LAUSR

This paper addresses the landing problem of a quadrotor on an unpredictable moving vehicle, using a robust image-based visual servoing (IBVS) method. The circle-based image moments are defined to construct image dynamics, and the passivity-like property of the circle features is preserved by reprojecting to the virtual image plane. The landing control system is decoupled into translation and rotation modules due to the rotation invariance of the proposed circle features. First, by exploiting the error transformation in the image space, a robust IBVS controller can overcome the lack of both the desired depth information of target features and the velocity feedback of the target. Next, an adaptive geometric attitude controller is developed directly using rotation matrices to avoid the singularities of Euler-angles and the ambiguity of quaternions. One benefit of the proposed scheme is that it can potentially improve the camera visibility, guarantee the transient and steady-state behaviors in image space, and be efficiently implemented on the low-cost quadrotor. Finally, The stability analysis is presented using Lyapunov stability theory on cascaded systems, and the effectiveness of the proposed control strategy is demonstrated through simulations and experiments. Note to Practitioners—The motivation of this paper is to investigate a practical control strategy for the image-based landing control of underactuated quadrotors on an unpredictable moving vehicle. In most of the existing image-based landing control schemes for underactuated quadrotors, having the prior predictive model of the moving landing vehicle to provide a feed-forward compensation during the landing maneuver. However, due to the fact that the landing environment and vehicle are primarily stochastic, resulting in no predictive models are valid in practice. Therefore, this paper suggests a robust image-based landing control strategy without the model or state of the moving landing vehicle. In particular, a novel virtual circle feature, possessing the characteristic of rotation invariance, is designed for the landing of underactuated quadrotors, which decouples the landing system and simplifies the control design. Moreover, the image feature errors are directly retained within prescribed performance funnels in the image space. As a result, the transient and steady-state landing behaviors can be implicitly guaranteed in Cartesian space. The stability and convergence of the system are analyzed mathematically and the experiment using quadrotors provides promising results. In ongoing research, we are addressing the issues of collision avoidances and unknown disturbances to provide a more realistic setup for the autonomous deployment and recovery of underactuated quadrotors in GPS-denied environments.