Underwater passive manoeuvring target tracking with isogradient sound speed profile

Compared with the traditional tracking problem, underwater 3-D passive manoeuvring target faces following challenging problems: (1) Since signal propagation delay is varying and unknown, relationship between two adjacent states hard to describe; (2) limited by environment, it more difficult establish a motion model; (3) speed of acoustic varies depth, path will be curved instead straight. Various parameters including delay, pitch angle receiving frequency measured observer cannot calculated as usual. In this paper, we improved constant turn (3D-CT) model match motion. For problems (3), paper proposes novel interacting multiple Gauss-Helmert unscented Kalman filter (IMM-UGHUKF) isogradient sound velocity profile, which analytically describes state estimated measurement. This method augments unknown emission time into implicit equations, transits Gauss–Helmert model. Simulation tests have been carried out, results show that IMM-UGHUKF can significantly reduce estimation error compared other approaches.