## 5 Conclusions  
In this study, we present the design of a dual-function landing gear that enables ultra-fast grasping and landing for drones. This system has been integrated into a coaxial twin-rotor drone, theoretically allowing the drone to capture target objects while in flight. The innovative mechanical design described herein allows the drone to stably grasp soft and moderately sized objects without the need for additional mechanical hands, offering a novel approach to drone weight reduction and enhancing payload capacity. The proposed quick-release mechanism, which utilizes a single DC-geared motor to achieve both landing gear opening and ultra-fast closing, simplifies the system's complexity while maintaining reliable performance.  
Experimental results confirm the system's functionality. The landing gear achieves an ultra-fast grasping speed of 0.167 s, suitable for rapid response tasks. The grasping force depends on the gear's geometry, with a maximum of 8.5 N for the smallest radius (8 mm) and approximately 4.2 N for larger radii (16 mm). Larger radii reduce initial gripping force due to lower contact pressure, and this trend persists over time. While the model aligns well with experimental data, it slightly overestimates gripping force at later stages for certain radii, likely due to unaccounted nonlinear factors. The experiment was limited to spherical objects and did not consider other shapes, such as elongated or irregular forms, which could affect grasp stability. Additionally, the assumption of stable vertical object orientation and the fatigue performance of springs were not addressed, potentially reducing long-term reliability and increasing the risk of slippage.  
Future work will enhance the landing gear's adaptability to various object shapes, sizes, and materials. This includes reconfiguring the quick-release mechanism for other gripper designs and increasing the lever arm of the cable driving the linkage rod to install higher-stiffness tensile springs, potentially achieving a gripping force beyond 10 N. Research will also explore dynamic grasping during flight to evaluate real-world performance. Further experiments will test objects of different shapes and materials under dynamic conditions. Fragile or irregularly shaped objects will receive special attention to prevent damage during rapid closure. Improving spring fatigue resistance will be key to ensuring long-term stability and reliability. Comprehensive tests in realistic environments will further validate the dual-function landing gear's performance.  
Conceptualization, X.L. and J.Z.; data curation, L.K. and X.L.; investigation, Y.Z., C.L. and J.Z.; methodology, C.W., Y.Z., C.L., X.L. and J.Z.; software, Y.Z.; validation, C.L.; visualization, L.K.; writing--original draft preparation, C.W. and L.K. All authors have read and agreed to the published version of the manuscript.  
This study was supported by the National Natural Science Foundation of China (Grant Nos. 62103131 and 62203044), the Natural Science Foundation of Hebei Province, China (Grant No. E2022202171), the Fundamental Research Funds for the Central Universities (Grant No. FRF-TP-24-016A), and the Anhui National Natural Science Foundation of China Regional Innovation and Development Joint Fund (Grant No. U23A20338).  
Figure 13: The super-fast closure of the landing gear while in a fixed state to effectively grasp the U-shaped pillow, with the operation captured at a rate of 30 frames per second.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The raw data supporting the conclusions of this article will be made available by the authors upon request.  
**Conflicts of Interest:** The authors declare no conflicts of interest.