Autonomous safe landing-area determination for rotorcraft UAVs using multiple IR-UWB radars

In recent years, the important advances that have been made in unmanned aerial vehicles (UAVs) are being widely applied for civil purposes. However, several difficulties continue to exist in the implementation of missions, such as delivery and surveillance, in the private sector. Autonomous safe landing-area determination for small rotorcraft UAVs (RUAVs) is one of these unresolved issues, for the successful implementation of which adequate terrain information on the potential landing area is necessary. Previously, vision and light detection and ranging (LIDAR)-based methods were investigated for solving this problem. However, these light-based sensors have the disadvantage of being affected by weather or light conditions. The impulse radio ultra-wide band (IR-UWB) radar is a radar sensor with a wide frequency band that generates short-wavelength pulses. It has advantages such as light weight, small size, low power consumption, robustness to external environmental changes, and high range and distance resolutions. In this paper, we propose a novel safe landing-area determination system based on multiple IR-UWB radars, suitable for small RUAVs. Methods for detecting the ground and obstacles and estimating the ground slope and roughness values, based on the signals acquired by multiple IR-UWB radars are proposed. Through experiments, we demonstrate the feasibility and performance of the proposed method.