Papers by Keyword: Wavelet Packet

Abstract: During robotic heading machine working, it often encounters the coal seam hardness changing tremendously. So the cutting mechanism will be easy to break down. For this problem, put forward a strategy, which using wavelet packet technology to study the vibration signal of cutting mechanism. Filtered the signal with wavelet packet; extracted vibration signal characteristics; established the energy eigenvector; used the Hilbert technology to extract frequency characteristics. According to the energy eigenvector and the frequency characteristics, estimated the cutting mechanism running status. The simulation in MATLAB proves that the control strategy can estimate the running state of cutting mechanism real-time, and lay an important foundation for the realization of coal mine roadway drivage unmanned working face.

Abstract: As an important part of pipeline safety, pipeline leak detection is usually done by extracting feature vectors of leakage signal. Many researchers used wavelet packet algorithm to extract feature vector, but because of mixing effects of wavelet packet, the acquired feature vector may be not accurate. To solve this problem, the authors propose an improved wavelet packet algorithm to extract the feature vector. The improved algorithm is different from the traditional algorithm in decomposition and reconstruction and the feature vector is constituted by three time-frequency domain parameters. A lot of experiments have been performed to extract feature vector based on the proposed algorithm, with the results showing that the proposed algorithm can overcome the mixing effects and accurately extract the feature vector.

Abstract: A fault diagnosis approach of hydraulic system based on Hybrid Particle Swarm Optimization (HPSO) algorithm and Wavelet Packet Energy Entropy (WP-EE) is presented. A heuristic algorithm is adopted to give a transition from particle swarm search to gradient descending search. A HPSO algorithm is formed with the heuristic algorithm, which is used to optimize BP neural network weights and threshold. Then an application of fault diagnosis with HPSO and WP-EE based on a valve-controlled hydraulic motor system is presented. After wavelet packet decomposition of the acquired hydraulic pressure signal, the WP-EE is extracted; the eigenvector of wavelet packet is constructed. Taking this eigenvector as fault sample, the neural network based on HPSO algorithm is trained to implement the fault diagnosis for the hydraulic system. The test result shows that the fault recognition accuracy and the efficiency in the hydraulic system are improved by this method.

Abstract: For the problem of rolling bearing mechanical fault detection, this paper proposed a fault detection method based on wavelet packet energy spectrum and partial least squares (PLS). Firstly, the collected vibration signal was decomposed by wavelet packet into independent frequency bands. The different frequencies energy spectrum could be collected from the independent frequency bands. That means the energy spectrum feature vectors whose changes reflect the running state could be constructed. Then analyze the energy spectrum feature vector by PLS, and establish the fault detection model. The fault could be detected by the T² and SPE statistics. Finally, the experimental results showed that the method is feasible and effective.

Abstract: Abstract. Radio propagation on wireless channels depends on many static and dynamic factors like, buildings, trees, mountains, frequency of operation, velocity of mobile stations and interfering sources. Mathematical models for channel are considered for various communication functions like, predicting radio coverage, estimation of interferences from various sources, estimating the characteristics of an alternate transmitter and receiver, achievable data rates and for determining the location for wireless infrastructure. Signal propagation in fading channels cause degradation of signal QoS. OFDM is often used to mitigate fading effects in wireless channels; the paper describes the disadvantage of OFDM and provides a wavelet based solution to surmount it. The paper also investigates the BER vs. SNR performance of modified OFDM using wavelet packet in Rayleigh and Rician Channels and the results are compared with conventional OFDM.

Abstract: The signal obtained through measurement is inevitably with noise and interference. Traditional signal denoising method often takes the threshold way to process the wavelets or wavelet packets of noise signal for the purpose of denoising. Denoising by making use of slip threshold value of wavelet packets is proposed by this paper, to quantize the slip threshold value of wavelet packet decomposition coefficient, so as to obtain the reconstructed signal denoising. It is shown by the computer simulation results that the slip threshold value is with good practical value.

Abstract: The issue of food safety is increasingly becoming the focus of social concerns, and breakage of packaging film is the main threat to the safety of sealing packaging food. For the small damage that is difficult to see with the naked eyes, according to that the impedance of damaged position is different from that of other position, the discharge signals of sealing packaging food in different damaged conditions are different in high voltage dielectric barrier discharge circuit, and then they are collected and analyzed. In order to solve the problem that different discharge signals are similar and characteristics are confused, wavelet packet and the EEMD method are novelly used to analyze discharge signals and the characteristic parameters of sealing packaging food that is intact or has pinholes are successfully extracted. This method solves the problem that the tiny damage is difficult to identify and detect, and it also provides a new train of thought for online test of sealing packaging food.

Abstract: The wavelet packet transform is a new time-frequency analysis method, and is superior to the traditional wavelet transform and Fourier transform, which can finely do time-frequency dividion on seismic data. A series of simulation experiments on analog seismic signals wavelet packet decomposition and reconstruction at different scales were done by combining different noisy seismic signals, in order to achieve noise removal at optimal wavelet decomposition scale. Simulation results and real data experiments showed that the wavelet packet transform method can effectively remove the noise in seismic signals and retain the valid signals, wavelet packet transform denoising is very effective.

Abstract: An interference image edge detection method for laser interferometer hydrophone based on wavelet packet is investigated. Considering the effect of ocean background noise on the interference image, we propose the use of a class of wavelet packet functions to make decomposition on noisy interference image, and then make reconstruction on approximate parts of the decomposed image. The approximate parts with the wavelet packet decomposition is of more clear image layers comparison to the original image, and the wavelet packet decomposition method can reduce the influence of background noise on the interference image. Taking the wavelet packet decomposition method and other edge detection algorithms for contrast, it is proved that the wavelet packet decomposition method for edge detection algorithm is more effective than the other algorithms.

Abstract: The wavelet packet decomposition and reconstruction technique is applied to time-frequency analysis of bite steel impact vibration signal by big rolling machine, it is obtained the bite steel impact signal wave packet. According to the size of the wavelet packet energy, it is reconstructed the signal of No.1 and No.2 wavelet packet. According to reconstruction of the signal time domain waveform and FFT spectrum chart, some meaningful conclusions are obtained.