Fundamental Study on Adaptive Shock Response Control for Emergency Landing of UAVs and Its Experimental Investigation

Unmanned aerial vehicles (UAVs) are widely used in many fields, including agriculture and industry. Touchdown of a UAV without tipping over is a crucial but challenging issue owing to disturbances and uncertainties in the landing phase. In particular, when a breakdown occurs in a UAV system and the UAV free falls, sensors can be destroyed or the integrity of the UAV can be compromised. Therefore, developing an emergency landing system that can suppress rebound after free falling and preserve the integrity of UAVs is necessary. This paper proposes an adaptive shock response mechanism as a safe and robust emergency landing system for UAVs. A spring-damper system combined with a plastic deformation part serves as this emergency landing system to absorb and mitigate the impact during the landing phase to avoid tipping over of a UAV by reducing the rebound height. A release system that unlocks the plastic deformation part when the landing height is sufficiently high is proposed. Numerical simulations are conducted to evaluate the performance of the proposed emergency landing system, which is compared with those of two other mechanisms. The results reveal that the proposed method can deliver satisfactory rebound-reducing performance and high robustness against variations in the UAV weight and falling height. Additionally, the effectiveness of the proposed mechanism is experimentally validated using an equivalent model.