# Development of Portable Magnetic Adsorption Amphibious Robot
## 1 Introduction  
Offshore platform legs and ship exterior walls are essential parts of offshore engineering facilities, and their structural safety is crucial to the stability and safety of the entire facilities associated with them. Taking the pile leg of an offshore platform as an example, after being eroded by seawater and marine organisms being attached to it for a long time, its surface will gradually accumulate dirt and biological attachments, which will not only affect its appearance, but, more importantly, cause potential damage to the structure. These attachments will weaken the strength of the pile leg and increase its risk of breakage when impacted by natural forces, such as waves and currents. The pile legs of offshore platforms play a supporting and fixing role in offshore engineering facilities, and their operation efficiency directly affects the performance of the whole facilities. Dirt and organisms attached to a pile leg affect its thermal conductivity, resulting in reduced heat exchange efficiency between the pile leg and seawater. The accumulation of dirt and living organisms can also affect the finish of the pile leg, increasing the resistance of water flow and reducing its ability to resist wind and wave erosion. These problems will greatly reduce the life of offshore platform pile legs [1]. Therefore, regular cleaning of marine pile legs is an important measure to ensure their structural safety. The cleaning work can remove corrosion products and biological attachments on the surface of pile legs, reduce the corrosion rate, and delay the aging and damage process. It can extend the service life of pile legs and reduce maintenance and replacement costs. Regular cleaning of marine pile legs can ensure that they are kept in good working condition, avoid various problems caused by the accumulation of dirt and organisms, and further improve the operating efficiency of the equipment. At present, the cleaning of pile legs and outer walls of offshore platforms is still dominated by traditional manual methods. There are many problems with this mode of operation. First of all, workers carry out the cleaning work at high altitude, the risk factor is extremely high,and often there are equipment failures or workers are injured. Secondly, due to labor shortages and inefficiency, it is sometimes difficult to achieve the desired cleaning effects, resulting in a prolonged stay of cargo ships in port, increasing freight costs [2]. The development of wall-climbing cleaning robots has become an effective solution to this problem. Such robots use ultrahigh-pressure water for cleaning, which can reach the upper part of a cargo hold that is difficult to reach manually, greatly improving cleaning efficiency. In addition, the use of these robots frees the rigging required for artificial high-altitude work and provides safety for workers. The robots are not only environmentally friendly, but also provide an efficient and viable solution for the cleaning and maintenance of the cabins of large cargo ships. Examples of the robots' operating environments are shown in Figure 1.  
[PERSON] et al. [3] proposed a wall-climbing robot that can be adsorbed on the wall of a steel structure. Due to the design and optimization of the suction characteristics of the magnetic adsorption component, it has a larger load bearing capacity and more flexible motion ability. [PERSON] et al. [4] proposed an amphibious hexapod robot with composite motor limbs which can move underwater with multiple degrees of freedom and climb stably on slopes of different gradients. In Japan, [PERSON] et al. [5] developed a small underwater crawling-type four-swing-arm robot. The robot is equipped with a track motor to drive the track and force arms on both sides of the track, which can also adjust the walking posture of the robot at will.