# The Kinematic Analysis of a Wind Turbine Climbing Robot Mechanism
## 2 Mechanical Design  
### Robot Design/Model  
The structure of the climbing robot in a wind turbine tower is shown in Figure 2. The tower is a stand-alone steel tube with a varying diameter. The diameter varies between 330 mm at the tower top up to 400 mm at the tower bottom. The tower has a height of 1200 mm which has been adopted from a real 2 MW wind turbine which has a height of around 78,000 mm. The design of the wind turbine climbing robot consists of three parts: the driving mechanism, winding mechanism, and body frame is quite similar to what was demonstrated in [10] the first prototype. The second prototype addresses maneuverability and stability, resolving some of the issues that emerge in the first prototype. The driving mechanism are the four motorized mecanum wheels coated with rubber rollers around wheel circumference. It is adopted for obtaining maximum climbing speeds and includes different movement states: the up-down motion, rotational motion, and spiral motion. The maneuverability of the mecanum wheel possess three DOFs (degree of freedom) without slips due to its rubber-based roller. The first DOF is in the direction of the wheel orientation, and the second DOF is the motion of rollers mounted around the periphery of the main wheel. In principle, the roller axes can be mounted at any nonzero angle \(\varphi\) with respect to the wheel orientation. The mecanum wheel is shown in Figure 3, with roller axis angles of \(\varphi=\pm 45^{\circ}\) to the wheel axis. The third DOF is a rotational slip on the point of contact of the roller on the surface [11]. The construction of mecanum wheel rollers are left-handed wheels (rollers at \(-45^{\circ}\) to the wheel axis) and right-handed wheels (rollers at \(+45^{\circ}\) to the wheel axis). For left-handed mecanum wheels, rollers are orientated from lower right to upper left. Rollers for right-handed wheels are installed in the opposite way. The four motorized mecanum wheels will move along to a circular truncated cone tower with DC power supplies of 12 V. The CHP-36 GP-BL3650 (Shenzhen Chihai Motor Co. Ltd., Shenzhen City, Guangdong, China) DC motors provide high torque and high power to drive the robot to its movement states. It is essential to emphasize that in the mecanum wheel, it is the wheel hub being controlled by a DC motor, but the wheel rollers are not. One of the key features of the climbing robot is the winding mechanism that utilizes a PL 36-37-42 HS03 (Shenzhen Leadshine Control Technology Co. Ltd., Shenzhen City, Guangdong, China) step motor connected with a fabricated twin pulley and Bowden cable to provide the force to adhere the climbing robot on the tower surface. This mechanism will adjust to the different diameters of the circular truncated cone tower to grip on the  
Figure 2: Wind Turbine Climbing Robot Model (1—Winding Mechanism with Twin Pulley, 2—Step Motor, 3—Bowden Cable, 4—Body Frame, 5—Caster Wheel, 6—Cable, 7—Motor, 8—Mecanum Wheel, 9—Electronic Casing-Embedded Micoprocessor and Electronic module). tower surface without falling to the ground. It maintains a safe distance through the help of a TOF10120 (Shenzhen Heng HongTong Electronics Technology Co. Ltd., Shenzhen City, Guangdong, China) laser range distance sensor that is attached to the robot's body frame. The distance sensor gives feedback signals to the embedded microprocessor module which is the Arduino MEGA 2560 (Shenzhen Ke Zhi You Technology Co. Ltd., Shenzhen City, Guangdong, China) that integrates all the controls of the movement states, winding mechanisms, and distance sensors. It will adjust depending on the tower diameter surface as it moves in different up-down motions, rotational motions, and spiral motions. With this design, the robot has the potential to adapt to the tapering wind turbine tower diameter structures and provides superior maneuverability capabilities to examine any physical problem of the tower, or taking specific application tasks.