Research On Fast Alignment Of Mechanically Dithered Ring Laser Gyro SINS

Currently, the laser gyro strapdown inertial navigation system is increasingly and extensively used in the military warships, fighter plane, missiles, fighting vehicles, etc. The weapons precision strike ability and rapid reaction capability are directly restricted by the alignment precision and convergence time. Taking the launch vehicle for example, several essential procedures such as static-state alignment after starting the vehicle and missile initial alignment after arriving at the launch position must be implemented,which consumes a lot of time. So it has a crucial effect on the improvement of weapon equipment’s mobility if we can speed up the convergence rate or just skip the static-state alignment. Fast alignment and alignment on moving base of mechanically dithered ring laser gyro SINS are studied in the paper, which includes the following works:(1) Comparison of current fast alignment methods of SINS. The principles of the three current fast alignment methods including analytical alignment, compass alignment and inertial frame based alignment are presented and analyzed, and their applicable range are compared with alignment accuracy, large misalignment angle and different form of disturbances. Alignment simulations are carried out for SINS on stationary base.(2) Analysis of the convergence time of inertial frame based alignment. The convergence rate of inertial frame based alignment was analyzed in detail by theory and simulation. The convergence time and the alignment accuracy of the 90-and 50-type mechanically dithered ring laser gyro based SINS were experimental verified under static-state base, swaying base, as well as static-state vehicle condition. It proved out that the inertial frame based alignment can meet the requirement of outputting the attitude angles with certain accuracy in a short time, and has good engineering application value.(3) SINS fast alignment on moving base by Laser Doppler Velocimeter(LDV). It is difficult to realize independent alignment of SINS when the base is in linear movement, and traditional coarse alignment algorithms may lead to great error under this unfavorable condition. By introducing the external velocity and acceleration items, fast alignment can be realized during the vehicles’ aperiodic linear motion. Simulations and experiments confirmed that, this method can meet the requirement of fast alignment on moving base in certain accuracy range.(4) Fine alignment on moving base of LDV/SINS integrated navigation system. A preliminary analysis was finished about fine alignment on moving base of LDV/SINS. With the designed 18-dimensional Kalman filter, the misalignment angle was further estimated and the filtering fine alignment was completed. Its efficiency was confirmed by the follow-up navigation verification.