scholarly journals APPLICABILITY OF NATURAL FREQUENCY MEASUREMENT AS A DIAGNOSTIC METHOD OF INVISIBLE PORTION FOR FISHING PORT FACILITIES

2018 ◽  
Vol 74 (2) ◽  
pp. I_103-I_108
Author(s):  
Takayasu FUJITA ◽  
Masaki SAITO ◽  
Atsushi MIKAMI ◽  
Tetsuro KASAI ◽  
Masahiro OKUNO ◽  
...  
Keyword(s):  
Natural Frequency ◽  
Diagnostic Method ◽  
Frequency Measurement ◽  
Port Facilities

An Optimal Sensitivity-Enhancing Feedback Control Approach via Eigenstructure Assignment for Structural Damage Identification

2007 ◽  
Vol 129 (6) ◽  
pp. 771-783 ◽  
Author(s):  
L. J. Jiang ◽  
J. Tang ◽  
K. W. Wang
Keyword(s):  
Feedback Control ◽  
Frequency Shift ◽  
Natural Frequency ◽  
Structural Damage ◽  
Closed Loop ◽  
Damage Identification ◽  
Frequency Measurement ◽  
Sensitivity Enhancement ◽  
Stiffness Reduction ◽  
Structural Damage Identification

The concept of using sensitivity-enhancing feedback control to improve the performance of frequency-shift-based structural damage identification has been recently explored. In previous studies, however, the feedback controller is designed to alter only the closed-loop eigenvalues, and the effect of closed-loop eigenvectors on the sensitivity enhancement performance has not been considered. In this research, it is shown that the sensitivity of the natural frequency shift to the damage in a multi-degree-of-freedom structure can be significantly influenced by the placement of both the eigenvalues and the eigenvectors. A constrained optimization problem is formulated to find the optimal assignment of both the closed-loop eigenvalues and eigenvectors, and then an optimal sensitivity-enhancing control is designed to achieve the desired closed-loop eigenstructure. Another advantage of this scheme is that the dataset of frequency measurement for damage identification can be enlarged by utilizing a series of closed-loop controls, which can be realized by activating different combinations of actuators in the system. Therefore, by using this proposed idea of multiple sensitivity-enhancing feedback controls, we can simultaneously address the two major limitations of frequency-shift-based damage identification: the low sensitivity of frequency shift to damage effects and the deficiency of frequency measurement data. A series of case studies are performed. It is demonstrated that the sensitivity of natural frequency shift to stiffness reduction can be significantly enhanced by using the designed sensitivity-enhancing feedback control, where the optimal placement of closed-loop eigenvectors plays a very important role. It is further verified that such sensitivity enhancement can directly benefit the damage identification accuracy and robustness.

Structure Damage Diagnostic Method of High-Flow Control Valve Stem

2015 ◽  
Vol 667 ◽  
pp. 408-412
Author(s):  
Fang Cao ◽  
Rong Jian Kang
Keyword(s):  
Flow Control ◽  
Natural Frequency ◽  
Diagnostic Method ◽  
Control Valve ◽  
High Flow ◽  
Working Environment ◽  
Flow Control Valve ◽  
Analysis Model ◽  
Structure Damage ◽  
Valve Stem

According to the real structure and work condition of a high-flow mixed gas control valve used in recycling generating electricity project, a modal analysis model based on fluid-structure coupling system of control valve is set up. The natural frequency and mode of valve plug and stem is obtained. The structure damage diagnostic method of high-flow valve stem is put forward. According to the change of natural frequency of the valve stem to judge appearance of fracture cracks is explored. According to the amount by which the variation of natural frequency to determine the size of crack is discussed. It is the preliminary diagnosis to the damage of a high-Flow control valve stem in the special working environment, to avoid the gas leaks, the failure of valve action, adjust or commutation, etc.

Diagnosing Coupled Lateral-Torsional Vibrations in Turbomachinery

2008 ◽  
Author(s):  
Vinayaka N. Rajagopalan ◽  
John M. Vance
Keyword(s):  
Mathematical Model ◽  
Natural Frequency ◽  
Real World ◽  
Diagnostic Method ◽  
Natural Frequencies ◽  
The Other ◽  
Torsional Vibrations ◽  
Test Rig ◽  
Objective Being ◽  
Heavy Damage

Rotordynamic instability, commonly observed as subsynchronous vibration, is a serious problem that can cause heavy damage to a turbomachine or make it incapable of operation due to high vibration levels. However, all subsynchronous vibrations are not necessarily unstable. A way to quickly diagnose them would be helpful. In an earlier paper, the authors presented data from experiments that simulated various causes of sub-synchronous vibrations, some causes being genuine rotordynamic instabilities and some others being benign (stable), and identified ways to diagnose and classify the subsynchronous motions. In a continuation of the same study, subsynchronous vibrations due to coupled lateral-torsional effects are experimentally simulated, the objective being to signal-analyze these vibrations to find unique signatures that identify this cause and also be able to recognize if they are a true rotordynamic instability or not. To this end, a test rig was built with parallel shafts coupled by gears, driven by a DC motor at one end and loaded at the other end, to closely simulate a real-world machine. A torsional mathematical model for the test rig is also presented to predict its torsional natural frequencies. Experiments were conducted wherein the first torsional natural frequency was externally excited, with the shaft spinning at a higher speed. The result was a false sub-synchronous “instability” signal in the lateral measurements. A method to distinguish these vibrations from a genuine lateral non-synchronous instability is presented. Also, a new diagnostic method to classify the subsynchronous vibration as benign is elucidated.

scholarly journals A temperature compensation method of measuring frequency for cylindrical vibratory gyroscope in frequency split trimming

2018 ◽  
Vol 175 ◽  
pp. 03042
Author(s):  
Youwang Hu ◽  
Kai Zeng ◽  
Haofang Wang ◽  
Chang Liang ◽  
Yongping Zhou ◽  
...  
Keyword(s):  
Natural Frequency ◽  
Temperature Compensation ◽  
Environmental Temperature ◽  
Measuring Method ◽  
Frequency Measurement ◽  
Effect Of Temperature ◽  
Vibratory Gyroscope ◽  
Before And After ◽  
Measuring Frequency ◽  
Frequency Split

In the process of frequency split trimming, the fluctuation of environmental temperature causes a deviation in measuring the natural frequency, which is bigger than the request trimming accuracy. Therefore, a measuring method with temperature compensation is proposed to reduce this impact. Firstly, the relationship between natural frequency of resonator and environmental temperature are studied by experiments. Furthermore, the corresponding model of temperature compensation is proposed, which is written into the measuring unit to calculate the compensated frequency. The frequencies before and after temperature compensation are measured to prove the correctness of this method. At last, a real time measuring experiment is accomplished to verify the feasibility in frequency split trimming. Results show that the effect of temperature on the natural frequency reduced significantly with the temperature compensation measuring method. The proposed method is applicable for other types of vibratory gyroscope in precision frequency measurement.

Vibrating Beam Technique for Measuring Animal Natural Frequency

1995 ◽  
Vol 14 (3) ◽  
pp. 119-133 ◽  
Author(s):  
John M Randall ◽  
Chaoying Peng
Keyword(s):  
Resonant Frequency ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Frequency Measurement ◽  
System Response ◽  
Single System ◽  
Design Requirements ◽  
Modal Mass ◽  
Two Degree Of Freedom ◽  
Beam Technique

The discomfort to animals arising from vibration during transport is likely to be greatest at their natural resonant frequency. This frequency can be measured without compromising animal welfare by placing them on a simple beam support at each end which is caused to vibrate by a small impulse. The optimum beam to give stable and accurate results for this technique is evaluated using a two-degree-of-freedom model. Some design requirements are contradictory, for example sensitivity to the resolution of frequency measurement and the benefits of having a single system response. These problems are alleviated by specifying a unified accuracy at both of the system natural frequencies. In this case the natural frequency of the beam should be twice that of the animal and the modal mass of the beam should equal that of the animal.

Dynamic Analysis on PCI Girder Bridge

2015 ◽  
Vol 747 ◽  
pp. 375-378
Author(s):  
Made Suangga ◽  
Santi
Keyword(s):  
Natural Frequency ◽  
Field Measurements ◽  
Frequency Measurement ◽  
Measurement Results ◽  
Frequency Calculation ◽  
Calculation Results ◽  
Bridge Girder ◽  
Girder Bridge ◽  
Natural Frequency Calculation ◽  
Value Measurement

To produce a quality bridge then it should be taken into account with the correct parameters and the condition of the bridge. One of the parameters is an important bridge natural frequency incurred due to dynamic loads. The purpose of this study was to conduct a comparative analysis of the natural frequency of bridge girder value measurement results in the field of natural frequency calculation results using Midas Civil programs and manuals, as well as knowing the value of the condition value of natural frequency of bridge between the actual value of natural frequency measurement results on the field and the value of natural frequency calculation program results Midas Civil. In the analysis, use design bridge gelagar PCI with a span of 21,95 meters. And bridge specifications will be made from the analysis of the natural frequency of the load calculation of structures with Midas program manual and Civil that would then be compared with the results of field measurements to find out the condition of the bridge. The natural frequency obtained from calculation manual for a bridge girder single of 5,95 Hz, and multi girder of 5,72 Hz.While value natural frequency of program midas civil for singles girder of 6,16 Hz, and for multi girder of 5,93Hz.

Development of three-dimensional dynamic grinding force measurement platform

2016 ◽  
Vol 232 (2) ◽  
pp. 331-340 ◽  
Author(s):  
Zhi Huang ◽  
Shihang Chen ◽  
Hongyan Wang
Keyword(s):  
Natural Frequency ◽  
High Frequency ◽  
Force Measurement ◽  
Three Dimensional ◽  
Frequency Measurement ◽  
Grinding Force ◽  
Force Detection ◽  
Performance Requirements ◽  
Force Monitoring ◽  
And Control

In order to accurately measure and control high-frequency grinding force in the process of grinding, a novel measurement method of three-dimensional grinding force with mutual perpendicular and independent elastic elements is proposed in this paper. To detect the high frequency grinding force, a resistance strain-type three-dimensional grinding force measurement platform was designed and developed. The key performance indicators of the measurement platform were investigated via finite element simulation. In addition, the detection performance of the measurement platform was researched and verified through natural frequency measurement experiments, static calibration experiments, and grinding experiments. The results show that the proposed method can effectively alleviate the inherent contradiction between natural frequency and sensitivity in the traditional dynamometer; the measurement platform as-established fully meets the performance requirements of three-dimensional dynamic grinding force detection. To this effect, the results discussed here provide technical support for achieving accurate detection of high frequency grinding force, monitoring grinding processes, optimizing grinding parameters, and improving grinding quality.

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