Juhyun Pyo

The development of multi-functional autonomous amphibious vehicle

This paper addresses multi-purpose autonomous amphibious vehicle. It could operate 3 terrains; land-sea-air, a 3-in 1 amphibious vehicle. Usually the vehicle runs as AUV in underwater. It has tracks to run on-land and seabed and works as AGV, ACV. On the pressure hull, there is a waterproof cargo with self-sealing hatch. This enables agent vehicles launch such as UAV, on seabed. This study focuses on the feasibility the proposed vehicle. Experiments were carried out to demonstrate the feasibility.

A robust loop-closure method for visual SLAM in unstructured seafloor environments

This paper addresses the problem of visual simultaneous localization and mapping (SLAM) in an unstructured seabed environment that can be applied to an unmanned underwater vehicle equipped with a single monocular camera as the main measurement sensor. Monocular vision is regarded as an efficient sensing option in the context of SLAM, however it poses a variety of challenges when the relative motion is determined by matching a pair of images in the case of in-water visual SLAM. Among the various challenges, this research focuses on the problem of loop-closure which is one of the most important issues in SLAM. This study proposes a robust loop-closure algorithm in order to improve operational performance in terms of both navigation and mapping by efficiently reconstructing image matching constraints. To demonstrate and evaluate the effectiveness of the proposed loop-closure method, experimental datasets obtained in underwater environments are used, and the validity of the algorithm is confirmed by a series of comparative results.

Development of passive acoustic landmark using imaging sonar for AUV's localization

We proposed and tested a passive acoustic landmark that can provide accurate navigation information for an autonomous underwater vehicle (AUV). The AUV used imaging sonar mounted on the vehicle to recognize shadows of the columntype landmark, and can measure vehicles own pose and relative position from the landmark which was set in a known position. The results of the proposed method had acceptable error (<;1 %) in the calculated position of the AUV. The proposed localization method will be useful to correct drift errors of inertial navigation systems for the AUV or to find the same position repeatedly.

Development of energy-harvesting unit and propulsion unit for a robotic buoy system

In this paper, we described about development of a robotic buoy for Internet of maritime thins (IoMT) technology. For IoMT, stand-alone data conllector is a key technology. The energy harvesting robotic buoy is proposed in the context. The proposed system is composed of three components: propulsion system, energy harvesting system, and buoyancy control system. The proposed system can hold its position within an uniform bound without mooring, and harvests wave energy. As a preliminary study, we developed hydrodynamic model for the whole system, and conducted simulation. Through the simulation, we implemented station keeping algorithm, and investigated optimal design parameters. To verify the simulation results we constructed prototype and carried out a series of experiments: station-keeping test, and power generation test. As a result, the whole system was proved that the propulsion system has sufficient manoeuvrability for station keeping within 3 m, and peak power generation was 8 W.

Experimental results of rapid underwater object search based on forward-looking imaging sonar

In case of marine accident, the rapid search for missing object such as an underwater wreckage is one of the most important tasks. For this task, an autonomous underwater vehicle (AUV) that equips forward-looking imaging sonar can be utilized. The search task is accomplished by the following strategy. In the first phase, the AUV scans the target underwater area in a fast speed, and detects some suspected objects. In the second phase, the AUV approaches to the object and investigates it to determine whether the suspected object is the target object to be found. This paper provides experimental results of underwater object search in a fast speed for realizing the first phase of the strategy.

Agent based localization method for underwater docking

This paper addresses an agent and high resolution image sonar based underwater vehicles localization method for underwater docking. A novel concept of AUV docking system is proposed. The agent and the support AUV are connected with a tether. For sensing, the agent uses the optical camera and the AUV uses the image sonar. For the agents localization, the AUVs image sonar guides the agent, wide range with low precision and high reliability. The agents optical camera guides itself precisely in narrow range. This cooperation enables reliable and accurate localization of the agent. For the feasibility test, a prototype agent and acoustic landmark were fabricated and experiments were carried out.

System identification of hovering type AUV using Kinematic model based neural network

In this paper, we proposed identification methods for hovering type Autonomous underwater vehicle (AUV) based on neuro fuzzy network. We conducted sea trial using Cyclops which is hovering type AUV. [1] We verified the proposed identification method from the sea trial.

Beam Slice-Based Recognition Method for Acoustic Landmark With Multi-Beam Forward Looking Sonar

Autonomous underwater vehicles (AUVs) have been widely used for many risky underwater tasks. For these tasks, AUVs require navigational aids, such as active beacon-type underwater acoustic landmarks, which are the most widely used. It requires heavy installation loads and regular maintenance with high price sensors. In this paper, we propose a novel localization method in shallow water with a multi-beam forward looking sonar (MFLS), where positioning is based on passive-type acoustic landmarks. The proposed landmark comprises a combination of concrete pillars with a highly reliable and efficient recognition method for the real-time use of AUVs. The proposed landmark system has many advantages in the practical use, such as no maintenance, being strong on the marine bio-fouling, and light installation load with low price concrete pillars. The proposed recognition method is divided into two processes to verify the landmark. First, a pillarlike object is separated from the background, and the height of the pillar is calculated by the length of the shadow, which has a very high recognition rate and accuracy. Through modeling, the distance from the landmark to the MFLS can be calculated. The proposed method stochastically updates the navigation data based on the positional relationship with the landmark. The performance of the proposed landmark and its recognition method is verified through a water tank and field experiments using the AUV (Cyclops). The recognition rate and accuracy are also discussed.

The convolution neural network based agent vehicle detection using forward-looking sonar image

We propose the convolution neural network (CNN) based underwater object recognition and detection solution using forward-looking sonar image for localization of agent vehicle (small ROV). We designed the multiple underwater vehicle system with the autonomous underwater vehicle (AUV) equipped with the forward-looking sonar and the agent vehicle linked to the AUV through a tether cable. For localization of agent vehicle, we use the forward-looking sonar images. The CNN based object recognition algorithm trained the agent vehicles sonar image and detected it in the overall sonar images. We found that the CNN algorithm successfully recognized the agent vehicle in the sonar image. The goal of our research is to propose a solution to apply the CNN based recognition algorithm to the underwater robotics. Finally, it shows the elevated recognition rate in the underwater and we can get the agent vehicles localization data.

Development of AUV (MI) for strong ocean current and zero-visibility condition

The typical autonomous underwater vehicles (AUVs) are widely used in underwater exploration. However, there are difficulties to use AUVs in constrained environments such as the strong current or poor visibility. In this paper, we proposed the novel design and operation strategy of AUV that can overcome these restricted condition. The proposed AUV is composed by upper and lower body with specific technologies. Two bodies have different shape and role. The lower body is firmly fixed on the seafloor, and guides the upper body connected by tether to the target. The upper body is in close proximity to the target to obtain the optical information. In this process, it is important that such buoyancy control, winch control and sensor fusion.