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Regularized automatic frequency response function acquisition of a milling robot operating in a high-dimensional workspace

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Science China(Technological Sciences) 2024年第6期67卷 1783-1797页

作者： LUO WenLong TANG XiaoWei MA Tao GUO QiuShuang XU YanYan YUAN Xing ZHANG Lei MAO XinYong School of Mechanical Science and Engineering Huazhong University of Science and TechnologyWuhan430074China State Key Laboratory of Smart Manufacturing for Special Vehicles and Transmission System Baotou014030China Wuhan Heavy Duty Machine Tool Group Corporation Wuhan430205China

Because robotic milling has become an important means for machining significant large parts,obtaining the structural frequency response function(FRF)of a milling robot is an important basis for machining process ***,because of its articulated serial structure,a milling robot has an enormous number of operating postures,and its dynamics are affected by the motion *** accurately obtain the FRF in the operating state of a milling robot,this paper proposes a method based on the structural modification *** the traditional excitation method,the proposed method uses robot joint motion excitation instead of hammering excitation to realize *** address the problem of the lack of information brought by motion excitation,which leads to inaccurate FRF amplitudes,this paper derives the milling robot regularization theory based on the sensitivity of structural modification,establishes the modal regularization factor,and calibrates the FRF *** to the commonly used manual hammering experiments,the proposed method has high accuracy and reliability when the milling robot is in different *** the measurement can be performed directly and automatically in the operation state,and the problem of inaccurate amplitudes is solved,the proposed method provides a basis for optimizing the machining posture of a milling robot and improving machining efficiency.

关键词： milling robot structural dynamics frequency response function automatic identification modal regularization factor high-dimensional workspace

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Uncertainty analysis of strain modal parameters by Bayesian method using frequency response function

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Earthquake Engineering and Engineering Vibration 2007年第2期6卷 183-189页

作者：徐丽易伟建易志华 Beijing University of Technology Guangzhou University Guangzhou 510405 China Hunan University City College of New York NY 10031 USA

Structural strain modes are able to detect changes in local structural performance, but errors are inevitably intermixed in the measured data. In this paper, strain modal parameters are considered as random variables, and their uncertainty is analyzed by a Bayesian method based on the structural frequency response function （FRF）. The estimates of strain modal parameters with maximal posterior probability are determined. Several independent measurements of the FRF of a four-story reinforced concrete flame structural model were performed in the laboratory. The ability to identify the stiffness change in a concrete column using the strain mode was verified. It is shown that the uncertainty of the natural frequency is very small. Compared with the displacement mode shape, the variations of strain mode shapes at each point are quite different. The damping ratios are more affected by the types of test systems. Except for the case where a high order strain mode does not identify local damage, the first order strain mode can provide an exact indication of the damage location.

关键词： frequency response function uncertainty strain mode Bayesian method local damage damage detection concrete flame

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Research on the iterative method for model updating based on the frequency response function

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Acta Mechanica Sinica 2012年第2期28卷 450-457页

作者： Wei-Ming Li Jia-Zhen Hong Department of Engineering Mechanics Shanghai Jiaotong University200240 ShanghaiChina

Model reduction technique is usually employed in model updating process. In this paper, a new model updat- ing method named as cross-model cross-frequency response function （CMCF） method is proposed and a new iterative method associating the model updating method with the mo- del reduction technique is investigated. The new model up- dating method utilizes the frequency response function to avoid the modal analysis process and it does not need to pair or scale the measured and the analytical frequency re- sponse function, which could greatly increase the number of the equations and the updating parameters. Based on the traditional iterative method, a correction term related to the errors resulting from the replacement of the reduction ma- trix of the experimental model with that of the finite element model is added in the new iterative method. Comparisons be- tween the traditional iterative method and the proposed itera- tive method are shown by model updating examples of solar panels, and both of these two iterative methods combine the CMCF method and the succession-level approximate reduc- tion technique. Results show the effectiveness of the CMCF method and the proposed iterative method .

关键词： Model updating Model reduction frequency response function Iteration

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Crack detection using a frequency response function in offshore platforms

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Journal of Marine Science and Application 2007年第3期6卷 1-5页

作者： ZHANG Zhao-de CHEN Shuai College of Engineering Ocean University of China Qingdao 266071 China College of Mechanical Engineering and Automation North University of China Taiyuan 030051 China

Structural cracks can change the frequency response function (FRF) of an offshore platform. Thus, FRF shifts can be used to detect cracks. When a crack at a specific location and magnitude occurs in an offshore structure, changes in the FRF can be measured. In this way, shifts in FRF can be used to detect cracks. An experimental model was constructed to verify the FRF method. The relationship between FRF and cracks was found to be non-linear. The effect of multiple cracks on FRF was analyzed, and the shift due to multiple cracks was found to be much more than the summation of FRF shifts due to each of the cracks. Then the effects of noise and changes in the mass of the jacket on FRF were evaluated. The results show that significant damage to a beam can be detected by dramatic changes in the FRF, even when 10% random noise exists. FRF can also be used to approximately locate the breakage, but it can neither be efficiently used to predict the location of breakage nor the existence of small hairline cracks. The FRF shift caused by a 7% mass change is much less than the FRF shift caused by the breakage of any beam, but is larger than that caused by any early cracks.

关键词： offshore platform crack detection numerical simulation frequency response function

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AN IMPROVED METHOD OF STRUCTURAL DAMAGE DETECTION BASED ON frequency response function

AN IMPROVED METHOD OF STRUCTURAL DAMAGE DETECTION BASED ON F...

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第六届国际振动工程会议

作者： H.F. Yang* Y.J. Yan Z.Y. Wu (School of Mechanics Civil and Architecture Northwestern Polytechnical University XI’AN 710072)

This paper presents a improved method to measure the location and degree of structural damage based on frequency response *** method can refine dynamic model’s stiffness matrix by using a subset vectors from the full set of frequency response functions that are extracted from test data and calculated from analytical *** a result,frequency response functions obtained from the updated analytical model are coinciding with those *** location and degree of structural damage can be found through the *** method has definite physical meaning,avoid modal analysis, and can come into being the on-line monitor system. One numerical example checks the method’s validity and precision.

关键词： structural damage detection frequency response function parameter inversion

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Pilot study on the Non-Invasive Detectability of Femoral Neck Fractures with frequency response functions

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World Journal of Mechanics 2014年第7期4卷 210-216页

作者： Wolfgang Witteveen Carina Wagner Patrick Jachs Stefan Froschauer Harald Schoffl Upper Austrian University of applied Sciences WelsAustria BioMed-zet Life Science GmbH LinzAustria

A suspicion of a femoral neck fracture is a frequently recurring situation, especially in nursing homes. For the clarification of such a suspicion normally imaging techniques are used. Such equipment is expensive and therefore is located in hospitals. In addition to the costs, a transport causes stress for the patient. This pilot study is devoted to the question whether the detection of a femoral neck fracture with vibration measurements is possible in principal. In such a case, the clarification could be done on-site by an ordinary person using much cheaper equipment. This would reduce the stress for the patient and save money. For this purpose vibration measurements on a dead body with intact, with partially fractured and with complete cut femoral neck have been performed. Two different methods for the vibration initiation have been investigated, the so called impact testing and the shaker testing. The frequency response function has been determined for all combinations on both sides of the body. It turned out that there is a clear difference in the frequency response functions of the fractured bone with respect to the intact bone when shaker testing is used. This indicates that the method could have the potential to be a cost-saving alternative to imaging techniques. However, in a next step a statistically reliable clinical survey on living persons needs to be done.

关键词： Biomechanics Vibrations frequency response function FRF Femoral Neck Fracture

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Damage detection of 3D structures using nearest neighbor search method

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Earthquake Engineering and Engineering Vibration 2021年第3期20卷 705-725页

作者： Ali Abasi Vahid Harsij Ahmad Soraghi Department of Civil and Environmental Engineering Western UniversityLondonONCanada Department of Civil Engineering Amirkabir University of Technology(Tehran Polytechnic)TehranIran Department of Civil Engineering University of AkronASEC 210Sumner StAkronOH 44325USA

An innovative damage identification method using the nearest neighbor search method to assess 3D structures is *** frequency response function was employed as the input parameters to detect the severity and place of damage in 3D spaces since it includes the most dynamic characteristics of the ***-dimensional principal component analysis was utilized to reduce the size of the frequency response function *** nearest neighbor search method was employed to detect the severity and location of damage in different damage *** accuracy of the approach was verified using measured data from an experimental test;moreover,two asymmetric 3D numerical examples were considered as the numerical *** superiority of the method was demonstrated through comparison with the results of damage identification by using artificial neural *** levels of white Gaussian noise were used for polluting the frequency response function data to investigate the robustness of the methods against noise-polluted *** results indicate that both methods can efficiently detect the damage properties including its severity and location with high accuracy in the absence of noise,but the nearest neighbor search method is more robust against noisy data than the artificial neural network.

关键词： damage identification damage index frequency response function two-dimensional principal component analysis nearest neighbor search artificial neural network white Gaussian noise

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Relative Varying Dynamics Based Whole Cutting Process Optimization for Thin‑walled Parts

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Chinese Journal of Mechanical Engineering 2022年第6期35卷 194-206页

作者： Yuyang Tang Jun Zhang Jia Yin Lele Bai Huijie Zhang Wanhua Zhao State Key Laboratory for Manufacturing Systems Engineering Xi’an Jiaotong UniversityXi’an 710054China AVIC Xi’an Aircraft Industry Group Company Ltd Xi’an 710089China

Thin-walled parts are typically difficult-to-cut components due to the complex dynamics in cutting *** dynamics is variant for part during machining,but invariant for machine *** variation of the relative dynamics results in the difference of cutting stage division and cutting parameter *** paper develops a novel method for whole cutting process optimization based on the relative varying dynamic characteristic of machining system.A new strategy to distinguish cutting stages depending on the dominated dynamics during machining process is proposed,and a thickness-dependent model to predict the dynamics of part is *** cutting parameters change with stages,which can be divided by the critical thickness of *** on the dynamics comparison between machine tool and thickness-varying part,the critical thicknesses are predicted by an iterative *** proposed method is validated by the machining of three *** agreements have been obtained between prediction and experimental results in terms of stages identification,meanwhile,the optimized parameters perform well during the whole cutting process.

关键词： Thin-walled parts Varying dynamics frequency response function Whole cutting process Optimization

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Optimization of the Tuned Mass Damper for Chatter Suppression in Turning

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Chinese Journal of Mechanical Engineering 2010年第6期23卷 717-724页

作者： YANG Yiqing LIU Qiang WANG Min School of Mechanical Engineering andAutomation Beihang University Beijing 100191 China Research and Application Center of Advanced CNC Machining Technology Beihang University Beijing 100191 China College of Mechanical Engineering and Applied Electronics Technology Beijing University of Technology Beijing 100124 China

The tuned mass damper（TMD） has been successfully applied to the vibration control in machining, while the most widely adopted tuning is equal peaks, which splits the magnitude of the frequency response function（FRF） into equal peaks. However, chatter is a special self-excited problem and a chatter-flee machining is determined by FRF at the cutting zone. A TMD tuning aiming at achieving the maximum chatter stability is studied, and it is formulated as an optimization problem of maximizing the minimum negative real part of FRF. By employing the steepest descend method, the optimum frequency and damping ratio of TMD are obtained, and they are compared against the equal peaks tuning. The advantage of the proposed tuning is demonstrated numerically by comparing the minimum point of the negative real part, and is further verified by damping a flexible mode from the fixture of a turning machine. A TMD is designed and placed on the fixture along the vibration of the target mode after performing modal analysis and mode shape visualization. Both of the above two ttmings are applied to modify the tool point FRF by tuning TMD respectively. Chatter stability chart of the turning shows that the proposed tuning can increase the critical depth of cut 37% more than the equal peaks. Cutting tests with an increasing depth of cut are conducted on the turning machine in order to distinguish the stability limit. The tool vibrations during the machining are compared to validate the simulation results. The proposed damping design and optimization routine are able to further increase the chatter suppression effect.

关键词： tuned mass damper frequency response function chatter suppression optimization ~rning

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Centrifuge modelling of ground-borne vibrations induced by railway traffic in underground tunnels

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Earthquake Engineering and Engineering Vibration 2022年第2期21卷 517-528页

作者： Yang Wenbo Qian Zhihao Tu Jiulin Zhou Ziyang Yan Qixiang Fang Yong He Chuan Key Laboratory of Transportation Tunnel Engineering the Ministry of EducationSouthwest Jiaotong UniversityChengdu 610031China

Increased attention has been given to ground-borne vibrations induced by railway vehicles and to the effects of these vibrations as they propagate through the ground into nearby *** studies,mainly based on numerical methods as well as physical modelling,have been carried out to investigate this *** study the dynamic response of tunnels and the surrounding soil due to train-induced vibration loads,a centrifuge test was conducted with a small-scale model in 1 g and 50 g stress field *** aluminum tube was embedded in sand to model the underground tunnel.A small parallel pre-stressed actuator(PPA)was employed to apply vibration loads on the tunnel *** model responses were measured using *** time and frequency domain analyzes were *** test results demonstrated that electronic noise had a clear impact on the test results and should be *** also found that the dynamic response of both the tunnel and soil were affected by the stress ***,it is important to account for the stress field effects when assessing the ground-borne vibration from tunnels.

关键词： centrifuge test stress field frequency response function peak particle acceleration dynamic response

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