Abstract
This article presents a design method for the three-dimensional trajectory tracking control of an underactuated autonomous underwater vehicle with unknown current disturbances. To simplify the complexity of the controller and avoid the singular problem induced by initial state constraints, a novel nonlinear backstepping technique based on virtual control variables is employed to design the kinematics and dynamics controllers. The control law is developed by building virtual errors, which can solve the problem of differential explosion in the traditional backstepping. Specifically, an ocean current observer based on the kinematics model is proposed to estimate unknown current disturbances, where the estimation is integrated into the autonomous underwater vehicle kinematics and dynamics equations. The convergence of tracking errors and system stability are proven by using Lyapunov stable theory. Finally, the simulation studies were provided to illustrate the effectiveness and good performance of the above trajectory tracking strategy.
Highlights
The autonomous underwater vehicle (AUV) is one of the most modern and widespread equipment in the naval sector across the world,[1] since AUVs could be employed in various settings such as military applications, mineral resources sampling, gas operations, and recovery of lost artificial objects.[2,3] The complex missions require AUVs to track an inertial trajectory, which is concerned with the design of control laws that guide and keep the vehicle on the reference trajectory
A novel nonlinear backstepping technique is developed for dynamics controller design, where the AUV managed to be controlled in five DOFs
This article considered the problems of 3-D trajectory tracking control for a single underactuated AUV under unknown current disturbances
Summary
The autonomous underwater vehicle (AUV) is one of the most modern and widespread equipment in the naval sector across the world,[1] since AUVs could be employed in various settings such as military applications, mineral resources sampling, gas operations, and recovery of lost artificial objects.[2,3] The complex missions require AUVs to track an inertial trajectory (a reference curve with timevarying), which is concerned with the design of control laws that guide and keep the vehicle on the reference trajectory. Based on the Lyapunov direct method and backstepping technique,[25] an adaptive controller is proposed, and the likelihood of actuators’ saturation is considered for an underactuated AUV in six DOFs, which interestingly guarantees robustness against parameter uncertainties and bounded signals using saturation function.[26] The control strategy is developed using Port-Hamiltonian theory and interconnection and damping assignment passivity-based control in the study by Valentinis et al.,[27] and the trajectory of a virtual fully actuated plant is guided onto a vector field using energy routing. A novel nonlinear backstepping technique is developed for dynamics controller design, where the AUV managed to be controlled in five DOFs. Besides, the virtual speed variables based on kinematics equations are employed here to avoid the singular problem by initial state constraints, which simplify the virtual control input compared to the traditional backstepping. An example with the WL-II is carried out in the “Simulation studies” section, and conclusions are stated in the final section
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