# Resonant Power Supply for Plasma Cleaning Based on Fuzzy Logic Power Tracking
## 4 Analysis of Test Results
Although PFM and PWM modulations are superior to hybrid modulation in a certain aspect such as low power operation, the PFM algorithm is more efficient. The PWM algorithm has a higher power matching accuracy in each power. However, considering efficiency, power matching accuracy, and working power range, the hybrid modulation  
Figure 23: Power matching curve. Figure 22: Efficiency curve. algorithm is obviously superior to the other two modulation methods. Therefore, it is appropriate and efficient to select the hybrid modulation algorithm as the control mode of the resonant power supply system for plasma cleaning. The cover plate of a glass mobile phone was taken as the test object, and the contact angle measuring instrument was used to fix the acting distance at 1.5 cm. The air pressure was 0.15 MPa, the neutral gas temperature was 85 \({}^{\circ}\)C, the working frequency was 25 kHz, the processing speed was 100 mm/s, the resonant inductance was 34 mH, and the working gas was compressed air. The contact angle before and after the cover plate was cleaned at different powers and was measured, as shown in Figure 23. The contact angle here refers to the angle formed when the liquid phase is sandwiched between the two tangents of the gas-liquid interface and the solid-liquid interface. As shown in Figure 24, the contact angle decreases gradually with the increase in the set power, indicating that the hydrophilicity of the material is greatly improved, and the cleaning effect of the resonant power supply system for plasma cleaning meets the requirements. In order to further study the influence of working distance on cleaning effect, the power was set to 500 W\(\sim\)1000 W, and the working distance was set to 0.5 cm\(\sim\)2.5 cm, respectively. The change of contact angle before and after cleaning of the mobile phone cover plate is measured and recorded, as shown in Table 5.  
The data in Table 5 are arranged into curves as shown in Figure 25. The analysis shows that the change angle of the contact angle is positively correlated with the set power, that is, the higher the set power, the better the cleaning effect. This negatively correlated with the acting distance, that is, the larger the acting distance, the worse the cleaning effect. However, the contact angle of the mobile phone cover plate after cleaning has a lower limit, that is, there is a minimum contact angle, its value is about 12\({}^{\circ}\), that is, the maximum change angle of the contact angle is about 105\({}^{\circ}\). When the contact angle of the mobile phone cover is close to the maximum value, no matter how the set power increases and how the acting distance decreases, the change of the contact angle will not increase, that is, the contact angle will not decrease after cleaning. The working distance was set to a fixed value of 1.5 cm, and the power was set to 500 W-1000 W, respectively. Under the same test conditions, two materials, glass and aluminum, were tested. The change data of the material contact angle before and after cleaning are shown in Table 6.  
The data in Table 6 are arranged into the curve shown in Figure 26, and the analysis shows that the properties of the acting materials have a significant impact on the cleaning effect. In the same case, under the action of plasma, glass material is obviously more easily activated than aluminum material, the surface free energy is more easily improved, and the flatness changes more, that is, it is easier to be modified. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Setting**} & \multicolumn{5}{c}{**Contact Angle Change Angle (\({}^{\circ}\))**} \\ \cline{2-6}  & **0.5 cm** & **1 cm** & **1.5 cm** & **2 cm** & **2.5 cm** \\ \hline
500 & 87.14 & 78.14 & 68.92 & 58.62 & 39.47 \\
600 & 92.93 & 86.74 & 71.52 & 63.14 & 60.59 \\
700 & 95.