Abstract
This paper studies three-dimensional (3D) straight line path following and obstacle avoidance control for an underactuated autonomous underwater vehicle (AUV) without lateral and vertical driving forces. Firstly, the expected angular velocities are designed by using two different methods in the kinematic controller. The first one is a traditional method based on Line-of-sight (LOS) guidance law, and the second one is an improved method based on model predictive control (MPC). At the same time, a penalty item is designed by using the obstacle information detected by onboard sensors, which can realize the real-time obstacle avoidance of the unknown obstacle. Then, in order to overcome the uncertainty of the dynamics model and the saturation of actual control input, the dynamic controller is designed by using sliding mode control (SMC) technology. Finally, in the simulation experiment, the performance of the improved control method is verified by comparison with two traditional control methods based on LOS guidance law. Since the constraint of an AUV’s angular velocities are considered in MPC, simulation results show that the improved control method uses MPC, and SMC not only improves the tracking quality of the AUV when switching paths near the waypoints and realizes real-time obstacle avoidance but also effectively reduces the mean square error (MSE) and saturation rate of the rudder angle. Therefore, this control method is more conducive to the system stability and saves energy.
Highlights
At present, autonomous underwater vehicles (AUVs) have gradually become an important tool in many fields such as ocean exploitation and scientific research
The expected angular velocities qd and rd are designed by using two different methods, and the obstacle avoidance penalty is designed based on the obstacle information detected by onboard sensors, where qd and rd are the expected pitch rate and yaw rate, respectively
When obstacle avoidance is completed, velocity is designed by using model predictive control (MPC), and the penalty item for obstacle avoidance is designed by using the AUV returns to the desired path by setting the expected lateral error to zero
Summary
Autonomous underwater vehicles (AUVs) have gradually become an important tool in many fields such as ocean exploitation and scientific research. Underactuated marine surface vessels and AUVs must calculate their ideal attitude in real time to realize path-following control This task is accomplished by the kinematic controller according to the guidance law. In order to reduce the computation and simplify the structure of the controller, this paper designs the kinematics and dynamics controllers by using cascade control strategy, thereby providing a solution for the 3D straight line path following and obstacle avoidance of the AUVs. In the design of the kinematics controller, an improved control method is proposed by using MPC. The optimal expected angular velocity satisfying the constraint can be obtained by using the improved control method, which can reduce the MSE and saturation rate of the rudder angle and realize real-time obstacle avoidance. The remaining four sections of this paper are about the analysis of the control problem, the design of the kinematics and dynamics controller, the results and analysis of the simulation experiment, and the conclusion
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