# Vision-Guided Hierarchical Control and Autonomous Positioning for Aerial Manipulator
## 5 Experimental Results
### Motion Test of the Aerial Manipulator  
Before performing tasks, the vision-guided aerial manipulator required a series of debugging operations, including flight controller calibration, ESC initialization, PID parameter configuration, camera activation, and setting the initial position of the manipulator. At the system's initial takeoff, the uneven terrain may have introduced uncertainty and error into the subsequent task execution. To further enhance the success rate of the mission, in our practical testing, we selected a flight scenario with dimensions of 4 m \(\times\) 5 m \(\times\) 4 m and a flight speed of 0.6 m/s. Additionally, testing and experimental analysis of the motion process were conducted for the aerial manipulator system to ensure that the quad-rotor UAV maintained stable aerial operational capability and flight performance after mounting the manipulator. Figure 10: LiDAR-based SLAM autonomous navigation: (**a**) LiDAR scanning; (**b**) Autonomous navigation. First, the flight stability during hovering was tested. Figure 12 provides height variation curves for the manipulator in the z-direction at hover heights of 0.5 m, 2 m, and 3 m. At a hover height of approximately 0.5 m, a slight fluctuation occurred in the UAV's attitude due to ground effects. However, when flying at \(\sim\)2 m, the flight was stable. Meanwhile, at a hover height of \(\sim\)3 m, significant attitude variation occurred. Therefore, the selected hover height for this study was 2 m.  
Second, to minimize the impact of manipulator motion on the stability of the flying platform, tests were conducted on the servo motor speeds. The testing scenario involved controlling the servo motor speed of the manipulator through the upper computer while the UAV was in stationary hover. Figure 13 provides the attitude angle variation curves of the servo motor at different speeds (35, 48, and 55 rpm). Moreover, the manipulator moved slowly at 48 rpm, and under conditions that ensured the operational efficiency of the manipulator, the impact of its motion on flight stability was minimized. Figure 11: Comparison of algorithm trajectory results. Figure 12: The z-direction height variation of the manipulator. As shown in Figure 14, for the grasping task of the aerial manipulator, a segmented grasping strategy was applied. Specifically, five poses were designed, including the initial pose, pre-grasping pose, grasping pose, flight pose in operation, and delivery pose. The specific process was as follows:  
Initial flight pose (Figure 14a): The UAV took off and approached the target object, while the manipulator remained in the initial retracted state. During the target search process, the SLAM mapping and scene reconstruction were performed with LiDAR, followed by autonomous positioning and target object search. Pre-grasping pose (Figure 14b): The UAV navigated to the target object's position using LiDAR-based SLAM for localization. The visual guidance system was activated to identify the target object. The UAV hovered and descended in altitude while the manipulator adjusted its position in advance. It vertically descended to approach the target object in the optimal pose for grasping. The manipulator reached the pre-grasping pose. Grasping pose (Figure 14c): The aerial manipulator iteratively searched the target object, while the No. 2 TFmini continuously detected the height information between the  
Figure 14: Main steps of aerial manipulator motion:(**a**) Initial pose, (**b**) pre-grasping pose, (**c**) grasping pose, (**d**) flight pose in operation, and (**e**) delivery pose. UAV and target object. Once the grasping height of the aerial manipulator fell within the threshold range, the mechanical gripper quickly closed to grasp the target object. Flight pose (Figure 14d): After the aerial manipulator grasped the target object, it flew away from the operating point and proceeded to the target delivery location. Delivery pose (Figure 14e). The aerial manipulator reached the target position for delivery, and then took off to land at the original point.