一类不确定非线性系统的鲁棒状态观测器设计

本文研究了一类具有参数不确定性的非线性系统鲁棒状态观测器的设计问题。提出了一种新的非线性鲁棒渐近状态观测器设计方案,证明了状态观测误差的指数渐近收敛性。最后将所得结果应用于一轴盘传动系统,仿真结果表明本文提出的设计方案是有效的。     

一类欠驱动机械系统的全局鲁棒控制

针对具有质心参数不确定性的Acrobot系统,提出一种全局的鲁棒控制方法.首先,给出系统具有质心参数不确定的系统模型;其次在摇起区,分析系统不确定性条件下的能量变化情况,基于能量不断增加的思想设计出摇起控制器;在平衡区,把系统的不确定性转化为模型状态矩阵的不确定性,引入H标准设计方法,得出存在H状态反馈控制器的充要条件,通过求解线性矩阵不等式使系统有效地克服不确定性的影响实现二次稳定;最后通过仿真实验验证了所提方法的有效性.     

基于观测器的不确定广义时滞系统鲁棒预测控制

针对一类不确定广义时滞系统,讨论了其基于观测器的鲁棒预测控制问题,给出了系统观测器型预测控制器的设计方法.通过构造带有误差项的Lyapunov函数,应用线性矩阵不等式,将无穷时域二次性能指标"min-max"优化问题转化为凸优化问题,得到了鲁棒预测控制器存在的充分条件和显式表达式.证明了优化问题在初始时刻的可行解能保证广义闭环系统渐近稳定且正则无脉冲.仿真实例验证了所提出方法的有效性.     

Flocking of networked uncertain Euler–Lagrange systems on directed graphs

This paper investigates the flocking problem of networked nonlinear Euler–Lagrange systems with parametric uncertainties, and they are assumed to interact on directed graphs with a directed spanning tree. We propose an adaptive controller to achieve the flocking objective, and the resultant closed-loop networked system bears the cascade structure. Using a new similarity decomposition approach, a critical-characteristic-root based approach, and the input–output stability analysis, we demonstrate the convergence of the position/velocity synchronization errors among the uncertain nonlinear Euler–Lagrange agents. We also show that the velocities of the Euler–Lagrange systems converge to the weighted average velocity value. Simulation results are provided to demonstrate the performance of the proposed controller.     

Stable nonlinear adaptive controller for an autonomous underwater vehicle using neural networks

In general, the dynamics of autonomous underwater vehicles (AUVs) are highly nonlinear and their hydrodynamic coefficients vary with different operating conditions. For this reason, high performance control system for an AUV usually should have the capacities of learning and adaptation to the time-varying dynamics of the vehicle. In this article, we present a robust adaptive nonlinear control scheme for an AUV, where a linearly parameterized neural network (LPNN) is introduced to approximate the uncertainties of the vehicle's dynamics, and the basis function vector of the network is constructed according to the vehicle's physical properties. The proposed control scheme can guarantee that all of the signals in the closed-loop system are uniformly ultimately bounded (UUB). Numerical simulation studies are performed to illustrate the effectiveness of the proposed control scheme.     

极值搜索控制系统的一体化设计研究

针对传统极值搜索控制系统设计中,极值搜索算法与控制器采取单独设计易导致系统难以发挥其最佳性能的问题,提出一套极值搜索控制系统的一体化设计方法.此方法充分考虑到系统的非线性和不确定性,建立了极值搜索算法与被控对象的一体化设计模型,运用终端滑模切换面和相应的控制策略,使极值搜索算法在较短时间内搜寻到系统的最优值,而且其输出值可很快收敛至此最优值.理论分析和仿真结果分别验证了此方法的稳定性和有效性.     

时滞相关型离散时变时滞奇异系统的鲁棒镇定

讨论含参数不确定的离散时变时滞奇异系统的时滞相关的鲁棒状态反馈稳定化问题. 在一系列等价变换下, 阐述了其和一个不确定正常线性离散时变时滞系统的鲁棒状态反馈稳定化问题的等价关系;利用矩阵不等式方法, 给出一个对所有容许的不确定, 使得闭环系统正则、因果且稳定的时滞相关鲁棒状态反馈稳定化控制器存在的充分条件以及无记忆状态反馈控制器的一个解.     

Evaluating uncertainties of future marine flooding occurrence as sea-level rises

As sea-level rises, the frequency of coastal marine flooding events is changing. For accurate assessments, several other factors must be considered as well, such as the variability of sea-level rise and storm surge patterns. Here, a global sensitivity analysis is used to provide quantitative insight into the relative importance of contributing uncertainties over the coming decades. The method is applied on an urban low-lying coastal site located in the north-western Mediterranean, where the yearly probability of damaging flooding could grow drastically after 2050 if sea-level rise follows IPCC projections. Storm surge propagation processes, then sea-level variability, and, later, global sea-level rise scenarios become successively important source of uncertainties over the 21st century. This defines research priorities that depend on the target period of interest. On the long term, scenarios RCP 6.0 and 8.0 challenge local capacities of adaptation for the considered site.     

The importance of uncertainties in the ROP detector layout design process for CANDU reactors

In CANDU® reactor design, the regional overpower protection (ROP) systems protect the reactor against overpower in the fuel which could reduce the safety margin-to-dryout. The increase in fuel power could be caused by a localized power peaking within the core (for example, as a result of a certain reactivity device configuration) or a general increase in the core power level during a slow-loss-of-regulation (SLOR) event. This overpower could lead to fuel sheath dryout. In the CANDU® 600 MW (CANDU 6) design, there are two ROP systems in the core, one for each fast-acting shutdown system. Each ROP system includes a number of fast-responding, self-powered flux detectors suitably distributed throughout the core within vertical and horizontal assemblies. A new methodology for designing the detector layout for the ROP system, called the DETPLASA algorithm, has been developed recently. This method utilizes the simulated annealing (SA) technique to optimize the placement of the detectors in the core. The evaluation of the trip setpoint (TSP) corresponding to each detector layout configuration (i.e., each history in the SA algorithm) is performed probabilistically using the ROVER-F code. In this evaluation, there are uncertainties related to both the detector components (i.e., related to the margin-to-trip) and to the fuel channel components (i.e., related to the margin-to-dryout). In this paper, the importance of these uncertainties on the outcome of the detector layout optimization process is evaluated. Some parametric studies have been performed to quantify the effect of uncertainties on the resulting detector layout. Two types of investigations have been performed. First, a given detector layout will be used to explicitly determine the effect of changing the uncertainty values. In this study, 343 sets of uncertainty values are used to produce the corresponding TSP values. The variation in the TSP values is analyzed. Second, three sets of uncertainty values (a subset of uncertainties from the first study) are used in independent DETPLASA executions. The resulting detector layout configurations will be examined to observe the effect of these uncertainties on the final design. Results from these investigations are presented in this paper.     

Numerical simulation of steady state heat transfer in a ceramic-coated gas turbine blade

As gas turbine entry temperature (TET) increases, thermal loading on first stage blades increases and, therefore, a variety of cooling techniques and thermal barrier coatings (TBCs) are used. In the present work, steady state blade heat transfer mechanisms were studied via numerical simulations. Convection and radiation to the blade external surface were modeled for a super alloy blade with and without a TBC. The effects of surface emissivity changes, partial TBC coatings and uncertainties in external heat transfer coefficient were also simulated. The results show that at 1500 K TET, radiation heat transfer rate from gas to an uncoated blade is 8.4% of total heat transfer rate which decreases to 3.4% in the presence of a TBC. The TBC blocks radiation, suppresses metal temperatures and reduces heat loss to the coolant. These effects are more pronounced at higher TETs. With selective coating, substantial local temperature suppression occurs. In the presence of radiation and/or TBC, the uncertainties in convection heat transfer coefficient do not have a significant effect on metal temperatures.