Numerical and Experimental Investigation for Recoil Dynamics of Machine Gun Used in Small Size – Unmanned Aerial Vehicle

Abstract In Unmanned Aerial Vehicle (UAV) with machine gun system, recoil dynamic is very critical phenomenon that occurs when a fast-moving object collides with a stationary or moving object causing a transfer of momentum. In this study, the main objective is to quantify differences in the recoil dynamic behavior of the machine gun affected by UAV structure including its weight, recoil reduction spring and damping pad properties. To do this, dynamic modeling of the whole system is established. Through the study, the effect of UAV structural properties is investigated to meet design requirements basically defined as higher shooting performance and higher stability of platform. The significance of all parameters is evaluated using with Pareto chart. Also, to verify these simulations, a recoil force measurement system on the ground is developed. In this equipment, a compression-type load cell is used together with the data acquisition system to measure the recoil forces. Since the recoil event is expected to be quite short, a high data sample rate is needed. The sampling frequency of the data acquisition system is selected as 20 kHz to be able to observe the recoil dynamics. Several firing tests have been conducted on the ground and impact force versus time data has been presented for each test. In addition, a finite element model of the UAV structure with a machine gun is generated to obtain the dynamic response of the structure in the air. It is found that the numerical simulation with ground test condition results show a good agreement with the data gathered from the experiments. In future, with the help of the verified model, it is aimed that firing performance during a mission in the air can be estimated according to main design goal which is to have higher platform stability while firing.