On Saturated NL-PID Control for Depth Trajectory Tracking of a Hybrid Underwater Glider: Real-Time Evaluation

Abstract

Abstract Hybrid Underwater Gliders combine classical thruster propulsion actuators with the buoyancy engine and internal pitch and roll moving masses present in buoyancy-driven Autonomous Underwater Gliders. This paper presents a pitch-based depth tracking controller for a Hybrid Underwater Glider propelled by a constant forward force applied through a single thruster. The proposed control consists of a two-stage nonlinear PID modified by a set of saturation functions that increase the robustness of the standard controller. The asymptotic stability of the closed-loop tracking system is proved using the Lyapunov approach. Real-time experimental results are presented to demonstrate the proposed nonlinear PID feasibility.