## 6 Results and Discussion  
### Impact of Rotating Brushes on Vibration  
The vibration of the PV panel is affected by its elasticity when subjected to the excitation of rotating brushes. To evaluate the PV panel's response-induced vibration, the SPCR was intentionally stopped while the brushes continued to rotate. The robot was then placed at various locations on the PV panel, including the center (Figure 16a), along the long edge (Figure 16b), and close to the short edge (Figure 16c). Deflection measurements were taken using the DG placed beneath the PV panels, aligning with the SPCR's center. Figure 17 displays the raw data depicting PV panel deflections induced by the SPCR's rotating brushes, both with and without the multi-suspension unit. When the SPCR was centered (Figure 17a), along the long edge (Figure 17b), and near the short edge (Figure 17c), peak deflection values of the PV panel without the multi-suspension unit were observed to be 1.65 mm, 1.79 mm, and 0.29 mm, respectively. In contrast, with the multi-suspension unit equipped on the SPCR, the corresponding deflection values reduced to 0.55 mm, 0.49 mm, and 0.19 mm. In these experiments, the influence of the SPCR's mass on the PV panel is not taken into account, as they focus solely on stationary conditions. Therefore, it is essential to note that these deflection values exclude the initial deformation caused by the SPCR's mass affecting the PV panel. The variation in deflection mainly stems from variations in the strength of the PV panels at different positions. Specifically, the PV panels demonstrate greater resistance to deformation near the strength-supporting bar, such as the short edges. Consequently, deflections are lower when the SPCR is positioned near the short edge of the PV panel. Furthermore, the mass of the SPCR is not evenly distributed across the entire aluminum frame but is concentrated predominantly along the long edge of the PV panel. As a result, significant deformation occurs in the photovoltaic panel when the SPCR approaches its long edge. The effectiveness of the multi-suspension unit in reducing peak deflection exhibited a significant reduction of 66.67%, 72.63%, and 34.48% compared to the case without using the multi-suspension unit when the SPCR was positioned at the center, along the long edge, and in close proximity to the short edge, respectively. These results reveal a gradual decrease in the multi-suspension unit's efficacy as the SPCR's position moves to areas with lower PV panel deformation. This phenomenon can be attributed to the compressed spring experiencing substantial deflection, leading to increased compressive force when the SPCR is located in regions with less PV panel deformation. Moreover, the compressive strain of the rubber tank track pads is directly affected by the reaction force from the  
Figure 16: Placement of SPCR on PV panel to investigate the effect of the multi-suspension unit on vibration with solely rotating brushes: (**a**) At the middle of PV panel; (**b**) At the middle of the PV panel’s long edge; (**c**) At the middle of the PV panel’s short edge. freewheels, resulting in greater compression as the SPCR approaches the short edge of the PV panel. Consequently, this reduces the damping ratio [21] of the multi-suspension unit and subsequently diminishes its vibration absorption capability [22]. It is worth noting that the reduction in the effectiveness of the multi-suspension unit when the SPCR is situated at the short edge of the PV panel is relatively minor in the SPCR's overall operation. Figure 18 displays the variation in \(\Delta z\) values during a 45-s experimental period, comparing the SPCR with and without the integration of the multi-suspension unit at different positions on the PV panel. The results reveal a substantial reduction or even the absence of many significant \(\Delta z\) values (exceeding 0.5 mm) when the SPCR is equipped with the multi-suspension unit, particularly when positioned at the center (Figure 18a) or the long edge (Figure 18c) of the PV panel.