Motion control methods for X-rudder underwater vehicles: Model based sliding Mode and non-model based iterative sliding mode

Abstract

This paper focuses on motion controller design for x-rudder underwater vehicles with four independent stern rudders where the conventional ganging method for maneuvering is not applicable. To realize the cooperation of the stern rudders, motion controller of an x-rudder underwater vehicle is divided into two parts, a dynamics controller and a control allocator. The controller design is conducted under both scenarios that model parameters are known and unknown. For known models, the desired maneuvering moments are generated by model based sliding mode control method. For unknown models, non-model based iterative sliding mode control method is utilized to calculate virtual steering rudder commands. The control allocator of both methods are based on sequential quadratic programming to solve the mixed minimum problem, with varied evaluation criterions and constraints. By conducting numerical simulations under various conditions, the functionality of the two proposed control methods are verified, and comparison in terms of accuracy, energy saving, and computation consumption are also discussed in detail.