## 1 Introduction  
With the development of science and technology, many countries and space agencies are committed to space exploration, and the Moon is also proposed to be used as a gateway and entry point for future human space missions. Scientists have come up with the concept of building infrastructure on the Moon, such as a moon base [1; 2; 3]. Therefore, the exploration of the Moon is very important for the above tasks. According to sources, the surface of the Moon is covered with a layer of loose rock fragments, often referred to as lunar regolith [4]. Through the analysis of lunar soil samples, it can be seen that most of the regolith layer is composed of particles with a size of less than 1 cm, which can be subdivided into three categories: dust (\(<\)50 \(\upmu\)m), soil (\(<\)1 mm) and coarse fine (1-10 mm), which are very loose due to long-term weathering, so the lunar soil is very soft, the overall hardness is low and it has strong adsorption [5; 6; 7]. In addition, the Moon's surface is riddled with craters of various sizes, ranging in diameter from a few microns to hundreds of kilometers, with most moon craters being circular or elliptical, with larger diameters and lower depths, and often with complex topographic features [8; 9; 10]. In the face of loose lunar soil, craters and craters on the Moon, as well as low-pressure, low-temperature and oxygen-deficient environments in space, it is very difficult and expensive to carry out exploration missions on the Moon [11]. Robots have great potential to achieve planetary exploration missions, which can help people explore a wide variety of unknown environments and protect their lives. So far, most of the robots that have successfully carried out cosmic exploration missions have been wheeled robots; however, several experiments have proven that wheeled robotsaccumulate a large amount of substrate material in their tire portion as they move forward, thus generating a high compaction resistance and making it difficult to avoid obstacles in complex environments [12; 13]. Since most of the legged robots are designed with biomechanical principles, they are flexible, efficient and highly adaptable, and they have very good maneuverability to traverse complex environments, making them more suitable for exploring unstructured terrain [14; 15]. The development of legged robots can be traced back as far as the mid-20 th century, and with the continuous research of scientists, legged robots have made significant progress in different fields [16]. Among many legged robots, hexapods have great research value in planet exploration due to their better stability and gait diversity [17]. In the 1980s, Carnegie Mellon University in the United States developed a series of robots for planet exploration, such as Ambler and Dante II [18; 19]. Each of the Ambler robot's legs is a right-angled coordinate leg, with the help of a rack and pinion inside the leg to adjust the vertical position of the body to cross the obstacles. Subsequently, Carnegie Mellon University developed the hexapod robot Dante II in the early nineties of the twentieth century to meet the needs of the exploration of large slopes and steep terrain on the surface of the planet and conducted experiments on active volcanoes. Each leg can independently adjust its vertical height to adapt to the rough terrain and use ropes for traction so that it can climb up and down the cliff face. In recent years, Chiba University in Japan has developed a large-scale hexapod robot, COMET-4, driven by hydraulic cylinders [20], with a fuselage weight of 2120 kg and a load capacity of 40 kg. Each leg has four degrees of freedom, and the leg joints are driven by hydraulic cylinders. The forward and backward swing of the base joints is driven by hydraulic motors, which have better driving ability. With the whole machine updated and tuned, the walking speed can approach 1 km/h. It has the capacity to traverse vertical obstacles up to 1 m in height and the ability to overcome a 20\({}^{\circ}\) slope resistance.