Fault estimation observer design for discrete‐time systems in finite‐frequency domain

This paper proposes a framework of fault estimation observer design in finite‐frequency domain for discrete‐time systems. First, under the multiconstrained idea, a full‐order fault estimation observer in finite‐frequency domain is designed to achieve fault estimation by using the generalized Kalman–Yakubovich–Popov lemma to reduce conservatism generated by the entire frequency domain. Then, a reduced‐order fault estimation observer is constructed, which results in a new fault estimator to realize fault estimation using current output information. Furthermore, by introducing slack variables, improved results on full‐order fault estimation observer and reduced‐order fault estimation observer design with finite‐frequency specifications are obtained such that different Lyapunov matrices can be separately designed for each constraint. Simulation results are presented to illustrate the advantages of the theoretic results obtained. Copyright © 2014 John Wiley & Sons, Ltd.     

Petri net based test case generation for evolved specification

Model-based testing can use a model to test a concrete program’s implementation. When the model is changed due to the evolution of the specification, it is important to maintain the test suites up to date, such that it can be used for regression testing. A complete regeneration of the whole test suite from the new model, although inefficient, is still frequently used in practice. To address this problem effectively, we propose a test case reusability analysis technique to identify reusable test cases of the original test suite based on graph analysis, such that we can generate new test cases to cover only the change-related parts of the new model. The Market Information System (MIS) is employed to demonstrate the feasibility and effectiveness of the proposed method. Our experimental results show that the use of our method saves about 31.5% test case generation cost.     

Active disturbance rejection control: between the formulation in time and the understanding in frequency

With the rapid deployments of the active disturbance rejection control (ADRC) as a bonafide industrial technology in the background, this paper summarizes some recent results in the analysis of linear ADRC and offers explanations in the frequency response language with which practicing engineers are familiar. Critical to this endeavor is the concept of bandwidth, which has been used in a more general sense. It is this concept that can serve as the link between the otherwise opaque state space formulation of the ADRC and the command design considerations and concerns shared by practicing engineers. The remarkable characteristics of a simple linear ADRC was first shown in the frequency domain, followed by the corresponding analysis in time domain, where the relationship between the tracking error and the ADRC bandwidth is established. It is shown that such insight is only possible by using the method of solving linear differential equations, instead of the more traditional techniques such as the Lyapunov methods, which tend to be more conservative and difficult to grasp by engineers. The insight obtained from such analysis is further demonstrated in the simulation validation.     

Editorial

Nowadays control systems can find applications in many areas, like aerospace, motion tracking, chemical engineering, physics, biology, economics. To improve control performance is a perpetual goal. With recent progresses of computing technologies, better control performance can be achieved by more judicious control strategies based on more precise and more complicated, such as time-varying, nonlinear, models. Another trend to improve control performance is built upon the divide-and-conquer philosophy, i.e., a complicated control task is cooperatively accomplished by multiple controllers/agents, instead of a single super-powerful controller. This trend is made possible due to great advances in communication, which enable the information exchange among agents and may unite the less powerful agents. The cost for such control performance improvement is higher spatial complexity of control systems. Although high model complexity and spatial complexity can be physically handled by current powerful controllers/agents, the lack of efficient analysis and synthesis methods prevents the performance improvement of control systems with high model or/and spatial complexity. As we know, conventional control methods are mainly developed under the assumptions of linear, time-invariant and centralized models. In order to resolve the issues due to the aforementioned two types of complexities, new methods are expected, which is exactly the major aim of the present special issue.     

上卓沟泥石流流动特性及流体—结构流固耦合数值模拟研究

甘肃省卓尼县上卓沟曾多次发生较大规模泥石流,灾害损失极其严重。为了有效治理,急需对泥石流的流动特性及拦挡结构在泥石流冲击荷载下的结构响应进行深入研究。本文首先利用图形建模软件RHINO建立上卓沟三维沟谷模型,泥石流流变模型选用宾汉流体模型,在合理确定各计算参数及边界条件的基础上应用CFX对上卓沟泥石流进行了三维数值模拟,得到流速等流场数据。将所得流场数据导入ANSYS进行泥石流与拦挡结构的双向流固耦合分析,得到了泥石流在沟谷内的运动规律及拦砂坝的应力和位移,为工程设计提出了建议,可为类似工程提供参考。     

南通地区地下水咸化机理分析及改良措施

为了给南通地区地下水的合理开发和利用提供理论依据,利用各种水化学系数和变化图示对研究区内深层和浅层地下水的咸化机理进行了分析。结果表明:研究区内深层地下水中、西部水化学演化以正常的水-岩作用为主,东部沿海特别是寅阳镇一带深层地下水则主要因淋滤古海相地层盐分而使TDS增高;远离海边的大部分地区浅层地下水TDS增高主要与溶解地层盐分和蒸发作用有关,沿海地带尤其是东南角寅阳镇、海晏镇一带浅层地下水由于受到一定程度的现代海水入侵影响,其TDS显著增高。针对该区域地下水水化学变化特征,提出地下水系统改良措施:合理开发利用高TDS地下水可增加区域水资源量,增强调蓄能力,减轻对深层淡水资源的潜在威胁;逐渐增大地下咸水的开采量,从长远意义上逐步改良盐碱地,以利于水土资源利用及生态环境改善。