脉冲电流探头的时域标定研究

 介绍了一种Rogowski线圈脉冲电流探头时域标定和标定数据处理的方法,将脉冲法时域标定的结果和频域标定结果进行了比较。针对电流探头的低频失真,采用系统辨识方法建立了测量系统的动态模型,并对探头输出信号的失真进行校正。实测数据验证了所建模型的有效性,设计出的数字补偿滤波器可将测量系统校正为一理想的比例环节。     

基于Wiener模型的传感器动态非线性辨识研究

针对实际测量中传感器存在较大非线性的缺点,提出利用改进型Wiener模型描述传感器动态非线性模型;将Wiener模型的动态线性环节和静态非线性环节分别利用Laguerre函数和最小二乘支持向量机进行辨识,最终实现传感器模型的建立;通过仿真实验验证比较不同方法的辨识误差与速度,最终结果表明该方法在非线性动态传感器模型辨识方面具有明显的速度和精度优势。     

基于最小二乘支持向量机的混沌控制

利用支持向量机良好的非线性函数逼近和泛化能力，提出基于最小二乘支持向量机非线性补偿的混沌控制新方法.应用最小二乘支持向量机离线辨识混沌系统的非线性部分，并用辨识模型补偿系统的非线性，同时应用线性状态反馈控制混沌系统.对三种典型连续混沌系统的仿真研究表明，提出的控制方法可以有效的控制混沌系统到达设定的目标状态，并且由线性状态反馈控制器构成的闭环系统稳定. 关键词： 混沌控制 支持向量机 最小二乘支持向量机 状态反馈 稳定性     

基于高阶色散管理和相位共轭技术的色散补偿

相位共轭技术能够同时且高效地补偿二阶色散及非线性效应，且该技术同信号比特率、调制方式无关，是最有前景的色散补偿技术之一。理论分析了在高阶色散作用下，超短高斯脉冲信号在中距相位共轭通信系统中的传输演化特性，数值模拟了在二阶、三阶和四阶色散作用下，飞秒高斯脉冲信号在基于中距相位共轭技术的光纤色散管理链中的动态传输过程。结果表明，相位共轭技术和高阶色散管理相结合，不仅可以补偿和复原包括奇数阶和偶数阶色散在内的全部色散和非线性所引入的信号失真和畸变，而且能够减弱时分复用系统中脉冲之间的相互作用，使得信号在传输一个周期后恢复波形，从而提高了相位共轭系统对失真信号的补偿性能。     

电动舵机非线性系统的辨识研究

本文针对所设计的三闭环电动舵机系统,为了提高舵机的控制精度,提出了采用非线性系统辨识的方法,并且利用辨识的参数对系统进行补偿。根据电动舵机的模型分别采用了前馈补偿的方法和反馈辨识的方法对系统的摩擦进行仿真建模研究,并且将建模数据加入到电动舵机中进行试验验证,系统的位置跟踪误差和速度跟踪误差均有大幅度减小。试验结果证明,本文所提出的辨识研究方法可以准确地实现摩擦模型的建立,并且从该模型出发进行补偿可以有效地提高电动舵机的控制精度。     

HL-2A 装置LHCD 微波功率测量系统设计

为了解决在功率测量中检波器输出的非线性曲线和动态输入功率范围小等问题,为500kW/3.7GHz 的LHCD 系统设计了对数检波器,并由其组成新型线性微波功率测量系统。测试结果表明,该测量系统具有更大的动态功率测量范围,其特征曲线在本系统功率参数内具有优良的线性特性,对数一致性误差在-1dB~+1dB 范围内可输入微波功率动态范围>40dB,在系统可用范围内利用线性拟合获得的相关系数大于0.999。该结果优于以前设备测试结果。     

火电厂CO2捕集系统的LSSVM-Hammerstein建模方法

针对火电厂燃烧后CO_2捕集过程的强非线性及大惯性等动态特性,研究准确性高的建模方法是系统优化设计的前提,本文从控制角度研究CO_2捕集系统的非线性动态辨识建模方法。首先介绍火电厂CO_2捕集系统工作原理,将系统抽象为二输入二输出的受控对象;然后采用基于最小二乘支持向量机的Hammerstein模型(LSSVM-Hammerstein)辨识方法,将CO_2捕集系统表示为静态LSSVM模型与动态线性模型的组合。辨识结果表明该模型有很高的辨识精度和泛化能力,能精确描述CO_2捕集系统非线性动态特性,为后续研究先进控制算法提供仿真平台和设计依据。     

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为了解决在功率测量中检波器输出的非线性曲线和动态输入功率范围小等问题,为500k W/3.7GHz的LHCD系统设计了对数检波器,并由其组成新型线性微波功率测量系统。测试结果表明,该测量系统具有更大的动态功率测量范围,其特征曲线在本系统功率参数内具有优良的线性特性,对数一致性误差在-1d B~+1d B范围内可输入微波功率动态范围>40d B,在系统可用范围内利用线性拟合获得的相关系数大于0.999。该结果优于以前设备测试结果。     

压电式倾斜镜迟滞特性及其实验研究

空间激光通信精瞄系统中压电式倾斜镜存在的迟滞非线性特性,不仅降低了精瞄系统定位精度,而且对信标光的捕获以及链路的稳定性造成影响。针对该问题,提出一种基于PLAY迟滞算子改进Prandtl-Ishlinskii(P-I)数学模型及参数辨识方法,利用该模型对迟滞特性进行前馈线性化逆补偿。为进一步提高系统跟踪精度,在线性化的基础上,设计了静态输出反馈控制器,形成复合控制方法,并设计了激光通信终端精瞄系统实验,验证了该复合方法的有效性。通过对系统输入不同频率等幅和减幅正弦控制信号进行测试,结果表明,改进P-I模型最大拟合误差在1%之内,前馈模型逆补偿使压电陶瓷执行器(PEA)的线性度误差由5%减小到1%以内,复合控制方法系统跟踪误差降低了80%。     

原子相干引起的五阶非线性增强

采用腔透射谱法测量了Λ型三能级系统的五阶克尔非线性系数。对二能级和Λ型三能级系统的五阶非线性系数进行数值模拟,比较发现,原子相干对非线性系数具有增强作用。同时将三阶和五阶极化率的模拟结果与测量结果进行对比,发现两者具有很好的一致性。     

Frequency domain analysis and identification of block-oriented nonlinear systems

Block-oriented nonlinear models including Wiener models, Hammerstein models and Wiener-Hammerstein models, etc. have been extensively applied in practice for system identification, signal processing and control. In this study, analytical frequency response functions including generalized frequency response functions (GFRFs) and nonlinear output spectrum of block-oriented nonlinear systems are developed, which can demonstrate clearly the relationship between frequency response functions and model parameters, and also the dependence of frequency response functions on the linear part of the model. The nonlinear part of these models can be a more general multivariate polynomial function. These fundamental results provide a significant insight into the analysis and design of block-oriented nonlinear systems. Effective algorithms are therefore proposed for the estimation of nonlinear output spectrum and for parametric or nonparametric identification of nonlinear systems. Compared with some existing frequency domain identification methods, the new estimation algorithms do not necessarily require model structure information, not need the invertibility of the nonlinearity and not restrict to harmonic inputs. Simulation examples are given to illustrate these new results.     

A three-level non-deterministic modeling methodology for the NVH behavior of rubber connections

Complex built-up structures such as vehicles have a variety of joint types, such as spot-welds, bolted joints, rubber joints, etc. Rubber joints highly contribute to the nonlinear level of the structure and are a major source of uncertainties and variability. In the general framework of developing engineering tools for virtual prototyping and product refinement, the modeling of the NVH behavior of rubber joints involve the computational burden of including a detailed nonlinear model of the joint and the uncertainties and variability typical of that joint in a full-scale system model. However, in an engineering design phase the knowledge on the joint rubber material properties is typically poor, and the working conditions a rubber joint will experience are generally not known in detail. This lack of knowledge often do not justify the computational burden and the modeling effort of including detailed nonlinear models of the joint in a full-scale system model.Driven by these issues a non-deterministic numerical methodology based on a three-level modeling approach is being developed. The methodology aims at evaluating directly in the frequency domain the sensitivity of the NVH behavior of a full-scale system model to the rubber joint material properties when nonlinear visco-elastic rubber material behavior is considered. Rather than including directly in the model a representation of the rubber nonlinear visco-elastic behavior, the methodology proposes to model the material nonlinear visco-elastic behavior by using a linear visco-elastic material model defined in an interval sense, from which the scatter on the full-scale system NVH response is evaluated. Furthermore the development of a multi-level solution scheme allows to reduce the computational burden introduced by the non-deterministic approach by allowing the definition of an equivalent linear interval parametric rubber joint model, ready to be assembled in a full-scale system model at a reasonable computational cost.By using a commercial finite element code the developed methodology is illustrated through a numerical case-study: the low-frequency dynamic analysis of automotive door weather-strip seals.     

Nonlinear structural identification by the “Reverse Path” spectral method

When dealing with nonlinear dynamical systems, it is important to have efficient, accurate and reliable tools for estimating both the linear and nonlinear system parameters from measured data. An approach for nonlinear system identification widely studied in recent years is “Reverse Path”. This method is based on broad-band excitation and treats the nonlinear terms as feedback forces acting on an underlying linear system. Parameter estimation is performed in the frequency domain using conventional multiple-input–multiple-output or multiple-input–single-output techniques. This paper presents a generalized approach to apply the method of “Reverse Path” on continuous mechanical systems with multiple nonlinearities. The method requires few spectral calculations and is therefore suitable for use in iterative processes to locate and estimate structural nonlinearities. The proposed method is demonstrated in both simulations and experiments on continuous nonlinear mechanical structures. The results show that the method is effective on both simulated as well as experimental data.     

Nonlinear chirp compensation by scan filtering in SAIL

The nonlinear chirp of a tunable laser generates the phase errors and damages the range resolution in synthetic aperture imaging ladar (SAIL). In the compensation algorithms establishing matched and nonmatched reference paths, the phase errors were compensated in a whole echo pulse. In this paper a compensation algorithm of nonlinear chirp by scan filtering is proposed.The heterodyne signals of different echoes from all target points in a footprint are scan filtered from one whole heterodyne signal of one whole echo pulse in the spectrum. The phase errors of these heterodyne signals are measured by phase-shifting algorithm in reference path and compensated separately. Then all the compensated signals are combined back into a whole heterodyne pulse and compressed in range. After all heterodyne pulses are compressed in range, the azimuth compensation is followed.The mathematical flow of this compensation algorithm is established. The simulation of the airborne SAIL model validates the feasibility, and the bandwidth of range compression decreases obviously. The effects of nonlinear chirp and the pass bandwidth of the scan filter are analyzed and discussed finally.     

Research on application of polynomial fitting technique in rotary kiln infrared temperature measurement system

Aiming at the linear temperature compensation algorithm’s disadvantage of temperature measurement error in rotary kiln infrared scanning temperature measurement process, this paper proposes a precise nonlinear cubic polynomial fitting temperature compensation algorithm. The proposed algorithm compensates the temperature values of scanning points on rotary kiln surface by following steps: Calculating temperature difference between the real temperature value of rotary kiln and temperature value measured by infrared scanning temperature measurement system; Fitting the temperature difference data with cubic polynomial; Using the obtained function to compensate temperature. Experimental result shows that compared with the usual linear temperature compensation algorithm, the accuracy of proposed algorithm has raised about 2.25 times when cubic polynomial is used.     

基于交叉偏振波产生的脉冲净化技术研究与应用

本文利用交叉偏振波产生技术(XPW)对800 nm波段钛宝石飞秒激光器输出的激光脉冲进行时域净化, 提高脉冲时域对比度, 并测量验证了10¹¹对比度的脉冲, 达到测量仪器的动态范围极限, 比初始脉冲时域对比度有三个量级的提高, XPW的效率为22%. 同时发现净化后脉冲光谱宽度也得到一定展宽, 进一步利用啁啾镜对和补偿片对净化后的脉冲进行色散补偿, 得到25 fs脉宽的脉冲. 利用该净化后的激光脉冲作为种子注入已有的太瓦级钛宝石啁啾脉冲放大系统中, 在输出脉冲能量250 mJ, 宽度50 fs, 对应峰值功率5 TW的情况下, 在主脉冲前100 ps以外的范围内测量验证了10¹¹的脉冲对比度.     

实现光束变换的连续位相衍射光学器件的研制

本文利用基于模拟退火法和爬山法相结合的混合优化算法,实现光束变换的连续位相衍射光学器件的设计。通过灰阶掩膜板及离子刻蚀工艺,研制了 Φ１００ｍ ｍ 的连续位相衍射光学器件。通过多级衰减片及ＣＣＤ 实现了焦斑光强分布测量。测量结果表明：边缘陡峭、旁瓣小、中心主瓣具有一定均匀性,且没有中心零级锐脉冲的焦斑光强分布     

Differential group delay monitoring using an all-optical signal spectrum-analyser

We demonstrate an all-optical device that monitors differential group delay (DGD) degradation of picosecond optical pulses. This device is based on an ultrafast all-optical signal analyser that uses nonlinear effects (cross-phase modulation) to transfer rapid temporal fluctuations into frequency domain effects that can be measured on an conventional optical spectrum analyser (incorporating a slow-detector). This monitoring scheme will enable rapid dynamic monitoring and compensation of DGD in ultrafast optical networks, at 160 Gb/s data rates and beyond, where electronic monitoring techniques cannot operate. We discuss the required signal polarisation condition.     

Identification of cascade of Hammerstein models for the description of nonlinearities in vibrating devices

In a number of vibration applications, systems under study are slightly nonlinear. It is thus of great importance to have a way to model and to measure these nonlinearities in the frequency range of use. Cascade of Hammerstein models conveniently allows one to describe a large class of nonlinearities. A simple method based on a phase property of exponential sine sweeps is proposed to identify the structural elements of such a model from only one measured response of the system. Mathematical foundations and practical implementation of the method are discussed. The method is afterwards validated on simulated and real systems. Vibrating devices such as acoustical transducers are well approximated by cascade of Hammerstein models. The harmonic distortion generated by those transducers can be predicted by the model over the entire audio frequency range for any desired input amplitude. Agreement with more time consuming classical distortion measurement methods was found to be good.     

A HYBRID FINITE SEGMENT/FINITE ELEMENT MODELLING AND EXPERIMENT ON A FLEXIBLE DEPLOYMENT SYSTEM

This paper focuses on the dynamic responses of a flexible deployment system that has a central rigid body and four articulated flexible beams and undergoes locking impact. A hybrid finite segment/finite element model and an experiment are presented for the deploy-ment system. The flexible beam components in the system are modelled with the finite segments connected by massless beam elements, wherein the finite segments describe the inertia of the large rotation flexible beam and the massless elastic elements describe the elas-ticity of the flexible beam by taking the advantage of small deformation in the relative co-ordinate system. To model the internal impacts in the articulate joints due to clearances, a continuous contact force model of locking joint is also proposed. The governing differential-algebraic equations of the system are established by the Newton-Euler method with Lagrange multipliers and are solved with the method of generalized co-ordinate partitioning. To accelerate the numerical integration, a “longitudinal constraint” is suggested to alleviate the stiff problem of the dynamic equations. In addition, a physical model of the deployment system is constructed. The deployment is released by the compressed springs in the joints. A position measuring system of linear CCD cameras is used to measure the large displacement of the system. Correlations between the mathematical model and the experiments are also presented. Reasonable results are obtained.