# On the Unification of Legged and Aerial Robots for Planetary Exploration Missions
## 3 Experimental Evaluation  
In this section, results will be presented on the experimental evaluation of the proposed designs of the landing platforms.  
Both landing platforms were experimentally evaluated in the lab environment, while the platform for Shafter was also evaluated in the field tests, as is shown in the video ([[https://youtu.be/UDn_q-Ju9F8](https://youtu.be/UDn_q-Ju9F8)]([https://youtu.be/UDn_q-Ju9F8](https://youtu.be/UDn_q-Ju9F8)), accessed on 20 February 2022). In the case of the landing platform for the reconfigurable drone, the first part of the evaluation process aimed to identify the presence of collisions between Spot legs and the landing platform. In this test, to manually control Spot, extreme body positions and rotations were commanded, as shown in Figure 11; however, during these tests, collisions were not detected.  
The next set of tests concerned the evaluation of the drone take-off capabilities in which the drone was locking and unlocking itself from the platform and performing take off (Figure 12). In these tests, the R-Shafter was manually controlled. The evaluation tests demonstrated viability of the proposed design.  
Figure 11: The Spot robot carrying the R-shafter drone in different poses.  
Figure 10: Communication architecture for the proposed legged-aerial system.  
The main focus of the experimental evaluation was given to the landing platform for the Shafter drone. The evaluation process included the evaluation of the robustness of the locking mechanism to securely keep drone manual (Figure 13) and autonomous (Figure 14) take-off tests from the landing platform in the lab environment. In the autonomous take-off tests, for position estimation and waypoint navigation, a Vicon motion capture system was utilized. All the evaluation tests were accomplished successfully.  
The self-alignment capability of the landing platform was tested while performing manual landing maneuvers on the standalone platform (Figure 15). The tests carried out demonstrated the viability of self-aligning functionality of the landing platform.  
Overall, the completed set of tests with Spot and Shafter proved the feasibility of the unification concept in the lab. The conducted experiments also proved that the platform is robust enough for testing in the field. Furthermore, the platform for Shafter was evaluated as a part of large-scale experiments in the underground tunnel (Figure 16). At the beginning of this experiment, the drone was attached and locked on the platform. In the sequel, the Spot robot autonomously navigated from the starting point to the point of drone release. At this point, the platform was unlocked and the drone performed autonomous take-off, as depicted in Figure 17. All the field tests successfully demonstrated the robustness of the Spot-Shafter unification and proved the robustness of the designed landing platform.  
Figure 14: Autonomous take-off of the Shafter drone from the platform while Spot robot is in standing pose.  
Figure 13: Manually controlled Shafter drone takes off from the platform while the Spot robot is in sitting position.