PLACEMENT OF SURFACE SENSORS FOR COOPERATIVE LOCALIZATION OF SUBMERGED AUTONOMOUS UNDERWATER VEHICLES

Cooperative localization using surface sensors is an effective method for localization of submerged Autonomous Underwater Vehicles (AUVs), especially for long duration and wide area operations. However, placement of surface sensors such that the corresponding sensor formation maximizes the observability of AUVs is a challenging task. In this paper, a new method for obtaining optimal formation of surface sensors has been presented for multiple AUVs cooperative localization system. Most of the real world constraints/situations such as characteristics of acoustic signals in water, multiple-AUVs cooperative localization and computation complexity with the increase in number of AUVs have been considered. Firstly, an evaluation function based on acoustic signal transmission characteristics and Fisher information matrix theory has been formulated for AUVs whose position is known. In order to obtain the optimal formation for a given system, the value of evaluation function must reach its maximum. A recursive optimization algorithm has been used for the solution of the evaluation function. Simulation examples are then presented to calculate optimal formation for single AUV and multi-AUVs systems. Finally, to verify the effectiveness of the proposed method, various simulations have been performed using Extended Kalman Filter (EKF) to compare the localization error between optimal formations and random formations. The simulation results indicate that the optimal formation is able to decrease the noise error and enhance the observability of the system.