The use of a continuous wavelet transform in the diagnostics of technical condition of a shock absorber built in automotive vehicle

2018 ◽  
Vol 121 ◽  
pp. 171-179
Author(s):  
Łukasz Konieczny ◽  
Rafał Burdzik
Keyword(s):  
Wavelet Transform ◽  
Shock Absorber ◽  
Technical Condition ◽  
Morlet Wavelet ◽  
Continuous Wavelet ◽  
Nonlinear Characteristics ◽  
Shock Absorbers ◽  
Acceleration Sensors ◽  
Research Experiment ◽  
Difficult Issue

Diagnosing the technical condition of shock absorbers installed in automotive suspensions is a difficult issue due to the fact that these are elements of a complex mechanical system containing elastic and damping elements with nonlinear characteristics that degrade during operation. The paper presents the result of testing car with shock absorbers with programmed faults on the harmonic stand. The test object was a Fiat Seicento passenger car. The research experiment consisted in stimulating the vehicle to vibrations of forced masses, unsprung and sprung, and registration of vibration accelerations of these masses. The tests were subjected to shock absorbers with programmed faults in the form of loss of shock absorber fluid from 100% to 35% for rear shock absorbers. The acceleration of plates, swingarm (unsprung masses) and bodywork (sprung masses) were recorded by acceleration sensors. The results obtained in this way were subjected to wavelet analysis using the Morlet wavelet in the MatLab environment and based on these transformations the maximum of vibration amplitudes were determined depending on the degree of loss of the shock absorber fluid.

scholarly journals An asymptotic expansion of continuous Wavelet transform for large dilation parameter

2018 ◽  
Vol 36 (3) ◽  
pp. 27-39
Author(s):  
Ashish Pathak ◽  
Prabhat Yadav ◽  
M. M. Dixit
Keyword(s):  
Asymptotic Expansion ◽  
Wavelet Transform ◽  
Continuous Wavelet Transform ◽  
Morlet Wavelet ◽  
Continuous Wavelet ◽  
Mexican Hat Wavelet ◽  
Mexican Hat ◽  
Special Cases ◽  
Morlet Wavelet Transform

In this paper , we derive asymptotic expansion of the wavelet transform for large values of the dilation parameter a by using Lopez and Pagola technique. Asymptotic expansion of Mexican Hat wavelet and Morlet wavelet transform are obtained as a special cases.

Fatigue Data Analysis Using Continuous Wavelet Transform and Discrete Wavelet Transform

2011 ◽  
Vol 462-463 ◽  
pp. 461-466 ◽  
Author(s):  
Shahrum Abdullah ◽  
S.N. Sahadan ◽  
Mohd Zaki Nuawi ◽  
Zulkifli Mohd Nopiah
Keyword(s):  
Wavelet Transform ◽  
Data Analysis ◽  
Discrete Wavelet Transform ◽  
Wavelet Transforms ◽  
Data Extraction ◽  
Morlet Wavelet ◽  
Analysis Time ◽  
Discrete Wavelet ◽  
Continuous Wavelet ◽  
Fatigue Data

The wavelet transform is well known for its ability in vibration analysis in fault detection. This paper presents the ability of wavelet transform in fatigue data analysis starts from high amplitude events detection and it is then followed by fatigue data extraction based on wavelet coefficients. Since the wavelet transform has two main categories, i.e. the continuous wavelet transforms (CWT) and the discrete wavelet transform (DWT), the comparison study were carried out in order to investigate performance of both wavelet for fatigue data analysis. CWT represents by the Morlet wavelet while DWT with the form of the 4th Order Daubechies wavelet (Db4) was also used for the analysis. An analysis begins with coefficients plot using the time-scale representation that associated to energy coefficients plot for the input value in fatigue data extraction. Ten extraction levels were used and all levels gave the damage difference, (%∆D) less than 10% with respect to original signal. From the study, both wavelet transforms gave almost similar ability in editing fatigue data but the Morlet wavelet provided faster analysis time compared to the Db4 wavelet. In comparison to have the value of different at 5%, the Morlet wavelet achieved at L= 5 while the Db4 wavelet at L=7. Even though it gave slower analysis time, both wavelets can be used in fatigue data editing but at different time consuming.

Reducing Vertical and Angular Accelerations With Nonlinear Asymmetrical Shock Absorber in Passenger Vehicles

2013 ◽  
Author(s):  
Marcos Silveira ◽  
Bento R. Pontes ◽  
José M. Balthazar
Keyword(s):  
Shock Absorber ◽  
Ride Comfort ◽  
Nonlinear Characteristics ◽  
Passenger Vehicles ◽  
Car Model ◽  
Shock Absorbers ◽  
Nonlinear Shock ◽  
Angular Oscillations ◽  
Impact Absorption ◽  
Severity Parameter

The behaviour of linear and nonlinear shock absorbers are compared to diminish vertical and angular (pitch) accelerations of passenger vehicles, improving comfort by result. A 4-dof half-car model is used with three configurations of dampers: symmetrical, asymmetrical and front asymmetrical. The analyses use three standard road inputs and include variation of the severity parameter, the asymmetry ratio and the velocity of the vehicle. The comparison shows that the asymmetrical system, with nonlinear characteristics, tends to have a smoother and more progressive behaviour. The results show that the use of the front asymmetrical system diminishes angular oscillations of the vehicle. As lower levels of acceleration are essential for improved ride comfort, the use of asymmetrical systems for vibrations and impact absorption is a superior choice for passenger vehicles.

scholarly journals On alternative wavelet reconstruction formula: a case study of approximate wavelets

2014 ◽  
Vol 1 (2) ◽  
pp. 140124 ◽  
Author(s):  
Elena A. Lebedeva ◽  
Eugene B. Postnikov
Keyword(s):  
Wavelet Transform ◽  
Wide Class ◽  
Continuous Wavelet Transform ◽  
Morlet Wavelet ◽  
Continuous Wavelet ◽  
Reconstruction Formula ◽  
Physical Processes ◽  
Admissibility Condition ◽  
Oscillatory Dynamics

The application of the continuous wavelet transform to the study of a wide class of physical processes with oscillatory dynamics is restricted by large central frequencies owing to the admissibility condition. We propose an alternative reconstruction formula for the continuous wavelet transform, which is applicable even if the admissibility condition is violated. The case of the transform with the standard reduced Morlet wavelet, which is an important example of such analysing functions, is discussed.

The influence of selected operating parameters on assessment of technical condition of shock absorber at EUSAMA station

2018 ◽  
Vol 123 ◽  
pp. 55-61
Author(s):  
Łukasz Konieczny ◽  
Zdzisław Niedziela ◽  
Jan Łukowski ◽  
Marcin Stańczyk
Keyword(s):  
Shock Absorber ◽  
Test Bench ◽  
Operating Parameter ◽  
Technical Condition ◽  
Technical State ◽  
Operating Parameters ◽  
Tabular Form ◽  
Shock Absorbers ◽  
Vehicle Inspection ◽  
The Impact

The article presents the results of the technical state of shock absorbers on the stand with harmonic Eusam type kinematic forcing applied at vehicle inspection stations. As operating parameter, the pressure in the tires was assumed (assumed a reduced value in relation to the recommended nominal value) and the impact of this parameter on the values obtained during testing on the test bench was determined. The measurements were carried out several times. The results are summarized in tabular form and in the form of a graph and based on them final conclusions were formulated.

scholarly journals Damping identification in multi-degree-of-freedom systems using the continuous wavelet transform

2005 ◽  
Vol 27 (1) ◽  
pp. 41-50 ◽  
Author(s):  
Nguyen Phong Dien
Keyword(s):  
Wavelet Transform ◽  
Continuous Wavelet Transform ◽  
Damping Ratio ◽  
Morlet Wavelet ◽  
Wavelet Function ◽  
Degree Of Freedom ◽  
Damping Coefficient ◽  
Steel Beam ◽  
Continuous Wavelet ◽  
Modal Damping

The identification of damping in multi-degree-of-freedom vibration systems is a well-known problem and appears to be of crucial interest. Compared to an estimation of the stiffness and mass, the damping coefficient or, alternatively, damping ratio is the most difficult quantity to determine. In this paper, the continuous wavelet transform based on the Morlet-wavelet function is used to identify the modal damping ratios of multi-degree-of-freedom vibration systems. A new wavelet-based method for the damping identification from measured free responses is presented. The proposed method was also tested by experiments on a steel beam.

scholarly journals A wavelet neural control scheme for a quadrotor unmanned aerial vehicle

2018 ◽  
Vol 376 (2126) ◽  
pp. 20170248 ◽  
Author(s):  
F. Jurado ◽  
S. Lopez
Keyword(s):  
Neural Network ◽  
Wavelet Transform ◽  
Unmanned Aerial Vehicle ◽  
Continuous Wavelet Transform ◽  
Morlet Wavelet ◽  
Wavelet Neural Network ◽  
Continuous Wavelet ◽  
Continuous Wavelets ◽  
Control Scheme ◽  
Aerial Vehicle

Wavelets are designed to have compact support in both time and frequency, giving them the ability to represent a signal in the two-dimensional time–frequency plane. The Gaussian, the Mexican hat and the Morlet wavelets are crude wavelets that can be used only in continuous decomposition. The Morlet wavelet is complex-valued and suitable for feature extraction using the continuous wavelet transform. Continuous wavelets are favoured when high temporal and spectral resolution is required at all scales. In this paper, considering the properties from the Morlet wavelet and based on the structure of a recurrent high-order neural network model, a novel wavelet neural network structure, here called a recurrent Morlet wavelet neural network, is proposed in order to achieve a better identification of the behaviour of dynamic systems. The effectiveness of our proposal is explored through the design of a decentralized neural backstepping control scheme for a quadrotor unmanned aerial vehicle. The performance of the overall neural identification and control scheme is verified via simulation and real-time results. This article is part of the theme issue ‘Redundancy rules: the continuous wavelet transform comes of age’.

Defects Diagnosis of Bearing by Means of Acoustic Emission and Continuous Wavelet Transform

2009 ◽  
Vol 413-414 ◽  
pp. 651-657 ◽  
Author(s):  
Ru Jiang Hao ◽  
Zhi Peng Feng ◽  
Fu Lei Chu
Keyword(s):  
Acoustic Emission ◽  
Wavelet Transform ◽  
Continuous Wavelet Transform ◽  
Rolling Bearing ◽  
Morlet Wavelet ◽  
Wavelet Function ◽  
Continuous Wavelet ◽  
Test Rig ◽  
Ae Signal ◽  
Transform Coefficients

The acoustic emission signals of rolling bearing with different type of defects are de-noised and illustrated by the continuous wavelet transform and scalogram. Morlet wavelet function is selected and the wavelet parameters are optimized based on the principle of minimal wavelet entropy. The soft-threshold de-noising is used to filter the wavelet transform coefficients. The de-noised signals obtained by reconstructing the wavelet coefficients show the obvious impulsive features. Based on the optimized waveform parameters, the wavelet scalogram is used to analyze the real AE signal from the defective rolling bearing in experimental test rig. The results indicate that the proposed method is useful and efficient for signal purification and features extraction.

Sign in / Sign up

Export Citation Format

Share Document