Shojiro Ishibashi

Accuracy Improvement of an Inertial Navigation System Brought about by the Rotational Motion

An autonomous underwater vehicle (AUV) is equipped with an inertial navigation system (INS) in order to understand its own position in real time while it cruises without the communication with the external environment such as a support ship and GPS. Japan Agency for Marine-Earth Science and Technology has the cruising AUV URASHIMA, and it is also equipped with the INS. However the INS outputs its own absolute position containing the error that increases with time. It means, it is very difficult for URASHIMA to cruise dependent only on the position data outputted by the INS for a long time. So we have proposed the method to improve the performance of the INS, and its effect was confirmed in experiments. In the method, it was put on a turntable with assumption that it is fixed inside URASHIAM and the INS has been rotated by it around one rotation axis according to some rules. Consequently, the INSs position error was decreased by the rotational motion. In order to cause this effect, a precondition had to be met. It was that URASHIMA keeps its own posture to near-horizontal while cruising. However URASHIMA usually cruises with the roll motion which is caused by its shape. So the roll motion such as URASHIMAs one in a sea trial was applied to the turntable, and the INS was rotated in the situation. As the result, the INSs position error was decreased about half of the original one.

The Rotation Control System to Improve the Accuracy of an Inertial Navigation System Installed in an Autonomous Underwater Vehicle

An Autonomous Underwater Vehicle (AUV) is equipped with an Inertial Navigation System (INS) in order to detect its own current position for the autonomous cruise. It has a sensor part and an arithmetical part. The sensor part is composed of three gyros and three accelerometers, and the three-dimensional coordinate system (INS coordinate system) is defined in the arithmetical part. And an accelerometer and a gyro are set on each axis in the coordinate system. The INS calculates AUVs position using outputs of the sensors. So the position accuracy of it depends strongly on the precision of the sensors. However they have drift-bias errors which increase with the passage of the time. So, a method, which applies the rotational motion to the INS, is proposed in order to reduce the errors. In this method, the INS is put on the turntable and the INS is rotated by it around an axis of the INS coordinate system. And the errors of sensors, which are set on non-rotation axis, were reduced on average. This causes the position accuracy improvement. As the experimental results, the position error of the INS is reduced up to four times if suitable methods are given to it.

The untethered remotely operated vehicle PICASSO-1 and its deployment from chartered dive vessels for deep sea surveys off Okinawa, Japan, and Osprey Reef, Coral Sea, Australia

The untethered remotely operated vehicle (uROV) PICASSO-1, which is controlled in real time from a surface support vessel via a F0.9 mm fiber optic cable, is capable of dives to 1,000-m depth at a duration of up to 6 h and yet is deployable from ships of sizes as low as 17 tonnes. The vehicle was developed at the Japan Agency for Marine-Earth Science and Technology, has carried out 63 dives to date, and is now operable by a team of four biologists and one technician. PICASSO-1 can collect video (HDTV × 1, NTSC × 3) and environmental information (depth, temperature, salinity, dissolved oxygen concentration, fluorescence [chlorophyll a proxy], turbidity) concurrently, and this is output with vehicle heading, camera zoom, and other vital statistics via Ethernet. Acoustically obtained vehicle position information, deck and control room video, and sound data streams are also output via Ethernet, and the whole dive is recorded in a synchronous fashion on a logging/playback system that enables dives to be re-enacted in their entirety to facilitate analyses back in the laboratory. Operations have been successfully carried out overseas using a chartered dive boat, and the system represents a leap forward for exploration of the oceans to significant depths but at relatively low cost and with no loss in data quality.

The stereo vision system for an underwater vehicle

A vision system and a working system are particular important because they are indispensable for works of an underwater vehicle like remotely operated vehicle (ROV). So, generally, the ROV is equipped with TV cameras as the vision system and manipulators as the working system. However the manipulator operation watching a monitor, which appears the working environment taken by a TV camera, is very difficult because the operator can not have a sense of distance in the working environment. So the work ability of the manipulator depends strongly on the operators experience and skill. Based on that, in this paper, the stereo vision system, which calculates three dimensional position data of an object in the working environment, is described. It is hoped that the position data causes the manipulator operation without the operators experience and skill. And also, it is hoped that the dimension of the underwater object such as a marine organism can be got by the position data. In order to realize these, a camera calibration method applying the manipulator in the water was designed. And experiments were carried out to confirm the effect of the stereo vision system based on the camera model. As the result, its position accuracy was result in line with expectations.

Autonomous Underwater Vehicle for surveying deep ocean

There are concerns about the impact that global warming will have on our environment, and which will inevitably result in expanding deserts and rising water levels. AUVs (Autonomous Underwater Vehicle) were considered and chosen, as the most suitable tool for conduction survey concerning these global environmental problems. JAMSTEC has started to build a long range cruising AUV. The plan for its development is in several steps. As the first step an AUV, named URASHIMA was built in 1999, and sea trials have been held since 2000. URASHIMA dived to 3,518m depth in 2001. At the end of February 2005, the vehicle was able to cruise autonomously and continuously for 317km. This paper describes outline of the vehicle, presents some experimental results.

Sea Trial Results of ROV “ABISMO” for Deep Sea Inspection and Sampling

JAMSTEC (Japan Agency for Marine-Earth Science and Technology) has been developing the deep sea ROV ABISMO (Automatic Bottom Inspection and Sampling Mobile) having the capability to dive to the deepest sea. The purposes of ABISMO are to inspect on the seabed in the deep sea and to obtain sediment samples from there. ABISMO consists of a launcher and a vehicle which is launched from the launcher and surveys on the seabed to determine the place for sampling. Core sampling system, which is exchangeable with a gravity piston type or a grab type, is equipped in the launcher. The both of the launcher and the vehicle have cameras to observe. One of the features of ABISMO is that the vehicle has crawlers in addition to thrusters in order to advance mobility. ABISMO is operated with the support ship KAIREI and dived by means of its onboard equipment including a primary cable. We conducted sea trials in January and September 2007 at the areas with the water depths up to 1,300m in Sagami Bay as primary function tests. And we conducted the third sea trial at Izu-Ogasawara trench in December 2007 and made the successful results of diving to the depths up to 9707 m and obtaining a sediment sample from the seabed in 9760 m water depth. This paper describes the features and the outline of ABISMO as well as the sea trial results.Copyright

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.

MR-X1 — An AUV equipped with a space distributed CPU system and a satellite telecontrol interface

JAMSTEC has planned development of a long-rang cruising AUV. This vehicle will enable over 20 days autonomous cruising. To achieve this vehicle, we need various basic technology developments. In this article, a space distributed CPU system development for achieving highly redundant system control and a stationary satellite control system for remote control of the vehicle are described. We carried out sea trial to make sure the each system function using a test bed vehicle. It was shown that the satellite communication system is more effective.

The uROV PICASSO, the Visual Plankton Recorder, and other attempts to image plankton

A recently developed untethered but remotely operated survey platform, the PICASSO system, is described. This vehicle was designed specifically for surveys of macro- and megazooplankton and marine particulates (maximum depth 1000 m), to link information on gelatinous zooplankton diversity, behaviour and community structure with their function as packagers and producers of marine snow. In addition, an autonomous Visual Plankton Recorder, which is also deployable on the PICASSO vehicle, has been used to investigate particle profiles and plankton distribution vs. depth. Some results from these two systems from eastern Antarctica, the Coral Sea in Australia, and off Japan are introduced. Other techniques for imaging plankton in three dimensions are also introduced.

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.