## 4 Dynamics and Experiments
### Workpiece Adaptability Test  
The experiment aims to simulate the capability of a gripper in achieving its design objectives during operation on a UAV. To assess the adaptability of the dual-function landing gear for objects of varying sizes, shapes, and materials, a series of grasping tests were conducted with a selection of objects. The experimental subjects, (listed in Table 1), are a subset of the Yale-CMU-Berkeley (YCB) Object Set, which is widely used as a benchmark for gripper evaluation [25]. Figure 11 presents a selection of grasping images of representative objects. The results indicate that the landing gear struggled to securely grasp small, rigid objects, as the gaps between the links caused the objects to move or even slip during rotation. Additionally, the rapid closing time of the landing gear led to objects being impacted by the main link, allowing them to escape through the gaps. In contrast, the landing gear effectively secured soft objects, such as clothing and U-shaped pillows, leveraging support fingers to maintain stability during rotation. Furthermore, for heavier objects, the main link experienced excessive torsional loads during lateral twisting, leading to failure; thus, it is necessary to utilize springs with a higher stiffness coefficient to provide greater counter-torque. \begin{table}
\begin{tabular}{c c c c} \hline
**Item** & **Mass (g)** & **GS** & **Displacement** \\ \hline Plastic Banana & 50 & \(\bullet\) & \(\bigcirc\) \\ Plastic Apple & 100 & \(\bullet\) & \(\bullet\) \\ Tennis Ball & 57 & \(\bullet\) & \(\bigcirc\) \\ Cardboard Box * & 200 & \(\bullet\) & \(\bullet\) \\ Aluminum Can & 15 & \(\bullet\) & \(\bigcirc\) \\ Plastic Bottle * & 30 & \(\bullet\) & \(\bullet\) \\ Dice & 10 & \(\bigcirc\) & \(\bigcirc\) \\ Ruler & 50 & \(\bigcirc\) & \(\bigcirc\) \\ Pen & 20 & \(\bigcirc\) & \(\bigcirc\) \\ Tube * & 100 & \(\bullet\) & \(\bullet\) \\ Pillow * & 300 & \(\bullet\) & \(\bullet\) \\ T-shirt * & 150 & \(\bullet\) & \(\bullet\) \\ \hline \end{tabular}  
* denotes large objects; the GS column indicates the state of the grasping mechanism, where solid black circles represent successful grasps and hollow circles indicate failure to perform the task. The Ds column describes the displacement of target objects during multi-axis rotation, where solid black circles signify no displacement and hollow circles indicate displacement.  
\end{table} 
Table 1: YCB grasping test results for dual-function landing gear. Although the YCB Object Set covers common object types, it does not represent the full range of objects encountered in real-world applications. In particular, when dealing with fragile or highly irregularly shaped objects in special environments, the rapid closing of the gripper could potentially impact the object, leading to damage. Therefore, future work should include additional grasping tests in more realistic environments, especially under dynamic conditions, to thoroughly assess the performance of the dual-function landing gear system. Additionally, we tested the closing speed of the landing gear equipped with springs of varying stiffness coefficients, as illustrated in Figure 12. Under conditions k\({}_{1}\), k\({}_{2}\), and k\({}_{3}\), a significant increase in closing speed was observed with increasing spring stiffness. However, once the stiffness coefficient exceeded k\({}_{2}\), the variation in closing time became stable. Therefore, selecting a spring stiffness coefficient of k\({}_{2}\) resulted in a closing time of approximately 0.14 s, effectively achieving a rapid closing speed while ensuring substantial grasping force. Figure 13 presents dynamic images captured by a high-speed camera, illustrating the rapid closing process of the landing gear.