A novel adaptive backstepping sliding mode control for a lightweight autonomous underwater vehicle with input saturation

Abstract

Accurate depth and heading control play an essential role for autonomous underwater vehicles (AUVs) in near-seabed exploration and ocean surveys. This paper proposed a novel adaptive backstepping sliding mode control (ABSMC) algorithm for a lightweight autonomous underwater helicopter (AUH) subject to highly coupled nonlinearities, unknown system parameters, disturbances uncertainties, and input saturation. This algorithm adopted a conditional adaptation algorithm to govern adaptation so that gains only adapt when necessary to improve stability. Different reaching laws were selected for heading and depth control to reduce system chattering. For thruster saturation, we proposed an anti-windup compensator for auxiliary dynamic compensation based on system states; it can make the controller output change smoothly in the event of input saturation to better meet the response characteristics of the actual physical actuator. The mathematical proofs of the proposed algorithms are presented. Simulation results are presented to illustrate the effectiveness of the proposed control method. Moreover, extensive experimental results show that the proposed algorithm has better control performance than PID and sliding mode controllers and demonstrate its adaptive capability to system state changes.