Target tracking filter using vision information for a flight vehicle with low cost imu and strap-down imaging seeker

Abstract

Target state estimation algorithm with bearing-only measurement has been covered in many studies. However, since a strap-down imaging seeker measures not a line-of-sight angle but a boresight error, it is required to convert this boresight error measurement into the line-of-sight angle measurement using missile attitude information obtained from an INS in order to utilize previously developed target tracking method with bearing-only measurement. Because the bias of a low cost IMU is large, the attitude information diverges rapidly, resulting in performance degradation of the target tracking filter. This thesis shows that quite accurate target state estimation is possible for a missile with a strap-down imaging seeker and a low cost IMU when gyro bias is estimated from the vision information, especially optical flow, which is noisy but unbiased. The engagement between a ground-to-ground missile operated with lock-on-before-launch mode and a target like a tank which is slower than the missile, is considered. Target tracking filter with bearing-only measurement is designed and the observability of this estimation problem is analyzed. Body angular rate estimation filter is developed by applying optical flow equations for non-translating rigid body to optical flow measurements arise at the horizon which is almost always detected wherever the missile tries to intercept a ground target. Using this body angular rate estimates and gyro measurements, a gyro bias estimation algorithm is introduced. Simulations are conducted to show that, through gyro bias compensation using proposed gyro bias estimation method, the estimation performance of a target tracking filter with inaccurate attitude information due to a gyro bias is similar to that with perfect attitude information. It is important for missiles, which are unable to be reused, to reduce their production cost, and sensors like an IMU or a seeker take the largest part of this cost. Therefore, utilizations of strap-do...