A Maneuverable Underwater Vehicle (NS-MUV): Resistance to External Disturbance Part 3 of 4

Original video: https://youtu.be/ziCflrkoltg

Underwater robots can collect comprehensive information on species and habitats when conducting seabed operations, enhancing localized insights and expanding underwater ecological understanding. One approach uses autonomous underwater vehicles, but proximity operations may disturb sediments and compromise observation quality. Another approach uses wheeled or legged benthic robots, but unavoidable contact limits their application in delicate ecosystems like coral reefs. To address these challenges, we propose a maneuverable underwater vehicle for near-seabed observations. This vehicle moves with minimal turbulence and shows strong resistance to external disturbances, enabling high-quality seabed observation as close as 20 cm. It rapidly detects intense disturbances like turbulence and wall effects, allowing real-time path planning to prevent bottoming. Multiple tests in various marine environments, including sandy areas, coral reefs, and sheer rock, show low sediment disturbance and improved adaptability to rugged underwater terrain.

This video (Part 3 of our NS-MUV series) presents a comparative analysis of different algorithms tested for the underwater vehicle's resistance to external disturbances. We compare the performance of an adaptive algorithm and a traditional PID controller against the algorithm implemented in the NS-MUV. The adaptive algorithm, utilizing both an adaptive term and tanh-sigmoid-surface control laws, demonstrated a faster response speed in counteracting disturbances compared to the PID controller. However, during the weight block stabilization phase, the adaptive algorithm exhibited significant fluctuations in the pitch angle.

In contrast, the algorithm used in the NS-MUV showed much smaller fluctuations in pitch angle during the stabilisation stage, with the adaptive algorithm's fluctuations being over seven times larger. While the NS-MUV's algorithm (a PD controller) has a slightly slower initial response than the adaptive algorithm's tanh-sigmoid-surface control laws, it offers superior control stability by quickly and effectively compensating for external disturbances. The experimental results confirm the robust ability of the NS-MUV to maintain a consistent distance from the seabed. The implemented disturbance resistance algorithm effectively stabilizes the pitch angle after strong, sudden disturbances, significantly reducing unwanted fluctuations in both pitch and depth. This ensures the NS-MUV can maintain its intended course and avoid hitting the bottom even when faced with external forces.

Watch Part 1: https://youtu.be/adjkmXAoWXE

Watch Part 2: https://youtu.be/fDrT12Qm1SQ

Watch Part 4:

Keywords: NS-MUV, Disturbance Resistance, Algorithm Testing, Adaptive Algorithm, PID Controller, Control Stability, Response Speed, Pitch Angle, Depth Control, Underwater Vehicle.

Citation:

Liu, K., Ding, M., Pan, B. et al. A maneuverable underwater vehicle for near-seabed observation. Nat Commun 15, 10284 (2024). https://doi.org/10.1038/s41467-024-54600-8

Published on: 27 November 2024

Attribution 4.0 International — CC BY 4.0 - Creative Commons