An Adaptive Hierarchical Sliding Mode Controller for Autonomous Underwater Vehicles

Abstract

The paper addresses a problem of efficiently controlling an autonomous underwater vehicle (AUV), where its typical underactuated model is considered. Due to critical uncertainties and nonlinearities in the system caused by unavoidable external disturbances such as ocean currents when it operates, it is paramount to robustly maintain motions of the vehicle over time as expected. Therefore, it is proposed to employ the hierarchical sliding mode control technique to design the closed-loop control scheme for the device. However, exactly determining parameters of the AUV control system is impractical since its nonlinearities and external disturbances can vary those parameters over time. Thus, it is proposed to exploit neural networks to develop an adaptive learning mechanism that allows the system to learn its parameters adaptively. More importantly, stability of the AUV system controlled by the proposed approach is theoretically proved to be guaranteed by the use of the Lyapunov theory. Effectiveness of the proposed control scheme was verified by the experiments implemented in a synthetic environment, where the obtained results are highly promising.

Critic-Only Learning Based Tracking Control for Uncertain Nonlinear Systems with Prescribed Performance

“…Remark 1. There exist many plants, such as autonomous underwater vehicles [1] and quadrotors [3], which can be modeled as System (1) with disturbance. Unlike the investigated controllers in [1] and [3] regardless of control consumption, the proposed optimal tracking controller was designed to achieve the stability of a closed-loop system with an adequate control input.…”

“…Theorem 2. For nonlinear uncertain system (1) with constraint (3), the optimal control is designed with weight update (42), the tracking error is uniform ultimate boundedness and evolves within predefined region. Proof of Theorem 2.…”

“…Theorem 2. For nonlinear uncertain system (1) with constraint ( 3), the op signed with weight update (42), the tracking error is uniform ultimate boun…”

“…Nowadays, many plants in the real word can be formulated as uncertain nonlinear systems, such as autonomous underwater vehicles [1], mobile robots [2], and quadrotors [3]. Thus, tracking problems for uncertain nonlinear systems have become one of the issues, and various control methods have been developed and employed in many physical systems to achieve tracking performance.…”

Recursion Based Control and Separation Sliding Manifold Based Control of Under-Actuated 4-DOF Autonomous

“…HSMC control is a good solution for nonlinear systems [15,16]. Nevertheless, it has the potential to induce high-frequency oscillations, impacting the actuators, dissipating energy, and generating wing oscillations in the AUV, consequently resulting in instability [17,18]. Therefore, the evaluation to obtain solutions for specific cases is necessary.…”