  In this paper, we introduce a dynamic fiducial marker which can change its
appearance according to the spatiotemporal requirements of the visual
perception task of a mobile robot using a camera as the sensor. We present a
control scheme to dynamically change the appearance of the marker in order to
increase the range of detection and to assure a better accuracy on the close
range. The marker control takes into account the camera to marker distance
(which influences the scale of the marker in image coordinates) to select which
fiducial markers to display. Hence, we realize a tight coupling between the
visual pose control of the mobile robot and the appearance of the dynamic
fiducial marker. Additionally, we discuss the practical implications of time
delays due to processing time and communication delays between the robot and
the marker. Finally, we propose a real-time dynamic marker visual servoing
control scheme for quadcopter landing and evaluate the performance on a
real-world example.
