Development of the Autonomous Underwater Vehicle Cyclops and Control System Design

Abstract

We developed a novel hovering-type autonomous underwater vehicle (AUV) named `Cyclops' for precise observation. The concepts for the AUV are high performance maneuverability, expandability and easy maintenance. To achieve the concepts, we designed symmetric hull of the AUV, propulsion system, communication system and electric devices, and developed operating software to control the AUV. For the safety, we analyze structural rigidity using FEM. In terms of control of the AUV, we proposed an integral sliding mode controller (ISMC) and a second-order sliding mode controller (2-SMC) to stabilize an autonomousunderwater vehicle which suffers from unknown disturbances. The ISMC compensates for uncertain hydrodynamics uncertainties and rejects the effect of unknown disturbances such as waves, tides, currents and buoyancy. The ISMC is comprised of an equivalent controller and a switching controller to suppress the parameter uncertainties and external disturbances. The structure of 2-SMC is similar to the ISMC. The difference lies in that it increases the order of sliding surface, thereby reducing the chattering phenomenon. The closed loop systems for each controller are exponentially stable in the presence of hydrodynamics and unknown disturbances. We tested the proposed methods using computer simulation of an AUV model and a real AUV. We compared the performance of proposed controllers without and with switching controller in the simulation and experimental results, which confirmed that the methods improve the trajectory tracking performance against external disturbances. Finally, we conducted sea-trial to check the whole AUV systems. Through sea-trial, we validate hull structure safety, propulsion system, communication system and control system.