压力容器分析设计中应力线性化原理及其计算

扼要介绍压力容器分析设计中应力线性化的基本原理,并详细阐述了非轴对称模型和轴对称模型下应力线性化的基本计算方法。目的在于为压力容器的分析设计提供参考,以准确地分析器壁的应力情况。     

Understanding of resonance phenomena on a catalyst under forced concentration and temperature oscillations

Resonance is an interesting phenomenon that may be observed for reactions on catalytic surfaces during periodic forcing of operating variables. Forcing of the variables for non-linear systems may result in substantially changed time averaged behaviour. These resonance phenomena have been observed experimentally by coincidence rather than by systematic analysis. It is not clear for what type of reaction kinetics such behaviour may be expected and predictions are therefore impossible. Clearly, this forms a serious obstacle for any practical application. In this work we set out to analyse the nature of resonance behaviour in heterogeneously catalysed reactions. A Langmuir Hinshelwood microkinetic model is analysed. It is demonstrated that for weakly non-linear forcing variables — as inlet concentrations — forcing leads to resonance phenomena in terms of the reaction rate only in case high total surface occupancies exist in the steady state. In contrast, forcing of strongly non-linear variables — like temperature — may give rise to resonance phenomena for both low and high surface occupancies. Necessary conditions for resonance to occur are derived. The analysis of resonance phenomena is greatly simplified by the availability of explicit analytical expressions as can be derived from Carleman linearization. We will demonstrate the merits of Carleman linearization as compared to numerical integration.     

基于状态反馈线性化法的多馈入高压直流输电系统控制器设计

高压直流输电（HVDC）系统的附加控制器可以改善系统的稳定性。针对多馈入高压直流输电系统,应用非线性控制理论中的状态反馈线性化法设计了直流系统的附加控制器。首先建立了多馈入高压直流输电系统的数学模型,然后推导出稳定控制规律,推导过程中考虑了2条直流系统附加控制的相互影响,最后以一个3机和2条直流线路构成的系统为例进行了仿真研究。研究结果表明：与传统控制器相比,该控制器能更好地改善系统的稳定性。     

时延丢包网络控制系统的分析与控制

针对网络控制系统中同时存在时延和丢包问题,基于零阶保持器的工作机制,将同时受时延和丢包影响的网络控制系统建模为输入带有时延的控制系统,根据李雅普诺夫稳定性理论和时滞系统理论得出控制系统的时滞相关稳定性条件,进一步基于锥补线性化的方法给出控制器的设计方法,有效解决了网络控制系统中同时存在时延和丢包的控制问题。仿真算例表明所提方法的有效性。     

基于LabVIEW的非线性励磁控制器

本文介绍了以LabVIEW为开发平台设计的非线性励磁控制器。文中首先介绍了直接反馈线性化理论 ,然后介绍了软件和硬件的设计 ,并给出了仿真结果。仿真结果表明该控制器能显著改善系统的暂态稳定性。LabVIEW的使用为设计带来许多便利和强大的功能。     

Uncertainty modeling and robust minimax LQR control of multivariable nonlinear systems with application to hypersonic flight

For a class of multi‐input and multi‐output nonlinear uncertainty systems, a novel approach to design a nonlinear controller using minimax linear quadratic regulator (LQR) control is proposed. The proposed method combines a feedback linearization method with the robust minimax LQR approach in the presence of time‐varying uncertain parameters. The uncertainties, which are assumed to satisfy a certain integral quadratic constraint condition, do not necessarily satisfy a generalized matching condition. The procedure consists of feedback linearization of the nominal model and linearization of the remaining nonlinear uncertain terms with respect to each individual uncertainty at a local operating point. This two‐stage linearization process, followed by a robust minimax LQR control design, provides a robustly stable closed loop system. To demonstrate the effectiveness of the proposed approach, an application study is provided for a flight control problem of an air‐breathing hypersonic flight vehicle (AHFV), where the outputs to be controlled are the longitudinal velocity and altitude, and the control variables are the throttle setting and elevator deflection. The proposed method is used to derive a linearized uncertainty model for the longitudinal motion dynamics of the AHFV first, and then a robust minimax LQR controller is designed, which is based on this uncertainty model. The controller is synthesized considering seven uncertain aerodynamic and inertial parameters. The stability and performance of the synthesized controller is evaluated numerically via single scenario simulations for particular cruise conditions as well as a Monte‐Carlo type simulation based on numerous cases. It is observed that the control scheme proposed in this paper performs better, especially from the aspect of robustness to large ranges of uncertainties, than some controller design schemes previously published in the literature. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

改进控制律的变结构STATCOM无功补偿控制

静止同步补偿器(STATCOM)是柔性交流输电系统(FACTS)的重要组成部件,本文建立了静止同步补偿器在三相静止坐标系下的数学模型,通过PARK变换将ABC坐标转化为d-q坐标。鉴于STATCOM在d-q坐标下的强耦合性,采用状态反馈精确线性化方法将该模型线性化解耦,构造出一个伪线性模型。然后,采用一种改进的指数趋近律变结构控进行了STATCOM无功补偿控制器的设计。最后,使用Matlab/Simulink对所设计的控制器进行了计算机仿真,并与传统的PI控制器比较,说明了变结构控制的STATCOM无功补偿控制器设计的可行性和有效性,同时也证明了改进的指数趋近律变结构控制的优越性。     

基于最大反馈线性化的两轮机器人平衡控制

为了对两轮直立式机器人进行平衡控制研究,首先应用一种拉格朗日方法对两轮直立式机器人系统进行动力学建模,以力矩作为模型控制输入并且考虑到了系统无滑动的非完整约束方程.求出了系统的最大相对阶并对非线性系统进行了部分反馈线性化,经过坐标变换和输出反馈得到了2个由两链积分器构成的子系统,外加3个代表系统内动态的非线性方程.根据...     

A critical review of the most popular types of neuro control

In this review article, the most popular types of neural network control systems are briefly introduced and their main features are reviewed. Neuro control systems are defined as control systems in which at least one artificial neural network (ANN) is directly involved in generating the control command. Initially, neural networks were mostly used to model system dynamics inversely to produce a control command which pushes the system towards a desired or reference value of the output (1989). At the next stage, neural networks were trained to track a reference model, and ANN model reference control appeared (1990). In that method, ANNs were used to extend the application of adaptive reference model control, which was a well‐known control technique. This attitude towards the extension of the application of well‐known control methods using ANNs was followed by the development of ANN model‐predictive (1991), ANN sliding mode (1994) and ANN feedback linearization (1995) techniques. As the first category of neuro controllers, inverse dynamics ANN controllers were frequently used to form a control system together with other controllers, but this attitude faded as other types of ANN control systems were developed. However, recently, this approach has been revived. In the last decade, control system designers started to use ANNs to compensate/cancel undesired or uncertain parts of systems' dynamics to facilitate the use of well‐known conventional control systems. The resultant control system usually includes two or three controllers. In this paper, applications of different ANN control systems are also addressed. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

基于非线性干扰观测器的不确定非线性系统鲁棒轨迹线性化控制

针对一类不确定非线性系统，基于轨迹线性化控制方法(TLC)及非线性干扰观测器技术(NDO)研究了一种新的非线性鲁棒控制策略．TLC是一种有效的非线性跟踪和解耦控制方法，但当系统中存在内部未建模动态和外界干扰时，当前TLC控制器性能将显著下降．本文利用NDO对系统中的不确定项进行估计，其输出与TLC控制律结合来对消不确定性的影响．最后通过一个数值仿真实例验证了本文提出的方法的有效性,仿真结果表明该鲁棒轨迹线性化控制方法具有很好的干扰衰减能力和鲁棒性能．