###### Abstract  
The development of control technology on wind turbine application robots has played an integral role in facilitating the digitization of inspection and maintenance in the wind energy industry. This paper presents a wind-turbine-climbing robot that determines the service lifespan of the wind turbine components subject to its payload capacity. The model has four rubber wheels, as the driving mechanism for its locomotion is being supported by a Bowden cable as a winding mechanism for its adhesion. The design further incorporates an Arduino microcontroller, distance sensors, motors, and a step motor to form its electromechanical structure. The overall capability of the robot has been analyzed through its kinematics and dynamics. Practical indoor experiments using a wind turbine tower mockup have been conducted for the validation of the various speeds and payload capacity of the prototype. The results indicate the effectiveness of its driving and winding mechanism to climb at the various speeds and with or without a payload. The advantage of the operations of its mechanism conformed with the wind turbine application robots. wind-turbine-tower-climbing robots; locomotion; adhesion; winding mechanism; driving mechanism +
Footnote †: journal: Applied Sciences  
levels of moisture and salt, can suffer from material degradation [13]. Lightning strike is a major challenge due to wind turbines being tall structures, especially when placed in flat planes [14]. Two types of lightning may occur: (1) a downward initiated lightning, which starts in a thunderstorm and propagates downward, attaching to the turbine tip, and (2) an upward lightning, which happens when the turbine is very tall and itself starts to generate lightning. Other surface defects are caused by erosion (rain erosion, sand, and hail) and small object impacts [12]. Overall, these external defects severely shorten the wind turbines' service life and restrict the cost per MW. Thus, this study aims to resolve the major issues related to the short lifespan of the wind turbines components and to improve the overall efficiency of wind turbine components, optimize manpower, identify issues early on and schedule maintenance to prevent unnecessary costs and catastrophic external wind turbine failures in the future through the benefits of a climbing robot. This suggests that the study of the wind-turbine-climbing robots to carry out surface maintenance in the different wind turbine components is extremely necessary and is deemed to become a common activity in the succeeding years, as the number of installed wind turbines is rising globally, necessitating further research for this topic. Studies on wind-turbine-climbing robots mostly focused on two important mechanisms: the adhesion and locomotion [15; 16; 17]. Adhesion is the mechanism that makes firm contact to the surface/object without slipping. Various adhesion mechanisms have been identified in the application of wind turbines with its prototype models. Among these adhesion mechanisms are magnetic adhesion [2; 17; 18], vacuum/air suction adhesion [19; 20], ropes/rubber bands traction [21], and mechanical-spring traction [22; 23]. Locomotion is the mechanism that enables the robot to move unbounded throughout its environments. Several types in terms of locomotion mechanism are being classified on wind-turbine-climbing robots, such as wheeled [14; 23], tracked [2; 15], and legged [19]. Depending on the features of structural components, robots have a variety of climbing mechanisms. Some of the recent studies on wind-turbine-climbing robots' application [2; 18; 19; 20; 21; 23; 24; 25] use experimental prototypes. One of the applications of a magnetic climbing robot is for the inspection and maintenance of a wind tower, using magnets to keep it in contact with the tower [2].