Dynamic Response of a Servovalve Controlled Hydraulic Motor Driven Centrifugal Pump

1996 ◽  
Vol 118 (2) ◽  
pp. 253-258 ◽  
Author(s):  
Liangji Xu ◽  
John K. Schueller ◽  
Roy Harrell
Keyword(s):  
Centrifugal Pump ◽  
Natural Frequency ◽  
Damping Ratio ◽  
Experimental System ◽  
Estimation Procedure ◽  
Dynamic Responses ◽  
Physical Parameters ◽  
Model Estimation ◽  
Hydraulic Motor ◽  
Output Flow

A servovalve controlled hydraulic motor driven centrifugal pump was dynamically modelled using linearized analysis. The expressions for the system gain, natural frequency, and damping ratio in terms of component physical parameters were derived. An optimization model estimation procedure was developed and applied to the step responses of such a system constructed of common commercial components. The experimental system had a 4.2 Hz natural frequency and 1.2 damping ratio. The research indicates that the dynamic responses of a servovalve controlled centrifugal pump can be appropriately modelled for applications in industry and agriculture where the output flow rate needs to be dynamically changed.

An experimental study of static and dynamic responses of prestressed concrete box irder bridges

1990 ◽  
Vol 17 (3) ◽  
pp. 481-493 ◽  
Author(s):  
M. Saeed Mirza ◽  
O. Ferdjani ◽  
A. Hadj-Arab ◽  
K. Joucdar ◽  
A. Khaled ◽  
...  
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Prestressed Concrete ◽  
Damping Ratio ◽  
Physical Models ◽  
Dynamic Responses ◽  
Box Girder Bridges ◽  
Box Girder ◽  
Girder Bridges ◽  
Bridge Models

Experimental data from static and dynamic tests on [Formula: see text] direct models of simply supported, one- and two-cell, box girder bridges are presented. Variation of flexural and torsional stiffnesses and dynamic characteristics, such as the natural frequency of vibrations and damping ratios of the bridge models at different levels of cracking damage, are examined; in turn, these dynamic characteristics can be used to estimate the cracking damage in the bridge. The physical model proved to be an adequate tool for the study of static and dynamic responses of box girder bridges at all load levels. Key words: box girder bridges, direct physical models, damping ratio, flexural and torsional stiffnesses, level of cracking damage, load–deformation response, load distribution characteristics, longitudinal and transverse strains, natural frequency of vibrations, simulated OHBDC truck.

scholarly journals Fluid-Induced Vibration Elimination of a Rotor/Seal System with the Dynamic Vibration Absorber

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Qi Xu ◽  
Junkai Niu ◽  
Hongliang Yao ◽  
Lichao Zhao ◽  
Bangchun Wen
Keyword(s):  
Natural Frequency ◽  
Nonlinear Differential Equations ◽  
Damping Ratio ◽  
Force Model ◽  
Vibration Absorbers ◽  
Dynamic Vibration Absorber ◽  
Major Purpose ◽  
Rotating Speed ◽  
Dynamic Vibration ◽  
Nonlinear Responses

The dynamic vibration absorbers have been applied to attenuate the rotor unbalance and torsional vibrations. The major purpose of this paper is to research the elimination of the fluid-induced vibration in the rotor/seal system using the absorber. The simplified rotor model with the absorber is established, and the Muszynska fluid force model is employed for the nonlinear seal force. The numerical method is used for the solutions of the nonlinear differential equations. The nonlinear responses of the rotor/seal system without and with the absorber are obtained, and then the rotating speed ranges by which the fluid-induced instability can be eliminated completely and partially are presented, respectively. The absorber parameters ranges by which the instability vibration can be eliminated completely and partially are obtained. The results show that the natural frequency vibration due to the fluid-induced instability in the rotor/seal system can be eliminated efficiently using the absorber. The appropriate natural frequency and damping ratio of the absorber can extend the complete elimination region of the instability vibration and postpone the occurrence of the instability vibration.

scholarly journals Influence of Structure on the Aseismic Stability and Dynamic Responses of Liquefiable Soil

2021 ◽  
Author(s):  
Pengfei Dou ◽  
Chengshun Xu ◽  
Xiuli Du ◽  
Su Chen
Keyword(s):  
Earthquake Engineering ◽  
Damping Ratio ◽  
Free Field ◽  
Shaking Table ◽  
Dynamic Responses ◽  
Seismic Stability ◽  
Geotechnical Earthquake Engineering ◽  
Liquefiable Soil ◽  
Porewater Pressure ◽  
Lateral Displacements

Abstract In previous major earthquakes, the damage and collapse of structures located in liquefied field which caused by site failure a common occurrence, and the problem of evaluation and disscusion on site liquefaction and the seismic stability is still a key topic in geotechnical earthquake engineering. To study the influence of the presence of structure on the seismic stability of liquefiable sites, a series of shaking table tests on liquefiable free field and non-free field with the same soil sample was carried out. It can be summarized from experimental results as following. The natural frequency of non-free field is larger and the damping ratio is smaller than that of free field. For the weak seismic loading condition, the dynamic response of sites show similar rules and trend. For the strong ground motion condition, soils in both experiments all liquefied obviously and the depth of liquefaction soil in the free field is significantly greater than that in the non-free field, besides, porewater pressure in the non-free field accumulated relately slow and the dissapited quikly from analysis of porewater pressure ratios(PPRs) in both experiments. The amplitudes of lateral displacements and acceleration of soil in the non-free field is obviously smaller than that in the free field caused by the effect of presence of the structure. In a word, the presence of structures will lead to the increase of site stiffness, site more difficult to liquefy, and the seismic stability of the non-free site is higher than that of the free site due to soil-structure interaction.

Enhancement of vibration characteristics in filament wound FRP composite shafts using nitinol wires

2018 ◽  
Vol 47 (5) ◽  
pp. 377-385 ◽  
Author(s):  
Kannan Murugesan ◽  
Kalaichelvan K. ◽  
M.P. Jenarthanan ◽  
Sornakumar T.
Keyword(s):  
Natural Frequency ◽  
Damping Ratio ◽  
Filament Winding ◽  
Fiber Reinforced ◽  
Content Type ◽  
Fiber Reinforced Plastic ◽  
Damping Characteristics ◽  
Filament Wound ◽  
Reinforced Plastic ◽  
Hollow Shafts

Purpose The purpose of this paper is to investigate the use of embedded Shape Memory Alloy (SMA) nitinol wire for the enhancement of vibration and damping characteristics of filament-wound fiber-reinforced plastic composite hollow shafts. Design/methodology/approach The plain Glass Fiber-Reinforced Plastic (GFRP) and plain Carbon Fiber-Reinforced Plastic (CFRP) hollow shafts were manufactured by filament winding technique. Experimental modal analysis was conducted for plain hollow shafts of C1045 steel, GFRP and CFRP by subjecting them to flexural vibrations as per ASTM standard C747, with both ends clamped (C-C) end condition to investigate their vibration and damping behavior in terms of first natural frequency, damping time and damping ratio. Nitinol wires pre-stressed at various pre-strains (2, 4 and 6 per cent) were embedded with CFRP hollow shafts following same manufacturing technique, and similar experimental modal analysis was carried out by activating nitinol wires. The first natural frequencies of all the shaft materials were also predicted theoretically and compared with experimental measurements. Findings Among the three materials C1045 steel, plain GFRP and plain CFRP, the vibration and damping behavior were found to be the best for plain CFRP. Hence, CFRP shafts were considered for further improvement by embedding nitinol wires at pre-stressed condition. For CFRP shafts embedded with nitinol wires, the damping time decreased; and damping ratio and first natural frequency increased with increase in percentage of pre-strain. In comparison with plain CFRP, 7 per cent increase in first natural frequency and 100 per cent increase in damping ratio were observed for nitinol embedded CFRP shafts with 6 per cent pre-strain. Theoretical predictions of the first natural frequencies agree well with the experimental results for all the shaft materials. Originality/value The effect of nitinol on vibration and damping characteristics of filament wound hollow CFRP composite shafts with different pre-strains has not been studied extensively by the previous researchers. This paper addresses the effect of embedded nitinol wires pre-stressed at three varied pre-strains, that is, 2, 4 and 6 per cent on the vibration and damping characteristics of composite hollow CFRP shafts manufactured by filament winding technique.

Dynamic Vibration Absorber for a Ropeway Carrier

1997 ◽  
Author(s):  
Hiroshi Matsuhisa ◽  
Osamu Nishihara
Keyword(s):  
Natural Frequency ◽  
Damping Ratio ◽  
Vibration Absorber ◽  
Moving Mass ◽  
Dynamic Vibration Absorber ◽  
Damping Effect ◽  
The World ◽  
Dynamic Absorber ◽  
First Time ◽  
Suspended Bridge

Abstract Ropeways such as gondola lifts have attracted increasing interest as a means of transportation in cities. However, swing of ropeway carriers is easily caused by wind, and usually a ropeway cannot operate if the wind velocity exceeds about 15m/s. The study of how to reduce the wind-induced swing of ropeway carriers has attracted many researchers. It had been said that it was impossible to reduce the vibration of pendulum type structures such as ropeway carriers by a dynamic absorber. But in 1993, Matsuhisa showed that the swing of carrier can be reduced by a dynamic absorber if it is located far above or below from the center of oscillation. Based on this finding, a dynamic absorber composed of a moving mass on an arc-shaped track was designed for practical use, and it was installed in chairlift-type carriers and gondola type carriers in snow skiing sites in Japan in 1995 for the first time in the world. It has been shown that a dynamic absorber with the weight of one tenth of the carrier can reduce the swing to half. The liquid dynamic absorber was also investigated. It has the same damping effect as the conventional solid absorber. It is easy to adjust the natural frequency and the damping ratio, and the structure is simple. Therefore, it will be applied for not only ropeway carriers but also ships and rope suspended bridge and others.

scholarly journals Multi-Physical Design and Resonant Controller Based Trajectory Tracking of the Electromagnetically Driven Fast Tool Servo

Actuators ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 28
Author(s):  
Imran Hussain ◽  
Wei Xia ◽  
Dongpo Zhao ◽  
Peng Huang ◽  
Zhiwei Zhu
Keyword(s):  
Natural Frequency ◽  
Trajectory Tracking ◽  
Voice Coil Motor ◽  
Diamond Turning ◽  
Analytical Models ◽  
Physical Parameters ◽  
Fast Tool Servo ◽  
Element Analysis ◽  
Loop Control ◽  
Resonant Controller

In this paper, a voice coil motor (VCM) actuated fast tool servo (FTS) system is developed for diamond turning. To guide motions of the VCM actuator, a crossed double parallelogram flexure mechanism is selected featuring totally symmetric structure with high lateral stiffness. To facilitate the determination of the multi-physical parameters, analytical models of both electromagnetic and mechanical systems are developed. The designed FTS with balanced stroke and natural frequency is then verified through the finite element analysis. Finally, the prototype of the VCM actuated FTS is fabricated and experimentally demonstrated to achieve a stroke of ±59.02 μm and a first natural frequency of 253 Hz. By constructing a closed-loop control using proportional–integral–derivative (PID) controller with the internal-model based resonant controller, the error for tracking a harmonic trajectory with ±10 μm amplitude and 120 Hz frequency is obtained to be ±0.2 μm, demonstrating the capability of the FTS for high accuracy trajectory tracking.

Recent progress in NMR microscopy towards cellular imaging

1990 ◽  
Vol 333 (1632) ◽  
pp. 469-475 ◽  
Keyword(s):  
Molecular Diffusion ◽  
Signal To Noise Ratio ◽  
Pulse Sequences ◽  
Cell Lineage ◽  
Experimental System ◽  
Cellular Imaging ◽  
Physical Parameters ◽  
Nmr Microscopy ◽  
Resolution Limits ◽  
Finite Line

Recent advances in NMR microscopy based on fundamental physical parameters and experimental factors are discussed. We consider fundamental resolution limits due to molecular diffusion and the experimental system bandwidth, as well as practical resolution limits arising from poor signal-to-noise ratio due to small imaging voxel size and finite line broadening due to signal attenuation brought about by diffusion. Several microscopic imaging pulse sequences are presented and applied to elucidating cellular imaging problems such as the cell lineage patterns in Xenopus laevis embryos. Experimental results obtained with 7.0 T NMR microscopy system are presented.

The Optimization of Thermocouple Galvanometer System Dynamics When Measuring Temperature Transients

1973 ◽  
Vol 6 (9) ◽  
pp. 384-388
Author(s):  
W. H. McKenzie ◽  
A. H. Richards
Keyword(s):  
System Dynamics ◽  
Natural Frequency ◽  
Time Constant ◽  
Exponential Type ◽  
Natural Frequencies ◽  
Low Voltage ◽  
Damping Ratio ◽  
Dynamic Performance ◽  
Ultra Violet ◽  
Dimensional Parameter

When using thermocouples directly connected to ultra-violet galvanometers for recording temperature transients, the low-voltage outputs necessitate the use of galvanometers with low natural frequencies. This puts a limitation on the overall dynamic performance. In a particular application, the user has to select the damping resistor for the galvanometer and the work describes how this is done so that the system is optimised for minimum integrated errors during a transient. The transient considered was of an exponential type which occurs frequently in practice and it is shown that the correct damping ratio and hence damping resistor for the galvanometer depends upon the non-dimensional parameter defined by the product of the natural frequency of the galvanometer and the time constant of the exponential. The results show that the usual value of damping ratio of 0·64 based on minimum sinusoidal distortion has to be modified for best dynamic performance. However, if the non-dimensional parameter is sufficiently large, higher values of damping can be used, which produce a large trace with acceptably small errors.

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