周期荷载下岩石分数阶黏弹塑性本构模型研究

为研究周期荷载下岩石疲劳变形特性,基于分数阶微积分构建分数阶黏壶,将分数阶黏壶替换西原模型黏塑性体中的一般黏壶,并在西原模型中串联一个黏性元件,分别建立了可描述周期荷载下岩石变形规律的一维和三维分数阶黏弹塑性本构模型。在高动应力状态下,模型为反映岩石减速、等速、加速3个变形阶段变形规律的岩石分数阶黏弹塑性疲劳本构模型;反之,则为反映岩石减速、加速变形规律的Burgers模型。对既有的岩石疲劳试验结果拟合表明:基于分数阶黏弹塑性模型所建立的岩石疲劳本构方程可较好地描述周期荷载下岩石各种变形特征,拟合系数在0.96以上。研究成果可丰富岩石力学理论,为相关研究提供参考。     

分数阶异结构超混沌系统完全同步与反相同步控制

以分数阶Lü混沌系统和分数阶Chen超混沌系统为例,研究了维数不同、分数阶次不相等的异结构的混沌系统和超混沌系统的完全同步和反相同步.首先,基于分数阶系统稳定性理论和非线性动力学理论,构造出相应的非线性控制器,实现了两个维数不同,分数阶次不相等异结构混沌系统与超混沌系统的完全同步和反相同步;其次,基于分数阶稳定性理论,对上述两类同步给出了严格的数学证明;最后,借助于预估-校正算法,利用数值模拟验证了所提方法的有效性.     

An implementation methodology for supervisory control theory

In this study, a methodology for PLC implementation of Supervisory Control Theory is introduced and realized on a pneumatic manufacturing system. The implementation methodology resolves the problem of avalanche effect and enhances program readability. We use local modular approach, which exploits modular structure of the plant and of the specifications. Local modular approach, together with the implementation methodology presented in this study provides an effective way for synthesizing and realizing supervisors for Discrete Event Systems (DES) control problems. The resulting PLC program is also modular in structure, making it handable for modification and error detection.     

H∞ filtering for continuous fractional-order 2D Roesser model: The 0<α≤1 case

This paper investigates the $H_{\infty }$ filtering for the continuous fractional-order (FO) two-dimensional (2D) Roesser model with the FO between 0 and 1. Firstly, a sufficient condition to ensure the stability and bounded realness in the sense of $H_{\infty }$-norm for the continuous FO 2D Roesser model is given in the form of linear matrix inequalities (LMIs). Secondly, based on the bounded real lemmas proposed above, the $H_{\infty }$ filtering problem for continuous FO 2D Roesser model is addressed through some congruent transformation and matrix transformation. The results are given in LMI form, and the parameters of the continuous FO 2D filters can be achieved from the LMIs easily. In the end, the effectiveness of the proposed results is verified by two numerical examples.     

Experimental analysis of battery charge regulation in photovoltaic systems

The influence of charge regulation on batteries for stand‐alone photovoltaic systems is analysed in relation to two factors: battery lifetime and the daily energy service supplied. The regulation thresholds adjusted in the charge controller (for disconnection and reconnection), in overcharge and deep discharge conditions, determine the whole system operation. Laboratory testing procedures are proposed and applied to different components of the photovoltaic rural electrification market. Finally, technical recommendations for charge regulation of lead–acid batteries are presented. Copyright © 2003 John Wiley & Sons, Ltd.