AUV Specification:

Bracu DUBURI 4.0 Mechanical System

The body of the hull is built with Marine 5083 grade aluminum. Because of its low density, high strength-to-weight ratio, resistance to corrosion, and good thermal conductivity, this specific aluminum was chosen. The top enclosure along with the front and bottom camera openings are sealed with acrylic windows having brass frames. Although this gave the AUV an upper edge in terms of weight there was a significant rise in manufacturing cost. Further- more working with aluminum in particular required expert involvement in terms of welding which also increased production time.

Hull Design Of Duburi 4.0

In terms of this design Duburi has now went ahead with a octagonal shape compared to the previous year’s hexagonal shape. The design choice was made keeping previous year’s findings in mind. The flat surface in a pentagon shaped design in previous years AUV led to increased drag when it tried to go in reverse which greatly reduced the AUV’s efficiency and put excessive yet unnecessary load on the rover to reach the same level of compe- tence compared to this year’s design. This year the hydrodynamic hexagonal shape allowed equal flow over the AUV’s surface reducing turbulance. It also massively reduced the drag caused when operating in reverse. Although to keep the rover hydrodynamic in this year’s design the outer support structure used to mount thrusters was removed hence resulting in the thrusters being more prone to physical damage in an event of collision.

TORPEDO DESIGN OF DUBURI 4.0

Duburi uses an elastic force induced propulsion system for its torpedo. The mechanism works by holding back two torpedoes using elastic bands which store the energy for propulsion. When the rover needs to launch the torpedo a servo is used as a trigger. The servo moves in one certain direc- tion releasing the torpedo. Furthermore when one torpedo is launched the mechanism prepares for the next launch and the servo moves to another direction hence completing two launches with the mechanism. The major drawback with this design approach is that it only holds two torpedos. An- other drawback it being less accurate compared to independent onboard propulsion based systems.

Grabber DESIGN OF DUBURI 4.0

We have upgraded to a custom-made grabber with a two-finger design, incorporating a specialized linear actuator for enhanced stability and grip. The grabber's body is constructed from aluminum, with rubber tips on the fingers for improved traction. To ensure a secure hold, two fingers are positioned on one side and one on the other, creating an interlocking mechanism during gripping. Additionally, we have integrated a Sharp sensor to determine the object's proximity and confirm if it remains securely held, enabling us to achieve precise and reliable grasping. In the event of a failed attempt, the sensor promptly detects the error.

Bracu DUBURI 4.0 Electrical Architecture

Power-flow OF DUBURI 4.0

We have used 2 LiPo Battey in our rover, One of them is a 12.6V 5400 mAh 3 Cell battery and another one is a 12.6V 5200 mAh 3 Cell battery. We are using one of our batteries to power T200 Thrusters ESC. In this part, we are directly using full battery voltage without using any buck module, From Battery to the Thruster power connection we have implemented our DIY underwater switch, which can kill the thruster power in case of Emergency. Also, we are using another battery to power our main Jetson Nano SBC, 1 ONU (Optical Networking Unit), and 1 Ethernet switch. In this time we have used a buck module to convert the 12.60V voltage to 5V voltage, We have also used a kill switch in this time to kill the power of our Jetson Nano, 1 ONU, and 1 Ethernet Switch. So For the battery safety requirements, we have implemented 2 DIY Underwater Kill switches that can be controlled from the outer back part of the body of the rover.

NAVIGATION SYSTEM

Duburi uses a Vectornav VN-200 GNSS aided INS. That ensures maximum performance and efficiency. The INS combines 3-axis gyros along accelerometer and magnetometer. The results are further improved by applying advanced Kalman filters that ensure very low deviation of values over an extended period of testing.

Micro-controller

Previously Duburi relied on 8bit ATMega2560 micro-controller for its control unit. Which had ma- jor drawbacks such as high latency,slow processing and most importantly lacked real time engagement required for optimal performance. This year the issue is solved by relying on 32 bit STM32 based system Pixhawk further integrated with Vectornav VN200 INS,ensuring greater performance and reliability with real time communication.The faster pro- cessing speed has massively increased the AUV’s overall performance.

Bracu DUBURI 4.0 Software Architecture

Interfacing

Duburi's microcontroller board, the Arduino Mega, strikes at the core of its operation. It functions as a control surface between the sensor payload's inputs and the actuators and end effectors on the Duburi, it manipulates the Duburi's thrusters in line with the data signals it receives to maintain steady locomotion.

In our AUV we have implemented visual homing which figures out the detection center, then calculates the offset. Then using a calculative approach we fix the AUV’s position to align with center of the computer vision detection. The AUV constantly holds the center position by keeping the center of the detection as the point of interest.

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