反向回转双机驱动振动系统基于频率俘获的控制研究

建立了反向回转双机驱动振动系统的动力学模型和感应电机的数学模型,运用动力学理论分析了振动系统的动力学特性,得到了反向回转双机驱动振动系统实现频率俘获的条件．根据振动系统的频率俘获条件,分析了对2个2偏心转子相位差的控制策略．分别运行自同步条件下的系统仿真程序和基于振动系统频率俘获条件的相位差控制仿真程序,计算机仿真结果表明对振动系统施加控制后,该系统能够快速实现速度同步和相位同步,验证了控制策略的有效性．     

非线性振动系统基于频率俘获现象的谐振同步分析

基于单质体非线性振动系统的机电耦合动力学模型,在对非线性振动系统起动过程中出现的频率俘获现象定量描述的基础上,考虑非理想振动系统的激振源与系统非线性振动运动的相互影响,研究了双激振源非线性振动系统基于频率俘获作用,实现谐振同步的理论条件。并依据激振电动机驱动系统与振动机械系统之间的耦合动力学模型及试验测定的试验台机械特性参数,通过数值仿真及试验,验证和解释了非线性振动系统频率俘获现象下,系统双激振源的谐振同步问题,指出非理想非线性振动系统的频率俘获现象,以及该现象下的多激振源谐振同步运动与振动系统的非线性强度、刚度、阻尼等参数之间的关系。研究结果对多激振源激励非线性振动系统的谐振同步运动现象分析,提供一定的理论支持和试验依据。     

同向回转双机驱动振动系统的自同步特性

采用了一种新的分析方法研究同向回转双机驱动振动系统的自同步特性,通过引入激振器平均角速度和相位差的两个小参数,对振动系统的参数进行无量纲化处理,提出了频率俘获力矩的概念,得到了振动系统的频率俘获方程,把同步问题转化为频率俘获方程零解的存在和稳定性问题。计算机仿真结果表明,当振动系统的参数满足频率俘获和自同步稳定运转的条件时,振动系统能很快实现频率俘获并达到稳定的自同步运转状态,验证了理论分析的正确性。     

自同步振动系统的动力学耦合特性及实验

为了研究双机驱动自同步振动系统的动力学耦合特性,引入两个激振器的平均角速度和相位差两个参数,对振动系统的参数进行无量纲化处理,得到振动系统的同步性条件和稳定性条件。定量分析了振动系统两个激振器的动力学耦合特性,发现系统的频率俘获力矩与相位差正弦值乘积的一半以阻力矩形式加在相位超前的电动机上以降低其角速度,另一半则以驱动力矩形式加在相位滞后的电动机上以增加其角速度。同步实验台振动系统的实验验证了该理论分析的正确性。     

在振动筛上实现振动同步传动及试验研究

在自同步理论研究中,存在着一种现象,无直接驱动源的激振器仍能跟随另外一个或多个有源驱动的激振器同步运转,即称振动同步传动。针对直线振动筛的振动机构,应用Lagrange能量方程建立动力学模型,根据线性叠加原理得到系统稳态时的响应,利用时间双尺度法获取频率俘获方程,并给出直线振动筛实现"振动同步传动"的同步性判据及同步状态下的稳定性判据。在供电频率50Hz的试验条件下,测量得到电机2断电前后稳态时系统的响应及两激振器的相位差和转速,验证了理论方法的正确性,为直线振动筛在振动同步传动理论方面的应用提供了依据。     

不对称滞回振动系统频率俘获情况下的同步现象

对具有不对称滞回性的自同步振动系统在频率俘获情况下的同步特性进行研究。建立不对称滞回模型和具有不对称滞回特性的自同步振动系统的非线性动力学模型,利用Matlab/Simulink仿真呈现频率俘获情况下的系统双激振电机的同步运行和系统的同步运行稳定特性。通过仿真分析系统可实现频率俘获现象以及在频率俘获情况下仍能实现同步特性。研究表明具有不对称滞回性的非线性振动系统仍能实现频率俘获情况下的双激振电机的同步运转和系统的同步稳定性。     

高速电主轴电动机—主轴系统的机电耦合动力学建模

针对高速电主轴系统具有复杂机电系统的特点,提出对高速电主轴系统进行机电耦合分析的观点。提炼并归纳了高速电主轴系统中存在的多物理过程、多参数耦合现象,给出高速电主轴系统全局耦合关系的框图。通过分析高速电主轴电动机—主轴子系统的结构及其耦合情况,得到了该子系统的机电耦合关系框图,并建立其物理模型。基于机电系统分析动力学理论,采用变分原理法,应用拉格朗日方程建立电动机—主轴子系统的电压方程和机械运动方程,将两组方程联立得到与该子系统物理模型相对应的数学模型,导出子系统的动力学方程,为进一步研究高速电主轴系统的机电耦合动力学性能提供理论基础。     

基于ADAMS的曲轴连杆活塞建模与仿真

基于多体系统动力学理论,利用ADAMS建立了曲轴连杆活塞的机构模型,然后在模型上施加主动载荷及约束,最后建立机构的动力学方程,求解得出多个工况下曲轴连杆轴颈在弹性支承条件下的载荷。     

环形极板机电耦合强非线性系统主共振-1/2亚谐参数共振

研究环形极板机电耦合系统的强非线性问题。按照弹性力学理论建立环形极板机电耦合系统的动力学方程,利用Galerkin方法将其转化为非线性振动方程。转化后的振动方程是杜芬-马修方程,有两个外激频率。应用改进多尺度法求得系统的主共振-1/2亚谐参数共振的幅频响应曲线,分析了不同的系统参数对共振的影响。     

多锤联动系统的振动耦合理论及试验研究

针对多锤联动时出现耦合问题,对"锤—桩—土"系统进行合理简化,在此基础上以两台桩锤联动为对象建立打桩过程中的动力学数学模型,并由此构建系统的机电耦合方程,然后利用小参数周期平均法对机电耦合过程中电动机的负载转矩进行近似解析,得出系统运行过程中电动机负载转矩的影响因素、平衡方程及机电耦合强度表达式,揭示系统出现耦合现象的机理。利用Matlab/Simulink建立仿真模型并对系统机电耦合过程进行数值仿真,得到系统在不同电动机转速、初始相位差及土壤参数下的机电耦合过程及基本规律。最后通过实际打桩试验验证数学模型、理论推导及仿真结果的正确性。这些结论为电控联动方式的控制策略制定提供理论依据,也为机械联动结构设计及"机械—电控"复合联动方式的工程应用提供参考。     

风机叶片疲劳加载振动频率特性分析与试验

针对风机叶片疲劳加载过程振动特性,建立旋转偏心块驱动的叶片疲劳加载系统动力学模型。基于拉格朗日方程推导出系统的数学模型,利用平均法近似解析系统动力学方程,得出振动过程中电机转矩平衡方程。分析振动频率的变化规律,建立仿真模型,对系统频率捕获过程进行数值仿真,揭示系统的自同步振动特性。风机叶片疲劳加载试验表明:叶片在受迫振动时,叶片振动频率并不总等于驱动频率;驱动频率与叶片固有频率偏差较大时,叶片振动幅值及频率波动明显;频率偏差在较小区间范围(0.47~0.62Hz)时,偏心块驱动系统与叶片容易发生频率捕获,振幅较小并趋于稳定;在负载转矩较大而电机功率不足时,偏心块会发生转速跳变。     

机械系统动力学参数动态测试的频域辨识法

提出了机械系统动力学参数动态测试的频域辨识法。该法的要点为：计算机产生多谐差相激振信号，在该信号激励下机械系统产生与激振信号同周期的振动响应，对激励信号和响应信号作等间隔采样并作快速富里哀变换（ＦＦＴ），获得的频谱代入机械系统的频域动力学方程，再用最小二乘法辨识出各参数。由于富里哀变换将时域内的微分运算转变成频域内的代数运算，从根本上避免了噪声的微分放大作用，并且由于对信号整周期截断时ＦＦＴ具有理想的选频滤波特性，所以该法具有很强的抗干扰性。本文以动力调谐陀螺的挠性接头为例，用仿真计算验证了该法的有效性。     

Nonlinear dynamic response of cable-suspended systems under swinging and heaving motion

In order to enhance the fidelity, convenient and flexibility of swinging motion, the structure of incompletely restrained cablesuspended system controlled by two drums was proposed, and the dynamic response of the system under swinging and heaving motion were investigated in this paper. The cables are spatially discretized using the assumed modes method and the system equations of motion are derived by Lagrange equations of the first kind. Based on geometric boundary conditions and linear complementary theory, the differential algebraic equations are transformed to a set of classical difference equations. Nonlinear dynamic behavior occurs under certain range of rotational velocity and frequency. The results show that asynchronous motion of suspension platform is easily caused imbalance for cable tension. Dynamic response of different swing frequencies were obtained via power frequency analysis, which could be used in the selection of the working frequency of the swing motion. The work will contribute to a better understanding of the swing frequency, cable tension and posture with dynamic characteristics of unilateral geometric and kinematic constraints in this system, and it is also useful to investigate the accuracy and reliability of instruments in future.     

COMPUTER AIDED ANALYSIS OF FLEXI－BLE MEMBER IN CONSIDERATION OF THE EFFECTS OF DYNAMIC STI－FFEN－ING

ＣＯＭＰＵＴＥＲＡＩＤＥＤＡＮＡＬＹＳＩＳＯＦＦＬＥＸＩ－ＢＬＥＭＥＭＢＥＲＩＮＣＯＮＳＩＤＥＲＡＴＩＯＮＯＦＴＨＥＥＦＦＥＣＴＳＯＦＤＹＮＡＭＩＣＳＴＩ－ＦＦＥＮ－ＩＮＧＣＯＭＰＵＴＥＲＡＩＤＥＤＡＮＡＬＹＳＩＳＯＦＦＬＥＸＩ－ＢＬＥＭＥＭＢＥＲＩ...     

单叶片推进器及其运动特性

提出了一种新型的流体推进器——单叶片推进器,通过对叶片的运动学和负载的分析,建立了该推进器的运动方程。基于ADAMS环境,建立了单叶片推进器的虚拟样机,并进行了推进器系统的动力学仿真。仿真分析表明:单叶片推进器能够在设定转速下稳定运行;有效推力是脉动变化的,但在稳定转速下,有效推力的幅值和频率是稳定的,可以产生稳定的推动效果。     

A trigonometric series expansion based method for the research of static and dynamic characteristics of eccentric seals

Static and dynamic characteristics of labyrinth seals are important in the prediction of the stability of turbomachinery. The paper presents an effective numerical method to predict the static and dynamic performance characteristics of seals at off-center conditions with different rotor whirling frequency. Modifications are introduced for the traditional turbulent bulk flow model to consider the circumferentially varying flow. A trigonometric series expansion method is used to approximate parameters such as pressure and velocity in seals cavity. Numerical simulations show that 8–10 series terms with 5–10 iterations are enough for the solution of this set of nonlinear equations. The resulting nonlinear algebraic equations can be solved rapidly. The analytical results are verified by comparison with the simulated CFD results. Parametric investigations showing the influence of eccentricity and whirling frequency on seals dynamics are also presented. The results show that the trigonometric series expansion based method gives an effective prediction of the static and dynamic characteristics of the eccentric seals.     

Vibratory synchronization transmission of two exciters in a super-resonant vibrating system

In this study, vibratory synchronization transmission (VST) of two exciters is investigated in a super-resonant vibrating system to save energy. First, the frequency capture equation of two exciters (FCETE) is deduced by the average method of small parameters. The criterion of VST being the equivalent effective residual torque of motor with power supply should be smaller or equal to the frequency capture torque of the system by setting the disturbance parameters of angular velocities in FCETE to zero. The stability criterion of synchronous states is derived by complying with the generalized Lyapunov equations. Lastly, experiment and computing simulation on VST are conducted. The VST regime of two exciters is discussed in detail from coupling characteristic, current change, visual picture, phase relation, and direct verification of parameters, respectively by comparison and analyses of corresponding data. Results indicate that the key factor in VST implementation is the torque of frequency capture, which serves as the ‘vehicle’ in transferring energy. Thus, the distance between rotational centre of each exciter and mass centre of the rigid frame should be far enough to enhance the ability of VST and ensure energy saving. The theory, experiment, and computing simulation prove that the theoretical approach used in this study is useful and feasible.     

Dynamic analysis of tapping mode atomic force microscope (AFM) for critical dimension measurement

Transient dynamics of tapping mode atomic force microscope (AFM) for critical dimension measurement are analyzed. A simplified nonlinear model of AFM is presented to describe the forced vibration of the micro cantilever-tip system with consideration of both contact and non-contact transient behavior for critical dimension measurement. The governing motion equations of the AFM cantilever system are derived from the developed model. Based on the established dynamic model, motion state of the AFM cantilever system is calculated utilizing the method of averaging with the form of slow flow equations. Further analytical solutions are obtained to reveal the effects of critical parameters on the system dynamic performance. In addition, features of dynamic response of tapping mode AFM in critical dimension measurement are studied, where the effects of equivalent contact stiffness, quality factor and resonance frequency of cantilever on the system dynamic behavior are investigated. Contact behavior between the tip and sample is also analyzed and the frequency drift in contact phase is further explored. Influence of the interaction between the tip and sample on the subsequent non-contact phase is studied with regard to different parameters. The dependence of the minimum amplitude of tip displacement and maximum phase difference on the equivalent contact stiffness, quality factor and resonance frequency are investigated. This study brings further insights into the dynamic characteristics of tapping mode AFM for critical dimension measurement, and thus provides guidelines for the high fidelity tapping mode AFM scanning.     

RV减速器的动力学模型与固有频率研究

建立ＲＶ减速器的动力学模型并推导运动微分方程,通过求解振动方程得到系统的固有频率,并就针轮齿数对ＲＶ减速器振动的影响等进行了研究,得到对ＲＶ减速器的设计和应用具有指导意义的结论。