  This paper presents a novel solution for UAV control in cooperative
multi-robot systems, which can be used in various scenarios such as
leader-following, landing on a moving base, or specific relative motion with a
target. Unlike classical methods that tackle UAV control in the world frame, we
directly control the UAV in the target coordinate frame, without making motion
assumptions about the target. In detail, we formulate a non-linear model
predictive controller of a UAV, referred to as the agent, within a non-inertial
frame (i.e., the target frame). The system requires the relative states (pose
and velocity), the angular velocity and the accelerations of the target, which
can be obtained by relative localization methods and ubiquitous MEMS IMU
sensors, respectively. This framework eliminates dependencies that are vital in
classical solutions, such as accurate state estimation for both the agent and
target, prior knowledge of the target motion model, and continuous trajectory
re-planning for some complex tasks. We have performed extensive simulations to
investigate the control performance with varying motion characteristics of the
target. Furthermore, we conducted real robot experiments, employing either
simulated relative pose estimation from motion capture systems indoors or
directly from our previous relative pose estimation devices outdoors, to
validate the applicability and feasibility of the proposed approach.
