Development of the automatic autorotation landing control system by using a small unmanned helicopter

Abstract

Automatic autorotation landing system for helicopters that is applicable under various flight conditions is proposed. This system consists of a control system that stabilizes rotational speed of the main rotor and reduces the descent speed before landing, and the ground altitude calculation algorithm to obtain reliable data. The control system is designed and validated based on the comprehensive helicopter dynamics model with an induced velocity model which is newly developed for descent at low speed. A rotational speed controller stabilizes main rotor speed during dive and is switched to descent speed / thrust controllers which reduce descent speed during flare. Velocity reference trajectories are adjusted based on control simulation results and empirical philosophy by a skilled flyer. The ground altitude calculation algorithm combines a barometer and a LiDAR to eliminate invalid data at both high and low altitude. By conducting flight tests in the actual environment, autorotation dive, flare and soft landing are successfully achieved without any aircraft damages. Comparing experimental and simulation results, the accuracy of the developed model at low speed descent is validated. In addition, results of flight envelope calculations suggest capabilities of the proposed system for various initial flight conditions.