Vision-Based Optimal Landing Guidance Law for VTOL UAVs on a Moving Platform

This paper proposes a vision-based autonomous landing strategy for vertical take-off and landing (VTOL) UAVs on a moving platform. The approach uses visual measurements to estimate the relative position and speed between the landing pad and the UAV. Challenges arise when the landing pad moves out of the camera’s field of view or when visual measurements become unstable due to excessive UAV maneuvers, leading to degraded landing performance. To address this, the study introduces a novel tracking guidance law that controls the UAV’s position to keep the camera oriented toward the landing pad. An optimal landing guidance law is also developed to minimize attitude angle variations during the approach phase, ensuring stable image acquisition for improved state estimation and maintaining the camera’s field of view. We proposed a state machine-based landing procedure, incorporating landing decisions and go-around logic, enabling full autonomy. The proposed strategy’s performance is validated through flight tests with a multicopter and a fixed-wing VTOL UAV.