A method for compensating platform attitude fluctuation for helicopter-borne LiDAR: Performance and effectiveness

Attitude fluctuation of helicopter-borne platform is an important factor influencing the quality of point cloud products from airborne LiDAR, especially the roll and pitch parts. Therefore, we proposed a method to compensate the attitude fluctuation for helicopter-borne laser scanning; an attitude compensation prototype was designed, to eliminate the impact of both the roll and pitch fluctuations on point cloud products. The mechanical structure and control system of the prototype were designed. In order to test the dynamic compensation effectiveness of the prototype for airborne LiDAR, we established a semi-physical simulation system. In the experiment setup, the prototype, a laser rangefinder as well as a position and orientation system (POS) were all mounted on the platform of a three-axis turntable. The inner and middle shafts of the three-axis turntable rotated with sinusoidal movements to simulate the roll and pitch fluctuations of helicopter-borne platform. The x-axis and y-axis frameworks of the prototype were controlled to rotate inversely halves of the measured rotation angles of the simulated attitude fluctuations by the POS. Hence, the emitting orientations of the pulsed laser beams reflected by the scanning mirror embedded in the prototype would not be affected by the dynamic changing of the roll and pitch fluctuations. Total 11 groups of experiments were carried out to verify the control performance and dynamic compensation effectiveness of the compensation prototype under 11 sets of sinusoidal attitude fluctuations with different frequencies and amplitudes. Experimental results show that, under the impact of different frequencies and amplitudes sinusoidal attitude fluctuations, the attitude compensation prototype can always significantly decrease the unfavorable influence of the attitude fluctuations and have good dynamic compensation effectiveness.