of successive approximations typical of perturbation methods. The approximation to first order is obtained solving a system of two first‐order non‐linear differential equations in the leading terms of solution (dc component and fundamental harmonic), whereby the dominant dynamics, the stationary states and their stability can be easily analysed. Unlike existing approaches, our method also enables us to determine the higher harmonics as well as the frequency shift from the system's natural frequency in the exact solution through analytical formulae. In addition, formulae for higher‐order approximations of the above quantities are determined. The proposed method is applied to a practical circuit to show its usefulness in both analysis and design problems. Copyright © 2001 John Wiley & Sons, Ltd.     

A finite frequency approach to filter design for uncertain discrete‐time systems

This paper studies the problem of finite frequency filter design for linear time‐invariant discrete‐time systems with polytopic uncertainties. Generalized Kalman–Yakubovich–Popov lemma is exploited to formulate the filter design problem in finite frequency domain. A design method is presented in terms of solutions to a set of linear matrix inequalities. A numerical example is given to illustrate the effectiveness of the proposed method. Copyright © 2007 John Wiley & Sons, Ltd.     

The optimal fuzzy robust regulator for TS discrete‐time systems: An LMI approach

In this work, the problem of designing an optimal regulator for discrete‐time nonlinear systems when the plant can be modelled by a Takagi–Sugeno (TS) fuzzy system is addressed. The approach analyzed in this paper, under certain conditions, guarantees the tracking of references and allows the performance of the controller to be improved by means of the inclusion of some cost functions. The main result is given in terms of linear matrix inequality techniques, meaning that the design of the controller can be obtained in a practical way. Finally, numerical simulations are carried out in order to illustrate the validity of the fuzzy regulator. Copyright © 2008 John Wiley & Sons, Ltd.     

An offset cancellation technique of complementary input pair buffers for continuous time applications

This letter describes an offset cancellation technique for rail‐to‐rail complementary input pair operational amplifiers in unity gain loop configuration that overcomes the variable offset and minimizes distortion. The simulated buffer exhibits up to 40 dB increase in spurious‐free dynamic range and up to 30 dB increase in signal‐to‐noise and distortion ratio. When used to buffer a continuous time modulator, the performance matches that of chopping. Measurement results verify the technique, illustrating effective offset cancellation regardless of the input signal level. Copyright © 2016 John Wiley & Sons, Ltd.     

A useful identification method to build low‐order transfer function models based on frequency response for small‐signal stability analysis

This paper presents a scheme of small‐signal stability analysis for very large radial power systems. Generally, a radial power system can be easily classified as one main system and some external systems. Therefore, if accurate low‐order model of the external systems could be identified, the analysis effort for small‐signal stability can be reduced. Some dynamic reduction methods are proposed. Especially, the frequency‐domain least‐squares approximation methods, which are powerful and have high numerical reliability. This paper proposes a modal rebuild logic to improve the result obtained by the frequency‐domain least‐squares approximation methods. The proposed method provides high accuracy and a practical low‐order transfer function model. This paper introduces the usefulness of the proposed method with some numerical examples. In addition, merging sophisticated data handling and advanced applications in order to reduce human efforts is also discussed. This paper mentions the importance of automated node ID handling in order to realize the classification of system data into some partial data sets. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

An improved finite frequency approach to robust filter design for LTI systems with polytopic uncertainties

In this paper, the finite frequency robust filtering problem (‐FFRFP), design of a robust filter minimizing the norm from the disturbance input to the estimation error evaluated over a prescribed finite frequency domain, is considered for continuous‐time and discrete‐time linear time‐invariant (LTI) systems with polytopic parameter uncertainties. By means of the generalized Kalman–Yakubovich–Popov (KYP) lemma in combination with a result known as Finsler's lemma, the ‐FFRFP is cast as a linear matrix inequality (LMI) optimization. Examples are given to demonstrate that the proposed condition can achieve improvement over the previous ones in the literature. Copyright © 2012 John Wiley & Sons, Ltd.     

模块化多电平换流器型多端高压直流输电控制参数优化方法

针对模块化多电平换流器型多端直流(MMC-MTDC)输电系统的稳定性受不同换流站控制系统之间相互作用的影响,不恰当的控制参数可能会降低MMC-MTDC系统的稳定裕度问题,提出一种MMC-MTDC控制参数的优化方法以提升系统的稳定裕度.首先,建立包括MMC主回路、控制系统、交流系统与直流系统的MMC-MTDC小信号模型....     

Bottom‐up performance analysis of focal‐plane mixed‐signal hardware for Viola–Jones early vision tasks

Focal‐plane mixed‐signal arrays have traditionally been designed according to the general claim that moderate accuracy in processing is affordable. The performance of their circuitry has been analyzed in these terms without a comprehensive study of the ultimate consequences of such moderate accuracy. In this paper, for the first time to the best of our knowledge, we do carry out this study. We move expectable performance of mixed‐signal image processing hardware directly into the vision algorithm making use of it. This permits to close a wider design loop, enabling a more aggressive design of this kind of hardware provided that the algorithm, at the highest level—semantic interpretation of the scene—, can afford it. Thus, we present a thorough analysis of the non‐idealities associated with the implementation of a QVGA array tailored for the distinctive characteristics of the Viola–Jones processing framework. The resulting deviation models are then introduced in the processing flow of this framework provided by the OpenCV library. We have found, contrary to what could be expected, that these deviations do not necessarily degrade the performance of the Viola–Jones algorithm. They could be even beneficial for certain high‐level specifications. Additionally, we demonstrate the architectural advantages of our approach: exploitation of focal‐plane distributed memory and ultra‐low‐power operation. Copyright © 2014 John Wiley & Sons, Ltd.     

Inverse optimal adaptive control for non‐linear uncertain systems with exogenous disturbances

A Lyapunov‐based inverse optimal adaptive control‐system design problem for non‐linear uncertain systems with exogenous ℒ︁₂ disturbances is considered. Specifically, an inverse optimal adaptive non‐linear control framework is developed to explicitly characterize globally stabilizing disturbance rejection adaptive controllers that minimize a nonlinear‐nonquadratic performance functional for non‐linear cascade and block cascade systems with parametric uncertainty. It is shown that the adaptive Lyapunov function guaranteeing closed‐loop stability is a solution to the Hamilton–Jacobi–Isaacs equation for the controlled system and thus guarantees both optimality and robust stability. Additionally, the adaptive Lyapunov function is dissipative with respect to a weighted input–output energy supply rate guaranteeing closed‐loop disturbance rejection. For special integrand structures of the performance functionals considered, the proposed adaptive controllers additionally guarantee robustness to multiplicative input uncertainty. In the case of linear‐quadratic control it is shown that the operations of parameter estimation and controller design are coupled illustrating the breakdown of the certainty equivalence principle for the optimal adaptive control problem. Finally, the proposed framework is used to design adaptive controllers for jet engine compression systems with uncertain system dynamics. Copyright © 2000 John Wiley & Sons, Ltd.     

A step‐up PWM DC–DC converter for renewable energy applications

A step‐up pulse width modulation (PWM) direct current (DC)–DC converter is presented in this paper, which has its origin in quasi Z‐source inverter. Analysis of this converter in steady state is presented, and relevant expressions are derived for the proposed converter operating in continuous conduction mode. The power loss expressions for each component of the converter are derived, and thereby, obtained expressions for overall converter efficiency are presented. Further, a dynamic model is derived to design an appropriate controller for this converter. The simulation and experimental results are presented to support the theoretical analysis. The advantages such as continuous input current, high step‐up gain at lower duty ratio, and common ground for source, load, and switch makes the converter suitable for renewable energy applications. Copyright © 2015 John Wiley & Sons, Ltd.     

Dissipativity and passivity analysis for discrete‐time complex‐valued neural networks with leakage delay and probabilistic time‐varying delays

In this paper, the problem of dissipativity and passivity analysis is investigated for discrete‐time complex‐valued neural networks with time‐varying delays. Both leakage and discrete time‐varying delays have been considered. By constructing a suitable Lyapunov–Krasovskii functional and by using discretized Jensen's inequality approach, sufficient conditions have been established to guarantee the (Q ,S ,R ) ? γ dissipativity and passivity of the addressed discrete‐time complex‐valued neural networks. These conditions are derived in terms of complex‐valued linear matrix inequalities (LMIs), which can be checked numerically using Yet Another LMI Parser toolbox in Matrix Laboratory. Finally, three numerical examples are established to illustrate the effectiveness of the obtained theoretical results. Copyright © 2016 John Wiley & Sons, Ltd.