Abstract: A method to estimate the attitude of micro UAV based on the sparse line optical flow field is proposed according to the requirements for UAV vision-based navigation system.The concept of sparse line optical flow field of images is described, and an algorithm of sparse line optical flow field is presented. A new method to estimate the attitudes of micro UAV, including pitch rate, roll rate and yaw rate, is proposed based on the sparse line-optical flow field and the established horizon projection model. The proposed method and the classic Horn algorithm are used to numerically simulate a group of test images for calculating the optical flow field. The results show that the proposed method has the same calculation accuracy as the classic Horn algorithm, while the calculating time-cost of the former is only 6% of Horn algorithm. Taking an aerial image sequence as test samples, an off-line simulation is conducted to verify the method of UAV attitude estimation based on sparse line-optical flow field. The information calculated with the measured values of angular velocity gyro on UAV is compared. The comparative result shows that the proposed method is efficient for estimation of pitch, roll, and yaw rates of UAV. The calculated error of pitch rate is less than ±10(°), while the errors of roll and yaw rates are less than ±5(°)/s .

Key words: control and navigation technology of aircraft, sparse line-optical flow field, micro UAV, attitude estimation, visual navigation