Super Short Baseline Research Articles

Pointing Error Control of Underwater Wireless Optical Communication on Mobile Platform

This letter discusses pointing errors in underwater optical communication caused by environmental disturbances and uncertainties that cannot be well measured and controlled in previous optical alignment methods. The bore-sight and jitter effects are identified in the motion model of the mobile platform. We propose to use the sensor suite that includes a pressure sensor, super short baseline (SSBL) acoustic system, Doppler velocity log (DVL), and fiber optic gyro (FOG) to observe and estimate pointing errors during communication. The pointing errors updated by the particle filter can be shared with the pointing, acquisition, and tracking (PAT) system and thruster system. The sea experiments reveal that the proposed method can measure pointing errors and limit error growth by maneuvering the mobile platform.

Experimental Evaluation of Accuracy and Efficiency of Alternating Landmark Navigation by Multiple AUVs

This paper presents the experimental evaluation of the alternating landmark navigation (ALN) by multiple autonomous underwater vehicles (AUVs) using latest results of sea experiments and tank tests in terms of accuracy and efficiency. Self-localization is essential for AUV navigation, and AUVs are typically supported by long base line or super short base line of the support system. Against these methods, the ALN was proposed, where each AUV alternately becomes a landmark, which remains stationary on the seafloor, whereas the other AUVs can navigate based on acoustic positioning with the landmark AUV. The ALN realizes stable navigation without any support. Our goal is to realize surveying near the seafloor using only AUVs. The performance of the ALN in obstacle-existing environments was evaluated through the simulation to discuss the expandability of the ALN. The ALN was implemented on AUVs “Tri-Dog 1,” “Tri-TON,” and “Tri-TON 2.” On the basis of the sea experiments and the tank tests conducted with these AUVs, the performance of the ALN was verified. In particular, accuracy and efficiency of the ALN were evaluated through the tank test. Finally, it is shown that the ALN can realize accurate and efficient survey of the seafloor by only AUVs without any support.

Alternating landmark navigation of multiple AUVs for wide seafloor survey: Field experiment and performance verification

AbstractThis paper reports the results of the sea experiments and the performance verification of a navigation method for wide area surveys of the seafloor using multiple autonomous underwater vehicles (AUVs). In the method, AUVs alternately land on the seafloor to act as landmarks for each other, and all AUVs can observe a wide area with accurate positioning relative to the landmark AUV. For self‐localization, AUVs are typically supported by long base line (LBL) or super short base line (SSBL) of the support system. Thanks to the proposed method, AUVs can perform near‐seafloor surveys requiring real‐time and accurate positioning, such as seafloor imaging and sampling, without these support systems. The method was implemented on two AUVs: “Tri‐Dog 1” and “Tri‐TON.” The performance of the method was verified using these AUVs through sea experiments and postprocessing simulation using experimental data. In addition, it was also verified that the performance of the method is comparable to high‐grade conventional navigation methods, such as LBL or SSBL, through simulations of long distance navigation.

AUV のためのナビゲーションシステムの開発

AUV is stable for a wide range of search because it does not have an umbilical cable. However, AUV cannot work for a long time because of internal power source. Utilization of charging station in the water is required for long-term operation to solve this problem. In this paper, it is described a navigation system to the station with acoustic positioning system that mounting is possible to the AUV. It has three hydrophones and receives signal from that pinger is mounted the station. Sound source detection is calculated by Cross Correlation Function and Super Short Base Line method. In addition, it is introduced chirp signal as the pinger to develop a robust the system against noises. It is applied the developed system and carried out the experiment for navigation to the pinger. The present result suggested that sound source detection and guidance to the station are feasible in this system.

考古学調査用水中ロボット開発と琵琶湖葛籠尾崎による利用

Due to wind and water flow, it is very difficult for divers to investigate the Tsuzuraozaki underwater remains at Biwa Lake in Japan. We have developed an underwater robot to overcome the difficulties of the archaeological investigation at the Tsuzuraozaki remains. The developed robot has 8 thrusters, a stereo camera, SSBL (Super Short Base Line) system and so on. The usefulness of the developed underwater robot was demonstrated by archaeological investigation at the Tsuzuraozaki remains.

Super Short Baseline Underwater Acoustic Positioning Supported by Inertial Navigation Data Using Spread Spectrum Communication for Autonomous Underwater Vehicle and Error Analysis in Deep Water

A tracking and positioning method achieved by integration of the super short baseline (SSBL) and inertial navigation system (INS) data for an autonomous underwater vehicle (AUV) is introduced. The proposed method uses a continuous acoustic signal as the response signal from the target AUV. The INS data obtained in the AUV is transmitted with the acoustic signal by the direct-sequence spread spectrum (DSSS) technique and the SSBL estimation is achieved using the same signal. The error of the SSBL, particularly the influence of a multipath, was analyzed. The use of a continuous signal showed that the multipath is influential even if its level is small relative to the direct wave. This influence was observed under actual conditions in an ocean experiment in a deep-water area. The proposed method was confirmed to be available and useful by simulations and experimental results.

Basic Study on Acoustic Communication Using Direct-Sequence Spread Spectrum for Underwater Acoustic Positioning

Supershort baseline (SSBL) underwater acoustic positioning is commonly utilized in estimating the positions of transponders, observation devices and submersibles. The new SSBL system in which a sea surface station and a sea bottom station communicate using the spectrum spread (SS) technique was studied with simulation. An M-sequence was adopted as pseudonoise (PN) code and PN code length was set for 15, 31, 63 and 127. Random noise and Doppler shift were considered as distortions. It became clear that the system becomes useless due to Doppler shift exponentially, and that under the condition with a large Doppler shift, the system is not available if the PN code length is longer than 31, that if the relative velocity between the transmitter and the receiver is less than 5 m/s, the system has the highest performance with a PN code length of 31 and that in case of a PN code length of 15 the system is stable under the same condition.

어류의 행동추적에 의한 SSBL · 핑거동기 바이오텔레메터리 방식과 시스템의 실용성 검증

SSBL <TEX>${\circ}$</TEX> 핑거동기 바이오텔레메터리 방식과 시스템을 사용하여 핑거를 부착한 어류의 행동 추적실험을 실시하였다. 이상의 연구 성과를 정리하면 다음과 같다. 1) 수조의 추적실험에서는 어류의 대략적인 행동을 관측할 수 있기 때문에 어류의 이동경로의 계측치와 대체적인 관측치를 비교하면서 어류의 이동경로와 속도 등을 조사하였다. 계측한 잉어의 행동이 관측치와 대체적으로 일치하였으며, 3차원으로 추적이 가능하였다. 잉어의 평균 이동속도는 11.2cm/s로 거의 적당한 결과를 얻을 수 있었다. 2) 계류장의 추적실험에서는 상하, 좌우 방향으로 회전가능한 지지 파이프에 수파기를 설치하고 수파기를 회전시키며 자연상태에서 어류의 이동경로와 속도 등을 조사하였다. 방어의 행동이 상세하게 추적 가능함을 확인할 수 있었으며, 방어의 평균이동 속도는 439cm/s이었다. 이상에 의해 본 연구에서 개발한 SSBL <TEX>${\circ}$</TEX> 핑거동기 바이오텔레메터리 방식에 의하면 수신계의 고도화만으로도 핑거를 부착한 어류의 상세한 행동추적 이 가능함을 확인할 수 있었다. The new biotelemetry method and system that the installation and the treatment of equipment is convenient and the instantaneously detailed position of the fish attached a pinger is able to track comparatively easily had been developed, an practicality of it were verified in the water tank and the small sea port through the tracking of fish. The biotelemetry method had been gotten the three dimensional locations of fish to the receiving transducer by combining of the super short base line (SSBL) method to detect the direction of pinger and the pinger synchronizing method to measure the range from receiving transducer to pinger. The receiving system had been designed to realize the high precision or wide detection range by application of the basic design method for receiving system of biotelemetry and the hydrophone array configuration. From tracking test of carp in the water tank, the migration course and the velocity of carp was investigated and the observed migration course was compared with measurement. The measured migration course of carp coincided with the observation in the main and the position of carp was able to track three dimensionally. The velocity of carp measured by the moving average method was 11.2cm/s. From tracking test of yellowtail in the small sea port, the migration course and the velocity of yellowtail was investigated at natural condition. The position of yellowtail was able to track three dimensionally and the velocity of it measured by moving average method was 43.9cm/s.

Performance improvement of in-flight alignment for autonomous vehicle under large initial heading error

The paper presents a new method of in-flight alignment (IFA) for a strapdown inertial navigation system (SDINS) aided by a super short baseline (SSBL) system under a large initial heading error. To handle the large heading error, a new attitude error model is introduced in which attitude errors are divided into heading and levelling errors using a newly defined horizontal frame. Some navigation error dynamic models are derived from the attitude error model for indirect feedback filtering of the IFA system. A Kalman filter with position measurements is designed to estimate navigation errors as an indirect feedback filter. Simulation results show that the newly developed model works effectively for coarse alignment of a large heading error. The proposed IFA method very quickly decreases the heading error from more than 40° to about 5°.

SSBL 방식과 핑거동기 방식을 조합한 바이오텔레메터리 방식의 개발 (2) -시스템의 정도 평가 -

SPB방식과 시스템을 수조실험에서 검증하였다. 이상의 연구 성과를 정리하면 다음과 같다. 1) 핑거와 비슷한 펄스를 하이드로폰으로부터 발생시켜 수파기의 협빔과 광빔의 양빔 모드의 위상빔어레이 중심간 거리를 보정하여 전후, 좌우의 위상빔에 대한 위치측정 정도를 비교, 분석하였다. 측정위치오차는 협빔 모드의 전후위상빔에서 6.4cm, 좌우위상빔에서 6.3cm로 위치측정 정도는 고정도 이었으며, 광범 모드에서는 각각 24cm, 23cm로 협빔 모드보다 위치측정 정도는 4 배 정도 낮았다. 2) 핑거를 이미 계산된 위치로 이동시켜 핑거동기방식에 의한 거리정보와 SSBL 방식에 의한 방위정보를 자동, 연속으로 측정하였으며, 핑거동기 방식에 의한 핑거의 측정거리, SSBL. 핑거동기 바이오텔레메터리 방식에 의한 핑거의 측정위치, 핑거의 측정이동속도를 구해 기존의 값과 비교하여 새롭게 개발한 방식과 시스템의 유효성을 검증하였다. 핑거동기 방식에 의해 구한 핑거의 측정거리 오차는 1.8cm, SSBL. 핑거동기 바이오텔레메터리 방식에 의해 구한 핑거의 측정위치 오차는 7.7cm로 고정도로 측정이 기능하였으며, 핑거의 측정이동속도는 기존의 값에 대체적으로 일치하였다. The new biotelemetry method and system that the installation and the treatment of equipment is convenient and the instantaneously detailed position of the fish attached the pinger is able to track comparatively easily had been developed, an availabilities of it were verified in water tank by using hydrophone and pinger. First of all, the receiving system for biotelemetry was calibrated so as to measure tracking of high precision or wide detection range. In the next place, the precision at narrow and wide beam array of receiving system by using hydrophone was investigated and the actual position was compared with measured hydrophone position. The mean standard deviations of the position by narrow beam array of receiving system were 6.4em in phase beam of fore-aft pair and 6.3em in starboard-port pair, and the wide beam array were 24em and 23em respectively. The precision of distance, position, and velocity at narrow beam array of receiving system by using pinger were investigated and the actual values were compared with measured values. The distance from receiving system to pinger was measured by the pinger synchronizing method, angle of direction of pinger was detected by the super short base line (SSBL) method. The three dimensional position of pinger to the receiving system was measured by combining of two kinds of methods (SPB method), the velocity of pinger was obtained with a differential of the three dimensional positions. The mean standard deviations of the distance by pinger synchronizing method in narrow beam array of receiving system was 1. 8 em, that of the position by SPB method was 7.7cm.

SSBL 방식과 핑거동기 방식을 조합한 바이오텔레메터리 방식의 개발 (1) -시스템의 설계 및 제작 -

이상의 연구 성과를 정리하면 다음과 같다. 1) 장비의 설치 및 취급이 간편하고, 해양생물의 순간적인 상세한 행동을 비교적 쉽게 추적할 수 있는 새로운 바이오텔레메터리 방식을 개발하였다. 바이오텔레메터리 방식에서 핑거에 수온, 압력센서 등의 추가는 핑거를 부착하는 어류에 많은 부담이 되기 때문에 수신계를 고도화함으로써 행동추적을 행하는 방법으로 하였다. 이 방식은 거리-방위의 측정원리를 이용한다. 즉, 거리를 계측하기 위해서 핑거동기 방식을 이용하고, 방위를 계측하기 위해서 SSBL방식을 채용하여, 거리와 방위를 조합(SPB 방식)함으로서 대상어의 수파기에 대한 상대위치를 구한다. 최대감도방식은 어류의 상세한 위치를 특정하기가 어렵고, 음원측위방식은 항주하는 선박에 의해 넓은 범위의 추적이 곤란하며, 또한 장비의 설치나 취급이 간편하지 못하였으나, SPB 방식에 의해 이들 결점을 대폭 해결할 수 있었다. 2) 새로운 방식으로서 개발한 SPB 방식의 시스템을 설계하였으며, 시작시스템을 제작하였다. 설계에서는 SSBL 방식과 핑거동기 방식의 기술을 조합함과 동시에 각각의 기술을 고도화하여 SPB 방식에 의해 고정도 또는 광범위 검지가 가능하도록 하였다. 따라서, 수파기는 1개로 하여 어레이의 구성의 변환에 의해 검지범위 또는 방위측정정도를 선택할 수 있도록 2개의 빔 모드로 구성 하였다. 주파수는 70kHz로 하였으며, 음원음압 136dB에서 최대검지거리 258m와 457m, 검지빔폭 76<TEX>$\circ$</TEX>와 29<TEX>$\circ$</TEX> 를 실현할 수 있었다. 전체적인 시작시스템은 핑거, 2개의 빔모드로 구성된 수파기, 2개의 빔 모드용에 각 2개의 채널로 구성된 수신기, 디지털오실로스코프, 퍼스널컴퓨터로 구축하였다. 핑거동기 방식의 이용에 따른 측정거리오차는 수온변화에 의한 송신주기의 변화를 측정하여 최소화하도록 하였다. 핑거 부근의 수온을 알 수 있다면 핑거 송신주기의 수온특성을 보정하여 74%정도 측정거리오차를 줄일 수 있지만, 장기간에 걸쳐 추적을 하기 위해서는 다른 보정방법의 개발이 필요함을 알 수 있었다. A new biotelemetry method that the installation and the treatment of equipment is convenient and the instantaneously detailed location of the fish attached the pinger is able to track comparatively easily was developed. The receiving system in this biotelemetry method was advanced for track the detailed behavior of the fish by the miniature tracking pinger, because it was a burden to fish to add the pinger with the water temperature and the pressure sensor. By combining of the super short base line (SSBL) method to detect the direction of pinger and the pinger synchronizing method to measure the range from receiving transducer to pinger, the three dimensional locations of fish to the receiving transducer is gotten instantaneously. The receiving system is devised to realize the high precision or wide detection range by application of the basic design method for receiving system of biotelemetry developed by the present authors and the hydrophone array configuration. The measurement distance error in the pinger synchronizing method is minimized through the correction of which the deviation of transmission pluse period of pinger is caused by changing water temperature. A prototype system which is able to track the instantaneously detailed location of the fish by the SSBL and pinger synchronizing biotelemetry (SPB) method was produced.

地学における先端テクノロジー 深海調査技術 有人潜水調査船と無人探査機

The development of deep sea research systems-manned and unmanned submersibles-made it possible to carry out visual surveys of the deep seafloor at any depth on the earth. These surveys have revealed a great number of phenomena that occur on the seafloor, such as hydrothermal vents and chemosynthetic biological communities at mid-oceanic ridges.Unmanned submersibles include ROV (Remotely Operated Vehicle), UROV (Untethered Remotely Operated Vehicle), which have thrusters and are operated by mother ship through a tether cable or a thin optical fiber respectively, AUV (Autonomous Underwater Vehicle) which moves under pre-programmed commands and does not have a cable, and deep-tow system which is also operated by mother ship through. a cable but does not have a thruster.In order to see objects under very low illumination in deep seas, a Super-HARP (High-gain Avalanche Rushing Amorphous Photoconductor) video camera which is far more sensitive than CCD cameras, was developed. Recently, the Super HARP Hi-vision video camera, which provides high-resolution video images, has been developed.The location of the submersible in water is obtained by three acoustic positioning systems. These are called LBL (Long Base Line), SBL (Short Base Line), and SSBL (Super Short Base Line) positioning systems.In order to achieve effective dive surveys by manned submersibles or ROVs, it is necessary to select dive points by considering the results of pre-surveys carried out over a wide area, including bathymetric mapping using multi-narrow beam echo sounder, side-scan sonar survey, and deep-towed camera surveys.Submersibles enable not only visual observation, but also sampling and geophysical measurement at aimed points on the deep seafloor. In order to construct multi-disciplinary real-time and long-term deep seafloor observatories, such as off Hatsushima Island Observatory and VENUS off Okinawa Island Observatory, or to carry out borehole measurements, submersibles have been playing important roles in installing instruments, extending cables, and connecting connectors of instruments to underwater telemetry systems, or in recovering data. Submersibles are also necessary when searching for the causes of events observed by the observatory.The ROV and the Super HARP Hi-vision video camera made it possible for many scientists on board to see high-resolution video images of the seafloor simultaneously as if they were viewing it with the unaided eye. The AUV will enable surveys over wide areas in the near future. However, observations by submersibles are limited by survey time. On the other hand, long-term observatories enable observations only at fixed points. Complimentary observations using both long-term observatories and submersibles are expected in order to extend survey area in terms of both temporality and spatiality to provide an understanding of phenomena that occur on the seafloor.

An advanced SSBL‐acoustic reference system using a planar hydrophone array

AbstractSSBL (super‐short‐base‐line) is an acoustic reference system in which the angle of incidence (direction cosine) and the slant range of the acoustic wave are estimated to locate the source position. A new SSBL acoustic reference system differing from conventional systems is proposed. The new system uses a planar hydrophone array consisting of many hydrophone elements. When a maximum likelihood estimate is implemented for the direction cosine and slant range measured by a planar hydrophone array, the estimate is given so that the envelope of the spatial‐temporal correlation between the array output and the reference signals is maximized. When the short array condition is satisfied for a planar hydrophone array, this spatial‐temporal correlation is given by the temporal correlation, phase compensation and addition. We obtained the lower bound of the mean‐square error of estimates of the direction cosine and slant range and compared the performance of the system with that of conventional systems. For example, when a square planar array of 4 × 4 = 16 elements is used, system gains of about 16 dB for the direction cosine and 12 dB for the slant range are attainable.