Method And Application Of Border Processing In Real-time Signal Wavelet Analysis

In the design process of petroleum drilling accidents warning system, Data processing is an important link. If these drilling data can not be processed rightly, the design of warning system will be affected and it will lead to great property loss, so processing the drilling data rightly is very important and necessary.Wavelet filtering method is acknowledged to be a better and practical method. In the derivation process of wavelet filtering, it is assumed that the signals are infinite, but in practical progress, the signals that will be processed are finite, therefore the border of composition signals will have great error. The theory source of border effect will be analyzed in chapter three.There are many methods of border processing, and border extending is a common border processing method, the common border extending methods are zero-extending, period-extending, symmetry-extending, smooth-extending and so on. This paper makes simple introduction of these border extending methods, but because of their drawbacks the using ranges are not wide. According to the feature of petroleum drilling signals, we will extend petroleum drilling signals using the way of Least Squares Curve Fitting, by the simulation, the error of Curve Fitting Extending and Standard Extending is least and the effect is best.The current signal is always located in the right of filtering window when these petroleum drilling signals are filtered. Because of border effect, the current signal can not be composed exactly, we will extend several signals in the right of the current signal, so the current signal will be located in the best position. By the simulation, the composition error of right border extending is much smaller than the composition error without right border extending. We made a comparison to different length filtering windows and different fitting orders, according to the signals feature, we can select the different length of filtering window and the order of curve fitting, the method of Least Squares Curve Fitting have strong versatility, flexibility and following performance of signals feature.