Masami Matsuura

An autonomous underwater vehicle with a canard rudder for underwater minerals exploration

Exploration and mining of natural resources in the region of seabed are needed for lasting economic growth, because an abundance of natural resources, including rare metal, is in Japans exclusive economic zone (EEZ). The cost down of exploration and mining is an important issue for industrialization. It is well known that unmanned and/or autonomous platforms for exploration are effective to reduce operation cost. JAMSTEC has developed a cruising type autonomous underwater vehicle (AUV) to perform exploration in hydrothermal activity areas up to depth of 3,000 meters since 2011. This specified purpose AUV (5 m long, 2.7 tons in weight) has capability of high maneuverability for eliciting high performance of sonars and is equipped with three sonars: a synthetic aperture sonar (SAS), an interferometry sonar (IFS) and a sub-bottom profiler (SBP). The cruising AUV, named Yumeiruka, is thus has a canard rudder to maintain a fixed posture in horizontal and vertical plane. In March 2013 the 15-days sea trial of the vehicle was carried out in the Sagami Bay and we achieved constant pitch control by using the canard rudder during an altitude change.

The organized motion control of multi-directional wave maker

This paper describes the hardware and associated software of the organized motion control of a multi-directional wave maker which has been developed in the seakeeping model basin. The developed wave maker is a flap type wave maker which consists of multi-segmented flaps, actuators (AC servo motors) which drive segmented flaps, and the computer system which manages the motion control of actuators. Waves can be generated by the forward and/or backward movement of flaps which are connected mechanically by ball screws rotated by AC servo motors. How the flaps are moved decides the type of waves such as the wave height, the wave period, and the wave spectrum, etc. The width of the test basin and a flap size are 30m and 0.4m, respectively. Therefore, the number of segmentation of flaps becomes 75. The computer system drives simultaneously these 75-axes AC servo motors. The organized motion control of 75-axes-servo-system for the multi-directional wave maker is completed and the high performance of the wave generation, especially the real time calculation of setpoints, is achieved by the organized motion control hierarchy design.

Conceptual Design of Navigation of an AUV for Monitoring CCS Site at Deep Sea Bottom

We, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), are developing an autonomous underwater vehicle (AUV) whose main mission is monitoring a site at the sea bottom for the carbon dioxide capture and storage (CCS). The AUV cruises very near the sea bottom, and is equipped with chemical sensors in order to detect escape of CO2 from sub-bottom. Of course, the position information of the AUV is critical information for the monitoring. In this paper, a conceptual design of navigation of the AUV is described. Recently, navigation of AUV is implemented by integrating multiple navigation devices including inertial navigation system (INS), Doppler velocity log (DVL), depth sensor, acoustic navigation system, and others. The AUV under construction will be equipped with these navigation sensors, and will integrate those sensors’ outputs to navigate herself. In order to measure the absolute position of the AUV the acoustic method is one of fundamental technique. At the first step of development of the AUV, three acoustic methods are considered to adopt. The three methods are super short baseline (SSBL) method which is a tracking from support ship or other surface station, long baseline (LBL) which is navigation based on preplaced acoustic transponders, and virtual LBL (VLBL) which is navigation based on only single transponder. These acoustic methods are integrated with the navigation result of INS, depth sensor, and DVL. The three methods are used in each appropriate case. Which feature of observation is desired simplicity, accuracy, or independence from support ship and time efficiency? The acoustic method is influenced by environment, and also output of other sensors is depending on the environment, for example the DVL miss the data when the terrain is with many up-hills and down-hills. The integration or filtering parameters of the navigation should be adjusted depending on the influential environmental factor.Copyright

Neural Networks for System Identification of Coupled Ship Dynamics

Abstract System identification of coupled ship dynamics is problematic with standard least squares methods due to the non-linear, multivariable nature of the system. Neural Networks have therefore been applied to this problem, as they are particularly suitable for approximating non-linear, multivariable functions. In this paper, results of identification with Neural Networks are given for a ship motion simulation based on a standard mathematical model, and for real data collected from a 1/50th scale model of the system. The method is seen to be successful at various operating points, and ideas for extension of the work are discussed.

The experimental results about maneuverability and survey ability of AUV “URASHIMA”

In late years, deep-sea investigation becomes important for a study about the global warming, study about ocean earthquake and so on. Recently the vehicle has begun to use for scientific applications. These applications require precise maneuvering of the vehicle for detailed investigations. For high performance maneuvering of the vehicle, it is necessary to design a control system based on a mathematical model for the vehicle. Since the vehicle was built, PI control has been adopted. In order to improve control performance, the motion controller can be designed by means of a model-based approach. An accurate mathematical model based on vehicle dynamics is needed for designing of the high-performance controller. It is necessary for the mathematical model to express the actual motions of the vehicle precisely. The paper reported that maneuverability test results and survey ability test results of autonomous underwater vehicle “URASHIMA” at sea trial.

Response Characteristics of a Trailer Type Multi-Connected Barge System in Waves

A trailer type multi-connected barge system is a new type of ocean transportation system composed of several barges connected to each other with a mechanical connecting device and a tug ship. To design the trailer type multi-connected barge system, it is necessary to grasp the exact response characteristics of the trailer type multi-connected barge system in waves. A model basin test was conducted for the trailer type multi-connected barge system in waves. In the model basin test, the tug ship and three barges were connected to each other by the mechanical connecting device, and the tug ship towed three barges in waves. As a result, the response characteristics of the trailer type multi-connected barge system in waves were obtained. A non-linear phenomenon of a longitudinal connecting force caused by relative pitch motions of barges was observed. A way to avoid the non-linear phenomenon and reduce the longitudinal connecting force could be found, and the realization of the trailer type multi-connected barge system was experimentally confirmed.Copyright

Response Characteristics of a Multi-Connected Floating Body System in Waves

A multi-connected floating body system composed of many connected small-scale floating body units has a number of advantages with regard to construction and performance compared with a united floating body. To design the multiconnected floating body system, it is necessary to grasp the exact response characteristics of the multi-connected floating body system in waves. A model basin test and a theoretical calculation were conducted for the multi-connected floating body system in waves. In the model basin test, three floating body unit models with a regular hexagonal water plane were connected to each other with a newly conceived mechanical connecting device. As a result, the response characteristics of the multi-connected floating body system in waves were clarified experimentally and theoretically, and the applicability of a theoretical calculation method was experimentally confirmed.Copyright

A COUNTERMEASURE AGAINST LOW FREQUENCY MOTIONS OF A MOORED SHIP USING SHIELDING STRUCTURE

This paper shows a countermeasure against low frequency motions of a moored ship. It is difficult to decrease the low frequency surge motions of the ship moored by fiber ropes, because breakwater cannot prevent the entrance of low frequency components of ocean waves. Furthermore the very small damping force of surge motion interferes reducing resonance motions in the low frequency range. The shielding structure, which is close to the weather side of the ship, is prevent the flow due to the low frequency waves so it decreases the wave exciting force. Then the effect of the shielding structure is confirmed by the tank tests. Moreover, the effect of the structure, which consists of flame structure and membrane, is also confirmed. This shielding structure effectively decreases the low frequency surge motions of a moored ship.

System Plan Considering Spare Capability Allowed for Weather Conditions for CO2 Marine Transport and Release in Deep Waters

Ocean storage of the captured CO2 from fossil fuel burning is a possible option for mitigating the increase of CO2 concentration in the atmosphere. Moving-ship type of CO2 ocean storage is a concept whereby captured CO2 is delivered by ship to a site and injected into the deep ocean by means of a pipe suspended beneath a ship as it slowly moves through the water. In case of bad weather conditions, CO2 marine transport and operation on the sea should be adjourned although CO2 would be captured at the plant every day. It is, therefore, required that the system would have the buffer storage at the port and the extra shipping ability to recover the delay of schedule. Since the large scale of such spare capability might lead to the increase in cost, it is needed to investigate how to plan the system allowed for weather conditions reasonably. In this study, a time series model of sea state through one year is generated for a hypothetic ocean storage site, based on the wind data observed with satellite remote sensing, and simulations of CO2 marine transport and operation on the sea are carried out considering the operational limit of sea state. In this approach, the continuing bad weather days or the frequent occurrences of rough sea condition during the specific season are counted. Three kinds of system are applied for the simulations and compared; 1) CO2 carrier and release ship are used separately and moored tandem for CO2 shift at the site, 2) CO2 carrier and release ship are used separately and moored in parallel for CO2 shift, 3) ship is used as a CO2 carrier and release ship. The third one would not need mooring and CO2 shift operations on the sea which are sensitive to the sea state, but would need long- and every-time operation of pipe handling. The results are assessed as capital and running cost per tonne of CO2 .Copyright

Development of Multi-Connected Floating Body System

A multi-connected floating body system composed of many connected small-scale floating body units has a number of advantages with regard to construction and performance. To realize the multi-connected floating body system, a new type of mechanical connecting device was developed. It is composed of multi-degrees of freedom connecting mechanism and restricting mechanism to control a restricting condition between floating body units, and its effectiveness was confirmed by model basin test in waves. Next, friction and wear tests in the seawater environment led to the discovery of suitable materials for oscillatory sliding parts in multi-degrees of freedom connecting mechanism. Finally, a field test performed for two floating body units connected by use of the mechanical connecting device proved that the developed mechanical connecting device was of practical use.Copyright