I. INTRODUCTION
We design a heterogeneous multi-robot system, containing a mini-quadrotor and a wheeled mini-robot (see Fig. 1). In this system an accurate 3D pose/motion estimation using multiple sensors is developed and a multi-rate control approach is implemented to enable the quadrotor hovering and tracking the moving ground robot. This testbed can be used to exploit control strategies of a 3D flying system, study various biologically inspired flying behaviors [1], and realize multi-agent applications. Based on [2], this paper describes our improved results of visionlIMU guided mini-quadrotor.