P20250: Finger Lakes Explorer ROV

Preliminary Detailed Design

Table of Contents

1 Team Vision for Preliminary Detailed Design Phase
2 Feasibility: Prototyping, Analysis, Simulation
- 2.1 Propulsion
3 Drawings, Schematics, Flow Charts, Simulations
- 3.0.1 ROV CAD Schematics
- 3.0.2 Software Detailed Design
  - 3.0.2.1 Base Station Domain Software
    - 3.0.2.1.1 Base Station Domain Software Subsystems
  - 3.0.2.2 ROV Domain Software
    - 3.0.2.2.1 ROV Domain Software Subsystems
4 Bill of Materials (BOM)
5 Test Plans
6 Design and Flowcharts
7 Risk Assessment
8 Design Review Materials
9 Plans for next phase

Team Vision for Preliminary Detailed Design Phase

Where as the the Subsystem design phase was largely design agnostic, this phase aims to reduce the ambiguity by committing to design choices and laying out specific, preliminary design plans for each phase. The main goal is to commit to subsystem solutions that will efficiently meet all of the engineering requirements while remaining within the project constraints.

This phase was fairly successful, with the team deciding on many of the high priority sub systems. Solutions included ranged from buying pre-built components to designing custom parts and systems. Final decisions were guided and supported by feasibility analysis and bench marking. The end product of this phase is a series of systems solutions which will be evaluated and improved upon until the final design is delivered.

Feasibility: Prototyping, Analysis, Simulation

Iterative analysis, prototyping, and simulations that accompany and guide our design decisions. These will progress in complexity as the design becomes more concrete.

Propulsion

Overview

Propulsion is important because it determines the ROV's ability to explore the environment. The amount of propulsion necessary determines and is determined by many of the other subsystems, thus making it a critical component to understand. Systems that are directly related to the propulsion system include the power supply system, the shell subsystem, and many others.

Initial Analysis

Because of its extensive influence, it was necessary to conduct a rough approximation of force necessary to move the ROV to help guide subsystem design for other components. This approach started with an estimate of the terminal velocity of the ROV in both vertical and horizontal directions based on a range of motor thrusts, ROV masses, and drag coefficients. Additionally, a set acceleration time was chosen to ensure that the system would be responsive in real time. While this model made a series of very general assumptions that add a lot of error, it was still useful to arrive at the correct order of magnitude for the thrust needed. The analysis and its results are documented here.

Updated Analysis

Once the design was better defined, it was prudent to update the propulsion analysis with guidance from Dr. Ghosh to further evaluate the choices for motors and shell design. This approach included the added mass of water that is dragged along with submerged bodies when undergoing acceleration and lifted the assumption of constant acceleration. With the model better defined, this analysis benefited from knowing an approximate shape and mass of the ROV and a force function. This allowed for a model based on a non-linear ODE from Morison's equation. Simulations were ran in MATLAB and the speed and position of the ROV as a function of time were solved for. This allowed the team to concluded that the motors provided will be able to provide sufficient thrust as defined by the team. The analysis and its results are documented here.

Simulation for movement with two 1.5 kgf thrusters in the horizontal direction

Simulation for movement with two 1.5 kgf thrusters in the vertical direction

Prototyping

A simple bilge pump motor, the Grainger RULE submersible marine 12V pump, was purchased to investigate the feasibility of using a pump motor as a waterproof propulsion system. While the motor was able to supply a decent amount of force (enough to move its own weight around quite easily), it was determined that the waterproofing was insufficient for our purposes. The waterproofing was primarily supplied by a plastic casing around the pump, which would have to be removed if the ROV were to use it as a propulsion system due to it only being able to supply force in one direction.

Pump that was purchased for testing.

Drawings, Schematics, Flow Charts, Simulations

ROV CAD Schematics

This schematic details the preliminary shell design. It was created around a central, cylindrical waterproof chamber which will hold all sensitive electronics. The fins to the primarily serve as a means to hold the thrusters at the appropriate position and orientation. The fins and handles are to be 3D printed, although additional material may be added or removed to help achieve neutral buoyancy. A model of the PCB was also used to facilitate spacing and arrangement of internal components.

Schematics for the preliminary ROV design.

Link to the schematic live document.

Software Detailed Design

Base Station Domain Software

The base station domain software contains all software relevant for maintaining a connection with the ROV via the tether. Also handles creating and updating the HUD screen as well as the archival and retrieval of past mission data. The base station software domain uses robot operating system (ROS) for passing messages between the various software subsystems via the use of rostopics.

Base Station Domain Software

Base Station Domain Software Subsystems

The various software subsystems seen in the figure above can be seen in the figures below in greater detail.

Data Archival Software Subsystem

HUD Generation and Management Software Subsystem

ROV-BaseStation Communications Manager Software Subsystem

User Input Collection Software Subsystem

ROV Domain Software

The ROV Software Domain contains all software relevant for maintaining a connection with the base station via the tether interface, handeling the collection and tranmssion of mission data, handeling the control of ROV interaction with the enviornment based on user input. The ROV software domain makes use of robot operating system (ROS) for passing messages between the various software subsystems via the use of rostopics.

ROV Software Domain

ROV Domain Software Subsystems

The various software subsystems seen in the figure above can be seen in the figures below in greater detail.

Single Board Computer Software Architecture

Microcontroller State Diagram

Bill of Materials (BOM)

A list of all current and planned expenses for the project. Its purpose is to confirm that all expenses and contingencies are afforded by the project financial allocation. As of the end of this phase, the project is over budget by $865. Even with considered component cuts and other budget trimming, the project would appear to be at least $150 over budget. Additional budget will be officially requested during the next phase.

Bill of Materials

Link to the live document.

Test Plans

Purpose

Demonstrate objectively the degree to which the Engineering Requirements are satisfied. Below are the proposed test plans to be carried out, starting this semester. Each of our engineering requirements are matched to at least one test.