共查询到20条相似文献，搜索用时 147 毫秒
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振动值是机组运行的重要参数之一，振动值过大，对机组的结构、强度、寿命和效率都有一定影响，严重时导致转子和轴承的破坏。1．振动原因：引起振动的原因很多，现从内在和外部原因进行分析。 相似文献
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“嗡嗡嗡，嗡嗡嗡……”调成振动的手机在抽屉里动个不停，萨金特皱了皱眉头，拿出来一看．又是那个陌生的号码，今天已经打来两次了。 相似文献
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汽轮机组振动是汽机现场比较普通存在的缺陷,此缺陷严重的危有到机组安全运行。在振动诊断过程中,我们可以通过振动频率和转速进行测定。振动水平与制造、安装、检修和运行等技术水平有关。我们所要测的主要振动（轴承振动）主要有垂直振动、水平和轴向振动． 相似文献
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新乡有“振动之乡”的美称。新乡市的振动机械设备产业规模、产业聚集度、市场占有率和产品研发能力在全国具有重要的地位。其中有一个由少数民族带领的企业．经过25年的发展,由一个名不见经传的手工作坊式的小厂发展了国内振动机械的龙头企业．产品远销印度、土耳其、东南亚、欧美和中东国家。 相似文献
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林文贤 《中国科学院研究生院学报》2012,29(5):594-598
获得一类具有连续偏差变元的非线性二阶阻尼泛函微分方程所有解振动的若干充分条件.所得结果包含和推广了已有文献中的相关结论,并给出2个应用实例. 相似文献
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本文报导了无金属离子或其络合离子存在的对氨基苯磺酸—KB-rO_3—H_2SO_4体系的化学振荡现象的研究结果,考察了不同反应物浓度对振荡诱导期、周期和波形的影响,找出了一些特殊规律。 相似文献
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Capillary wave phenomena are challenging to study, especially for microfluidics where the wavelengths are short, the frequencies are high, and the frequency distribution is rarely confined to a narrow range, let alone a single frequency. Those that have been studying Faraday capillary waves generated by vertical oscillation have chosen to work at larger scales and at low frequencies as a solution to this problem, trading simplicity in measurement for issues with gravity, boundary conditions, and the fidelity of the subharmonic capillary wave motion. Laser Doppler vibrometry using a Mach–Zehnder interferometer is an attractive alternative: The interface’s motion can be characterized at frequencies up to 40 MHz and displacements of as little as a few tens of picometers. 相似文献
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I.M. Boiko N.V. Kuznetsov R.N. Mokaev E.D. Akimova 《Journal of The Franklin Institute》2021,358(1):363-383
Asymmetric self-excited periodic motions or periodic solutions which are produced by relay feedback systems that have symmetric characteristics are studied in the paper. Two different mechanisms of producing an asymmetric oscillation by a system with symmetric properties are noted and analyzed by the locus of a perturbed relay system (LPRS) method. Bifurcation between the ability to excite symmetric and asymmetric oscillation with variation of system parameters is analyzed. An algorithm of finding asymmetric solutions is proposed. 相似文献
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Chung-Chieh Fang 《Journal of The Franklin Institute》2013,350(10):3293-3312
By transforming an exact stability condition, a new Nyquist-like plot is proposed to predict occurrences of three typical instabilities in DC–DC converters. The three instabilities are saddle-node bifurcation (coexistence of multiple solutions), period-doubling bifurcation (subharmonic oscillation), and Neimark bifurcation (quasi-periodic oscillation). In a single plot, it accurately predicts whether an instability occurs and what type the instability is. The plot is equivalent to the Nyquist plot, and it is a useful design tool to avoid these instabilities. Four examples are used to illustrate the accuracy of this new plot to predict instabilities in the buck or boost converter with fixed or variable switching frequency. 相似文献
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Transient delayed feedback control is proposed by applying the transient control technique to the original delayed feedback control, with the aim of enlarging the stable region of the stabilized periodic oscillation, where the stable region is a subset of the parameter space of feedback gains for which the periodic oscillation is stabilized. The control signal is activated when the system is in a certain subset (the controlling area) of the state space, and inactivated otherwise, which is different from the standard control signal of the original delayed feedback control. The specific control performances of the transient delayed feedback control are investigated through case studies. The relationship between the stable region of the stabilized periodic oscillation and the controlling area is obtained by calculating the maximum Lyapunov exponent, which is a function of the feedback gain. It is shown that the stable region varies non-smoothly with the change of the controlling area. When the controlling area is properly chosen, the stable region with transient delayed feedback control is much larger than the stable region with original delayed feedback control. 相似文献
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Mohamed Hamdy Raafat Shalaby Mostafa Sallam 《Journal of The Franklin Institute》2018,355(14):6286-6299
This paper presents the design of a hybrid partial feedback linearization and deadbeat control scheme for a nonlinear gantry crane with friction to control its position and sway angle. The partial feedback linearization is used to linearize the nonlinear model and to stabilize its internal dynamics. In many crane applications, it's necessary to accelerate the system response. As a result, this will cause oscillation in the position as well as the sway angle. So, the deadbeat controller is added to get the desirable accelerated response without any oscillation or adverse effects on the internal dynamics stability. By using Lyapunov stability method, the proposed scheme is proved to be globally stable, with converging tracking errors to the desired performance. The simulation results are accomplished to evaluate the effectiveness of the proposed scheme and to demonstrate its reliability to control crane systems with comparative results. 相似文献
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Farid Tajaddodianfar 《Journal of The Franklin Institute》2018,355(14):6435-6453
This paper proposes anti-oscillation and chaos control scheme for the fractional-order brushless DC motor system wherein there exist unknown dynamics, immeasurable states and chaotic oscillation. Aimed at immeasurable states, the high-gain observers with fast convergence are presented to obtain the information of system states. To compensate uncertainties existing in the dynamic system, a finite-time echo state network with a weight is proposed to approximate uncertain dynamics while its weight is tuned by a fractional-order adaptive law online. Meanwhile a fractional-order filter is introduced to deal with the repeated derivative of the backstepping. Based on the fractional-order Lyapunov stability criterion, the anti-oscillation and chaos control scheme integrated with a high-gain observer, an echo state network and a filter are proposed by using recursive steps of backstepping. The proposed scheme guarantees the boundedness of all signals of the closed-loop system in the sense of global asymptotic stability, and also suppresses chaotic oscillation. Finally, the effectiveness of our scheme is demonstrated by simulation results. 相似文献
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Xinyu Lu Saurin Patel Meng Zhang Sang Woo Joo Shizhi Qian Amod Ogale Xiangchun Xuan 《Biomicrofluidics》2014,8(2)
Electrophoresis plays an important role in many applications, which, however, has so far been extensively studied in Newtonian fluids only. This work presents the first experimental investigation of particle electrophoresis in viscoelastic polyethylene oxide (PEO) solutions through a microchannel constriction under pure DC electric fields. An oscillatory particle motion is observed in the constriction region, which is distinctly different from the particle behavior in a polymer-free Newtonian fluid. This stream-wise particle oscillation continues until a sufficient number of particles form a chain to pass through the constriction completely. It is speculated that such an unexpected particle oscillating phenomenon is a consequence of the competition between electrokinetic force and viscoelastic force induced in the constriction. The electric field magnitude, particle size, and PEO concentration are all found to positively affect this viscoelasticity-related particle oscillation due to their respective influences on the two forces. 相似文献