# Analysis of Electromagnetic Field Characteristics of Wave Glider
## 3 Analysis of Electric Field Noise Characteristics
### Analysis of Electric Field Characteristics under Different Motion States
The peak value of the electrostatic field is about 0.35 mV/m, and the peak value of the axial frequency electric field is about 1 mV/m. The increase in the traction body swaying directly leads to the significant increase in the interference electric field signal; by analyzing the power spectral density, it can be seen that the traction body swaying also leads to the increase in the adjustment angle of the underwater rudder, which makes the axial frequency electric field signal increase. Figure 8: 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. (5) Motion state (e)  
As shown in Figure 9, the floating body on the water surface enters the water but is perpendicular to the dock. At this time, the traction rope of the underwater towing body is not under force, and the shaking amplitude of the towing body decreases. The peak value of the electrostatic field is about 0.30 mV/m, and the peak value of the axial frequency electric field is about 0.8 mV/m. Compared to Figure 9, the reduction in axial frequency electric field signal is relatively small. It can be seen that when the floating body on the water surface is perpendicular to the dock, the azimuth angle changes greatly, and the working amplitude of the servo is large, resulting in a larger axial frequency electric field signal. Figure 9: 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. (6) Motion state (f)  
As shown in Figure 10, the floating body on the water surface is lifted off the water surface by a crane. At this time, only the underwater towing body is working underwater, and the shaking of the towing machine is small. The motion state can be regarded as a stable state with only the underwater servo working. At this time, the peak value of the electrostatic field is about 0.10 mV/m, and the peak value of the axial frequency electric field is about 0.2 mV/m. In the following paragraphs, we will summarize the electric field characteristics of wave gliders under different motion states. Figure 10: 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. By comparing Figures 5 and 10, it can be seen that when the mother ship leaves the water surface, the amplitude of the underwater towing body shaking decreases, and the electrostatic field generated by shaking is greatly reduced. However, the amplitude of the electric field generated by the operation of the towing body servo does not change much. By comparing Figures 6-9, it can be seen that the amplitude of the floating body's shaking on the water surface has a relatively small impact on the electrostatic field, while the amplitude of the underwater towed body's shaking has a more significant impact on the electrostatic field. By analyzing the working mechanism of the underwater towed rudder, it can be concluded that when it is perpendicular to the dock, the azimuth angle changes more as compared to when the floating body is parallel to the dock, resulting in a larger amplitude of rudder variation and a higher amplitude of axial frequency electric field. By analyzing the motion state and combining it with data analysis, the following conclusions can be drawn:  
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