System Architecture
This diagram outlines the architecture of our underwater positioning system. Beacons emit synchronized acoustic pulses received by the AUV, which transmits the data to a processing unit to calculate its position.
01
In this section, the concept ranging system is reverse engineered into a functional baseline document. The functional baseline will focus on the physical ranging system device. All functions of the system and their relationships are shown in the function flow block diagram (FFBD) below.
The second level of FFBD is shown below where F1 , F2 and F3 are further decomposed.Note that power inputs are required to all the functions in second level FFBD but they are omitted to make the demonstration concise.The decomposed functional flow presents the internal operations of the ranging system, specifically how sonar signals are generated, transmitted, received, processed, and converted into range data.
All the functions shown in the above figure are given in the following table.
02
Requirement list:
The system shall perform real-time distance measurements one by one to at least three stationary beacons using ultrasonic signals.
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The system shall combine sonar ranging data with RTK-GPS and IMU orientation data to give accurate 3D position.
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The system shall achieve a ranging accuracy of ±50 cm.
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The system shall provide a structured output dataset suitable for 3D underwater SLAM research.
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The system shall implement Frequency Division Multiple Access (FDMA) to distinguish signals from multiple beacons.
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The system shall use computational power that is suported by the stm32 chip
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The system shall support time synchronization mechanisms to ensure sensor alignment.
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The system shall operate at a minimum data acquisition rate of 1Hz (at least one measurement per second).
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The system shall resist background noise from water flow or other sonar systems.
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The system shall record and store synchronized sensor data (sonar, IMU) for processing and analysis.
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The system shall operate in freshwater environments without significant signal degradation.
The system shall perform well without error underwater.
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The system shall comply with safety regulations for underwater robotics and sonar equipment and environmental protection laws.
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The system shall maintain stable operation under varying environmental conditions, including minor water flow disturbances.
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The system shall achieve reliable communication with beacons within a range of 100 meters.
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The system shall function at depths of up to 50m meters without performance loss.
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The system shall be capable of continuous operation for at least 10 hours without failure.
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The system shall have redundant data logging to prevent data loss in case of power failure.
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The system shall be designed for easy maintenance and allow replacement of individual sensors or processing units.
03
Need list
N1: locate underwater robot accurately.
N2: no cross talking between beacons.
N3: Real time tracking while robot is moving.
N4: avoid transmission error via signal encoding and processing.
N5: cause no damage to the environments.
N6: Good underwater performance and ability to be used for long periods of time.
04
RBS
