挠性转子变刚度阻尼支承系统振动主动控制（二）：次优控制规律

从理论上研究了采用变刚度阻尼支承主动控制转子——轴承系统的振动问题,分析和提出了在振动最优主动控制规律的有效频率范围以外,对转子——轴承系统进行次优振动主动控制的策略思想,及变刚度阻尼支承振动次优主动控制规律。根据此规律,从理论上阐明了采用变刚度阻尼支承,对转子——轴承系统进行过临界转速时的振动主动控制的原理和依据。作为示例,就一个三圆盘双支承的转子系统进行计算机仿真。仿真结果说明了本文分析的正确性及其对采用变刚度阻尼支承系统实现挠性转子振动主动控制的的理论指导意义。     

机床磁悬浮导轨的动力学分析

以主动磁悬浮支承下的机床导轨为分析对象 ,采用磁悬浮支承系统分析理论和方法 ,研究了机床导轨系统的动力学特性。本文根据磁悬浮支承系统特有的刚度、阻尼特性理论和平台振动特点建立了五自由度磁悬浮支承直线导轨平台系统的数学模型 ,并针对正在研制的主动磁悬浮支承直线导轨做了动力学分析     

未知传递函数情况下主动电磁悬浮系统支承特性在线测量

分析了主动电磁悬浮系统支承的等效刚度和阻尼的理论计算方法。从闭环系统的角度出发,提出了一种不依赖于系统传递函数的等效刚度和阻尼的在线测量方法。以PID控制为例进行对比实验,分析了控制参数、激振幅度和激振频率对主动电磁悬浮系统支承等效刚度和阻尼的影响。结果表明,所提出的测量方法能够实时在线地对主动电磁悬浮系统支承的等效刚度和阻尼进行准确识别。     

最优控制规律

研究采用变刚度阻尼支承系统,实现挠性转子振动最优主动控制的一些理论问题。首先研究了在结构受迫振动最优主动控制规律的作用下,变刚度阻尼支承系统的动刚度子矩阵输出响应最优反馈矩阵的关系。由此可以确定转子的变刚度阻尼支承系统的各个动力学参数。然后,进一步分析了采用变刚度阻尼支承系统,实现振动最优主动控制的必要条件和有效频率范围。     

超精密机床的振动混合控制

研究了空气弹簧与作动吕相结合的主被动混合振动控制系统,空气弹簧起低通滤波作用,并支承机机床,主动隔振具有高能滤波特性,电磁作动器的控制电压取决于绝对位移、速度、加速度和相对位移、速度、加速度。电磁作动器的动态性能对振动传递率有明显的影响。实验表明,混合隔振系统对超精密机床的隔振效果明显优于空气弹簧系统。     

天然气压差发电机用主动磁轴承-转子系统支承特性参数分析

以490 kW天然气压差发电机为研究对象,对其高速电动机的主动磁轴承-转子系统进行稳定性分析.首先,根据实际工况给出的转子系统各部分物理参数设计了三维模型;其次,依据主动磁轴承的支承原理、结构参数和控制系统的相关理论得到转子系统的径向支承刚度和轴向支承刚度;最后,运用ANSYS-Workbench对转子系统进行模态分析...     

基于压电液压驱动器发动机主动支承系统的研究

设计和研究一种能用于主动控制的发动机支承系统,该系统由传统的橡胶支承与压电液压驱动器组成.以压电作动器做为系统的驱动源,确定了压电液压驱动器支承的基本结构形式,建立了系统物理模型,并对其进行仿真研究,提出了系统控制策略.     

变支承磁悬浮转子超临界运行仿真研究

针对工业中转子系统在跨越一阶临界转速时,振动幅度过大及失稳的问题,通过对转子系统平稳跨越一阶临界转速方法的归纳和研究,提出了一种基于主动控制下的磁悬浮轴承—转子系统变支承跨越一阶临界转速的方法。首先建立了主动控制下的变支承磁悬浮转子系统数学模型,并分析了两支承转子系统和三支承转子系统跨越一阶临界转速时的响应特性;然后利用ADAMS和Matlab联合仿真了主动控制下的变支承磁悬浮转子系统跨越一阶临界转速时的振动特性。仿真研究结果表明:变支承磁悬浮转子系统在超临界运行时具有良好的减振效果,与传统两支承转子系统相比,其最大振幅减小了52.6%。     

高速转子系统振动控制技术评述

高速转子系统在正常工作过程中必须通过临界转速,此时由于不平衡质量的作用,转子系统会产生共振,导致强烈的振动。降低系统支承刚度以降低临界转速、增大支承阻尼,以减小振幅,这些措施可以抑制系统通过临界转速时的振动幅值和外传力。在振动被动控制技术中,常用弹性支承和挤压油膜阻尼器、金属橡胶减振器、高聚物复合材料减振结构等,降低系统支承刚度,增大支承阻尼,以减小系统振动;在主动控制技术中,通过主动控制挤压油膜阻尼器的参数,改变支承的刚度和阻尼的大小,以控制系统的振动;以及采用形状记忆合金调节器、电磁阻尼器、压电调器等装置,来主动控制系统的振动。目前控制技术仍存在装置结构复杂、性能不稳定等问题,采用粘弹阻尼复合材料与滚动轴承钢外圈复合结构的一体化滚动轴承,足一种有发展前途的研究方向。     

磁力轴承转子系统非线性支承特性的研究

通过对磁力轴承非线性支承力特性的分析,可以看出控制器参数与支承特性之间有非常强的非线性耦合关系。虽然其支承的刚度和阻尼都能够通过改变控制器参数进行调整,但控制器参数的选择受非线性因素的影响较大。当比例增益越大,则在转子平衡点处的线性刚度就越大,能提供的最大支承力也越大,但支承实现正刚度的转子位移区间越小,系统稳定的转子位移区间就越小。通过对主动磁力轴承转子系统非线性支承特性的研究,揭示了控制器结构参数、机械结构参数与支承特性之间的耦合关系。     

主动控制节流气体润滑轴承静动态特性研究

将表面节流与主动控制节流相结合,提出了一种新型的主动控制节流气体润滑轴承,采用工程简化计算与有限元分析相结合,对轴承进行了理论分析,建立了该轴承的理论分析模型,较好地解决了数值计算中多重迭代与快速收敛问题,理论分析和试验研究结果表明,该轴承通过主动控制节流器对轴承压力的反馈控制,轴承静动态性能显著提高。     

主动控制狭缝节流气浮支承结构及承载特性研究

为实现气浮支承承载性能的主动调节,设计一种主动控制狭缝节流气浮支承,可通过调节狭缝节流面积来调节气浮轴承承载力。建立气浮轴承CFD模型,运用动网格技术研究径向狭缝高度、供气压力和气膜厚度对气浮支承承载力的影响。结果表明：通过主动调节狭缝节流面积可以实现承载力的动态调节;增大狭缝节流面积可以增大承载力变化范围,增大供气压力、径向狭缝高度及减小气膜厚度可提高气浮支承静态承载力。所设计主动控制狭缝结构可以实现气浮支承承载性能的动态调节,为今后主动控制气浮支承的应用与发展奠定了理论基础。     

A new 3-DOF Z-tilts micropositioning system using electromagnetic actuators and air bearings

A new 3-DOF Z-tilts (z, pitch, and roll motion) micropositioning system has been developed. It uses electromagnetic actuators and air bearings. An electromagnetic actuator produces an attraction force between the air bearing and the base plate. An air bearing has the role of suspension and guidance, with a clearance of several tens of micrometers in the z-direction. Therefore, this system has design features of guiding 3-DOF XYθ motion without limiting the plane motion and playing the role of a z-directional position actuator. With the control of current, the equilibrium position between magnetic attraction force and air bearing thrust force can be controlled with inherently infinite resolutions. The theoretical background of an electromagnetic actuator is explained. Then, an air bearing is analyzed in the point of z-directional positioning mechanism. The air bearing can be modeled as a second-order system with parameter variation—stiffness and damping vary with respect to the z-directional displacement. Therefore, a simple robust control algorithm is applied to improve the control performance. With the aid of robust control, this system provides 25 nm positioning resolution over the total range of 40 μm along the z-direction and, accordingly, 0.29 μrad resolution over the total range of 460 μrad in pitch and roll motion.     

磁悬浮轴承系统的模型辨识与控制

对某磁悬浮轴承系统进行了理论建模,并进行了试验.由于建模时忽略了功率放大器和位移传感器的影响,磁悬浮轴承系统理论模型与其实际特性有较大差异,磁悬浮轴承系统是一个三阶模型,而非理论模型的二阶模型,基于理论模型设计的控制器难以获得较好的控制性能,建模时需考虑功率放大器和位移传感器的影响.为优化控制性能,采用频域辨识法对实际...     

超精密车床溜板的模糊神经网络主动振动控制研究

提出了溜板的振动主动控制。作为器采用自行研制的主动空气轴承,实现无摩擦接触。控制方法彩和模糊神经网络控制,模糊控制为主控制器,用以逼近实际的复杂时变系统;神经网络控制补偿耦合效应。实验结果表明,基于主动空气轴承地模糊神经网络振动主动控制可以有铲减小溜板振动。     

液体静压支承动态特性分析、实验及其应用

本文在考虑油液及其含气体可压缩的基础上,对液体静压支承的动态特性进行了理论分析,求得静压支承系统动态稳定性的判别公式和动刚度公式。通过试验证明了上述理论的正确性,并总结出对静压支承的设计具有参考价值的理论依据。在生产实践中,运用上述理论解决了静压支承动态不稳定问题,从而提高了支承精度。     

On the modelling of the dynamic characteristics of aerostatic bearing films: From stability analysis to active compensation

Determination of the static characteristics of air bearings constitutes the necessary first phase in a design problem, which determines general feasibility. In order to realize a successful application, a good knowledge and assessment of the dynamic behaviour is needed to complement the previous step. In a conventional, passive bearing application, dynamically stable behaviour should be ensured by overcoming the occurrence of self-excited vibrations; the so-called “pneumatic hammering”. In active bearing applications, on the other hand, the dynamic bearing force, induced by actuation of the gap geometry or supply pressure, provides for a means of enhancing bearing static and dynamic performance, when integrated in a mechatronics system context.This paper presents on the one hand an overview of the methods used to model the dynamic characteristics of aerostatic films, deducing that the method of harmonic perturbation is often sufficient in providing a good estimate of the dynamic stiffness. This is confirmed by comparing theoretical results with dynamic response experiments. On the other hand, the general problem of active dynamic compensation is outlined and an application example is provided to show the high levels of performance achievable by employing this method.     

Active inherent restrictor for air-bearing spindles

An active control method for aerostatic bearings is proposed in this paper. The proposed method employs an active inherent restrictor AIR, (which was invented by the authors) to control pneumatic pressure on the bearing surface. The AIR consists of a piezoelectric actuator with a through hole, one end of which is small enough to function as an orifice when the actuator is embedded in the bearing to be controlled. Nine AIRS are incorporated into the aerostatic radial and thrust bearings of an air bearing spindle. According to the radial and/or thrust displacements of the spindle detected by sensors, a microcomputer changes the length of the piezoelectric actuators for controlling the orifice area of the AIRs and for compensating the displacements. Thus, the stiffness and the rotational accuracy in both radial and thrust directions can be improved without the occurrence of pneumatic hammer. Instead of ordinary passive inherent restrictors, the AIR can be incorporated into most conventional aerostatic bearings. An example of retrofit of the AIR to a commercially available air bearing spindle is also shown.     

Air bearing center cross gap of neutron stress spectrometer sample table support system

A support system is the main load-bearing component of sample table for neutron stress spectrometer, and air bearing is an important element of a support system. The neutron stress spectrometer sample table was introduced, and the scheme for air bearing combination was selected. To study the performance of air bearing center cross gap, finite element models (FEMs) were established based on air motion and Reynolds equations, effects of air supply pressure, and gap parameters on the overturning moment and bearing capacity of air bearing center cross gap were analyzed. Results indicate that the width, depth, and height differences of the marble floor gap played important roles in the performance of the air bearing. When gap width is lesser than 1 mm and gap depth is lower than 0.4 mm, bearing capacity and overturning moment would vary rapidly with the variation of the width and depth. A gap height difference results in the bearing capacity dropping rapidly. The FEM results agree well with experimental results. Further, findings of the study could guide the design of the support system and marble floor.     

基于气流黏性牵引原理的无接触输运建模仿真与试验研究

目前众多行业需要使用无接触的方式输运清洁、易损的产品。介绍了一种完全无接触的气浮输运平台,通过在物体下方产生气膜及可控气流实现牵引输送。建立了间隙内气流简化模型并针对黏性力进行了理论和实验研究,结果表明,气流在平台表面凹槽区和边缘区域内提供牵引力,且在一定流量条件下黏性力随气膜高度增加而降低。提出了一种基于有效驱动单元列数作为被控量的控制方法,设计PID控制器并对物体在一维方向上的输运与定位进行研究,结果验证了理论模型和控制方法的有效性。