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Tham khảo tài liệu 'autonomous underwater vehicles part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Development of a Hovering-Type Intelligent Autonomous Underwater Vehicle P-SURO 29 underwater path planning. Under this consideration we carry out a series of test measuring the minimum and maximum recognition range both in the air and in the water. Test results are shown in Fig. 8 and 9 from which we can see that the maximum recognition range in the water is approximately half of the one in the air. For the safety consideration we force the vehicle to keep from the basin wall at least 1.5m throughout the various basin tests. Fig. 8. Test environments. Fig. 9. Test results 5. SLAM using range sonar array In the past decades SLAM Simultaneous Localization and Mapping has been one of most hot issues in the robotics community Leonard Burrant-Whyte 1992 Castellanos Tardos 1999 Thrun et al. 2005 . SLAM problems arise when the robot does not have access to a map of the environment nor does it have access to its own poses Thrun et al. 2005 . 30 Autonomous Underwater Vehicles For P-SURO AUV as aforementioned most of its underwater operations are carried out in the engineering basin in PIRO. For this reason we have designed a relatively simple SLAM method with partially known environment. 5.1 Range sonar model There are three Micron Echosounder@Tritech 6o conical beamwidth with 500kHz operating frequency mounted on the vehicle each of forward backward and downward. Because of their narrow beam-angle we apply simple centreline model Thrun et al. 2005 for all of these sonar behaviour. Throughout its underwater operation the vehicle is forced to keep away from the basin wall at least 2m. In this case the maximum range error is about 2.2m dM in Fig. 10 . Another significant error source is misalignment of range sonar with AHRS. For vehicle s dynamics we observed that the yaw angular velocity of P-SURO was less than 10o s. Consider the 1500m s of acoustic velocity in the water 10o s of yaw motion may cause less than 0.1o of azimuth error. Therefore the effect of vehicle dynamics
