scholarly journals Joints dynamic identification and modeling based on FRFs data

2018 ◽  
Vol 189 ◽  
pp. 01010
Author(s):  
Guanhua Dong ◽  
Wei Wu ◽  
Jianhui Zhou
Keyword(s):  
Frequency Response ◽  
Dynamic Model ◽  
Dynamic Properties ◽  
Dynamic Stiffness ◽  
Least Square Method ◽  
Least Square ◽  
Experimental Results ◽  
Response Functions ◽  
Dynamic Identification ◽  
Inconsistent Equation

The problem of joints dynamic identification and modeling is discussed in this paper. The theoretical dynamic model of joints is established by FRFs (frequency response functions) data, and formulas for identifying the joints dynamic properties is deduced. The equivalent value of dynamic stiffness is extracted by solving the inconsistent equation using the least square method. The experimental example is provided to validate the feasibility and accuracy of the proposed method, the predicted result showing good fitting with experimental results.

Substructuring: Definition of the Analytical Dynamic Model of a Complex System During its Design Stage

1995 ◽  
Author(s):  
Fabrice Llorca ◽  
Alain Gerard ◽  
Denis Hennequin ◽  
Dominique Brenot
Keyword(s):  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Dynamic Properties ◽  
Least Square Method ◽  
Close Correlation ◽  
Least Square ◽  
Component Mode Synthesis ◽  
Design Stage ◽  
Synthesis Methods ◽  
Rectangular Plates

Abstract A structure is often an assembly of several components coupled by various joints such as bolted or riveted joints. Component mode synthesis methods are very practical tools to define a dynamic model. But, several points have to be examined and improved in order to give a complet representation of the modal behaviour of the whole structure. For example, rotational degrees of freedom on connecting points between adjacent substructures should be estimated to give a better representation of the multidirectional connecting forces. These informations may be evaluated through a method based on both interpolation and spatial derivation of the experimental translational displacements of the components. Unlike many other structural elements, the dynamic properties of a connection are very difficult to evaluate. So, we propose a method of determining joint stiffness characteristics. We consider only the conservative problem so the damping properties of the different components of the considered assembly are not taken into account. The joint characteristics are extracted comparing experimental modal data base and component mode synthesis simulation. The updating procedure is based on a nonlinear iterative least-square method. Results are presented concerning a particular assemblie of rectangular plates. Structural modification is applied for one component. We show that the joint properties stay the same if the connecting interface is not modified. The close correlation between predicted and experimental results demonstrate that this method is well adaptated to the study of structural modifications.

Determination of Johnson Cook Material Model Constants and Their Influence on Machining Simulations of Tungsten Heavy Alloy

2018 ◽  
Author(s):  
Chithajalu Kiran Sagar ◽  
Amrita Priyadarshini ◽  
Amit Kumar Gupta ◽  
Sidharth Kumar Shukla
Keyword(s):  
Least Square Method ◽  
Material Model ◽  
Least Square ◽  
Experimental Results ◽  
Tungsten Heavy Alloy ◽  
Fe Model ◽  
Abc Algorithm ◽  
Bee Colony ◽  
Aircraft Manufacturing ◽  
Heavy Alloys

Tungsten Heavy Alloys (WHA) are used in counterbalance and ballast weights for aerodynamic balancing in fixed and rotary wing aircraft. Manufacturing these components for closer tolerances using machining is a challenging task. The present work aims to develop a 2D Finite Element (FE) model to simulate the chip formation process during machining of WHA using Johnson Cook Material Model (JCMM). The model constants for 95%WHA are determined based on the high strain rate test data using least square method. The calculated values are further optimized using Genetic Algorithm (GA) and Artificial Bee Colony (ABC) algorithm, which are then used as material inputs for FE simulation of machining WHA. The predicted results such as cutting force, chip geometry, shear stress, shear angle are presented and compared with the experimental results under similar cutting conditions. It has been observed that the constants obtained from ABC algorithm show minimum error in the cutting performance measures for all the experimental results.

Detection of Damage Extension in Cantilever Beams Using Change Ratio of Frequency Response Functions

2011 ◽  
Vol 50-51 ◽  
pp. 875-879
Author(s):  
Hai Lei Jia ◽  
Yin Zhao
Keyword(s):  
Frequency Response ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Damage Index ◽  
High Sensitivity ◽  
Cantilever Beams ◽  
Response Functions ◽  
Full Spectrum ◽  
Structural Dynamic ◽  
Low Dimensional

Frequency response function (FRF) is a fundamental dynamic index, which is capable of reflecting structural dynamic properties using full-spectrum information. In spite of distinct merits over conventional modal parameters, the FRF has an observable drawback of multi-dimensionality, unsuited for damage characterization. Such a situation motivates an interesting subject, i.e., extracting low-dimensional, high-sensitivity damage index from the FRF. This study focuses on developing a valid damage index, called FRF change ratio, to detect extension of damage. An experiment towards cantilever beams is systemically conducted. The results show that the FRF change ratio can effectively reflects damage extension, and it is more sensitive than conventional natural frequencies. This new damage index holds promise for practical damage detection in beam-like structures.

Localization of Mobile Robot Based on Least Square Method

2013 ◽  
Vol 347-350 ◽  
pp. 808-811
Author(s):  
Jia Lu Li ◽  
Lin Bing Long ◽  
Bao Feng Zhang
Keyword(s):  
Motion Estimation ◽  
Mobile Robot ◽  
Mobile Robots ◽  
Least Squares ◽  
Least Square Method ◽  
Least Square ◽  
Experimental Results ◽  
Sift Algorithm ◽  
Key Techniques ◽  
Point Detection

Localization is the basis for navigation of mobile robots. This paper focuses on key techniques of localization for mobile robots based on vision. Firstly, the specific measures and steps of the algorithm are analyzed and researched in depth. In the study, SIFT algorithm combined with epipolar geometry constraint is used on the environment feature point detection, matching and tracking. And the method of RANSAC combined with the least squares is used to obtain accurate results of the motion estimation. Then the necessary experiments are carried out to verify the correctness and effectiveness of algorithms. The experimental results verified the accuracy of the improved algorithm.

scholarly journals Fault Diagnosis of Nonlinear Analog Circuit Based on Generalized Frequency Response Function and LSSVM Classifier Fusion

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Jialiang Zhang
Keyword(s):  
Support Vector Machine ◽  
Fault Diagnosis ◽  
Frequency Response ◽  
Frequency Response Function ◽  
Analog Circuit ◽  
Least Square ◽  
Classifier Fusion ◽  
Support Vector ◽  
Response Functions ◽  
Nonlinear Analog

For fault diagnosis of nonlinear analog circuit, a novel method based on generalized frequency response function (GFRF) and least square support vector machine (LSSVM) classifier fusion is presented. The sinusoidal signal is used as the input of analog circuit, and then, the generalized frequency response functions are estimated directly by the time-domain formulations. The discrete Fourier transform of measurement data is avoided. After obtaining the generalized frequency response functions, the amplitudes of the GFRFs are chosen as the fault feature parameters. A classifier fusion algorithm based on least square support vector machine (LSSVM) is used for fault identification. Two LSSVM multifault classifiers with different kernel functions are constructed as subclassifiers. Fault diagnosis experiments of resistor-capacitance (RC) circuit and Sallen Key filter are carried out, respectively. The results show that the estimated GFRFs of the circuit are accurate, and the fault diagnosis method can get high recognition rate.

scholarly journals A Steering-Following Dynamic Model with Driver’s NMS Characteristic for Human-Vehicle Shared Control

2020 ◽  
Vol 10 (7) ◽  
pp. 2626 ◽  
Author(s):  
Hanbing Wei ◽  
Yanhong Wu ◽  
Xing Chen ◽  
Jin Xu
Keyword(s):  
Dynamic Model ◽  
Unscented Kalman Filter ◽  
Autonomous Vehicle ◽  
Least Square ◽  
Experimental Results ◽  
Shared Control ◽  
Dynamic State ◽  
Dynamic Mode ◽  
Identification Algorithm ◽  
Control Authority

For investigating driver characteristic as well as control authority allocation during the process of human–vehicle shared control (HVSC) for an autonomous vehicle (AV), a HVSC dynamic mode with a driver’s neuromuscular (NMS) state parameters was proposed in this paper. It takes into account the driver’s NMS characteristics such as stretch reflection and reflex stiffness. By designing a model predictive control (MPC) controller, the vehicle’s state feedback and driver’s state are incorporated to construct the HVSC dynamic model. For the validation of the model, a field experiment was conducted. The vehicle state signals are collected by V-BOX, and the driver’s state signals are obtained with the electromyography instrument. Subsequently, the hierarchical least square (HLS) parameter identification algorithm was implemented to identify the parameters of the model based on the experimental results. Moreover, the Unscented Kalman Filter (UKF) was utilized to estimate the important NMS parameters which cannot be measured directly. The experimental results showed that the model we proposed has excellent accuracy in characterizing the vehicle’s dynamic state and estimating the driver’s NMS parameter. This paper will serve as a theoretical basis for the new control strategy allocation between human and vehicle for L3 class AVs.

Advanced Techniques for Measuring Structural Mobilities

1988 ◽  
Vol 110 (3) ◽  
pp. 345-349 ◽  
Author(s):  
J. A. Fabunmi ◽  
F. A. Tasker
Keyword(s):  
Frequency Response ◽  
General Equation ◽  
Theoretical Basis ◽  
Weighting Function ◽  
Experimental Results ◽  
Expected Improvement ◽  
Response Functions ◽  
Proper Selection ◽  
Special Cases ◽  
Selection Of

A unified formulation of the equations for estimating structural frequency response functions is presented. The more popular approaches are shown to be special cases of a general equation which involves a weighting function, the proper selection of which can yield substantial improvements in the accuracy and efficiency of the measurement process. The theoretical basis for selecting the weighting function is also presented, along with experimental results which confirm the expected improvement in accuracy of the advanced formulations over existing methods.

Change of modal parameters due to crack growth in a tripod tower platform

1993 ◽  
Vol 20 (5) ◽  
pp. 801-813 ◽  
Author(s):  
Yin Chen ◽  
A. S. J. Swamidas
Keyword(s):  
Finite Element ◽  
Frequency Response ◽  
Response Function ◽  
Frequency Response Function ◽  
Experimental Results ◽  
Modal Testing ◽  
Modal Parameters ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Strain Frequency

Strain gauges, along with an accelerometer and a linear variable displacement transducer, were used in the modal testing to detect a crack in a tripod tower platform structure model. The experimental results showed that the frequency response function of the strain gauge located near the crack had the most sensitivity to cracking. It was observed that the amplitude of the strain frequency response function at resonant points had large changes (around 60% when the crack became a through-thickness crack) when the crack grew in size. By monitoring the change of modal parameters, especially the amplitude of the strain frequency response function near the critical area, it would be very easy to detect the damage that occurs in offshore structures. A numerical computation of the frequency response functions using finite element method was also performed and compared with the experimental results. A good consistency between these two sets of results has been found. All the calculations required for the experimental modal parameters and the finite element analysis were carried out using the computer program SDRC-IDEAS. Key words: modal testing, cracking, strain–displacement–acceleration frequency response functions, frequency–damping–amplitude changes.

Comparing of Coordinate Transformation Based on Total Least Squares and Least Squares

2014 ◽  
Vol 522-524 ◽  
pp. 1211-1214
Author(s):  
Qing Wu Meng ◽  
Lu Meng
Keyword(s):  
Least Squares ◽  
Coordinate Transformation ◽  
Least Square Method ◽  
Coefficient Matrix ◽  
Total Least Squares ◽  
Least Square ◽  
Experimental Results ◽  
Transformation Models ◽  
Total Least Square

The coordinate transformation models based on least square method and total least square are built and discussed. The least square model only includes the errors of observation vectors, the total least square model simultaneously takes into consideration to the errors of observation vectors and the errors of coefficient matrix. The both models are verified and compared in experiment. The experimental results showed that the model of total least square is more in line with actual, and more reasonable than by least square theoretically, and the coordinate transformation solution result of total least square with least square is more near.

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