WEEK 15

PREFACE TO WORK

There is a problem in the distance estimation above the 80% of the antenna length. To analysis it more, a new sensor was mounted on mid point of the antenna and collect a new data set. As well as the previous data set was analyzed using the wavelet spectrogram .

PROGRESS and RESULTS

The vibration signal of the antenna beam was used for the analysis. The results, obtained using wavelet spectrogram for the 0.25L , 0.5L , 0.75L , 0.8L and 0.9L of the antenna length were discussed here. Figure 40 and Figure 41 shows the results for 0.25 and 0.5 . Both of these points are laid on the linear region. The dc component is laid in the 0.0 in the frequency axis. The most powerful frequency component for the 0.25 is between 0.05-0.1 in normalized frequency and it is between 0.1-0.15 for the 0.5L Both of these frequency components remained powerful during more than 300 samples of the signal. Therefore they act as a most dominant frequency component in the entire signal.

But when analyzing the vibration signals at 0.75 , 0.8 and 0.9 , the behavior of the spectrogram was totally different from the previous cases. Three spectrogram for the 0.75L , 0.8L and 0.9L are shown in Figure 42. Although all three cases had a powerful frequency component at the beginning (most yellow colored one), they disappeared with the time passes. Moreover, here many powerful frequency components could be obtained at the beginning than in the Figure 40 and Figure 41 cases. That means at the beginning there were many vibration modes and most of them disappeared after passing 100 samples and rest of them also had a very low power compared to the DC component. Therefore it was unable to identify a good dominant frequency component to carry out the properties of the entire vibration signal. Most significantly, 0.75 and 0.8 were at the beginning of the deviation from the linear behavior . and 0.9 could be observed in the deviated region.

Figure 42 Spectrogram of the norm of the vibration signal at 0.75L , 0.8L ,0.9 L

REFERENCES