SubSea
ROV
Problem Summary
Basic overview of the Project
To improve safety in hazardous underwater environments, this multi-year capstone project focused on developing a remotely operated vehicle (ROV) capable of replicating the agility and task performance of a human diver. Our team contributed to this broader effort by designing and constructing the chassis and propulsion systems, culminating in a fully assembled ROV with thrusters that enable six degrees of freedom. This configuration allows for diver-like maneuverability, and testing confirmed both the structural integrity and dynamic capabilities of the system marking a significant step toward more versatile subsea operations.
Quality Function Diagram
Prioritizing customer needs
The goal of this project is to create a Subsea ROV that possesses the ability to move and see like a human diver. This constitutes characteristics such as the ROV having 6 degrees of freedom, access to 360 degrees of visibility, and having a borescope to be able to look around objects the way a human head/neck combination provides. From the QFDs on the left, the team determined the top-level measures that produce a successful project, including keeping the overall cost of the ROV minimal within the team's budget and keeping the maneuverability of the ROV ahead of the current industry leaders in subsea ROV about tether accommodation and thruster capability.
As the design progressed, the focus shifted to the more fundamental deliverables. A well-designed frame that provided efficient use of space to accommodate electronics, a buoyancy system, and the rotating thrusters were paramount. We also put a deeper focus on completing the mounting of the thrusters to be able to represent our proof of concept within the time frame we were working within. We kept the needs of the QFD in mind by prioritizing the design of the frame conscious of buoyancy, as that is the determining factor in an ROV that functions under the water, as well as making sure the thrusters can provide the control that is key to our project.
Work Breakdown Structure
Division of labor into tasks
The WBS accounts for how the various tasks will be split between the three areas of the propulsion system, the chassis, and other administrative tasks. This rough division of labor was mostly consistent with who the work fell to (Chassis work to Bobby and Heath, administrative work to David, CAD Design & Analysis of Chassis and Thrusters to Marcus, and propulsion work to Eric).
Gantt Chart
Distribution of work on a timeline
As is visible in this chart, the procurement of the parts to assemble the chassis took much longer than expected, nearly a month and a half. The procurement of parts, however, was one of the most important steps, since every part needed to be verifiably resistant to saltwater at extreme depths. This however caused delays in several other areas of the project, most notably assembly. While the Gantt chart from the beginning of the semester was a good starting point, it did not account for unknown potential delays beyond what it had accounted for, requiring flexibility to complete what we completed on time. This delay in the procurement of parts caused the fabrication and testing of the ROV to be significantly constrained in time.
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Physical Layout
How the basic elements are arranged.
The Subsea ROV capstone project for the 2024-2025 school year consisted of chassis and propulsion design engineering. Provided is a cutaway view. The chassis was designed with the intention of providing a diver-like shape and size. The thrusters are also mounted diagonally in order to provide movement in all 6 degrees of freedom, with up and down movement at full thrust, moving forward at most thrust, and side strafing with the least amount of thrust, since it'll be used the least. A pegboard style faceplate allows for the mounting of extra hardware and manipulators, which can be balanced by the addition of weights or floats along the center spine, which is also where the electronics are mounted. They are all mounted on a sliding axis in the center of rotation to allow the ROV to be balanced no matter what tool is mounted, or imbalances can also be compensated with the controlled angles of the thrusters.
Syntactic foam also lines the top and bottom of the ROV, which is protected by polyethylene skin plates.
Stress Analysis
Performance under load
To evaluate structural integrity, various force scenarios were simulated in SolidWorks. Due to the detailed CAD model including every fastener and bolt, a simplified version was used to accommodate memory limitations during stress analysis. The figures on the left display the stress strain curve for 5052 aluminum. Its elastic region ends at approximately 175 MPa, indicating that stresses in the model must remain below this threshold to ensure the frame returns to its original shape after being subjected to load.
Design Analysis
Quantifying Design Choices
The Design Analysis of the Rover's Physical Properties was the most demanding part of this project. When creating an underwater ROV, everything must be accounted for in mass and volume, including wires, screws, nuts, and electronics. Every time an element is added, syntactic foam must be added to compensate for the buoyancy and balance, which adds additional mass and volume. The result of all of these calculations and considerations is a ROV that remains stable yet upright, but able to move degrees of motion under the force of it's own thrust. The position of each thruster, and distribution of foam has been fine tuned in order to compensate for the distribution of mass and buoyancy in the ROV.
Future Work
What's next?
This project is a multi-year endeavor, so future work is already laid out. The main components have had design input by the end of the 2024-2025 year. The future groups will be refining designs for the camera system, manipulator, chassis, and propulsion system to come together functionally with an optimized skillset. The main tasks that will follow this year are systems engineering and systems and component integration. The meat of the electronics is still to be designed, with providing power to the components on the ROV itself. Creating a tether system that works well and doesn’t interfere with the design requirements is also a need, as well as determining the system for tracking buoyancy and stability automatically, and relaying info through the tether to the operator via the cameras and other sensors. The thrusters must be paired to work together, as well as the manipulator must be programmed to function to industry expectations. Much more is to be done to see this ROV project through, but the reason this project was divided among so many years is so that all of the details could be refined for a design that is well thought out in such an extreme environment.
