Robust Control of Underwater Vehicles with Fault-Tolerant Infinity-Norm Thruster Force Allocation

There are to objectives to this paper. First, a chattering-free sliding mode controller is proposed for the trajectory control of remotely operated vehicles (ROVs). Secondly, a new approach for thruster force allocation is proposed that is based on minimizing the l_infin norm. With regards to the former, a new adaptive term is developed that eliminates the high frequency control action inherent in a conventional sliding-mode controller, and also removes the need for a priori knowledge of upper bounds on uncertainties in the dynamic parameters of the ROV. With regards to the latter, it is demonstrated that the l_infin norm optimization can be cast as a linear problem that affords easy incorporation of the thruster saturation limits. Using numerical simulations, it is shown that the proposed l_infin thruster allocation is capable of meeting the adaptive sliding mode controller´s demands in the presence of thruster failures and is therefore fault tolerant. Finally, a recurrent neural network is designed in order to obtain a real time solution rate to the thruster allocation problem.