RESULTS OF TESTING THE POSITIONING ALGORITHM AND DETERMINING THE ORIENTATION OF THE UNDERWATER VEHICLE BASED ON DATA FROM HYDRO-ACOUSTIC BEACONS

Abstract

The article deals with the determination of coordinates and orientation angles of the autonomous
underwater vehicle (AUV) relative to the stationary landing platform using high-frequency
near-range hydroacoustic system. The navigation task implies maneuvering the vehicle and approaching
the underwater station, which is associated with the formation of zones with different
acoustic visibility of the station's emitters by the receiving elements of the vehicle. Three zones of
acoustic visibility can be distinguished. The first zone is characterized by observation of signals of all
beacons of the underwater station. As a consequence, this zone is the most informative for solving the
problem of positioning and orientation determination of the AUV. The second zone corresponds to
partial reduction of the number of observed beacons, which does not critically influence the possibility
of problem solving. The third zone (landing) is defined by essential reduction of a number of observed
beacons, that, as consequence, considerably complicates the solution of the positioning problem,
taking into account the increased requirements on accuracy at the moment of landing of the
device caused by provision of safety. To maintain positioning accuracy and determine the underwater
vehicle orientation in the landing zone, it is proposed to use the results obtained in the early stages of
approach of the vehicle to the underwater station (the first and second zones). A mathematical statement
of the problem is given in the work, and the algorithm of its solution is described. When finding
the AUV in the first and second zones, the solution algorithm consists of two subtasks. The first subtask
is a rough estimation of location vicinity and angles of vehicle orientation using K-nearest
neighbors method; the second subtask is specification of estimations using pseudo-dimensional
method by solving system of algebraic equations with Levenberg-Marquardt algorithm. In addition,
estimation of beacon emission time is carried out. At finding ANPA in the third zone the algorithm is
reduced to solution of system of algebraic equations with use of forecast of time of signal emission by
a beacon, received at finding of the device in zones one and two. The results of simulation modeling
and results of algorithm approbation obtained using a mockup of the vehicle and a mockup of the
underwater station in the test pool are presented.