Concept and testing of an electromagnetic homing guidance system for autonomous underwater vehicles

An effective homing guidance system with precise vehicle dynamic attitude control capability is essential for reliable docking of Autonomous Underwater Vehicles (AUV). The paper describes the bio-inspired concept and electromagnetic finite element analysis-aided design and testing of an electromagnetic homing guidance system (EMHGS) comprising of an underwater dock with 400AT of electromagnetic dipole coil excited with the 20 Hz power supply; a twin-thruster AUV equipped with a differential magnetometer system, and operable in two degrees of freedom (DOF). The vehicle hydrodynamic behavior is characterized in 2 DOFs based on the thruster action and vehicle response method, and used for the control and homing guidance of the AUV. By sensing a magnetic field strength of 190nT, the EMHGS is found to have an effective range of 7 m, and capable of effecting AUV orientation correction by measuring the bearing angle. The FEA is found to comply with the experimental observations with an accuracy of 96% is extended for higher dock magnetic field strengths, and found that an EMHGS utilizing 6000AT dock coil and magnetic field sensors of same sensitivity could have a homing guidance range of 72 m. Based on a priori magnetic map, the system is capable of computing the vehicle range and velocity, serving critical inputs for realizing effective AUV short range homing and docking.