# Modeling of Walking-Gait Parameters and Walking Strategy for Quadruped Robots
## 1 Introduction  
Robot technology is an emerging technology that integrates computer technology, sensing technology, and vision technology [1]. It is undoubtedly one of the frontier areas of today's scientific and technological development [2]. In recent years, with the rise of artificial intelligence, robotics technology has developed vigorously, and its research has gradually expanded from the traditional industrial scope to new fields such as biomedicine, educational services, and exploration and rescue [3]. The prevalence of robots in daily life is increasingly evident. For example, pet robotic dogs can often be seen taking walks with their owners, while rescue robots are frequently deployed in disaster areas, providing a glimmer of hope for victims [4]. In addition, there are also small robots engaged in express sorting and load-bearing robots engaged in cargo transportation. The development of robot technology has made life more comfortable and faster [5]. Mobile robots are an important part of robotics technology. An increasing number of scientific research institutions have been dedicating significant human and material resources to research on mobile robots, due to their broad application markets and promising prospects [6]. One of the research hotspots in the field of mobile robots is footed robots. The reason is that nearly half of the terrain in the natural environment cannot be reached by wheeled or crawler robots, such as forests, grasslands, and disaster areas [7]. Forestsand grasslands are rich in resources, and disaster areas also need robots to find affected people and bring necessary supplies [8]. Compared with wheeled or crawler robots, the discrete-point-like feet of footed robots when they contact the ground are more suitable for non-continuous plane ground such as forests and disaster areas. Therefore, footed robots play an important role in human service and well-being and life [9]. Limbed robots are classified according to the number of feet, and the common ones are biped, quadruped, and hexapod [10]. Obviously, compared with two-limbed robots, quadruped robots have the characteristics of stable motion, diverse motion forms, and strong carrying capacity [11]. Compared with hexapod robots, and those with even more limbs, quadruped robots have simpler structure and easy-to-establish motion models, so quadruped robots appear more frequently in scientific research and life [12]. The quadruped robot can adjust its movement gait according to different environments and different speeds [13]. The accessibility of the ground and the pitch of the ground slope will affect the quadruped robot's choice of gait, which leads to a variety of movements by the quadruped robot. Common periodic symmetrical gaits on unobstructed hard surfaces include wave gait, diagonal gait, and running gait. At present, researchers have investigated single gaits of quadruped robots more, including the planning of foot trajectories, the coordination between the four limbs, and analysis of the stability of the whole machine. Many models have been proposed, such as the linear inverted-pendulum model and the virtual-limb model [14]. For foot-trajectory planning, an elliptical trajectory and a parabolic trajectory have been proposed [15]. This study found that, although the above research trajectories are diverse, their biological diversity is not strong. In addition, researchers have done little research on the gait transition process, and the research volume for this is far less than the research on single gaits. On the one hand, the gait-transition process itself is relatively complicated, and accurate calculation is required between the two gaits to achieve a smooth transition. On the other hand, during the gait-transition process, the stability and coordination of the whole machine must be greatly tested. Considering the existing bionic quadruped robots, it can be seen that in terms of the robot's body structure, its joints are limited, and there is still a significant gap compared to flexible organisms.