# Analysis of Electromagnetic Field Characteristics of Wave Glider
## 3 Analysis of Electric Field Noise Characteristics
### Analysis of Electric Field Characteristics under Different Motion States  
(1) Motion state (a)  
As shown in Figure 5, the tow rope above the floating body on the surface of the water is under tension and in a semi-submerged state. At this time, the peak value of the electrostatic field is about 0.3 mV/m, and the peak value of the axial frequency electric field is about 0.2 mV/m. According to the power spectral density, it can be seen that the energy of the interference electric field is mainly concentrated at 1 Hz. During the measurement, there were large ships docked in the harbor, so it is reasonable that the degree of wave shaking was relatively small. The working period of the rudder of the underwater towing body is about 2 s, and according to the analysis of the power spectral density of the axial-frequency electric field, it can be seen that at this time the rudder in the towing body is working normally, and the interference electric field generated is larger. Figure 5: Analysis of electric field characteristics. (**a**) electrostatic field; (**b**) shaft-rate electric field; (**c**) time frequency diagram of electrostatic field; (**d**) time frequency diagram of shaft-rate electric field; (**e**) power spectral density of electrostatic field; (**f**) power spectral density of shaft-rate electric field. (2) Motion state (b)  
As shown in Figure 6, the surface float enters the water and is parallel to the direction of the pier. Through the tow rope to control the floating body swaying, the peak value of the electrostatic field was measured at about 0.25 mV/m, and the peak value of the axial frequency electric field was about 0.4 mV/m. According to the power spectral density, it can be seen that the energy of the electrostatic field is mainly concentrated in the 0.4-0.7 Hz range, and the energy of the axial frequency electric field is mainly concentrated in the 0.5-1 Hz range. At the time of measurement, large ships were leaving the harbor, and the waves in the harbor were fluctuating, resulting in a large increase in the measured interference electric field signal. Figure 6: Analysis of electric field characteristics. (**a**) Electrostatic field; (**b**) shaft-rate electric field; (**c**) time frequency diagram of electrostatic field; (**d**) time frequency diagram of shaft-rate electric field; (**e**) power spectral density of electrostatic field; (**f**) power spectral density of shaft-rate electric field. (3) Motion state (c)  
As can be seen in Figure 7, at this point the surface float enters the water and is perpendicular to the dock. At this time, the surface floating body swaying is controlled by the tow rope. The peak value of the measured electrostatic field is about 0.25 mV/m, and the peak value of the axial frequency electric field is about 0.6 mV/m. Comparing with Figure 6, it can be seen that when the mother body is perpendicular to the dock, the peak value of the axial frequency electric field has a significant trend of increasing. Combining this observation with the analysis of the power spectral density of the axial frequency electric field, we observe that the energy is mainly concentrated in the 0.5-1.5 Hz range. This suggests that during the time when the submerged towing body is perpendicular to the dock, significant adjustments are required, resulting in greater rudder azimuth adjustments. Figure 7: Analysis of electric field characteristics. (**a**) Electrostatic field; (**b**) shaft-rate electric field; (**c**) time frequency diagram of electrostatic field; (**d**) time frequency diagram of shaft-rate electric field; (**e**) power spectral density of electrostatic field; (**f**) power spectral density of shaft-rate electric field. (4) Motion state (d)  
As can be seen in Figure 8, the surface floating body is still parallel to the dock. At this time, the tow rope directly controls the swaying of the underwater tractor, so the swaying amplitude of the tractor increases.