考虑红外焦平面器件非线性响应的一种非均匀性校正方法

针对红外焦平面阵列的非线性响应特性,提出了一种考虑非线性响应的“曲线—直线”校正方法,并给出了校正的计算公式.仿真实验结果说明此方法具有精度高,计算量小的优点,需要存储的参数少,易于硬件实现.     

W波段回旋行波管放大器速度零散的分析

通过包含速度零散影响的回旋行波管放大器的非线性理论模型,以W波段两段结构回旋行波管放大器为例,详细分析了速度零散对放大器电子注—波互作用的影响.模拟结果表明,通过合理地调整互作用长度,减小电子横纵速度比、调节工作磁场等方法可以有效地减小速度零散的影响,对回旋行波管放大器的优化设计提供了理论依据.     

Nonlinear analysis of cable structures using the dynamic relaxation method

The analysis of cable structures is one of the most challenging problems for civil and mechanical engineers. Because they have highly nonlinear behavior, it is difficult to find solutions to these problems. Thus far, different assumptions and methods have been proposed to solve such structures. The dynamic relaxation method (DRM) is an explicit procedure for analyzing these types of structures. To utilize this scheme, investigators have suggested various stiffness matrices for a cable element. In this study, the efficiency and suitability of six well-known proposed matrices are assessed using the DRM. To achieve this goal, 16 numerical examples and two criteria, namely, the number of iterations and the analysis time, are employed. Based on a comprehensive comparison, the methods are ranked according to the two criteria. The numerical findings clearly reveal the best techniques. Moreover, a variety of benchmark problems are suggested by the authors for future studies of cable structures.     

紧凑型人眼安全OPO激光器

提出了OPO与泵浦源激光器共用一个谐振腔的新型结构,保证了OPO谐振腔和基波谐振腔的腔模最佳匹配,OPO光束质量得到了很大提高。泵浦源激光器,采用布氏角切割的Cr∶YAG晶体作为被动Q开关,定向棱镜作为谐振腔全反镜,使得整个OPO激光器具有结构紧凑、抗失调能力强的特点。1. 57μm激光的输出能量8mJ、发散角5. 5mrad、重复频率1 /6Hz。     

剪切型结构地震破坏准则与抗震可靠度分析

对现有混凝土结构的几种常用地震破坏准则进行了简要的归纳与总结,结合一钢筋混凝土框架结构,在求得配筋结构层间极限变形能力的基础上,利用弹塑性层间位移增大系数法直接统计层间位移的反应结果,采用变形破坏准则的一次二阶矩法对考虑非线性因素的钢筋混凝土框架结构的抗震可靠度问题进行了分析,探讨了这一方法的实施要点.     

基于正态分布宽带信号的无源互调特征行为分析

在现代无线通信中,无源互调是影响通信信号传输质量的重要因素。双音互调测试能够有效衡量无源器件的非线性特性,却无法准确预测出器件在宽带信号激励下的非线性失真。因此本文提出了一种基于正态分布的宽带信号激励下的射频连接器无源互调特性分析方法。通过双音互调测试,建立射频连接器无源非线性传输数学模型,并将基于正态分布的等效宽带信号作为非线性传输模型的激励源进行模拟仿真。结果表明,宽带无源互调功率分布与宽带信号功率分布相同,n阶宽带无源互调带宽为原宽带信号带宽的n倍,宽带信号的无源互调产物相较于双音测试信号有所增强,且信号的信噪比下降,说明宽带信号在传输过程中受到的干扰更加严重。电路仿真和数值计算呈现出良好的一致性,证明了本分析方法的有效性。     

Nonsmooth stabilizability and feedback linearization of discrete-time nonlinear systems

We consider the problem of stabilizing a discrete-time nonlinear system using a feedback which is not necessarily smooth. A sufficient condition for global dynamical stabilizability of single-input triangular systems is given. We obtain conditions expressed in terms of distributions for the nonsmooth feedback triangularization and linearization of discrete-time systems. Relations between stabilization and linearization of discrete-time systems are given.     

Discrete-time sliding mode control of flexible rotor-magnetic bearing systems

This paper is concerned with the computer-based sliding mode control of flexible rotor—magnetic bearing systems (FR-MBS). The plant dynamics consisting of actuator dynamics and flexible rotor dynamics are described. The reduced-order model for controller design is given by eliminating higher-order modes of the mechanical and electrical magnetic interaction system. A discrete-time sliding mode controller with a new robust reduced-order variable structure system (VSS) observer is proposed and its robust performance is evaluated with several simulations based on a calculation model. This digital controller is implemented to replace a linear analogue PID compensator. Levitation tests using the proposed digital controller are performed and compared with those of the PID compensator. The unstable modes can be easily controlled with the good stability and the spillover phenomena due to ignored higher-order modes are not generated. It is indicated that the discrete-time sliding mode control has robustness to the model parameter variations and external disturbances. Using the discrete time sliding mode controller with the reduced-order VSS observer, the test rig of the magnetic bearing system can be successfully rotated in a speed range of 0–35 000 rpm, which includes the first critical shaft frequency of the flexible rotor.     

基于神经网络非线性模型的开关磁阻电机调速系统动态仿真

实现开关磁阻电机调速系统(SRD)的准确动态仿真是进行系统参数优化、控制策略研究的重要依据.本文在以实测开关磁阻电机(SRM)准确特性曲线为样本数据,并基于BP神经网络建立SRM非线性模型的基础上,构建了Matlab环境下SRD系统的整体动态仿真模型.通过仿真揭示了SRD系统的稳态、动态运行特性,实现了系统性能的准确分析,为设计SRD系统高性能控制提供了理论依据.经与实测电流、转速波形对比,验证了本文提出的SRD动态仿真方法的有效性.     

一类非线性不确定时滞系统的记忆与无记忆复合H∞状态反馈控制

针对一类具有状态非线性不确定性的线性时滞系统,基于Lyapunov稳定性理论,利用线性矩阵不等式（LMI）方法,讨论了该类时滞系统的记忆与无记忆复合H∞状态反馈控制器的设计问题。在非线性不确定性满足增益有界条件下,得到了该类时滞系统的满足鲁棒H∞性能的一个充分条件。通过求解一个线性矩阵不等式-LMI,即可获得鲁棒H∞控制器。