SHSA-based adaptive roll-safety 3D tracking control of a X-Rudder AUV with actuator dynamics

In this article, a novel adaptive robust trajectory tracking framework with roll control is created for a X-Rudder autonomous underwater vehicle (XAUV) subjects to system nonlinearities, unknown disturbances, and complex actuator dynamics. First, a roll control law is introduced to the kinematics control loop, and the hyperbolic-tangent Line-of-sight (HLOS) based guidance law is proposed, which considers the three-dimensional (3D) tracking errors, collaboratively governing heading, pitch, and roll. Second, a novel super-hyperbolic switching algorithm (SHSA) based sliding mode controller is deployed in the dynamics control loop to achieve trajectory tracking and roll control, which combines the advantages of the two hyperbolic functions, avoids the chattering problem while achieving rapid convergence, this enhancing the control accuracy and stability simultaneously. Besides, the robustness to unknown disturbances (including environmental disturbances and propeller reaction torque) is enhanced by nonlinear disturbance observers. To tackle the potential instabilities from compound actuator dynamics, an anti-windup compensator is resorted to compensate for the control truncation of propulsion system, and an optimal X-Rudder allocator is utilized to solve the rudder angle assignment problem with multiple constraints. Finally, comparative numerical simulations are carried out to verify the effectiveness of proposed controller.