旋转配流激振控制阀开槽参数的交互作用试验研究

提出一种旋转配流激振控制阀,为研究阀芯开槽参数交互作用对激振控制阀输出压力的影响,基于Fluent多参考系滑移网格方法,对激振控制阀的输出压力进行仿真,利用试验测定方法对仿真结果进行验证;采用二次回归正交试验法、中心复合试验法,建立开槽参数与输出压力的显著不失拟回归模型,通过方差分析得到开槽参数影响输出压力的显著性差异,获得开槽参数交互作用的响应曲面,讨论开槽参数交互作用对输出压力的影响趋势。研究结果表明:试验空间内,当开槽长度提高4 mm、开槽宽度提高2 mm、开槽深度提高4 mm时,激振控制阀输出压力分别增大8.3%、25.1%、22.3%,开槽参数对压力的影响程度由大到小依次为开槽宽度、开槽深度、开槽长度,开槽宽度与开槽长度、深度的交互作用对激振控制阀输出压力的影响最显著。

电磁动态塑化挤出机激振控制器的设计

本文为塑料电磁动态塑化挤出机设计出一种新型电流滞环跟踪控制激振控制系统 ,文中介绍了系统控制原理以及具体的设计方法。系统实验及其在新型塑料电磁动态塑化挤出机的实际应用结果令人满意。

液压激振技术的研究进展

分类阐述了各种液压激振技术的原理、性能优缺点及应用情况,介绍了典型液压激振装备的最新发展、系统结构与性能指标,简要介绍了国内外液压激振控制技术最新成果。指出多轴、高频液压激振技术是当今的研究热点,其中采用2D激振阀的激振方法是大幅度提高液压激振频率的新技术。

单直管科氏质量流量计──壳体振动的动力补偿减振

消除壳体振动的影响是单直管科氏质量流量计的关键技术。采用蚀立激振的补偿管，在一定的激振控制条件下，可以平衡测量管对壳体的作用力，从而达到降低壳体振动的目的。本文从理论上分析了补偿管的设计要求及对补偿管的激振控制条件，并用实验进行了验证。

Flow Control with Intermittent Disturbance for the Laminar Separation Bubble on a NACA633-421 Airfoil

This study investigates the aerodynamic performance of the NACA 633-421 airfoil and the effectiveness and feasibility of intermittent disturbance flow control methods on laminar separation bubbles(LSBs).It is found that the average velocity and influence range of the synthetic jet actuator increase with the increasing of driving frequency and driving amplitude.LSB occurs at Re=1.0×10^(5),and ruptures atα=6°.But with intermittent disturbance control,the stall angle of attack(AoA)increases while significantly reducing drag.Research shows that although certain disturbance cannot fully recover from LSB stall,decreasing driving amplitude partially restores wing aerodynamic performance,more effectively than increasing driving amplitude.

Saturation influence of control voltage on maglev stationary self-excited vibration

This work addresses the saturation influence of control voltage on the occurring of self-excited vibration of maglev vehicle-bridge interaction system, which greatly degrades the stability of the levitation control, decreases the ride comfort, and restricts the cost of the whole system. Firstly, the interaction model of vehicle-bridge system is developed. Based on the interaction model, the relationship between the control voltage and vibration frequency is solved. Then, the variation of the effective direct component and fundamental harmonic are discussed. Furthermore, from the perspective of energy transmission between the levitation system and bridge, the principle underlying the self-excited vibration is explored, and the influence on the stability is discussed. Finally, in terms of the variation of the characteristic roots, the influence is analyzed further and some conclusions are obtained. This study provides a theoretical guidance for mastering the self-excited vibration problems.

Synergetic Analysis and Possible Control of Vortex-Induced Vibrations in a Fluid-Conveying Steel Catenary Riser

This work aimed to demonstrate possibilities for both active and passive control of the vortex-induced vibration and fatigue life of steel catenary risers via an analysis of the self-organization and evolution of the structural vibration based on synergetic theory. An analysis of the complex interrelated and synergistic relationship between the order parameter and the fast variable was performed, and the master equation of the nodal displacements was established as the order parameter for the evolution of the riser's structural vibration. Passive control methods include modifying the structure's elastic modulus, the internal fluid velocity, the top tension and the structural damping ratio, while an active control involves adjusting the external flow rate. Optimized parameters were obtained by analyzing the non-steady state solution of the master equation. The results show that the fatigue life greatly increases as the riser's elastic modulus decreases. In contrast, the fatigue life decreases with an increase of the internal fluid velocity. With an increase of the top tension, the vibration amplitudes and the number of modes may decrease, resulting in fewer bending stress cycles and a longer fatigue life. Furthermore, the structural damping ratio should be as large as possible. Finally, an active and passive control of the riser structure's response to vortex-induced vibration and its fatigue life can be achieved by carefully modifying the parameters mentioned above. The results may provide a theoretical framework for engineering practice concerning the design and control of steel catenary riser structures which are affected by vortex-induced vibration.

地面颤振模拟试验技术研究进展

颤振问题是飞行器在飞行过程中应竭力避免,且可能导致灾难性后果的一种气动弹性动力学稳定性问题。作为一种新兴的颤振试验研究方法,地面颤振模拟试验是指直接采用飞行器原型结构或模型结构作为试验对象,利用激振器等气动力模拟加载装置模拟分布的气动力载荷,在地面获得飞行器结构颤振特性的一种半物理仿真试验技术。本文从非定常气动力降阶实时重构、非定常气动力模拟加载以及地面颤振模拟试验的实施3个方面,分析了地面颤振模拟试验技术的研究现状,最后展望了地面颤振模拟试验技术未来的发展方向。

Self-excited vibration problems of maglev vehicle-bridge interaction system

The self-excited vibration problems of maglev vehicle-bridge interaction system were addressed, which greatly degrades the stability of the levitation control, decreases the ride comfort, and restricts the cost of the whole system. Firstly, the coupled model containing the quintessential parts was built, and the mechanism of self-excited vibration was explained in terms of energy transmission from levitation system to bridge. Then, the influences of the parameters of the widely used integral-type proportion and derivation(PD) controller and the delay of signals on the stability of the interaction system were analyzed. The result shows that the integral-type PD control is a nonoptimal approach to solve the self-excited vibration completely. Furthermore, the differential-type PD controller can guarantee the passivity of levitation system at full band. However, the differentiation of levitation gap should be filtered by a low-pass filter due to noise of gap differentiation. The analysis indicates that a well tuned low-pass filter can still keep the coupled system stable.

Accurate method for determining vibration temperatures, and gain limitation in pulse RF-discharge CO_2 laser

An accurate method of determining gain coefficients of pulse RF-discharge CO2 laser is developed, which involves the use of both the regular 00o1 and 00o2 laser transitions as probes of CO2 laser. The results indicate that the majority of transitions in discharge have anomalous gain coefficients under RF-discharge condition. This fact has not been generally recognized and the neglect of overlapping transitions can lead to errors in determining rotational temperature.

A statistically refined Bouc-Wen model for the identification of structures under tri-directional seismic excitations

This paper presents a statistically refined Bouc-Wen model of tri-axial interactions for the identification of structural systems under tri-directional seismic excitations. Through limited vibration measurements in the National Center for Research on Earthquake Engineering in Taiwan conducting model-based experiments, the 3-D Bouc-Wen model has been statistically and repetitively refined using the 95% confidence interval of the estimated structural parameters to determine their statistical significance in a multiple regression setting. When the parameters＇ confidence interval covers the ＂null＂ value, it is statistically sustainable to truncate such parameters. The remaining parameters will repetitively undergo such parameter sifting process for model refinement until all the parameters＇ statistical significance cannot be further improved. The effectiveness of the refined model has been shown considering the effects of sampling errors, of coupled restoring forces in tri-directions, and of the under-over-parameterization of structural systems. Sifted and estimated parameters such as the stiffness, and its corresponding natural frequency, resulting from the identification methodology developed in this study are carefully observed for system vibration control.

Suppression of vortex-induced vibration of a circular cylinder by Lorentz force

The electro-magnetic control of vortex-induced vibration (VIV) of a circular cylinder is investigated numerically in the exponential-polar coordinates attached on the moving cylinder for Re=150 in the paper. Compared with the fixed cylinder, the vibration of cylinder leads to the shift of stagnation point, the shear layer strength and the inertial force, which affects the hydrodynamic forces on the cylinder. The effects of the instantaneous wake geometries and the corresponding cylinder motion on the hydrodynamic forces for one entire period of vortex shed are discussed in the drag-lift phase diagram. The Lorentz force for controlling the vibration cylinder is classified into the field Lorentz force and the wall Lorentz force. The field Lorentz force decreases the lift oscillation, and in turn, suppresses the VIV, whereas the wall Lorentz force has no effect on the lift.

Finite element simulation of wireless structural vibration control with photostrictive actuators

A recently emerging family of smart materials,photostrictive materials,exhibit large photostriction under uniform illumination of high-energy light.This photostriction mechanism arises from a superposition phenomenon of photovoltaic and converse piezoelectric effects.A photostrictive type of opto-electromechanical actuator activated by high-energy lights can introduce actuation and control effects without hard-wired connections.The control light intensity applied to the actuator is proportional to the transverse velocity at a positioned point,which is measured by a laser vibrometer.In this paper,photostrictive films are numerically analyzed to evaluate their use as wireless actuators for future remote vibration control of flexible structures.A novel opto-electromechanical solid shell finite element formulation is developed for accurate analysis of the multiple physics effects of photovoltaic,pyroelectric and thermal expansion of photostrictive materials.Available experimental data and analytical solutions have been used to verify the present finite element results.The simulation in this study demonstrates that the present formulation is very reliable,accurate and also computationally efficient and that the use of photostrictive actuators can provide good controllability of structural vibration.

Robust control of exciting force for vibration control system with multi-exciters

Due to the dynamical character of electromagnetic exciter and the coupling between structure and exciter(s),the actual output force acting on the structure is usually not equal to the exact value that is supposed to be,especially when multi-exciters are used as actuators to precisely actuate large flexible structure.It is necessary to consider these effects to ensure the force generated by each exciter is the same as required.In this paper,a robust control method is proposed for the multi-input and multi-output(MIMO)structural vibration control system to trace the target actuating force of each exciter.A special signal is designed and put into the coupled mul-ti-exciter-structure system,and the input and output signals of the system are used to build a dynamic model involving both the dynamical characters of the exciters and the structure using the subspace identification method.Considering the uncertainty factors of the multi-exciter/structure system,an H-infinity robust controller is designed to decouple the coupling between structure and exciters based on the identified system model.A MIMO vibration control system combined with a flexible plate and three electromagnetic exciters is adopted to demonstrate the proposed method,both numerical simulation and model experiments showing that the output force of each exciter can trace its target force accurately within the requested frequency band.

A switchable and tunable ytterbium-doped fiber ring laser with a Sagnac loop mirror

A switchable and tunable ytterbium-doped fiber ring laser(YDFL) is reported and demonstrated. Employing a Sagnac loop mirror fabricated by an 85-cm-long polarization-maintaining fiber(PMF), the proposed YDFL can operate with stable dual-wavelength lasing or tunable single-wavelength lasing around 1 064 nm. Both stable dual-wavelength lasing and tunable single-wavelength lasing are achieved by adjusting a polarization controller in the Sagnac loop mirror. The experimental results show that the output of the proposed fiber laser with two different operation modes is rather stable at room temperature.

Active control of vortex-induced vibration of a circular cylinder by using the oscillatory plate immersed in the cylinder wake at low Reynolds number

As a typical fluid-solid interaction problem,vortex-induced vibration(VIV)is common in engineering,so it is vital to study its control mechanism.Numerical simulations of the active control of VIV of a cylinder are carried out in this study.The splitter plate with harmonic oscillation is used as the control device for the dynamic response of the cylinder.The displacement response,lift and drag coefficient,vibration frequency of the cylinder,energy efficiency of control strategy,and characteristics of the flow field are widely analyzed to reveal the physical mechanism of the control system.The results show that the displacement response of the cylinder can be limited in a small range by the control without feedback in most cases except for high reduced velocity.In addition,the control strategy can be changed through feedback control to keep much superior control effects at the high reduced velocity.The oscillatory splitter plate delays the vortex shedding of shear layers generated on the cylinder,the wake vortices with opposite sense of rotation are paralleled with the streamwise direction,and crosswise distances of them are reduced.Thus,the lift on the cylinder is greatly decreased due to the modification of the flow pattern induced by the oscillatory splitter plate.

First-passage failure of harmonically and stochastically excited Duffing oscillator with delayed feedback control

The first-passage failure of Duffing oscillator with the delayed feedback control under the combined harmonic and white-noise excitations is investigated. First, the time-delayed feedback control force is expressed approximately in terms of the system state variables without time delay. Then, the averaged It? stochastic differential equations for the system are derived by using the stochastic averaging method. A backward Kolmogorov equation governing the conditional reliability function and a set of generalized Pontryagin equations governing the conditional moments of the first-passage time are established. Finally, the conditional reliability function, the conditional probability density and moments of the first-passage time are obtained by solving the backward Kolmogorov equation and generalized Pontryagin equations with suitable initial and boundary conditions. The effects of time delay in feedback control force on the conditional reliability function, conditional probability density and moments of the first-passage time are analyzed. The validity of the proposed method is confirmed by digital simulation.