When assessing the hitting accuracy of underwater attack weapons against the surface target, we need to convert different coordinate systems to a unified coordinate system. Typically, surface target track uses the geodetic coordinate system and underwater weapon trajectory uses a navigation coordinate system. Therefore, trajectory data in the navigation coordinate system needs to be converted to the geodetic coordinate system. Using an inertial measurement unit can only get the trajectory data in the navigation coordinate system. Because of the Doppler effect, underwater acoustic reverberation, and measurement period, using cooperative acoustic beacon or baseline positioning method makes a great error in underwater high-speed attack weapon trajectory measurement. In this paper, a method combining baseline positioning with an inertial measurement unit is proposed to solve the problem of trajectory measurement in the geodetic coordinate system of underwater high-speed weapons. The system composition, working principle, and test results are introduced, and the measurement errors are analyzed.
Testing is an essential tool in the process of product development, testing, and production. The trajectory parameters that can be obtained from underwater trajectory measurement include attitude angle, angular rate, velocity, displacement, ballistic inclination, ballistic deflection, tilt angle, angle of attack, sideslip angle, etc. According to the data measured by the ballistic measurement system, the ballistic trajectory, ballistic dispersion, action characteristics, and performance of the weapon can be determined as an important basis for parameter optimization and design improvement during product development, and the underwater ballistic testing process is extensive, difficult, and costly (Zhang, et al. 2018). In the process of underwater high-speed attack weapon and surface target trajectory rendezvous testing, since the trajectories of both are not measured under the same coordinate system, underwater high-speed attack weapon ballistic data are obtained under the navigation coordinate system, which is a customized coordinate system based on the navigational body, while the surface target trajectory is obtained under the geodetic coordinate system. In order to evaluate the weapon and equipment performance, optimize the ballistic control algorithm, and determine the strike point error, it is necessary to accurately measure the ballistic data of the underwater weapon in the geodetic coordinate system. In this paper, a ballistic measurement method for underwater high-speed attack weapons in geodetic coordinate system is presented.
