印刷作品版权保护中的数字图像水印技术

数字水印一个重要的应用扩展就是对纸质图像产品的保护。数字水印技术应用于音频、图像、视频和文本的版权保护,在该领域的各种不同分支都有很多学者做了大量研究。论文主要讨论了抵抗打印扫描信道的数字图像水印技术,并根据数据嵌入域的不同对这些技术进行了分类讨论。     

不同大地坐标系间坐标相互转换的抗差算法研究

不同大地坐标系间的坐标转换是采用两套坐标系下坐标的公共点,结合相应的转换模型,求取转换九参数来实现转换的过程。转换时若公共点坐标存在粗差,九参数的求解精度便会受到影响,致使转换失败。文章将传统的Baarda粗差数据探测法、抗差最小二乘法以及拟准检定法用于解决其转换时公共点坐标粗差导致的精度偏离问题。结合转换算例得出精度对比结论,为工程实际中的大地坐标转换算法的选择提供一定的参考依据。     

无速度传感器的感应电机神经网络鲁棒自适应控制

针对感应电机定子电阻和负载转矩参数的不确定性,提出了无速度传感器的感应电机神经网络鲁棒自适应控制方案。用反步法设计了一种可以将各状态变量跟踪误差和神经网络各权值限制在规定范围内的神经网络鲁棒自适应控制器,提出了相应的算法,用Lyapunov定理对其稳定性进行了证明。提出了一种可以估算转子磁链和转速的观测器及相应的算法。仿真研究表明,所提出的感应电机无速度传感器控制方案对电机定子电阻、负载转矩的鲁棒性强,动态性能好,速度估算较精确。     

基于RAFL非线性系统控制的研究及在HVDC系统中的应用

研究非线性系统的控制问题具有重要的理论意义和实用价值。高压直流输电系统(简称HVDC系统)是典型非线性系统,HVDC系统是高度可控的,其中控制系统是直流输电技术的核心。HVDC系统能否正常运行与其基本控制器的性能息息相关。论文对鲁棒近似反馈线性化控制方法进行了研究,研究结果解决了一类非线性系统的控制问题,同时应用到HVDC系统中,并设计了相应的控制器。     

A new discrete-time robust adaptive time-delay control for a class of uncertain nonlinear strict-feedback systems using sliding mode

This paper presents a new discrete-time adaptive second-order sliding mode control with time delay estimation (TDE) for a class of uncertain nonlinear time-varying strict-feedback systems. The existing researches on time delay control (TDC) are conventionally established based on a stability criterion that is subject to the infinitesimal time delay assumption. Recently, this criterion was rejected and a new criterion was proposed for the development of a controller for systems with fully known dynamics. In this study, this approach is extended to uncertain systems. Specifically, a new criterion is developed for the stability of the TDE-error within an adaptive robust controller design without the infinitesimal time delay assumption. With the proposed adaptive robust control, there is no need for determination of uncertainties upper-bounds. Simulation results illustrate the efficacy of the proposed controller.     

Delay‐dependent robust stability analysis for interval neural networks with time‐varying delay

This article deals with the problem of robust stability for interval neural networks with time‐varying delay. By constructing an appropriate Lyapunov–Krasovskii functional, using the S‐procedure and taking the relationship among the time‐varying delay, its upper bound and their difference into account, some linear matrix inequality(LMI) ‐based delay‐dependent stability criteria are obtained without ignoring any terms in the derivative of the Lyapunov–Krasovskii functional. Finally, two numerical examples are given to demonstrate the effectiveness and benefits of the proposed method. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Teaching sampled‐data H∞ control theory using arm robot experiment system

This paper explains how to use an arm robot experiment system to teach sampled‐data H_∞ control theory. A design procedure is presented for a digital tracking control system for a continuous plant with structured uncertainties; the target is the positioning control of an arm robot. To guarantee the robust stability of the closed‐loop system and provide the desired closed‐loop performance, the design problem is first formulated as a sampled‐data H_∞ control problem, and is then transformed into an equivalent discrete‐time H_∞ control problem. Finally, linear matrix inequalities are used to obtain a reduced‐order output‐feedback controller and a static state‐feedback controller. In a course, the design procedure is explained and practice is provided through simulations and experiments. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

H∞ control for uncertain one‐sided Lipschitz nonlinear systems in finite frequency domain

The current article discusses the H_∞ disturbance attenuation control design problem for one‐sided Lipschitz systems in finite frequency domain. Models containing norm‐bounded parameter uncertainties, disturbances, and input nonlinearities are considered. By contrast to existing full frequency methods, the H_∞ controller is computed depending on the frequency ranges of disturbances. The finite frequency disturbance attenuation index is initially defined. Thanks to Finsler's lemma, sufficient and less conservative analysis conditions are also derived for the closed‐loop system. Then, synthesis conditions in the low, middle, and high frequency ranges as well as the whole frequency range, are formulated in terms of linear matrix inequalities. At last, to prove the effectiveness and the superiority of the proposed approach, a physical example is used and a comparative study is done.     

Adaptive robust control of fully-constrained cable driven parallel robots

In this paper, adaptive robust control (ARC) of fully-constrained cable driven parallel robots is studied in detail. Since kinematic and dynamic models of the robot are partly structurally unknown in practice, in this paper an adaptive robust sliding mode controller is proposed based on the adaptation of the upper bound of the uncertainties. This approach does not require pre-knowledge of the uncertainties upper bounds and linear regression form of kinematic and dynamic models. Moreover, to ensure that all cables remain in tension, proposed control algorithm benefit the internal force concept in its structure. The proposed controller not only keeps all cables under tension for the whole workspace of the robot, it is chattering-free, computationally simple and it does not require measurement of the end-effector acceleration. The stability of the closed-loop system with proposed control algorithm is analyzed through Lyapunov second method and it is shown that the tracking error will remain uniformly ultimately bounded (UUB). Finally, the effectiveness of the proposed control algorithm is examined through some experiments on a planar cable driven parallel robot and it is shown that the proposed controller is able to provide suitable tracking performance in practice.     

Approximate causal output tracking for linear perturbed systems via sliding mode control

ABSTRACT

A new approach to the solution of what is termed causal output tracking problem for linear time-invariant systems in the presence of both matched and unmatched unmodelled disturbances is presented. The proposed solution is addressed through the design of a dynamic steady state estimator based on the desired system structure and an observer, considering the reference as the system output. The unmatched disturbance is estimated and used in the steady state estimator to achieve invariance, while the matched disturbance robustness is provided via sliding mode control using the super-twisting algorithm. A useful application of the presented techniques is output tracking for non-minimum phase systems; thus, the performed simulation results confirm the effectiveness of the proposed control scheme for this kind of systems.