# Design and Development of a Climbing Robot for Wind Turbine Maintenance
## 1 Introduction  
Bridges, dams, fuel storage tanks, cargo ships, vessels and onshore/offshore wind turbines are important industrial and economic structures. These complex structures ensure the worldwide distribution of products, energy supply and transportation, which are the foundations of modern life. The evolution of the wind turbine to generate carbon-free renewable energy is in the spotlight now because of the future target development leading to a clean energy technology. Thus, the rapid increase in wind turbine demand extended to a manifold task and will equate to face a different challenge in terms of its operation and maintenance. Like any outdoor surface, wind turbines naturally collect detritus sources such as ice, hail, dust, marine salt, grease, hydraulic oil, UV radiation and flying planktons. These actors affect the performance efficiency or may lead to the failure of wind turbine parts. The wind turbine structure parts, such as towers and rotor blades, still need regular and intense maintenance [1]. Maintenance in wind energy is a challenging task, where climbing such structures tends to be a hazardous job. The wind turbine maintenance remains a manual task, and it is performed by the technical climbers accessing a significant height with a crane or working while hanging down with a rope from a nacelle of the wind turbine, as shown in Figure 1. The inspection personnel may perform simple ground visual inspections, or a close-up tower visual inspection to assess on nominated areas at the different intensities of dirt, corrosion and cracking on the wind turbine parts.Therefore,these hazardous tasks are suitable for the climbing robot mission rather than human beings for safety and ease of inspection. To address the aforementioned issues, the idea of using a climbing robot is the optimum solution to perform tasks that involve a high risk for technical workers who have to climb the wind turbines tower. The development of a climbing robot that can conduct automatic detection and maintenance operations on the wind turbine parts at high altitude, even in a different weather conditions, was the aim of this manuscript. Climbing robots belong to a specialized field of mobile robots designed to safely perform maintenance and inspection. The main feature is mobility against the gravitational pull of the body. In designing these robots, one important aspect to consider is the mechanism of the adhesion that is strong enough to travel upwards with the different diameter and bear its weight. Therefore, the designer should not only consider the robot's locomotion method, as in conventional robots, but also its techniques for sticking to the wind turbine parts. There are different methods of adhesion initially designed for climbing a specific kind of structure or surface. The first type is magnetic adhesion for climbing on a ferrous surface via electromagnets or permanent magnets [2; 3]. The advantage of this form of adhesion is a strong and stable adhesion force; its drawback is that this type of adhesion is limited to only the ferromagnetic structure. The second type is vacuum/air suction adhesion for sticking the robot onto the walls. This adhesion process is stable but is accomplished by using air compressors or some other source of air [4; 5; 6]. The drawbacks of suction-based climbing robots are: (1) they need the perfect sealing of the suction cup; and (2) they take time to produce a vacuum and release the suction for locomotion. They can therefore operate only at low speed on smooth and non-porous surfaces (e.g., glass, metal walls, or painted walls). These limitations greatly limit the robots' applications. The third type is mechanical adhesion, which utilizes armed mechanisms or grippers to handle uneven surfaces that are only suitable for uneven and complex structures surfaces such as poles, branches of trees, and rough building surfaces [7; 8; 9]. The benefit of this type of adhesion is the ability to ascend on uneven and rough surfaces, but flat and smooth surfaces cannot be climbed.