Initial Alignment and Position Aiding Time Delay Compensation for SDINS of Deep Sea Underwater Vehicles

In the case of a vehicle descending to the deep sea floor, DVL (Doppler velocity log) usually loses the bottom lock for quite a long time. Therefore, various initial alignment methods available on the surface cannot guarantee its accuracy down to the sea floor and therefore cannot be directly applicable to this deep sea case. Besides, near the seafloor the vehicle’s USBL (Ultra-short baseline) aiding position usually includes range-related time delay which can be up to several seconds. This paper proposes an simple but effective initial alignment scheme for deep sea underwater vehicles combining with position aiding time delay compensation method. Some practical issues in the construction of SDINS (Strapdown inertial navigation system), such as lever arm effects compensation, are also discussed. Experimental tests are also carried out in the water tank environment to verify the effectiveness of proposed schemes.