# Vision-Guided Hierarchical Control and Autonomous Positioning for Aerial Manipulator
## 3 Hardware Structure and Control Method of Aerial Manipulator System  
### Hardware Structure of Aerial Manipulator System  
The aerial manipulator system combines the flexible operation of the manipulator with the maneuverable flight and precise hovering capabilities of the quad-rotor UAV. This system can actively influence the surrounding environment and perform tasks, including approaching, grasping, and delivering target objects [29]. Considering the payload, stability, and system complexity, the hardware platform of the aerial manipulator system is shown in Figure 1. It comprises two main components: the quad-rotor UAV body and a single-degree-of-freedom manipulator. The structure is constructed using lightweight materials, and the mechanical design is compact, light, and flexible. The system's overall weight is approximately 2016 g (including the battery), and it can achieve a flight endurance of approximately 18 min when equipped with a 5300 mAh 4S battery. The landing gear designed for this platform seamlessly integrates with the main body of the UAV. The footests utilize sponge balls with shock-absorbing capabilities, enabling safe landing and take-off even in complex and dynamic terrain conditions. In the event of a crash, only the landing gear will become damaged, preventing the destruction of other structural components of the aircraft. Figure 1: Hardware structure of the aerial manipulator. In this system, the quad-rotor UAV utilizes an F450 carbon fiber frame with a wheel-base length of 450 mm. It is equipped with 920 kV brushless motors and Hobbywing 20A ESCs and is fitted with 10-inch nylon propellers. The flight control system is the Pixhawk 4, an open-source flight controller based on the Nuttx operating system and developed by the Pixhawk team ([[http://docs.px4.io/main/en/flight_controller/pixhawk4.html](http://docs.px4.io/main/en/flight_controller/pixhawk4.html)]([http://docs.px4.io/main/en/flight_controller/pixhawk4.html](http://docs.px4.io/main/en/flight_controller/pixhawk4.html)), accessed on 5 March 2023). Pixhawk 4 has an integrated 3-axis 16-bit accelerometer/3-axis gyroscope ICM-20689. Furthermore, the UAV is equipped with the NVIDIA Jetson Xavier NX processor ([[https://www.nvidia.cn/autonomous-machines/embedded-systems/jetson-xavier-nx/](https://www.nvidia.cn/autonomous-machines/embedded-systems/jetson-xavier-nx/)]([https://www.nvidia.cn/autonomous-machines/embedded-systems/jetson-xavier-nx/](https://www.nvidia.cn/autonomous-machines/embedded-systems/jetson-xavier-nx/)), accessed on 8 March 2023), possessing powerful artificial intelligence computing capabilities. It also incorporates the Slamtec RPLIDAR S2, an omnidirectional LiDAR, for SLAM map construction and autonomous navigation ([[https://www.slamtec.com/cn/S27](https://www.slamtec.com/cn/S27) wt.mc_id=S1 bd_qg_ld_100142 pc&sdclkid=AL2G150615F_152R&bd_vid=6769858087028764337]([https://www.slamtec.com/cn/S27](https://www.slamtec.com/cn/S27) wt.mc_id=S1 bd_qg_ld_100142 pc&sdclkid=AL2G150615F_152R&bd_vid=6769858087028764337), accessed on 10 April 2023). The installation of a LiDAR on the UAV should meet the following requirements: horizontal angle between 0\({}^{\circ}\) and +2\({}^{\circ}\) (tilted upwards); opening angle of \(\geq\)+270\({}^{\circ}\), preferably in the front and rear of the UAV; angle of coverage of \(\geq\)+220\({}^{\circ}\). The sensor should avoid a scanning blind spot of 15\({}^{\circ}\) and the laser sensor TFmini ([[https://www.benewake.com/TFminis/index.html?roid=325](https://www.benewake.com/TFminis/index.html?roid=325)]([https://www.benewake.com/TFminis/index.html?roid=325](https://www.benewake.com/TFminis/index.html?roid=325)), accessed on 12 April 2023) is installed on the manipulator of the UAV for altitude control. In Figure 1, the TFmini labeled \"1\" represents the laser sensor mounted on the manipulator.