Variable Structure Depth Controller for Energy Savings in an Underwater Device: Proof of Stability

• Type: Article in International Scientific Journal
• Date: 2025

Authors

Pinto, JB (Author) Other; João Pedro Falcão Carneiro (Author) FEUP; de Almeida, FG (Author) Other; Cruz, NA (Author) Other

Journal

Title: Actuators

Vol. 14

Final page: 340

Publisher: MDPI

Indexing

ISI Web of Knowledge - 0 Citations

Scopus - 0 Citations

Other information

Authenticus ID: P-019-MPP

DOI: 10.3390/act14070340

Abstract (EN): Underwater exploration is vital for advancing scientific understanding of marine ecosystems, biodiversity, and oceanic processes. Autonomous underwater vehicles and sensor platforms play a crucial role in continuous monitoring, but their operational endurance is often limited by energy constraints. Various control strategies have been proposed to enhance energy efficiency, including robust and optimal controllers, energy-optimal model predictive control, and disturbance-aware strategies. Recent work introduced a variable structure depth controller for a sensor platform with a variable buoyancy module, resulting in a 22% reduction in energy consumption. This paper extends that work by providing a formal stability proof for the proposed switching controller, ensuring safe and reliable operation in dynamic underwater environments. In contrast to the conventional approach used in controller stability proofs for switched systems-which typically relies on the existence of multiple Lyapunov functions-the method developed in this paper adopts a different strategy. Specifically, the stability proof is based on a novel analysis of the system's trajectory in the net buoyancy force-versus-depth error plane. The findings were applied to a depth-controlled sensor platform previously developed by the authors, using a well-established system model and considering physical constraints. Despite adopting a conservative approach, the results demonstrate that the control law can be implemented while ensuring formal system stability. Moreover, the study highlights how stability regions are affected by different controller parameter choices and mission requirements, namely, by determining how these aspects affect the bounds of the switching control action. The results provide valuable guidance for selecting the appropriate controller parameters for specific mission scenarios.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 27