Undecimated Wavelet Packet Transform Research Articles

A Two-Stage Wavelet Decomposition Method for Instantaneous Power Quality Indices Estimation Considering Interharmonics and Transient Disturbances

As the complexity increases in modern power systems, power quality (PQ) analysis considering interharmonics has become a challenging and important task. This article proposes a novel decomposition and estimation method for instantaneous PQ indices (PQIs) monitoring in single- and three-phase systems with interharmonics and transient disturbances. To separate the interharmonic components, a set of new scaling filter and wavelet filter with narrow transition bands is designed for the undecimated wavelet packet transform (UWPT). Furthermore, a two-stage decomposition method for multitone voltage and current signals is proposed. The Hilbert transform (HT) is applied to calculate the instantaneous amplitude and phase of each frequency component, which accordingly allows the monitoring of different PQI parameters. Numerical tests are conducted to check the performance of the proposed method. The test results show that, compared to other conventional approaches, instantaneous PQIs estimated by the proposed method present significant advances for tracking transitory changes in power systems and could be considered as a helpful tool for high-accuracy PQ detections.

Measurement of Instantaneous Power Quality Parameters Using UWPT and Hilbert Transform and Its FPGA Implementation

This article presents a measurement technique based on the undecimated wavelet packet transform (UWPT) and Hilbert transform (HT) to estimate power quality parameters at every sample. Thus, it results in improved time resolution and allows us to track the variation of power quality parameters with respect to time. The proposed technique consists of three stages. In the first stage, harmonics and fundamental components are separated from the distorted signal using UWPT. In the second stage, the HT is used to extract the envelope of fundamental and harmonic components. In the last stage, power quality parameters are calculated at each instant according to the IEEE Standard 1459-2010. The proposed scheme has been successfully implemented on the Xilinx Virtex-6 FPGA ML-605 evaluation kit. The simulation and the experimental results demonstrate the effectiveness of the proposed method in terms of estimation accuracy, timing requirements, and resource utilization.

Field Programmable Gate Array-Based Measurement System for Real-Time Estimation of Single-Phase Electric Power Quantities

A measurement system for monitoring power components in the electrical distribution system as defined in IEEE Standard 1459–2010 is developed in this paper. The proposed scheme consists of two steps. In the first step, measured voltage and current waveforms are processed in parallel and their spectral components are computed by using an undecimated wavelet packet transform (UWPT)-based method. In the second step, power components are evaluated as per IEEE Standard 1459-2010. The proposed measurement system is developed on the field programmable gate array (FPGA) platform because of its intrinsic parallelism nature and low implementation complexity. The effectiveness of the proposed measurement system has been demonstrated through the simulation and experimental results. Simulation results show the accuracy and robustness of the proposed technique under different operating conditions. Furthermore, experimental results validate its performance in terms of hardware accuracy, resource utilization, and timing requirements.

Fast Amplitude Estimation of Harmonics Using Undecimated Wavelet Packet Transform and Its Hardware Implementation

Accurate and fast estimation of time-varying harmonics are essential requirements for online monitoring, analysis, and control of electrical power system. This paper presents a fast algorithm based on the undecimated wavelet packet transform (UWPT) to estimate the amplitude of fundamental and harmonic components of stationary as well as a time-varying power signal. The UWPT uses only one cycle of the fundamental frequency for precise measurement of time-varying harmonics while their amplitude has been determined accurately utilizing the time-invariant property of the UWPT. The robustness and accuracy of the proposed technique have been investigated on synthetic as well as experimental test signals using MATLAB tool. Further, the UWPT algorithm has also been implemented on the Xilinx Virtex-6 FPGA ML-605 board, using XSG/ISE design suite 14.2 and its performance, in terms of hardware accuracy, resource utilization as well as timing requirements have been tested using the experimental test signal.

Recursive Undecimated Wavelet Packet Transform and DAG SVM for Induction Motor Diagnosis

This paper is focused on the design of a new approach dedicated to solve classification problems for the detection of broken rotor bar (BRB) fault in induction motors (IM). This new method finds its origins in a novel combination of both recursive undecimated wavelet packet transform (RUWPT) and directed acyclic graph support vector machines (DAG SVMs). Most often, BRB frequency components are hardly detected in the stator current due to its low magnitude and closeness to the supply frequency component. To overcome this drawback, the RUWPT is applied to extract one parameter able to detect the fault with arbitrary working conditions and a great concern of low load cases. Different multiclass support vector machines (MSVMs) methods are evaluated with respect to accuracy, number of support vectors, and testing time. The experimental results confirm that the DAG SVMs and Symlet wavelet kernel function are fast, robust, and give the best classification accuracy of 99%.

An Undecimated Wavelet-based Method for Cochlear Implant Speech Processing

A cochlear implant is an implanted electronic device used to provide a sensation of hearing to a person who is hard of hearing. The cochlear implant is often referred to as a bionic ear. This paper presents an undecimated wavelet-based speech coding strategy for cochlear implants, which gives a novel speech processing strategy. The undecimated wavelet packet transform (UWPT) is computed like the wavelet packet transform except that it does not down-sample the output at each level. The speech data used for the current study consists of 30 consonants, sampled at 16 kbps. The performance of our proposed UWPT method was compared to that of infinite impulse response (IIR) filter in terms of mean opinion score (MOS), short-time objective intelligibility (STOI) measure and segmental signal-to-noise ratio (SNR). Undecimated wavelet had better segmental SNR in about 96% of the input speech data. The MOS of the proposed method was twice in comparison with that of the IIR filter-bank. The statistical analysis revealed that the UWT-based N-of-M strategy significantly improved the MOS, STOI and segmental SNR (P < 0.001) compared with what obtained with the IIR filter-bank based strategies. The advantage of UWPT is that it is shift-invariant which gives a dense approximation to continuous wavelet transform. Thus, the information loss is minimal and that is why the UWPT performance was better than that of traditional filter-bank strategies in speech recognition tests. Results showed that the UWPT could be a promising method for speech coding in cochlear implants, although its computational complexity is higher than that of traditional filter-banks.

Narrowband Interference Suppression in Frequency-Hopping Spread Spectrum Using Undecimated Wavelet Packet Transform

Suppression of narrowband interference in frequency-hopping spread spectrum (FH-SS) systems is treated in this paper. First, we analyze the effect of continuous-wave tone interference in noncoherent binary frequency-shift keying (BFSK) signaling with FH-SS. Based on this analysis, a new receiver for FH-SS systems is proposed, including a transform-domain interference suppression module. The algorithm is executed in two steps: 1) interference detection and 2) signal reconstruction. The novelty of this suppression algorithm is the combination of the undecimated wavelet packet transform with frequency shifts of the received signal to center the narrowband interference in a subband. Once the subband that contains the interference has been determined, the algorithm removes this subband and then reconstructs the signal. The performance of this receiver has been evaluated in a variety of situations with different types of narrowband interference. The results obtained show the improvement of the proposed receiver in comparison to the traditional FH-SS receiver.

Discrimination Between Closed and Open Shell (Turkish) Pistachio Nuts Using Undecimated Wavelet Packet Transform

Due to low consumer acceptance and the possibility of immature kernels, closed-shell pistachio nuts should be separated from open-shell nuts before reaching the consumer. A system using impact acoustics as a means of classifying closed-shell nuts from open-shell nuts has already been shown to be feasible and have better discrimination performance than a mechanical system. The accuracy of an impact acoustics based system is determined by the signal processing and feature extraction procedures. In this article, a new time-frequency plain feature extraction and classification algorithm was developed to discriminate between open- and closed-shell pistachio nuts produced in the Gaziantep region of Turkey. The proposed approach relies on the analysis of the impact acoustics signal of pistachio nuts, which are emitted from their impact with a steel plate after dropping from a certain height. Features are extracted by decomposing the acoustic signals into time and frequency components, using double-tree undecimated wavelet packet transform. The most discriminative features from the dual tree nodes are selected by a wrapper strategy that includes the structural pruning of the double-tree feature dictionary. The proposed approach requires no prior knowledge of the relevant time or frequency content of the acoustic signals. The algorithm used a small number of features and achieved a classification accuracy of 91.7% on the validation data set, while separating the closed shells from the open ones. A previously implemented algorithm, which uses maximum signal amplitude, absolute integration, and gradient features, achieved 82% classification accuracy on the same dataset. The results show that the time-frequency features extracted from impact acoustics can be used successfully for classification of open- and closed-shell Turkish pistachios.

Object Tracking in Crowded Video Scenes Based on the Undecimated Wavelet Features and Texture Analysis

We propose a new algorithm for object tracking in crowded video scenes by exploiting the properties of undecimated wavelet packet transform (UWPT) and interframe texture analysis. The algorithm is initialized by the user through specifying a region around the object of interest at the reference frame. Then, coefficients of the UWPT of the region are used to construct a feature vector (FV) for every pixel in that region. Optimal search for the best match is then performed by using the generated FVs inside an adaptive search window. Adaptation of the search window is achieved by interframe texture analysis to find the direction and speed of the object motion. This temporal texture analysis also assists in tracking of the object under partial or short-term full occlusion. Moreover, the tracking algorithm is robust to Gaussian and quantization noise processes. Experimental results show that the proposed algorithm has good performance for object tracking in crowded scenes on stairs, in airports, or at train stations in the presence of object translation, rotation, small scaling, and occlusion.

Narrowband Interference Suppression Using Undecimated Wavelet Packets in Direct- Sequence Spread-Spectrum Receivers

A new algorithm for narrowband interference suppression in direct-sequence spread-spectrum (DS-SS) communications is presented. The algorithm combines the undecimated wavelet packet transform (UWPT) with frequency shifts to confine the interference energy in a subband that is subsequently eliminated. Computer simulation shows a robust performance that appears to be independent of the interference frequency