scholarly journals EFFECTS OF DIFFERENT EXCITATION MECHANISMS IN MACHINE TOOLS WHEN PERFORMING OUTPUT-ONLY MODAL ANALYSIS

2021 ◽  
Vol 2021 (4) ◽  
pp. 4930-4940
Author(s):  
JAN BERTHOLD ◽  
◽  
MARTIN KOLOUCH ◽  
JOACHIM REGEL ◽  
MARTIN DIX ◽  
...  
Keyword(s):  
Control System ◽  
Machine Tool ◽  
Modal Analysis ◽  
Machine Tools ◽  
Dynamic Behaviour ◽  
Modal Parameters ◽  
Process Conditions ◽  
Noise Characteristics ◽  
Excitation Mechanisms ◽  
Output Only

Output-only Modal Analysis makes it possible to investigate the dynamic behaviour of machine tools, especially under process conditions. The differences between standstill and process state, which are important to be considered, result from process damping, gyroscopic moments of the rotating spindle, and changes in preloads and clearance in bearing and joints. Output-only Modal Analysis assumes a complete excitation of the structure by white noise characteristics. There are several mechanisms in a machine tool under process conditions that could cause a vibration response. Besides the cutting process itself, the movement of the NC-axes, as well as rotating fans of the control system and auxiliary units, can be excitation sources. This paper investigates to what extent several excitation mechanisms in machine tools fulfill the analysis assumption and in which way the identified modal parameters depend on the boundary conditions of the excitation characteristics.

scholarly journals A new modal analysis method applied to changing machine tool using clustering

2020 ◽  
Vol 12 (10) ◽  
pp. 168781402096832
Author(s):  
Xuchu Jiang ◽  
Xinyong Mao ◽  
Yingjie Chen ◽  
Caihua Hao
Keyword(s):  
Machine Tool ◽  
Modal Analysis ◽  
Natural Frequency ◽  
Efficient Method ◽  
Machine Tools ◽  
Vibration Signal ◽  
Modal Parameters ◽  
Analysis Method ◽  
Modal Parameter ◽  
The Difference

The states of the machine tool, such as the components’ position and the spindle speed, play leading roles in the change of dynamic parameters. However, the traditional modal analysis method that modal parameters manually identified from vibration signal is greatly interfered by harmonics, and the process of eliminating interference is very inefficient and subjective. At present, there is a lack of a standard and efficient method to characterize modal parameter changes in different states of machine tools. This paper proposes a new machine tool modal classification analysis method based on clustering. The characteristics related to the modal parameters are extracted from the response signal in different states, and the clustering results are used to reflect the changes of machine tool modal parameters. After the amplitude of the frequency response function is normalized, the characteristics related to the natural frequency are acquired, and the clustering results further reflect the difference of the natural frequency of the signal. The new method based on clustering can be a standard and efficient method to characterize modal parameter changes in different states of machine tools.

scholarly journals Identification of modal parameters of machine tools during cutting by operational modal analysis

Procedia CIRP ◽  
2018 ◽  
Vol 77 ◽  
pp. 473-476 ◽  
Author(s):  
Jan Berthold ◽  
Martin Kolouch ◽  
Volker Wittstock ◽  
Matthias Putz
Keyword(s):  
Modal Analysis ◽  
Machine Tools ◽  
Operational Modal Analysis ◽  
Modal Parameters

The Study of Control System for Reconfigurable Machine Tool Model

2011 ◽  
Vol 188 ◽  
pp. 499-502
Author(s):  
L. Zhou ◽  
Wen Jie Nie ◽  
Z.R. Liao ◽  
X.R. Liang ◽  
G.Q. Pan
Keyword(s):  
Control System ◽  
Machine Tool ◽  
Motion Control ◽  
Machine Tools ◽  
Single Chip ◽  
Single Chip Microcomputer ◽  
Precision Motion Control ◽  
Single Function ◽  
Precision Motion ◽  
Reconfigurable Machine Tool

With the higher requirements of product processing, single-function machine can not meet the production needs. By analyzing the principles of reconfigurable machine tools, based on 51 single-chip microcomputer, this article researches the control system of reconfigurable machine tool, implements precision motion control for motors. The research can also reduce costs, so the practicality and economy all have a certain advantage, which will help promote the use in practice.

scholarly journals Output-Only Modal Analysis Based on Improved Empirical Mode Decomposition Method

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Shiqiang Qin ◽  
Qiuping Wang ◽  
Juntao Kang
Keyword(s):  
Modal Analysis ◽  
Empirical Mode Decomposition ◽  
Modal Parameters ◽  
Band Pass Filter ◽  
Pass Filter ◽  
Random Decrement Technique ◽  
Mode Decomposition ◽  
Frequency Components ◽  
Output Only ◽  
Emd Method

The output-only modal analysis for bridge structures based on improved empirical mode decomposition (EMD) is investigated in this study. First, a bandwidth restricted EMD is proposed for decomposing nonstationary output measurements with close frequency components. The advantage of bandwidth restricted EMD to standard EMD is illustrated by a numerical simulation. Next, the modal parameters are extracted from intrinsic mode function obtained from the improved EMD by both random decrement technique and stochastic subspace identification. Finally, output-only modal analysis of a railway bridge is presented. The study demonstrates the mode mixing issues of standard EMD can be restrained by introducing bandwidth restricted signal. Further, with the improved EMD method, band-pass filter is no longer needed for separating the closely spaced frequency components. The modal parameters extracted based on the improved EMD method show good agreement with those extracted by conventional modal identification algorithms.

Research on Modal Analysis of Precision Micro Slitting Turn-Milling Machine Tool Based on Hammer Experimental Method

2019 ◽  
Vol 295 ◽  
pp. 67-72
Author(s):  
Zhong Peng Zheng ◽  
Xin Yang Jiang ◽  
Xin Jin
Keyword(s):  
Machine Tool ◽  
Modal Analysis ◽  
Experimental Method ◽  
Machine Tools ◽  
Processing Parameters ◽  
Milling Machine ◽  
Vibration Model ◽  
Vibration Modal ◽  
Turn Milling ◽  
Machine Structure

In order to improve the dynamic stability of precision micro slitting turn-milling machine tools, reduce or avoid the vibration problem during the cutting process, optimize the machine structure and processing parameters, the modal analysis of precision micro slitting turn-milling machine tool based on hammer experimental method was researched. In this paper, by analyzing the mechanism of precision micro slitting turn-milling machine tools, the multi degree-of-freedom mathematical vibration model of precision slitting turn-milling machine tools is constructed. The precision micro turn-milling machine tool is analyzed based on the hammer experiment analysis. The modal analysis obtained the first five natural frequencies and resonance speeds of the precision micro slitting turn-milling machine tool,including ST26, NN-25UB8K2 and NN-20UB87. The research results show that hammer experimental method can evaluate the vibration modal analysis of precision micro slitting turn-milling machine tools to some extent. The experimental modal analysis results guide and optimize the structural design and processing technology of precision micro slitting turn-milling machine tools.

Modal Testing for Heavy Machine Tool Using Active Excitation

2014 ◽  
Vol 536-537 ◽  
pp. 1326-1332 ◽  
Author(s):  
Bo Luo ◽  
Bin Li ◽  
Xin Yong Mao ◽  
Hui Cai
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Inertial Force ◽  
Modal Testing ◽  
Modal Parameters ◽  
Part Quality ◽  
Machine Tool Structure ◽  
Machining Speed ◽  
Heavy Machine ◽  
Large Machine

For application in large machine tools, the machined part quality, accuracy as well as machining speed depende greatly on the dynamics of the structure. In this paper, an active-excitation modal analysis (AEMA), using inertial force of the moving slider to excite the structural modes, is proposed. Modal parameters of the machine tool structure estimated by AEMA are experimentally validated. Since the artificial excitation produced by elaborate excitation equipment is replaced by the inertial force of the slider, the proposed method is much more practical and economical than traditional methods.

scholarly journals Active vibration control for a CNC milling machine

2013 ◽  
Vol 228 (2) ◽  
pp. 230-245 ◽  
Author(s):  
DG Ford ◽  
A Myers ◽  
F Haase ◽  
S Lockwood ◽  
A Longstaff
Keyword(s):  
Control System ◽  
Tool Wear ◽  
Machine Tool ◽  
Vibration Control ◽  
Surface Finish ◽  
Machine Tools ◽  
Active Vibration Control ◽  
Milling Machine ◽  
Cnc Machine ◽  
Active Vibration

There is a requirement for improved three-dimensional surface characterisation and reduced tool wear when modern computer numerical control (CNC) machine tools are operating at high cutting velocities, spindle speeds and feed rates. For large depths of cut and large material removal rates, there is a tendency for machines to chatter caused by self-excited vibration in the machine tools leading to precision errors, poor surface finish quality, tool wear and possible machine damage. This study illustrates a method for improving machine tool performance by understanding and adaptively controlling the machine structural vibration. The first step taken is to measure and interpret machine tool vibration and produce a structural model. As a consequence, appropriate sensors need to be selected and/or designed and then integrated to measure all self-excited vibrations. The vibrations of the machine under investigation need to be clearly understood by analysis of sensor signals and surface finish measurement. The active vibration control system has been implemented on a CNC machine tool and validated under controlled conditions by compensating for machine tool vibrations on time-varying multi-point cutting operations for a vertical milling machine. The design of the adaptive control system using modelling, filtering, active vibration platform and sensor feedback techniques has been demonstrated to be successful.

scholarly journals Transmissibilty-Based Operational Modal Analysis for Flight Flutter Testing Using Exogenous Inputs

2012 ◽  
Vol 19 (5) ◽  
pp. 1071-1083 ◽  
Author(s):  
Christof Devriendt ◽  
Tim De Troyer ◽  
Gert De Sitter ◽  
Patrick Guillaume
Keyword(s):  
Modal Analysis ◽  
Frequency Domain ◽  
Experimental Modal Analysis ◽  
Operational Modal Analysis ◽  
Modal Parameters ◽  
Input Output ◽  
Output Only ◽  
Flutter Testing

During the recent years several new tools have been introduced by the Vrije Universiteit Brussel in the field of Operational Modal Analysis (OMA) such as the transmissibility based approach and the the frequency-domain OMAX concept. One advantage of the transmissibility based approach is that the ambient forces may be coloured (non-white), if they are fully correlated. The main advantage of the OMAX concept is the fact that it combines the advantages of Operational and Experimental Modal Analysis: ambient (unknown) forces as well as artificial (known) forces are processed simultaneously resulting in improved modal parameters. In this paper, the transmissibility based output-only approach is combined with the input/output OMAX concept. This results in a new methodology in the field of operational modal analysis allowing the estimation of (scaled) modal parameters in the presence of arbitrary ambient (unknown) forces and artificial (known) forces.

Analysis of Impeller Vibration in Radial Compressors

1986 ◽  
Author(s):  
J. Wachter
Keyword(s):  
Finite Element ◽  
Dynamic Analysis ◽  
Modal Analysis ◽  
Dynamic Behaviour ◽  
Modal Parameters ◽  
Centrifugal Impeller ◽  
Experimental Investigations ◽  
Finite Element Program ◽  
Element Program ◽  
Detailed Application

The prediction of the dynamic behaviour of the impellers is of considerable importance in the design of turbomachines. The excitation possibilities of the radial impellers by the forces or imposed displacements are various and an appreciation of the life of radial impellers is strongly bounded to an accurate dynamic analysis. Therefore, it is necessary to analyze them in order to improve the geometry or modify the design. In order to better understand and explain the dynamic behaviour of impellers, a series of impeller models with various numbers of blades of radial or tangential extention have been examined. Because of complexity of analytical analysis shown in earlier works, the eigenfrequencies and modes of the impellers were evaluated using a Finite Element program. Interferometric holography served as a means to visualize the dynamic behaviour of the impellers. An experimental modal analysis was used to identify the modal parameters. A detailed application of these methods to an actual centrifugal impeller was also reported along with theoretical and experimental investigations on the impeller models.

Correct Use and Maintenance of Nc Machine Tools

2014 ◽  
Vol 651-653 ◽  
pp. 676-679
Author(s):  
Quan Fang Sun ◽  
Jun Ling Zhang
Keyword(s):  
Control System ◽  
Machine Tool ◽  
Machine Tools ◽  
Numerical Control ◽  
Numerical Control System ◽  
Nc Machine Tool ◽  
Important Index ◽  
Nc Machine ◽  
Nc Machine Tools ◽  
Reasonable Use

A country's level of Nc machine tool and ownership, is to measure the level of manufacturing and industrial modernization level of important indicators, is also an important index to measure national comprehensive competitiveness. Therefore, how to better use and maintenance of Nc machine tool is an important issue. This paper introduced how to reasonable use of Nc machine tools, as well as the use of the numerical control system and inspection.

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