The Hand Position Concept for Control of Underactuated Underwater Vehicles

This article extends the hand position concept to underactuated underwater vehicles. Compared with previous works that utilize this concept, our approach works on six degrees-of-freedom (DOFs) vehicles and does not introduce singularities. By choosing the hand position as the output of the controlled system, we can apply output feedback linearization to simplify the dynamics of the vehicle. Specifically, we can then transform the six DOFs nonlinear underactuated vehicle model into a double integrator. This transformation enables the use of numerous control strategies that could otherwise not be used on nonholonomic or underactuated vehicles. After defining the concept, we analyze the closed-loop behavior of a general hand position-based controller. Specifically, we analyze the effects of external disturbances on the hand position and derive the sufficient conditions under which the rotational dynamics of the AUV remain bounded. Next, we present two examples of hand position-based controllers for solving the trajectory-tracking and path-following problems and analyze their closed-loop behavior. The theoretical results are verified both in numerical simulations and experiments.