March 2024 OES Beacon

Okinawa Marine Robot Competition 2023 Report

Yuta Matsuoka, Shun Fukushima, Keisuke Nishimuta, Yuto Nakazuru and Xu Ha, Kyushu Technological University

Fig.1 Kyutech Underwater Robotics and KYUBIC


The Okinawa Marine Robot Competition 2023[1] was held on November 18th and 19th, and Kyushu Institute of Technology participated as a team called “Kyushu Institute of Technology Underwater Robotics.”

Since this tournament is held at a fishing port, it is necessary to control the robots by taking into account the effects of tides and ebbs and flows, and the tournament places more emphasis on operation in actual waters than tournaments held in pools.

Therefore, Kyushu Technological University Underwater Robotics participated in the competition believing that, through this competition, they would be able to gain knowledge and experience regarding AUV operation in actual sea areas.


There are two competitions: normal task and intelligence/measurement challenge. In a normal task, the robot travels back and forth through a course (Fig.2, Fig.3) that consisted of a start/end area (SG area), a diving and surfacing area, a diving area, and a sea navigation area. This is done twice in the preliminary rounds, and the teams are ranked based on the average of the points earned in the first and second rounds shown on Table 1, and the top two teams compete in the finals. Please note that in the AUB category, you will not be able to participate in the finals unless you complete tasks number 2 or 4.

Table.1 Tasks and scores

No. task point
1 Sea navigation from SG area to submersible surfacing area 15
2 Submarine navigation (diving time measurement) 25
3 Surfacing within the maritime navigation area 20
4 Submarine navigation (diving time measurement) 25
5 Sea navigation from diving surface area to SG area 15
Fig. 2 Competition venues

In the intelligence/measurement challenge, the developed acoustic positioning technology was used to find a pinger located 30m away from the starting area, hover within a 2m radius, and then return to the starting position and surface. During this mission, the vehicle must remain submerged at all times, and commercially available navigation (IMU, DVL, acoustic positioning system) is prohibited to use.


We entered this competition with KYUBIC [Figure 4], a hovering AUV, which we developed and improved in 2020. The origin of the name is kyutech and cubic.  KYUBIC is equipped with a high-precision IMU and DVL and is capable of accurate self-position estimation. Additionally, KYUBIC can also handle advanced missions with two cameras and a unique acoustic positioning module.

KYUBIC mainly consists of 5 hulls, 6 thrusters, 6 hydrophones, and a DVL. Inside the main hull, there is a PC that controls KYUBIC, an IMU, two cameras, etc. [2].

KYUBIC supports various programs by transmitting data using ROS network.

The development environment is available for

Control, image processing, communication with sensors.

The communication interface program is developed as a separate Simulink model and communicated via the ROS network.

Therefore, data can be exchanged with other programs using various programming languages, and highly scalable systems can be developed in a short period of time.

Fig. 3 Competition venue diagram


The developed acoustic positioning device consists of six hydrophones, an AD converter housed in a pressure-resistant container, and a Raspberry Pi. The connections of each device are shown in Fig.5. The analog signal obtained by the MEMS microphone passes through a bandpass filter and is input to the AD converter, and the converted digital signal is sent to the Raspberry Pi via USB2.0. On the Raspberry Pi, the location of the pinger relative to the robot is calculated from the difference in the timing when each hydrophone receives the pinger sound. The information is sent to KYUBIC’s control hull via Ethernet and used to control the robot.

Hydrophones are amplifiers that can amplify up to about 50 times.  Compatible with TLV316 and wide band from 100Hz to 80kHz.

Board is equipped with MEMS microphone SPU0410LR5H-QB. It was developed based on Structure of the developed hydrophone.

The structure is shown in Fig.6. Overall, it is a small pressure vessel.

Fig. 4 General arrangement of AUV KYUBIC

The sensor part is made of pressure-resident waterproof resin Jel-lafin, which ensures waterproofness and noise reduction.  Efforts have been made to receive waves. Also, the amplifier allows access to variable resistor to set amplification factor to ensure this, an O-ring is used between the aluminum housings.  It has a structure that can be disassembled.

Additionally, the shield of the communication cable between the AD converter and AD controller is grounded on the inverter side. Therefore, the structure makes it difficult for noise to enter during analog signal transmission.

Strategies for the intelligence/measurement challenge

We developed acoustic positioning technology for the intelligence measurement challenge. Because the development was not completed in time for this competition, only two of the hydrophones installed in KYUBIC could be used, and the pinger position was estimated only using SSBL. In position estimation using SBL and all hydrophones, reaching the estimated coordinates of the pinger can be used as a determination of arrival, but SSBL can only estimate the direction of Pinga relative to KYUBIC and cannot calculate the distance. Therefore, the captured sound pressure of the Pinga was used as a measure of the distance between the Pinga and the KYUBIC, and when the sound pressure exceeded a critical value, it was determined that the Pinga was sufficiently close to the Pinga. 


Fig. 5 Device connection

In the first preliminary round of the AUV normal task, KYUBIC started moving backwards immediately after starting it. After that, we restarted, but timed out in the diving area. In the second preliminary round, there was no problem starting the KYUBIC, but it suddenly sank in the diving area, stopped working, and had to be recovered. In the final race, after KYUBIC started up, it ran straight ahead diagonally to the left. Halfway through the diving area, the KYUBIC stopped near an embankment on the left side of the course. KYUBIC turned on the spot and faced the embankment, then turned toward the maritime navigation area and headed straight ahead. We turned around in the maritime navigation area, went straight to the left again, went off course, and recovered. Although many unexpected problems arose, the overall score in the AUV normal task category was 1st out of 4 teams, and we were able to receive a special award.

Table.2 Scores in normal task category

Presentation qualifying game1 qualifying game2 finals overall band score
30 15 15 30 70

In the “Intelligence Measurement Challenge” category, when the KYUBIC is activated, after a few seconds it is judged to have reached its goal and the KYUBIC returns. In the second preliminary round, KYUBIC arrived around Pinga and was spinning around, but it was not determined that they had arrived at the landmark, so they were unable to score points.

Fig. 6 Hydrophone

Table.3 Scores in the intelligence measurement challenge category

workshop points Competition score (average) Technical explanation points total rank
20 0 32.5 52.5 3


Yuta Matsuoka: At this Okinawa competition, the program we created could not be utilized well, so we thought it was necessary to debug and improve it.

Shun Fukushima: The Okinawa Underwater Robotics Competition was the first underwater robotics competition I participated in. I believe that developing underwater robots through this competition will greatly benefit my future career.

Keisuke Nishimuta: During the competition, we felt the difficulty of controlling an underwater robot in a rough sea. In addition, there were some unexpected accidents, which made us realize the importance of the ability to react on the spot.

Yuto Nakazuru: This time, since the competition was held in actual waters, various accidents occurred, and I was disappointed that I could not show my full performance in the actual race. I will try to improve KYUBIC in order to get a satisfactory result at the next competition.

Xu Han: Looking back, I realized how difficult it was to develop underwater robots and the importance of teamwork. Through cooperation with team members during the development process, I was able to not only increase team cohesion but also gain valuable team development experience. I believe that what I learned at this conference will definitely be of great help in my future research.

Fig.7 KYUBIC navigating underwater


The 2023 Okinawa Marine Robot Competition is organized by IEEE/OES Japan Chapter, Ia Co., Ltd., Marine Engineering Co., Ltd., Globalway Co., Ltd., Sankei Shimbun (Offshore Tech Japan), Tsuneishi Craft & Facilities Co., Ltd., Japan Marine Enterprises Co., Ltd. The event was sponsored by the Japan Underwater Drone Association, FullDepth Co., Ltd., Yanmar Holdings Co., Ltd., Kowa Co., Ltd., Space One Co., Ltd., Sensite Competition, Bell Techne Co., Ltd., and Osago Co., Ltd. We would like to express our sincere gratitude to all the sponsors for their tremendous support and cooperation in organizing the tournament.


[1] The 9th Underwater Robotics Competition in Okinawa.

[2] Yoshiki Tanaka, Toshimune Matsumura, Yuichiro Uemura, Kentaro Yanagise, Yuya Nishida, Kazuo Ishi, “Development of a Testbed AUV for Shallow Water Observation and Its Controller Evaluation,” Journal of Robotics, Networking and Artificial Life, Vol. 10(1), pp. 6–16, 2023.

Fig.8 KYUBIC and certificate
Fig.9 Competition participating members
From left, Mr. Nishimuta, Mr. Fukushima,
Mr. Matsuoka, Mr. Nakazuru, Mr. Han