Etsuro Shimizu

Thruster fault-tolerant control of a hovering AUV with four horizontal and two vertical thrusters

This paper deals with the motion control of a hovering autonomous underwater vehicle (AUV) with four horizontal and two vertical thrusters, when one or more thrusters are completely malfunctioned. Three thruster fault cases are considered: one horizontal thruster is faulty; two horizontal thrusters are faulty; and one vertical thruster is faulty. Through a series of simulations and an experiment, it is validated that the AUV can track a planned path in a 3-D space with minimally three thrusters (two are horizontal ones); however, some cases require the changes of the vehicle’s preferred direction of motion and its movement manner. Additionally, when the number of active horizontal thrusters is less than the required degree-of-freedom, a continuous state feedback control law does not exist due to the non-holonomic constraint. This paper highlights that the hovering AUV can overcome the non-holonomic constraint if using the feature that their translational and rotational motions can be controlled independently. Graphical Abstract

On the development of guidance system design for ships operating in close proximity

An international joint-industry research project for studies of hydrodynamic, control and operational aspects related to ship-to-ship (STS) operations has been initiated by the Norwegian Marine Technology Research Institute and received the funding from the Norwegian Research Council and industrial partners. The background for the project is an anticipated future demand for STS studies and the necessity to improve the mathematical models for multiple ship maneuvering in close proximity in order to further enhance quality of training on ship-handling simulators of operative key personnel involved in STS operations. A major objective with the ongoing research is to develop a decision support and guidance system for the ship navigation officers that can contribute to the operational safety and efficiency. Experienced Mooring Masters conducting lightering operations suggest that accurate information of relative distance and speed would assist in conducting a safe approach of the service ship towards the ship-to-belightered. The short-range distance measurement system RADius developed by Kongsberg Seatex AS of Norway has been proposed as one suitable technology platform towards a decision-support and guidance system for STS operations. A control strategy is proposed based on the availability of a relative distance sensor which can provide sufficient measurement accuracies.

Design and concept of a Biointeractive Autonomous Underwater Vehicle “BA-1”

To keep the precious protein source, it is thus extremely important to conserve the biodiversity of the ocean and at the same time to make use of its limited space as much as possible without doing any environmental harm. With this broad objective in mind, Tokyo University of Marine Science and Technology (TUMSAT) and Mitsui Engineering & Shipbuilding Co., Ltd. have started a research and development project, “Pen-free Offshore Aquaculture System using Biointeractive Autonomous Underwater Vehicles.” This project is part of a more comprehensive project, “Marine Biotechnology Innovation,” which has been funded by the Japanese government since 2007. In this paper, we propose a concept of a biointeractive AUV that monitors and takes care of schools of fish just like a sheep dog in a ranch. In a future plan of this system, multiple biointeractive AUVs monitor the environment spatially and accurately, feed the fish, monitor the growth of the fish, guide them, and report the data through satellite to the land while charging their batteries by docking with buoys. A first model of the biointeractive AUV “BA-1” has launched in early 2009. The design of the biointeractive AUV “BA-1” is described in this paper. The basic test result of the interaction system for fish is also described briefly.

A controller design for autonomous underwater vehicle “MR-X1” using linear matrix inequalities

The Independent Administrative Corporation Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has been developing light-and-small autonomous underwater vehicles (AUV), named “Marine Robot Experimental 1” (“MR-X1”). In this paper, the motion control problem of “MR-X1” is considered. Since the dynamics of “MR-X1” depends upon its own speed, the problem in question becomes a non-linear control problem. A new controller design method using linear matrix inequalities (LMIs) is proposed in order to adapt the problem in question. The algorithm, which gives a solution of a linear matrix inequality (LMI), can adapt to solve numerous LMIs simultaneously. LMIs can be obtained by substituting several speeds into the dynamics of “MR-X1”. The proposed controller, which can be derived from the solution of LMIs, becomes a stabilizing controller for all substituted speeds.

Motion planning for a manipulator equipped on an underwater robot

An approach for the motion planning of an underwater manipulator is described. This approach generates the secure path of the tip of the manipulator in its workspace, which includes obstacles, using the genetic algorithm. It also decides the manipulators posture to avoid obstacles using an evaluative function considering the drag force. In an environment setting with stationary obstacles or a dynamic obstacle, several experiments are made in order to confirm the validity of this approach.

Development of remotely operated unmanned boat with long-range Wi-Fi

Remotely monitored and operated unmanned vessels are effective for the working environment improvement of vessel crew, the solution of crew shortage, and the efficiency of marine survey. However, the development of unmanned vessels is delayed. One of factors is the communication problem. A bit rate of the current maritime communication using the satellite communication is about several hundred kbps from vessels. Therefore, this bit rate is insufficient for remote monitoring and operation. To solve this problem, a use of a long-range Wi-Fi communication is proposed. In this paper, the unmanned system capable of remote monitoring and operation with long-range Wi-Fi is developed and examined at Tokyo bay.

Design and development of Module-Composite Underwater Vehicle

Since underwater vehicles have been developed for a long time, those fundamental techniques are studied and established. In general, improvement of vehicle and/or attaching new equipments are quite difficult once the underwater vehicle is designed. Furthermore, vehicles are required various missions and/or different apparatus. In present, these problems are managed by changing attachment of manipulator in every mission. In this paper, underwater vehicle composed by modules is proposed. Every single function of underwater vehicle is separated to the module. The proposed vehicle is composed by these modules which are selected depend on necessity of instrument, area of investigation and environment. Each module are able to communicate by ZigBee which is one of wireless specification and unit.

A simulation system for an underwater robot based on visual data

In this paper, a simulation system for the autonomous working system of new underwater robot is referred. The simulation system has a dual arm system as the working part and a robot-eye system as the visual sensation part. As the first step to construct the simulation system, the cooperative control problem for an autonomous working system using the visual data is considered.

Biointeractive Autonomous Underwater Vehicle “BA-1”

This paper describes the design of a biointeractive AUV that has abilities to monitor schools of fish interactively. In the very large ocean it is very difficult to understand the habits of a swimming fish because the visibility of camera and range of sonar are limited while they swim widely. It is also hard to apply bio-logging techniques to fish because loggers are still large and heavy for them, furthermore, retrieving the data is tough. The biointeractive AUV can stay in the environment where fish is living and swim together with them to monitor their life style. The vehicle has capabilities to give stimulus to fish to observe their behavior caused by the stimulation. Future plan of the biointeractive AUV is to take a role of monitoring the environment spatially and accurately, feeding the fish, monitoring their growth and guiding them in a pen-free offshore aquaculture system. A first model of the biointeractive AUV “BA-1” has launched in early 2009. The length of the vehicle is 3m and the weight in air is about 430kg. The depth rating of the vehicle is 1,000m. It has both hovering and cruising capabilities for operations in test tanks, aquaculture pens and oceans. The design of the biointeractive AUV BA-1 is described with the test results in a test tank and the result of the interaction test with fish in an aquaculture pen.

Depth Control for Towed Vehicle

In this paper, a depth control problem for towed vehicle is considered. Generally the depth of the towed vehicle is not steady by the effect of the vibration of towing line. In order to keep the constant depth, a controller for variable horizontal tail fins, which are equipped on the towed vehicle considered this paper, is designed. Since the mathematical model of the towed vehicle can be expressed as a nonlinear equation, a nonlinear controller for the tail planes is derived by using linear matrix inequalities (LMIs).