Backstepping control strategy for an underactuated X4-AUV

A nonlinear control method is considered for stabilizing all attitudes and positions (x,y or z) of an underactuated x4-auv with four thrusters and six degrees-of-freedom (dofs),in which the positions are stabilized according to the lyapunov stability theory and angles are stabilized using backstepping control method. a dynamical model is first derived,and then a sequential nonlinear control strategy is implemented for the x4-auv,composed of translational and rotational subsystems. a controller for the translational subsystem stabilizes one position out of x-,y-,and z-coordinates,whereas controllers for the rotational subsystems generate the desired roll,pitch and yaw angles. thus,the rotational controllers stabilize all the attitudes of the x4-auv at a desired (x-,y- or z-) position of the vehicle. some numerical simulations are conducted to demonstrate the effectiveness of the proposed controllers. © 2015 penerbit utm press. all rights reserved.