Design of a deployable underwater robot for the recovery of autonomous underwater vehicles based on origami technique

The recovery of autonomous underwater vehicles (AUVs) has been a challenging mission due to the limited localization accuracy and movement capability of the AUVs. To overcome these limitations, we propose a novel design of a deployable underwater robot (DUR) for the recovery mission. Utilizing the origami structure, the DUR can transform between open and closed states to maximize the performance at different recovery stages. At the approaching stage, the DUR will remain closed state to reduce the drag force. While at the capturing state, the DUR will deploy to form a much larger opening to improve the success rate of docking. Meanwhile, the thrusters’ configuration also changes with the transformation of the robot body. The DUR can achieve a high driven force in the forward direction with the closed state which leads to a fast-approaching speed. While with the open state, the DUR can achieve more balanced force and torque maneuverability to prepare for agile position adjustment for the docking. CFD simulation has been used to analyze the drag forces and identify the hydrodynamic coefficients. A prototype of the robot has been fabricated and tested in an indoor water pool. Both simulation and experiment results validate the feasibility of the proposed design.

I. Introduction

A large portion of the earth is covered by the ocean. To explore the complex underwater environment, the AUVs have been widely used [1][2]. However, long-term deployment of the AUVs is constrained by limited data transmission bandwidth and battery capacity. As a result, the AUVs need to be recovered every several hours for recharging and data uploading. Various methods have been adopted to accomplish the recovery mission [3][4][5][6][7]. A cone shape docking station was proven to be an effective design for the recovery of AUV when the docking station is static [4]. When the AUVs were recovered by moving platforms such as USV and submarine, latching bar and rope were used as their low resistance profile can guarantee the movement efficiency of the recovery platform [5][6]. However, the small docking area can lower the success rate. In addition to the passive recovery methods mentioned above, active recovery approaches where the docking devices can adjust their position to compensate for the limited movement capability of the under-actuated AUV were also studied[8][9]. While most of the docking devices maintain a fixed shape through the recovery process, little attention has been paid to the transformable design. In this paper, we propose an active recovery method by designing a deployable underwater robot. The robot is equipped with eight thrusters and can transform between open and closed states to fulfill the different movement requirements during different recovery stages (Fig. 1). It can maintain a low resistance profile with a large propulsion force in the forward direction as it approaches the AUV. When the robot is ready for recovery, the origami-based structure deploys to form a pyramid opening which lowers the requirement of AUVs’ movement ability and localization accuracy. Meanwhile, the thruster’s configuration changes with the deployment of the robot, which results in high maneuverability of the DUR.