Imaging Attitude Control and Image Motion Compensation Residual Analysis Based on a Three-Axis Inertially Stabilized Platform

Abstract

The airborne area camera has received broad application in aerial reconnaissance, land resource surveying, environmental monitoring, photogrammetry mapping, and natural disaster information acquisition. A three-axis, inertially stabilized platform with a large rotation range for the roll axis is designed, which is based on the cantilever structure, in order to realize a large-angle sweep imaging function for airborne area cameras. An image attitude control algorithm in the inertial space is proposed, which can regulate the line of sight (LOS) as well as the image orientation. The area camera image motion calculation model and image motion compensation residual computing method are proposed, utilizing space position and velocity vector transformation mathematics and derivations. The variation of linear velocity of the image motion in the sensor frame is analyzed, and the changing laws of the maximum deviation of image motion with the image attitude are studied. Flight tests imply that the vertical imaging technique correctly regulates the LOS along the local geodetic vertical. The along-flight overlap rate is greater than 65%, which meets the stereo mapping requirement. The sweep imaging technique considerably enlarges the cross-flight angle of view. The LOS and image orientation during sweep imaging are correctly controlled, and gap-free coverage of the survey area is maintained. The image’s azimuth or roll deviation is less than 0.1°, and the image pitch deviation is less than 0.35°. The quality of the test images is superior. Black and white line pairs for evaluation can be clearly distinguished. The image’s motion is well compensated, and the image motion compensation residual is well constrained. These verify the validity of the proposed imaging technique and the image motion analysis model.