# Gait Planning Research for an Electrically Driven Large-Load-Ratio Six-Legged Robot
## 5 Applications and Experiments  
Based on our previous research results and the engineering technical indexes of the robot, a prototype of an electrically driven large-load-ratio six-legged robot is developed. The gait planning strategies are written in C++ language and downloaded to the system of the robot. Due to the same method of gait planning for the tripod gait, quadrangular gait, and pentagon gait, the tripod gait is only employed to verify the reasonableness of the gait planning strategies. Then, the experiments of the walking speed and surmounting obstacle are respectively performed. To check the reasonableness of the gait planning strategies, the robot uses 0.4 times the maximum walking speed as the goal speed to perform the walking speed test. The reasonableness of the gait planning can be verified when the robot achieves the above-stated walking speed.  
The ant-typed tripod gait is selected for the experiment of walking speed for the large-load-ratio six-legged robot. Then, the body of the robot carries the load of 1519 N. The movement time (TM) is set as 100 ms in the programmable multi-axis controller (PMAC). The support distance of the leg \(i\) is set as 0.2 m in the support phase. Hence, the theoretical walking distance should be \(2v_{\text{max}}T/5\) for the large-load-ratio six-legged robot in a gait period. The experiment using the walking speed \(2v_{\text{max}}/5\) under a load of 1519 N is shown in Figure 7. Based on the range sensor installed in the robot body, the walking distance \(l_{\text{b}}\) of the robot can be obtained with the change of time \(t\). Then, the curve of walking speed is drawn and is shown in Figure 7.  
Based on Figure 7, the actual walking speed of the robot can be calculated though the walking distance \(l_{\text{b}}\) and time \(t\). Then, the contrastive analysis is implemented between the actual walking speed of the robot and the theoretical walking speed \(2v_{\text{max}}/5\). The contrastive result shows that the data are both the same. The reasonableness of the gait planning is verified for the large-load-ratio six-legged robot.  
Based on Figures 3 and 7, it is concluded that legs 1 and 2 can fully reflect the characteristics of the support phase and transfer phase when the large-load-ratio six-legged robot walks using the ant-type tripod gait. According to the PMAC motion control card, the pulse number curves of the  
Figure 7: Experiment of walking speed \(2v_{\text{max}}/5\) under a load of 1519 N: (**a**) experiment of the walking speed of \(2v_{\text{max}}/5\) of the prototype; and (**b**) curve of walking speed for the robot body.  
servo motors are respectively obtained for the abductor joints, hip joints, and knee joints of legs 1 and 2; they are shown in Figure 8. In Figure 8, we can find that the pulse number curves of the servo motors are smooth. Hence, we conclude that the ride comfort of the rotation joints can be demonstrated. The correctness of the solution is verified in the analyses of the forward and inverse kinematics of the robot. In Figure 8, the minus sign only indicates that the steering of the servo motor is opposite to the specified positive steering.  
The prototype of the large-load-ratio six-legged robot employs the tripod gait to stride across the vertical obstacle under the load of 1519 N. The experiment of the surmounting obstacle is shown in Figure 9. The parts of the walking parameters are set for the robot prototype. The height of the body is defined as 0.6 m. The maximum swing height \(h_{\text{T-max}}\) is set as 0.34 m. The step pitch \(s\) is 0.3 m. Leg 4 and leg 6 trample on the vertical obstacle. Other legs do not trample on the obstacle. Then, it is found that the large-load-ratio six-legged robot can stride across the vertical obstacle under the tripod gait. The impact phenomenon does not appear between the foot and the ground. Hence, the rationality of the gait planning can be confirmed for the large-load-ratio six-legged robot.