A special class of multiplierless digital filters

This paper deals with the design of discrete low-pass filters, using a special class of polynomials of the second and third order, with coefficients which are powers of two. To take advantage of the characteristics of these polynomials, the discrete integrator is used as a basic component. The filters so derived are multiplierless resulting in hardware economy. Simulation indicates that the filters obtained are equally good or better than those obtained by the application of the impulse invariance method.     

Dynamic surface asymptotic tracking of a class of uncertain nonlinear hysteretic systems using adaptive filters

This paper is concerned with the problem of dynamic surface asymptotic tracking for a class of uncertain nonlinear systems preceded by Bouc–Wen type of hysteresis nonlinearity. By introducing the nonlinear filters with a positive time-varying integral function, a novel robust adaptive control algorithm is presented without constructing the hysteresis inverse. Unlike some existing adaptive control schemes for systems with input hysteresis, the proposed controller not only solves the issue of “explosion of complexity” inherent in the recursive procedure, but also produces the asymptotic tracking in spite of input hysteresis and external disturbances. Finally, two simulation examples are presented to confirm the effectiveness of the developed control strategy.     

A class of fast and accurate deterministic trend decomposition in the spectral domain using simple and sharp diffusive filters

This study proposes a spectral domain algorithm to remove the deterministic non-periodic trend from a time series using a class of fast, sharp and diffusive filters. These filters are principally the iterative moving least squares methods weighted using Gaussian windows. The responses of the filters expressed in analytic forms are proven to be diffusive. If it is a polynomial of finite degree, the embedded trend can be decoupled by the filters with specific order and iteration steps. The filters’ order, transition zone, error tolerance, iteration number and smoothing factor are subject to two algebraic equations to form a specific class. The operation counts of all filters are slightly larger than twice that applying a Fast Fourier Transform (FFT). It is numerically shown for a given transition zone and tolerance, there is a filter generating the shortest error penetration distance among all the filters. If either the trend or a spectral band is the main concern, there is an optimal strategy to shrink the error penetration distance. The numerical results show the filter has better performance than several existing methods. In addition, four examples successfully show direct applications of the filter’s response.     

Neural networks-based adaptive output feedback control for a class of uncertain nonlinear systems with input delay and disturbances

This paper focuses on the problem of adaptive output feedback control for a class of uncertain nonlinear systems with input delay and disturbances. Radial basis function neural networks (NNs) are employed to approximate the unknown functions and an NN observer is constructed to estimate the unmeasurable system states. Moreover, an auxiliary system is introduced to compensate for the effect of input delay. With the aid of the backstepping technique and Lyapunov stability theorem, an adaptive NN output feedback controller is designed which can guarantee the boundedness of all the signals in the closed-loop systems. Finally, a simulation example is given to illustrate the effectiveness of the proposed method.     

新课标中学化学课程教学

本文介绍了新一轮课程改革的核心理念，深入探讨了如何培养学生的学习兴趣、自主学习的能力、良好的习惯及创造性思维等，并在文章的最后给出了总结。     

New results on reachable sets bounding for delayed positive singular systems with bounded disturbances

This paper addresses the reachable sets bounding problem for time-delay positive singular systems subject to bounded disturbances. The time delays in the considered systems are assumed to be time-varying. Both invariant and time-varying singular systems are investigated in this paper. Existence conditions of componentwise ultimate bounds of the state vector of considered systems are derived and given in terms of the spectral abscissa of the system matrices, which are easy to be checked. The obtained results are demonstrated by two numerical examples.     

Transient responses of m-derived filters

The analytic expressions of the unit-impulse and the unit-step responses ofthe classical m-derived and the composite filters are derived. The equations have been computed by means of an IBM 360 Model 44 digital computer. Normalized curves of the unit-step response are presented. They are completely universal and can be applied to specific situations by rescaling the axes.     

Block implementation of two-dimensional digital filters

A novel principle known as block transformation is developed for the block implementation of two-dimensional (2-D) digital filters. It employs the one-dimensional (1-D) block implementation concept forwarded by Burrus (7) as a basic tool. Using this block transformation principle three distinct forms of 2-D block equations are derived. The generalized nature of the approach presented here facilitates the straightforward extension of this technique to higher dimensional digital filters.     

Rational approximation of three-dimensional digital filters

Two techniques are developed for approximating a given three-dimensional (3-D) digital filter by a 3-D rational function. The one is by a general 3-D rational function and the other by a 3-D rational function which is separable in the denominator. Each technique relies on the use of mixed first and second information, in the form of a finite portion of the impulse response and its autocorrelation sequence. The approximation is performed by solving a set of linear equations. The separable-denominator approximation is more advantageous due to the guaranteed stability and reduced amount of calculations.     

射频网络分析仪在腔体滤波器调谐中的应用

在民航甚高频通信共用天线系统中,腔体滤波器在降低电台之间的互调干扰与外界干扰方面发挥着重要作用。文章说明了腔体滤波器的特性,并介绍了使用射频网络分析仪来调谐滤波器的方法。该方法调谐滤波器简单快捷,并能够很好地满足技术规范的要求。     

New results on BIBO stability analysis for a class of neutral delay systems

This paper studies bounded input bounded output (BIBO) stability for a class of neutral systems with time-varying delays. Based on Lyapunov method and linear matrix inequalities, some new BIBO stability criteria are established. The numerical simulation is made to demonstrate the effectiveness of the theoretical results obtained in this paper.     

Error analysis in fixed-point digital filters using sign-magnitude truncation

The quantization error of a digital filter employing fixed-point arithmetic with sign-magnitude truncation is analyzed. The effect of coefficient quantization is also included. Exact analyses are presented first for Gaussian, sinusoidal and Gaussian plus sinusoidal inputs. Quasi-linearization is then employed to yield a simple computation method of the output noise variance. The resulting expression contains parameters that depend on the input signal statistics. An upper bound is given that is independent of these statistics. Explicit expressions are given for the second-order sections of the digital filter realized in the D1 and D2 forms together with a general expression for the cascade connection of the second-order sections.     

Frequency limitations of active-R filters using operational amplifiers

Active-R filters are designed using internally compensated operational amplifiers (OA) and resistors only. A one-pole or 6 dB roll off model for the PA's is assumed in these designs. This model is adequate for active-RC filters. However, for active-R filters such an assumption leads to serious accuracy as well as stability problems, thereby limiting the highest operating frequency of these filters to well below their potential maximum. It is shown in this article that a two-pole or 12 dB roll off model more accurately reflects the behaviour of the OA's for the above active-R realizations. A quantitative measure of the limitation imposed by this model on such realizations is also presented. Extensive computer simulation and experimental tests have been carried out that verify closely the theoretical predictions.     

Minimization of disturbances effects in time delay predictor-based sliding mode control systems

Stabilization problem for a linear plant with time delay control is considered. A new method of the sliding mode control design minimizing the effects of system disturbances is presented. It is based on a combination of the well-known predictor-based sliding mode control algorithm with the recently developed invariant ellipsoid method. The theoretical results are supported by numerical simulations.     

Sliding mode attitude tracking of rigid spacecraft with disturbances

The attitude tracking control problem of a spacecraft nonlinear model with external disturbances and inertia uncertainties is addressed in this paper. First, a new sliding mode controller is designed to ensure the asymptotic convergence of the attitude and angular velocity tracking errors against external disturbances and inertia uncertainties by using a modified differentiator to estimate the total disturbances. Second, an adaptive algorithm is applied to compensating the disturbances, by which another sliding mode controller is successfully designed to achieve a high performance on the attitude tracking in the presence of the inertia uncertainties, external disturbances and actuator saturations. Finally, simulation results are presented to illustrate effectiveness of the control strategies.