Free-running tests on a self-propelled submersible multi-state vehicle model

A submersible multi-state vehicle (SMV) has been designed as an unmanned surface vehicle with global deployment capability. It can switch between several states including underwater, semi-submerged, and surface states. Free-running tests on the self-propelled model are performed to validate the multi-state transition principle of the SMV, with kinematic and hydrodynamic parameters recorded during the tests. Three-dimensional force sensors are designed to measure the wing forces, which provide insights into the mechanism of the state transition process. A series of tests conducted using program control methods verify the feasibility of the multi-state sailing and continuous state transition of the SMV. Appropriate threshold values for the wings to control depth and trim angle of the vehicle are determined through case studies on the dynamic performance. The wing forces measured show extraordinarily different characteristics and functions in different states, which provides useful information for further improvements to the design. • The self-propelled model of a submersible multi-state vehicle featuring wings and ballast tanks is proposed. • The mechanism of multi-state transition relies on the balance between the hydrodynamic and hydrostatic loads. • The hull is the main source of the hydrodynamic forces in the state transition process rather than the wings. • The threshold values of the depth and trim angle for the wings are crucial for realizing the multi-state transition.