WEEK 7

PREFACE TO WORK

It is needed to find a unique feature to identify the contact distance to the obstacle from the rotating axis of the antenna. But the time domain features were failed at the close distances. So the frequency domain analyzing were done.

PROGRESS

For the same data set that used for the time domain analysis, were used for the frequency domain analyzing. First take the Discrete Fast Fourier transform of the collected data set in the discrete time domain and observed the following results.

RESULTS

The data sets for Aluminum and PVC were analysed in the frequency domain. Then it showed a unique feature which is corresponding to the distance even in the distances which are very close to each other.

Figure 12: Frequency domain acclamation of the X and Z axis at the 170mm from the motor axis for Aluminium

Figure 13: Frequency domain acclamation of the X and Z axis at the 175mm from the motor axis for Aluminium

The figures 12 and 13 show the frequency domain analysis for the very close distances. Although the distance is very close, the frequency of the maximum frequency component is different for those two cases. Even though the material is changed, the frequency of the maximum frequency component doesn’t change for the same distance. So it only depends on the distance and the figure 14 shows the results for PVC at the 170mm.

Figure 14: Frequency domain acclamation of the X and Z axis at the 170mm from the motor axis for PVC

The frequency of the maximum frequency component against the contact distances are plotted ( figure 15) and the variation isn’t a linear and also when the contact point is very close to the sensor it gives errors due to the noises or there can be a resonance at that point .

CONCLUSION

According to the figure 15, it was clear that there is some relationship with the frequency of the maximum amplitude component and the contact distance. But there was huge scatter when the contact distance close to the sensor.