## 1 Introduction  
Energy lays a solid material foundation for the existence and development of human society while significantly stimulating economic growth. However, with the continuous growth of energy demand in society and the reduction in conventional fossil energy supply, green energy has become the focus of attention. Among a wide variety of green energy sources, solar energy has aroused a significant amount of attention toward its advantages, and its development prospects are also broader. Compared with other green energy types, solar energy has the following advantages: (1) it is universal; (2) the storage capacity of solar energy is large and inexhaustible; (3) it is convenient; (4) it is not restricted by space and geographical location; (5) it is environment-friendly. The technology of photovoltaic power generation using solar energy has been extensively employed in numerous countries, such that it has served as a pillar industry of green energy. However, photovoltaic power stations are generally located in desert and Gobi regions characterized by dry climate, high sandstorms, and low precipitation. Dust particles were deposited on the surface of photovoltaic panels under their gravity or under the effect of wind. The accumulated dust can trigger the following problems: (1) blocking of the photovoltaic panel reduces the area of solar radiation received by the photovoltaic panel, affecting power generation efficiency; (2) the rise in its temperature results in hot spots; (3) the corroded surface of photovoltaic panels poses permanent damage to the panels [1; 2; 3; 4; 5; 6].  
With the increasingly serious accumulation of dust particles on the surface of photovoltaic panels, it has seriously constrained the efficiency of photovoltaic power generation, and the dust particles on the surface of photovoltaic panels should be cleaned. The existing disposal methods for dust particles deposited on the surface of photovoltaic panels are elucidated as follows: (1) manual cleaning method: waste of water resources, high labor intensity of workers, high labor cost, long cleaning cycle time, and uncontrollable cleaning effect; (2) self-cleaning of photovoltaic panels: high cost, inability to adapt to relatively harsh environmental conditions and large-scale applications; (3) track-type cleaning robot: reciprocating cleaning operation is performed relying on the guide rail on the photovoltaic panel; the cost of track laying is up-regulated under the irregular arrangement of the photovoltaic panel group, which cannot meet the needs of field operation; (4) mobile vehicle-mounted photovoltaic cleaning robot: capable of automatically adjusting and cleaning photovoltaic panels at different states, effectively cleaning dirt with different adhesion and performing cross-photovoltaic group operations on power plants in different regions [7; 8; 9; 10; 11; 12; 13]. Moreover, the manual cleaning method cannot satisfy the actual needs due to the harsh environment of the photovoltaic power station and the preciousness of water resources; photovoltaic panel self-cleaning technology and track-type cleaning robots cannot conform to the low-cost and high-efficiency cleaning operations with the rising scale of photovoltaic power stations; the complexity of the road surface of the photovoltaic power station makes the vehicle-mounted photovoltaic cleaning robot unstable in the walking process, resulting in damage to the photovoltaic panel surface by the cleaning device. Based on the above analysis, it is of great significance to develop a novel type of self-propelled photovoltaic panel cleaning robot to efficiently clean the dust particles, snow and dust covers on the photovoltaic surface without water so that it has the characteristics of modular mechanical structure, intelligent control system and automatic walking.