# The Evolution and Development Trends of LNG Loading and Unloading Arms
## 3 Development of Land-Used LNG Loading and Unloading Arms
### Land-Used Loading Arm Actuation and Its Intelligence and Automation
[32] used the find Contours function in OpenCV to identify flange contours and obtained depth values via binocular cameras, achieving a maximum error within millimeters and a relative error of less than 1%. However, this error margin only applies to marine LNG loading arms, not land-based ones. [PERSON] et al. [75] further developed an OpenCV-based flange center identification and positioning technique. This method first applies Gaussian and median filtering to images, then uses the Canny operator for binarization and Hough circle detection. Simulations of automatic loading arm docking on the ROS platform with Gazebo and Rviz revealed XYZ directional errors below 0.5 mm, meeting the precision requirements for land-based loading arms. Nonetheless, factors like lighting, oil contamination, and weather at loading sites currently prevent flange pose identification from meeting accuracy requirements. The identification algorithm needs further optimization to address these challenges. To achieve the automatic docking of land-used LNG loading and unloading arms, in addition to visual recognition technology for positioning the target flange, sensor technology, motion control systems, and automated control algorithms also need to cooperate with each other. To precisely control the movement of the loading arm, first, sensors detect and identify the docking target to determine the initial positions of the loading arm and the target. A path-planning algorithm is applied to calculate the optimal movement path. Control algorithms such as PID control and fuzzy control are used to process the information fed back by the sensors. The PLC control system then controls the driving device to adjust the speed and direction of the loading arm's movement in real time, thus completing the precise docking of the loading arm. For example, [PERSON] [76] proposed an automatic positioning truss loading spot system. With PLC automatic control as the core and motors as the driving force, a laser alignment device is used to guide the automatic alignment of the loading spout and sealed loading. During the loading process, traditional loading and unloading arms require manual operation by operators, which results in high labor intensity. In the case of emergencies, it is difficult for operators to handle the situation, and the risk is relatively high. [PERSON] [77] improved the traditional loading arm by upgrading all manual valves on the arm to cryogenic pneumatic ball valves. Through the corresponding control programs in the controller, the automatic control of the valves is realized; the case is depicted in Figure 15. A hydraulic control system is selected as the driving mechanism of the loading arm. The hydraulic motor and gear transmission cooperate to drive the loading arm to the corresponding position. Then, the operator docks and fixes the end-interface of the loading arm with the interface of the tank truck. [PERSON] et al. proposed a pneumatic-assisted loading arm. The rotation of the rotary joint is driven by an air cylinder, and a DCC quick-connect fitting is used to replace the loose flange, achieving rapid docking with the tank truck. This greatly reduces the labor intensity and improves the safety of operators and work efficiency. With continuous technological innovation, the intelligent and automated development of loading and unloading arms is showing a flourishing situation. The intelligent loading and management system for tank trucks at the Nanshan LNG Receiving Terminal in Longkou, Shandong Province, passed the review, achieving a deep integration of information and digitization [78]. At the tank truck filling station of Qingdao Liquefaction Company, the robotic arm at the no. 12 skid position automatically positioned itself to the filling port of the tank truck. After intelligent safety inspection, it successfully completed the entire process of transporting liquefied natural gas.