基于移动数据窗的传递函数多新息随机梯度辨识方法

一些工业过程可以近似用一个传递函数描述,结合统计辨识方法和非线性优化策略提出传递函数参数辨识方法.该方法采用动态数据方案,使用系统观测数据获得系统更多的模态信息.基于动态观测数据,提出传递函数随机梯度参数辨识方法.为进一步提高辨识精度,利用动态窗数据将随机梯度参数辨识方法中的标量新息扩展为新息向量,提出传递函数多新息随机梯度参数估计方法.最后通过仿真例子对所提出的方法进行了性能分析和模型验证.     

飞机颤振模态参数辨识的频域广义整体最小二乘算法

采用一种适用于噪声环境的广义整体最小二乘算法,准确地辨识飞机的颠振模态参数．该算法结合有理传递函数模型,将带噪系统的辨识问题转化为广义整体最小二乘问题．利用线性的广义奇异值分解求解模型系数,避免了非线性优化的复杂计算．通过迭代法更新加权项,获得了接近于极大似然估计的辨识效果．最后利用试飞试验数据辨识飞机的模态参数,验证了该方法的有效性．     

火箭结构系统纵向模态自动辨识方法

针对工程中需要从火箭结构系统的整体模态中识别纵向模态,根据模态有效质量理论,提出了一种识别火箭结构系统纵向模态的自动辨识方法.以具有集中质量系统的振动特性作为算例,通过有限元软件,建立了具有集中质量系统的梁模型,利用自动辨识的方法,自动辨识出系统的纵向模态,并与应用模态分析法所计算的系统模态信息相比较,这种自动辨识方法不仅能准确的辨识出振动系统的纵向模态,而且还具有自动高效的识别特点.为准确快速建立液体火箭POGO振动系统的动力学模型等工程系统的模型提供理论依据.     

力平衡加速度计在线动态测试及其传递函数辨识

为了实现六自由度强震观测系统中力平衡加速度计在线动态测试的自动化和传递函数辨识,提出一种嵌入到六自由度强震观测系统内的测试系统,该系统由模/数、数/模转换器以及微控制器组成。利用频域辨识算法—Levy法,实现了力平衡加速度计传递函数的辨识。试验结果证明:利用这种测试系统可以代替超低频标准振动台来进行力平衡加速度计动态模型的辨识。     

应用对消原理辨识传递函数

本文提出了一种辨识系统传递函数的新方法.它是通过引入预滤波器对输入信号进行 预处理,调整预滤波器的参数,使其实现与系统传递函数的部分对消,并应用对消原理而得到 的一种辨识方法.这种方法可以分别辨识传递函数的分子、分母及其因子,而且不需要对噪 声进行建模.此法还可以用来辨识误差模型.     

一种新的实用PI控制闭环辨识方法

对于有PI控制器的闭环系统,提出一种辨识方法,可以在闭环系统运转下得到控制对象的开环传递函数.首先,根据闭环系统的衰减振荡曲线,近似地求出闭环控制系统的二阶加时滞(SOPDT)闭环传递函数.然后,用方框图等效法,在所得的闭环传递函数中将PI控制器分离出去;再通过比较系数就得到对象的开环传递函数.数字仿真和辨识实验表明此法有很好的辨识精度,计算量小且非常易于在线实现,具有比较重要的现实意义.     

逆重复m序列及系统辨识

本文计论了逆重复m序列的产生、性质和功率谱密度,采用逆重复m序列辨识线性系统时纹波项的估算,以及由试验得到的互相关函数估算系统传递函数的计算方法.最后,归纳了采用逆重复m序列辨识系统的好处.文中附有试验结果和计算示例.     

线性时变反馈系统的状态空间模型和模态参数递推辨识

针对闭环系统中时变状态空间模型和模态参数的辨识问题, 提出一种递推辨识格式, 将这种格式与递推子空间方法结合, 得到一种辨识方法. 该方法通过重建输入输出数据之间的关系, 递推辨识得到闭环系统的时变状态空间模型和模态参数. 算例研究了系统在模态参数突变和周期变化两种情况下的辨识问题, 仿真结果表明, 所提出算法能有效辨识线性时变反馈系统的状态空间模型和模态参数.

     

对时域H∞插值算法误差上界的改进

1 引言 文[1]将文[2]在频域构造的H∞辨识问题推广到时域,提出了直接利用时域观测数据辨识系统传递函数的插值算法,并对这类算法在最坏情况下的H∞辨识误差推导了可计算的上界,该上界比较保守,本文对其进行改进.     

用双通道分析仪计算多输入系统的传递函数

本文提出了伪传递函数的新概念及其计算公式。应用该函数可以简单地利用双通道动态分析仪,扩展为能计算多输入多输出系统的传递函数,从而进行实验模态分析。对该方法还进行了实际应用,得到了机床的模态参数。     

电液伺服系统的多滑模鲁棒自适应控制

针对一类参数与外负载非匹配不确定的非线性高阶系统,提出了一种基于逐步递推方法的多滑模鲁棒自适应控制策略.应用逐步递推的多滑模控制方法简化了高阶系统的控制问题,同时在自适应控制中加入鲁棒控制的方法,以消除不确定性对控制性能的影响.首先利用逐步递推方法与状态反馈精确线性化理论,得出确定系统的多滑模控制器设计方法;然后基于Lyapunov稳定性分析方法,给出不确定系统的参数自适应律,及鲁棒自适应控制器的设计方法.本文把该控制策略应用到电液伺服系统的位置跟踪控制中,仿真结果显示,该控制方法具有较强的鲁棒性及良好的跟踪效果.     

一类多执行机构系的滑模控制设计及其应用

针对一类具有多执行机构的非线性系统,利用滑模控制和backstepping技术,研究了输出跟踪问题.针对执行机构的不同特点,利用离散执行机构实现滑模控制中的不连续控制量,利用连续执行机构实现滑模控制中的连续控制量.然后利用backstepping技术实现连续执行机构的输出对滑模控制中的连续控制量的有限时间收敛.将提出的设计方法应用于导弹直接侧向力与气动力复合控制系统设计,并进行了仿真验证.     

基于小波包的EMD分析在车削刀具监控中的应用

针对车削刀具振动信号在经验模态分析(EMD)时产生的模态混叠现象,采用小波包和EMD分析相结合的方法来提取刀具磨损时振动信号的敏感特征.首先利用EMD分析将采集的磨损信号分解为数个固有模态分量(IMF),然后采用小波包方法对与刀具磨损状态相关性大的IMF进行分解并重构.计算重构后的IMF与刀具磨损的相关系数,将相关系数大的IMF所包含的敏感特征作为支持向量机(SVM)的输入,进而对刀具的磨损状态进行识别.研究结果表明该方法能有效地提高对刀具磨损状态的识别精度.     

无杆气缸驱动的柔性机械臂振动控制

提出了一种无杆气缸驱动的柔性机械臂定位和振动抑制系统,采用脉冲码调制(pulse code modulation,PCM)方法实现.首先,推导了气动驱动柔性臂的系统模型,对采用的复合定位和振动抑制控制算法进行理论分析.其次,气缸行程长、气体具有压缩性以及气动驱动存在非线性和阀门开关有时延等因素会引起控制作用的滞后问题,容易激发高阶模态的极限环振荡,导致观测和控制溢出,这将影响控制系统的稳定性.为了克服上述问题,在控制算法中引入时延补偿、低通滤波法.最后,进行气动驱动柔性臂同时定位和振动抑制的试验研究.试验结果表明,采用的气动驱动控制方法可以有效地抑制柔性臂的低频模态振动,并同时实现定位.     

Mode‐dependent seamless transfer control strategy of a microgrid via a small‐signal stability approach

A microgrid is an effective solution to enhance the integration of distributed renewable energy resources, which can operate both in grid connected mode and islanded mode. In order to reduce the jumps of the system variables within acceptable limits to ensure the system has good transient performance and power quality in multiple operating modes, seamless transfer is the key problem to be considered. In this paper, due to the different multiple equilibrium points for the two operating modes, the dynamics of every operating mode re modeled as a subsystem with all the variables that are needed to be synchronized. Linearization is carried out respectively for the two operation modes on the different equilibriums in a state‐space form based on the small‐signal stability method. To reduce the conservatism of the unified controller, the concept of the relative Lyapunov function is introduced to derive a multiple segmental Lyapunov method and a robust feedback mode‐dependent switching controller is designed to achieve smooth transfer by making the deviation energy of the two modes both converge to the zero point. To rapidly detect the switching signal, a sparse communication network is introduced by the use of low bandwidth communication links to broadcast the switching signal to each distributed controller. Finally, two microgrid test systems were built in SIMULINK to show the feasibility and effectiveness of the proposed seamless transfer control strategies.     

Model order reduction of second-order systems with nonlinear stiffness using Krylov subspace methods and their symmetric transfer functions

In this investigation, Model Order Reduction (MOR) of second-order systems having cubic nonlinearity in stiffness is developed for the first time using Krylov subspace methods and the associated symmetric transfer functions. In doing so, new second-order Krylov subspaces will be defined for MOR procedure which avoids the need to transform the second-order system to its state space form and thus the main characteristics of the second-order system such as symmetry and positive definiteness of mass and stiffness matrices will be preserved. To show the efficacy of the presented method, three examples will be considered as practical case studies. The first example is a nonlinear shear-beam building model subjected to a seismic disturbance. The second and third examples are nonlinear longitudinal vibration of a rod and vibration of a cantilever beam resting on a nonlinear elastic foundation, respectively. Simulation results in all cases show good accuracy of the vibrational response of the reduced order models when compared with the original ones while reducing the computational load.     

Robust stability analysis of uncertain switched linear systems with unstable subsystems

The problem of robust stability for switched linear systems with all the subsystems being unstable is investigated. Unlike the most existing results in which each switching mode in the system is asymptotically stable, the subsystems may be unstable in this paper. A necessary condition of stability for switched linear systems is first obtained with certain hypothesis. Then, under two assumptions, sufficient conditions of exponential stability for both deterministic and uncertain switched linear systems are presented by using the invariant subspace theory and average dwell time method. Moreover, we further develop multiple Lyapunov functions and propose a method for constructing multiple Lyapunov functions for the considered switched linear systems with certain switching law. Several examples are included to show the effectiveness of the theoretical findings.     

FLEXIBLE SPACECRAFT VIBRATION SUPPRESSION USING PWPF MODULATED INPUT COMPONENT COMMAND AND SLIDING MODE CONTROL

This paper presents a dual‐stage control system design method for the rotational maneuver and vibration stabilization of a spacecraft with flexible appendages. In this design approach, attitude control system and vibration suppression were designed separately using lower order model. The design of attitude controller was based on sliding mode control (SMC) theory leading to a discontinuous control law. This controller accomplishes asymptotic attitude maneuvering in the closed‐loop system and is insensitive to the interaction of elastic modes and uncertainty in the system. The shaped command input controller based on component synthesis vibration suppression (CSVS) method is designed for reduction of flexible mode vibration, which only requires information about natural frequency and damping of the closed system. Additionally, to extend the CSVS method to the system with on‐off actuators, pulse‐width pulse‐frequency (PWPF) modulation is employed to control the thruster firing and integrated with the CSVS method. Simulation results have been proven the potential of this technique to control flexible spacecraft.     

基于DMA模式和多线程技术的振动信号高速采集系统

结合振动信号测量的试验要求,设计基于DMA模式和多线程技术的振动信号的高速数据采集系统。利用DMA直接内存存取的数据传输技术,提高了系统性能,解放了CPU,解决了大量数据高速采集的问题。介绍了DMA技术的软件实现步骤,并且结合多线程多任务管理的技术特点,构建了软件平台,保证在同一计算机控制进行其他试验的同时,对设备的振动情况进行监控,满足了试验要求。试验数据表明,该系统可以很好地反映实验设备的振动情况,对以计算机为核心的振动信号数据采集系统具有借鉴意义。     

Robust passive control of uncertain switched time-delay systems: a sliding mode control design

In this paper, the problem of sliding mode control (SMC) with passivity for a class of uncertain switched time-delay systems is studied. By means of the multiple Lyapunov functions techniques, a delay-dependent sufficient condition for the existence of linear sliding surface of subsystem is deduced in which the solution to the switched sliding mode dynamics is robustly exponentially stable and passive under a state-based switching law. Moreover, the sliding mode controller is designed to drive the system trajectories onto the predefined sliding surface of subsystem in finite time. Finally, a numerical example is provided to illustrate the effectiveness of the proposed method.