Robust adaptive control for a class of nonlinear system

A backstepping adaptive control method is proposed for a nonlinear system with unknown parameters, unmatched uncertainties and external disturbance. The parameters in each equation can be adjusted respectively. Nonlinear damp technology is used to eliminate uncertainties, and the L2 gain of the unknown disturbance less than or equal to a prescribed index. For nonlinear torpedo model, the input-output dynamic is established using the torpedo depth, climbing rate and attitude angular velocity as the state variables. The stable zero dynamic includes attitude angular and velocity. Considering attitude angular velocity as the virtual controller of torpedo climbing rate, the backstepping adaptive control strategy is used to control the torpedo navigation depth. In simulation, the depth can be controlled well in the conditions of uncertainties and various initial states.