Path tracking in dive plane for a class of torpedo-type underactuated AUVs

This paper considers the path tracking problem for a class of underactuated autonomous underwater vehicles (AUVs), where only surge force and stern plane are available for vehicle´s 3DOF diving motion. For these torpedo-type flying vehicles, the pitch moment is proportional to the vehicle´s forward speed. Therefore, if vehicle takes slow motion, then we cannot fully excite the vehicle´s pitch motion. In order to appropriately take these two control inputs - surge force and pitch moment as independent ones, we have to guarantee the vehicle to take the forward speed with considerable magnitude. Under this consideration, an asymptotic path tracking scheme is proposed. By introducing certain two polar coordinates transformations, vehicle´s tracking dynamics can be reduced to a certain two-input-two-output nonlinear strict-feedback form. To avoid possible singularity problem in the recursive control design, an asymptotic modification of orientation concept is applied. Proposed path tracking scheme guarantees asymptotic stability of closed-loop system in terms of polar coordinates. The same tracking property in the Cartesian frame is also discussed. Numerical simulations are carried out to illustrate the effectiveness of proposed tracking scheme.