Papers by Keyword: End Effect

Abstract: Through the forming of large and thick sheet metal cylindrical parts, it was found that symmetrical abnormal arching defects appeared at both ends of the first and tail ends in the length direction. In response to this phenomenon, the finite element simulation verification and comparison of the two processes of multi-point mold forming and integral mold forming are carried out. The analysis results show that this kind of end effect exists in both the multi-point mold forming and the overall mold forming process, and the overall mold forming effect is better. The multi-point mold has a small springback in the length direction, which is versatile and compatible.

Abstract: The end effect of the local Mean Decomposition (LMD) causes serious distortion of the LMD decomposition results. And the most important factor of influence end effect is the extreme point and its distance, so the paper extracted the several factors, and composed of different sequences, using support vector machine (SVM) method respectively on the sets of data to predict, makes the original data can be extended. The research on the simulation signal and vibration signal shows that the method can effectively restrain the end effect of the decomposition.

Abstract: The LMD is a new method for analyzing non-stationary signals. It can decompose complicated signals into a set of single-component signals, each of which has physical sense. But peforming the LMD will produce end effects which make results distortion. After analyzing the reasons for these, the ariticle takes adcantage of three normal methods to overcome the end effects of LMD. Experimental results of three models showed that the method of self-adaptive waveform matching was better than other methods.

Abstract: The external wind pressure coefficients are based on the measurements on the structures without free-end flow near the top of vertical structures. The end-effect factor takes into account reduction of the pressures due to specific flow around the top of atypical building. The article is based on the experimental measurements in BLWT tunnel in Bratislava on the model of building with cross section of the quarter circle. The model was tested in two spaces - in steady and turbulent wind flow, by changing of wind direction and wind velocity. The end-effect factor depending on the wind direction is shown in the graphs.

Abstract: The traditional signal processing methods are difficult to accurately extract fault information, because mechanical fault vibration signals have non-stationary, which will cause system instability. Local mean decomposition is adaptive signal processing method. However, in the local mean decomposition of the signal, the trend of the endpoint can not be predicted which cause contaminating the entire signal sequence, the original moving average of the signal used over-smoothing treatment, resulting in fault characteristics can not accurately extract. The article introduces waveform matching to solve the original features of signals at the endpoints, using linear interpolation to get local mean and envelope function, then obtain production function PF vector through making use of the local mean decomposition. The energy entropy of PF vector take as identification input vectors. These vectors are respectively inputted BP neural networks, support vector machines, least squares support vector machines to identify faults. Experimental result show that the accuracy of least squares support vector machine with higher classification accuracy has been improved.

Abstract: The Support Vector Regression Machines (SVRM) is considered to be an effective method for time series prediction, while it is not suitable for long-term prediction. In order to improve the SVRM application in eliminating the end effect of EMD, we apply the SVRM to achieve an accurate short-term extension in the end of the original signal before EMD, and then extend two extreme with the Self-adaptive Triangular Waveform Matching extension method (STWM) in the every sifting process of EMD. The results show that the new extension method can effectively contain end effect of EMD.

Abstract: To solve the end effect occurring in empirical mode decomposition adopted in the course of decomposition, we propose an improved method on the basis of time-sequence analysis and cosine window function. First, the ARMA (Autoregressive Moving Average) of time-varying parameter is adopted to extend signals, and thus the extended data can be smoothly connected with the original signal at the end. Second, the extended signals are processed with cosine window, so that the extended errors will exert no impact on the existing data. Finally, the signals processed as above mentioned will be decomposed with EMD to confine the end effect to the ends of the signal. The simulation and fault signal analysis prove that the proposed method can effectively reduce the impact of the end effect and be applied in rotating machinery fault diagnosis.

Abstract: In order to minimize the detent force of permanent magnet linear synchronous motor (PMLSM) caused by end effect, a novel auxiliary poles one-piece structure is proposed. Two auxiliary poles are extended directly from two ends of the armature core. And magnetic isolation bridges are set between auxiliary pole and armature core. Compared with the conventional discrete auxiliary poles, the one-piece structure will reduce the manufacture difficulty of PMLSM with auxiliary poles and improve the reliability of linear motor.

Abstract: The calculation of the roller contact and the bearing ring of the finite length is presented in this work. The influence of the end effect action, on geometry of the contact platform and the stressed state in the vicinity of the roller edge has been taken into account. The solution results are compared with analytical solution of the Hertz contact problem.

Abstract: Thrust characteristics of permanent magnet linear synchronous motor (PMLSM) are analyzed. It shows that frequency spectrums of thrust ripple, which are mainly caused by end-effect, are quite similar for linear motors with different pole/slot combinations. To apply magnet skew technology, a method using piecewise magnet for skewing factor computation is introduced. According to this piecewise method, a policy for analyzing 3D skew effect model using 2D FEM algorithm is investigated. The application on a 14-pole/12-slot PMLSM validated the algorithm.