Modelling and parameter estimation for fly-by-wire aircraft/control systems

This paper covers in detail the issues related to parameter estimation of open loop dynamics of fly-by-wire aircraft/control systems from closed loop data. System identifiability aspects in the closed loop and the effect of various feedback types on the parameterisation of the system matrices are reviewed. The methods commonly employed for the detection of collinearity in the data are discussed. A brief discussion of the common methods used for analysis of unstable/augmented aircraft are given. Also, controller information based identification method (CIBIM), which utilises knowledge of the controller in the analysis, is presented. The discussion is followed by numerical results of application of the techniques to simulated data.     

基于随机游走和输入估计方法的振动主动控制研究

摘要:为了研究未知外扰作用下动力学系统的振动主动控制问题,结合Kalman滤波和LQG(linear quadratic Gaussian)控制方法,提出了基于随机游走和输入估计的振动主动控制方法。为尽量获取未知外扰信息,首先采用随机游走模型构建求知外扰信号的离散递推形式,并将其作为辅助状态引进受控系统的状态方程。然后,借助具有信号识别和跟踪能力Kalman滤波原理,对含有辅助状态的系统进行状态估计,从而得到未知外扰的估计值．根据系统已知测量输出、未知状态及外扰的估计值构造系统目标函数,采用ＬＱＧ方法求解系统最优控制输入。最后针对sdof模型进行数值仿真。结果表明受控系统在非随机和随机外激励下都具有良好的控制效果,且控制精度优于传统ＬＱＧ方法     

Fast Bayesian approach for parameter estimation

This paper presents two techniques, i.e. the proper orthogonal decomposition (POD) and the stochastic collocation method (SCM), for constructing surrogate models to accelerate the Bayesian inference approach for parameter estimation problems associated with partial differential equations. POD is a model reduction technique that derives reduced‐order models using an optimal problem‐adapted basis to effect significant reduction of the problem size and hence computational cost. SCM is an uncertainty propagation technique that approximates the parameterized solution and reduces further forward solves to function evaluations. The utility of the techniques is assessed on the non‐linear inverse problem of probabilistically calibrating scalar Robin coefficients from boundary measurements arising in the quenching process and non‐destructive evaluation. A hierarchical Bayesian model that handles flexibly the regularization parameter and the noise level is employed, and the posterior state space is explored by the Markov chain Monte Carlo. The numerical results indicate that significant computational gains can be realized without sacrificing the accuracy. Copyright © 2008 John Wiley & Sons, Ltd.     

基于输入估计方法的振动主动控制试验研究

针对一种基于随机游走和输入估计策略的振动主动控制方法进行了试验研究。该方法涉及的动力学模型既依赖于受控系统的基本物理参数,又与未知的外扰激励密切相关。首先采用模态识别方法离线辨识系统的物理参数,以获得系统状态方程,再利用随机游走模型将未知外扰视为辅助状态量来构造新的状态方程,并借助Kalman滤波原理对新状态方程中的未知状态进行估计,进而得到未知状态和外扰的估计值。根据系统已知的测量输出、未知状态及外扰的估计值构造目标函数,应用LQG方法求解控制器增益,得到考虑未知外扰的最优控制输入。以柔性悬臂梁模型作为受控对象,对其实施振动主动控制,试验结果表明,该控制方法能有效抑制模型的前四阶模态振动,特别是对低阶模态的控制,其效果远优于经典LQG控制方法。     

Inverse modelling for parameter estimation and experiment design

Inverse modelling forced itself on the attention of scientists in the 1960s with the advent of satellites and other revelatory technologies, despite their putative ill-posedness, when it became clear that estimation of parameters of a system not in themselves directly observed but extractable from their signatures in measured data, constituted an ineluctable problem of modern society. This paper begins by formulating the basic statement of inverse problems which have a generic form and leads through philosophical and analytical approaches to their possible solutions that are inherently non-unique. Finally, an example is provided for inverse modelling of the shear wave velocity structure of the crust beneath the ancient granites around Hyderabad from an analysis of reverberations caused by it that appear in the early part of broadband seismograms.     

单输入多输出耦合设计任务二阶段迭代模型研究

产品开发过程中单输入多输出耦合设计任务间存在复杂的信息依赖关系。采用单阶段方法的任务执行方式时,因所执行的任务数量多并且需传递的信息量大,致使任务间存在的复杂信息关系难以被理清,从而导致任务执行过程中的方案分配不够合理,任务间的迭代返工次数过多,产品开发周期过长。针对这些问题,在深入分析单输入多输出耦合设计任务单阶段迭代模型的基础上,提出了一种任务迭代过程中的信息处理策略,并构建了一种单输入多输出耦合设计任务的二阶段迭代模型及其求解执行时间的数学模型。应用该数学模型,可以计算得到最佳二阶段设计任务分配方案。以某发动机开发项目为例,进行了该方法的应用分析。研究表明,采取二阶段迭代模型,任务迭代执行时间比单阶段短,并且通过合理分配在1,2两个阶段执行的任务,能够获得最短的二阶段任务迭代执行时间。该方法根据任务间不同的信息关系选择合适的任务迭代模型,能够有效缩短产品开发周期,可为产品设计人员在产品开发过程中选择合理的任务执行方式提供一定的理论参考。     

结构物理参数识别的贝叶斯估计马尔可夫蒙特卡罗方法

从结构动力特征方程出发,以结构主模态参数为观测量,推得结构物理参数线性回归模型。对该模型应用贝叶斯估计理论得到物理参数后验联合分布,再结合马尔可夫蒙特卡罗抽样方法给出各个物理参数的边缘概率分布和最优估计值,而提出了基于结构主模态参数的结构物理参数识别贝叶斯估计马尔可夫蒙特卡罗方法。对五层剪切型结构的数值研究表明,此方法能够利用少数主模态参数给出结构质量和刚度参数的概率分布和最优识别值,而且在主模态参数较准确时识别误差很小。     

压水型核反应堆功率控制系统的优化设计

在分析了压水型反应堆功率控制系统的前提下，针对其特殊的控制要求，运用基于输出反馈的次最优控制的设计方法和Matlab中的NCD模块，最终实现了系统的优化设计，并对系统进行了某一功率水平下的仿真试验和其它工况下的鲁棒性试验．结果表明。改进后的系统性能有了较大改善。     

Surface characterization and parameter estimation for industrial vision system

In this paper we have presented some geometric techniques to characterize and parametrize surfaces of industrial parts in range images. The surfaces are characterized to one of plane, sphere, cylinder and cone, because they form the majority of object surfaces in man-made industrial parts. The problem has been studied for two different situations. In the first case,a priori knowledge about the surface shape is assumed. In such a situation the problem of surface characterization reduces to that of surface parameter estimation. The standard deviations of the estimated parameters give a measure of uncertainty of characterizing a surface patch to one of the four surface types. In the second case, noa priori information regarding the shape of a surface is available. This includes partially visible surfaces also. To deal with such a situation, a fuzzy classifier is designed using the uncertainty values. The fuzzy classifier classifies the unknown surface patch (including partially visible surfaces) to one of the four surface types. Experimental results with synthetic range images are presented to highlight the distinctive features of our technique.     

The use of nested desirability functions and quality indices for multi-response robust parameter design problems

A multi-response robust parameter design (RPD) problem-solving technique based on desirability functions is presented in which the means and variances of all responses are placed on a level playing field. The proposal allows a decision maker to integrate their preferences for the individual means and variances. It is shown that the ensuing operating point is a system setting that produces a mutually robust set of responses. In addition, this article offers an approach to assess several RPD strategies via quality indices. The measures presented here allow for a more knowledgeable and comprehensive evaluation of the competing RPD strategies.     

Economic parameter design for ultra-fast laser micro-drilling process

The basic requirement in this type of micro-drilling process is to achieve high product quality with the minimum machining cost, which can be realised through parameter design. In this paper, we propose a new economic parameter design under the framework of Bayesian modelling and optimisation. First of all, the Bayesian seemingly unrelated regression (SUR) models are utilised to develop the relationship models between input factors and output responses in the laser micro-drilling process. After that, simulated response values which reflect the real laser micro-drilling process are obtained by using the Gibbs sampling procedure. Moreover, a novel rejection cost function and a quality loss function are constructed based on the simulated responses. Finally, an optimisation scheme integrating the rejection cost (i.e. rework cost and scrap cost) function and the quality loss function is implemented by using multi-objective genetic algorithm to find feasible economic parameter settings for laser micro-drilling process.     

Optimal process control for multiple dependent subprocesses

A renewal theory approach is proposed to derive the cost model for multiple dependent subprocesses. The optimal individual Y control chart and multiple cause-selecting control chart are thus constructed to monitor the overall product quality and specific product quality contributed by the multiple dependent subprocesses. They can be used to maintain the process with minimum cost and effectively distinguish which component of the subprocesses is out of control. The optimal design parameters of the proposed control charts can be determined by minimizing the cost model using a simple grid search method. An example is given to illustrate the application of the optimal individual Y control chart and multiple cause-selecting control chart. © 1998 John Wiley & Sons, Ltd.     

Robust parameter design using a supersaturated design for a response surface model

Recently, the application of response surface methodology (RSM) to robust parameter design has attracted a great deal of attention. In some cases, experiments are very expensive and may require a great deal of time to perform. Central composite designs (CCDs) and Box and Behnken designs (BBDs), which are commonly used for RSM, may lead to an unacceptably large number of experimental runs. In this paper, a supersaturated design for RSM is constructed and its application to robust parameter design is proposed. A response surface model is fitted using data from the designed experiment and a stepwise variable selection. An illustrative example is presented to show that the proposed method considerably reduces the number of experimental runs, as compared with CCDs and BBDs. Numerical experiments are also conducted in which type I and II error rates are evaluated. The results imply that the proposed method may be effective for finding the effects (i.e. main effects, two‐factor interactions, and pure quadratic effects) of active factors under the ‘effect sparsity’ assumption. Copyright © 2010 John Wiley & Sons, Ltd.     

Optimal design of material properties and material distribution for multiple loading conditions

An extension of recent work¹ on the simultaneous optimization of material and structure to address the design of structures under multiple loading conditions is presented. Material properties are represented in the most general form possible, namely, as elements of the unrestricted set of positive-semi-definite constitutive tensors of a linearly elastic continuum. Existence of solutions can be shown when the objective is a weighted average of compliances and a resource constraint measured as the 2-norm or the trace of the constitutive tensors is included. The optimized material properties can be derived analytically. The optimization of the layout of the material leads to a sizing problem of structural optimization involving a non-linear, non-smooth elasticity analysis. The computational solution of this problem is discussed and illustrated with examples.     

Sequential and parallel schemes for adaptive 2-D parameter estimation with application to image estimation

In this paper, the non-causal quarter plane 2-D Recursive Least Squares (2D-RLS) algorithm for adaptive processing is developed. The complexity of this algorithm turns out to beO(L ⁶) per iteration, for anL ×L window. With the aim of reducing this complexity, the matrix gains appearing in the algorithm are replaced by scalar gains. This approach yields the Approximate 2-D Recursive Least Squares (A2D-RLS) algorithm, which is shown to have a complexity ofO(L ²). With the objective of reducing the computation time even further, a parallel scheme is developed for the A2D-RLS algorithm. Since the algorithm is inherently sequential, its parallelization involves some more approximations. The desired accuracy of the estimated parameters is shown to place an upper bound on the number of processors. The parallel scheme is suitable for implementation on shared memory as well as distributed memory machines. The algorithm is applied to the problem of image estimation. Simulation results giving speed-up, efficiency, and the accuracy of the estimated image are presented.     

多管火箭定向管振动控制设计

为了减小多管火箭在发射过程中定向管振动对火箭弹起始扰动的影响,考虑多管火箭的噪声干扰,基于多体系统传递矩阵法建立了多管火箭动力学模型,在模态空间下设计了H2最优控制器控制定向管振动,进行了数值仿真,并把H2最优控制器与PD控制器进行了仿真对比,结果表明,采用H2最优控制器的系统不但具有良好的瞬态和稳态性能,而且具有较好的抗干扰能力,能有效地抑制噪声干扰,增强了控制系统的鲁棒性能.     

基于仿真的竞争失效产品综合应力加速寿命试验优化设计

针对竞争失效产品综合应力加速寿命试验存在试验时间长、费用高、效率低的问题,提出一种基于仿真的竞争失效产品综合应力加速寿命试验优化设计方法。采用Monte-Carlo进行仿真模拟,以正常使用应力下的p阶分位寿命渐进方差估计最小为目标,在各应力组合下试验截尾数大小给定的条件下,以试验应力水平大小作为设计变量,利用MLE理论进行统计分析,建立基于仿真的竞争失效产品综合应力加速寿命试验优化设计模型。通过实例分析表明该方法有效、可行,为电子装备寿命预测的加速试验方案优化设计提供技术支撑。     

Simultaneous Solution Strategies for Inclusion of Input Saturation in the Optimal Design of Dynamically Operable Plants

Recent work has considered the inclusion of input saturation in optimization-based integrated plant and control system design. Two mathematical formulations have been derived which allow saturation to be included within a simultaneous optimization framework; these are mixed-integer and bilinear formulations. The MIP formulation applied within an integrated design and control framework was found to be computationally intensive. This paper reviews these formulations and proposes an alternative solution strategy that uses an interior point approach to handle the complementarity constraints present in the bilinear formulation. A solution algorithm is presented and applied to an example problem.     

基于响应面法对桁架结构形状的优化设计

针对数学非线性回归问题,需不断改进设计模型和设计参数,从而使得设计效果达到最佳。求解约束条件下体积最小问题时经常用响应面法进行优化,即利用函数关系拟合仿真模型,采用筛选试验来确定优化方向。为了优化经典10杆桁架结构的形状,基于响应面法,编写并运行APDL（ANSYS parametric design language,参数化设计语言）程序,得到各桁架的初始应力和体积。以节点纵坐标值的改变来反映形状的变化,各因子设置三水平并编码为-1,0,1,通过响应面法（response surface method,RSM）进行寻优并调整中心点和水平。基于调整后的水平,先找到最佳邻域,再用优化软件在最佳邻域内求解桁架在许应力下体积的最优解,最后将确定好的节点纵坐标值回代到APDL程序中验证是否满足约束条件,若满足,则此时的体积为最优解。结果表明：利用响应面法优化桁架杆的迭代次数仅为3次,它能快速定位最优解,降低了前期设计成本。通过对比文献[9]可知响应面法对结构的形状优化更为有效,能快速定位出设计试验方案,在工程应用中对于寻找在约束条件下的最佳配比设计有着高效性。