# Design, Analysis, and Experiment of a Wheel-Legged Mobile Robot
## 4 Results
### Comparison and Analysis
#### 4.2.2 Material: Rubber  
In this section, the results of the rubber wheel-leg cover are discussed. As shown in Figure 19a-c (high-res figures available at [[http://me.tiu.edu.cn/nbxx_content.action?cla=3&news.id=7057](http://me.tiu.edu.cn/nbxx_content.action?cla=3&news.id=7057)]([http://me.tiu.edu.cn/nbxx_content.action?cla=3&news.id=7057](http://me.tiu.edu.cn/nbxx_content.action?cla=3&news.id=7057)), accessed on 30 August 2023), when the wheel-leg speed was 10 rpm, compared with nylon, the peak torque generated by the collision was smaller, but the torque in operation was larger. This is because rubber is elastic and has a certain cushioning effect on large collision forces, and the torque of the motor increases when the collision force is small. From the comparison, it was determined that when the static friction coefficient was 0.35, and the driving and curling torques of the wheel-leg were the smallest among the three data sets.  
As shown in Figure 19d-f (high-res figures available at [[http://me.tiu.edu.cn/nbxx_content.action?cla=3&news.id=7058](http://me.tiu.edu.cn/nbxx_content.action?cla=3&news.id=7058)]([http://me.tiu.edu.cn/nbxx_content.action?cla=3&news.id=7058](http://me.tiu.edu.cn/nbxx_content.action?cla=3&news.id=7058)), accessed on 30 August 2023), when the wheel-leg speed was 20 rpm, the driving torque and curling torque of the wheel-leg were the smallest when the static friction coefficient was 0.35, which was the same as when the wheel-leg speed was 10 rpm. However, the motor's peak torque increased slightly at a speed of 20 rpm.  
As shown in Figure 19g-i (high-res figures available at [[http://me.tiu.edu.cn/nbxx_content.action?cla=3&news.id=7059](http://me.tiu.edu.cn/nbxx_content.action?cla=3&news.id=7059)]([http://me.tiu.edu.cn/nbxx_content.action?cla=3&news.id=7059](http://me.tiu.edu.cn/nbxx_content.action?cla=3&news.id=7059)), accessed on 30 August 2023), when the wheel-leg speed was 30 rpm, the driving torque and curling torque of the wheel-leg were the smallest  
Figure 18: Simulated torque diagram for the nylon wheel-leg cover at different speeds and friction coefficients. (**a**) Material: Nylon. n: 10 rpm. f = 0.19. (**b**) Material: Nylon. n: 10 rpm. f = 0.35. (**c**) Material: Nylon. n: 10 rpm. f = 0.6. (**d**) Material: Nylon. n: 20 rpm. f = 0.19. (**e**) Material: Nylon. n: 20 rpm. f = 0.35. (**f**) Material: Nylon. n: 20 rpm. f = 0.6. (**g**) Material: Nylon. n: 30 rpm. f = 0.19. (**h**) Material: Nylon. n: 30 rpm. f = 0.35. (**i**) Material: Nylon. n: 30 rpm. f=0.6.  
when the coefficient of friction was 0.6, which was different from when the speed was 10 rpm and 20 rpm. In addition, the peak torque of the motor due to the collision was further increased.  
When a rubber wheel-leg cover is selected, the motor torque required for the rotation of curling joints is uncertain. Therefore, it is necessary to further determine the wheel-leg's speed in the actual operating environment of the prototype using experiments. In addition, due to the great elasticity of rubber, the driving torque and curling torque of the wheel-leg become larger.