An air-ground multi-robot system is designed for the purpose of applying bio-inspired sensor-motor modeling on technical systems. It consists of a flying mini-quadrotor equipped with inertial and visual sensors, and a wheeled minirobot equipped with active markers. The system modules, a multi-sensory pose/motion estimation approach and a closed-loop control of the flying quadrotor are described in this paper. The quadrotor can hover over the ground robot stably and track the ground robot movement. An accurate pose estimation is verified by a comparison between the estimated quadrotor pose and the actual pose during the flight.