ENGR 100-600 | University of Michigan

Lab Instructions

Here are the instructions for the labs in ENGR 100-600. These instructions are subject to change up as we continually revise the course, so make sure to refresh this page before you start lab each week.

Lab 1: Orientation & Buoyancy

Checklist

Overview

You will first meet Justin, our lab manager, and become oriented with the lab and watch a short video/presentation on lab safety. After the lab orientation is done, you will move on to the buoyancy experiment described below.

Lab Orientation and Safety Briefing (30 min)

This presentation is very important because it sets the tone for your entire lab experience. We want all of us to have a fun and safe time this semester.

Investigating Buoyancy and Stability (80 min)

You will work in teams of two to construct a marine vessel and determine how much flotation the vessel needs to make it nearly-neutrally buoyant (an ideal condition for your future ROV). Your marine vessel is a roughly-cube-shaped frame of PVC, as shown in Fig.

The vessel carries a payload, shown in Fig.

Follow these instructions to investigate how to balance weight and buoyancy in a marine vessel:

1. You have 8 corner joints (also known as a three-way joint) and 12 straight sections of PVC pipe, along with a mesh pouch and some zip ties
2. Assemble your vessel so it looks like the sample marine vessel shown in ; your vessel may be shorter or taller than the vessel pictured here
3. Talk with your partner and determine where you want to attach the payload (refer back to the hydrostatics videos if needed)
4. Attach the payload to the vessel using zip-ties
5. Weigh your vessel and payload; record this weight
6. Determine the total underwater volume, $\nabla_{max}$, needed for the vessel to be neutrally buoyant (refer back to the section on buoyancy)
7. Estimate how many ping pong balls are needed to get close to this volume. Take no more than 90 seconds on this! It's just a fast estimate; you'll revise this number based on experiential data shortly.
8. Put this many ping pong balls into the mesh carrier provided
9. Attach the mesh carrier to the vessel using zip-ties; refer back to the hydrostatics videos for guidance on the best place to attach your ping pong balls
10. Put the vessel into a tank of water and note whether it floats to the water surface (too much buoyancy), sinks to the bottom (not enough buoyancy), or "hovers" somewhere in the water column (nearly neutrally buoyant)
    1. If there is too much buoyancy, remove one ping pong ball, put the vessel back into the water, and note what happens
    2. If there is not enough buoyancy, add one ping pong ball, put the vessel back into the water, and note what happens
11. Repeat Step 10 until you reach a point where your marine vessel's buoyancy needs to change in a smaller amount than a single ping pong ball in order to achieve near neutrality for buoyancy.
12. Brainstorm with your partner ways you could have adjustable buoyancy and/or make small changes to the buoyancy of your future ROV; record these ideas
13. Remove your vessel and re-weigh the vessel including the mesh bag and ping pong balls
14. Record this weight, the number of ping pong balls used, and whether you ended your experiment with your vessel floating or sinking

This experiment is preparation for how you will make your ROV nearly neutrally buoyant. Keep track of your notes for this lab so that you can complete the questions in the Lab 1 assignment.

Lab 2: Controls

Checklist

Overview

In this lab, you will explore how your ROV will be controlled. We’ll start with a soldering demo first, so that everyone can see how soldering is done and have a chance to ask questions. Then we’ll look at a simply constructed demo ROV, and you will construct a basic control circuit to gain some experience with our equipment. After the soldering demo, you and your labmates will be split into two different groups. One group will start with the ROV demo and move to the control circuit exercise. The other group will start with the control circuit exercise and move to the ROV demo.

The ROV payload system is shown in Fig. The payload itself is the clear plastic cylinder with the electronics inside. A yellow, neutrally buoyant tether connects the payload to a blue and yellow float with black antennas at the top. This float stays at the surface of the water to transmit and receive wireless signals from your control box. Your control box will have buttons and/or switches (seen in the lower right of this picture) that are wired into a breadboard/Arduino circuit board system. The Arduino has its own antenna with which it transmits and receives data from the float.

The control circuit exercise will provide you with an opportunity to familiarize yourself with some of the skills required to build your control console, such as soldering, and it will provide you with an introduction to how the control system works. You will solder wires onto two push button switches and one toggle switch and connect those switches into a breadboard (prototyping circuit board) connected to an Arduino and an nRF24L01 transceiver (here’s a link about wireless communication with nRF24L01 transceivers if you want to learn more). You will demonstrate the operation of a radio link that transmits switch position information to a receiving ROV payload, lighting up LEDs and operating a thruster.

Soldering Demo (10 minutes)

Justin will demonstrate how to solder wires to one of the buttons that we use in the ROV project. You will be soldering in this lab, so pay attention to what he does and make sure to ask questions!

ROV Demo (30 minutes)

Justin or your IA will show you a demo ROV. Observe the following things about this ROV and ask questions about:

• Where is the payload? Why is it placed there?
• Where is the camera? Why is it placed there?
• Where are the thrusters? Why were they placed there?
• Where is the tether attached to the ROV? Why there?
• What does the control box look like? Why are the buttons and switches placed where they are?
• What does the inside of the control box look like? What are the main components? How are the buttons and switches connected to the electronic innards of the control box?
• How does the control box communicate to the ROV?

Keep track of your notes to these questions!

Next, your group will move to the test tank so that you can each drive the demo ROV around for 2-3 minutes. Use this time to observe the following about the ROV:

• Is the ROV easy to drive?
• Which directions are you able to drive in independently of the other directions (up, down, forward, backward, left, right)?
• Can you make the ROV yaw/pitch/roll?
• Do you like the arrangement of the control box?
• Do you think the thrusters are in a good location?
• What changes would you make to this ROV in a (hypothetical) second round of design?

Keep track of your notes to these questions!

Basic Control Circuit (70 minutes)

You will work in teams of 2 to construct and test the two switch options you will have available for the ROV project. One is a simple toggle button (recall this is a single-pole-single-throw switch) that turns the circuit either “on” or “off”. The second is a single-pole-double-throw toggle switch. The toggle switches are small; use a small vise to hold them securely. A switch “terminal” or “lug” is the little post that sticks out of the bottom of the switch; you attach wires to the terminals to create a circuit.

Once you have one switch and two buttons completed, you will connect the switch and buttons to a breadboard, and then connect the breadboard to the Arduino circuit board. You will then use a nRF24L01 transceiver to wirelessly transmit to an ROV payload to verify that your circuit is complete and functioning correctly. A completed basic control circuit with the ROV payload is shown in Fig. You can use this figure to help guide you through this exercise, but stop and ask Justin or your IA questions whenever you are unsure of what to do! This lab is all about learning as you go! 😊

The BreadBoard

Recall from the section on the ROV’s Control System that breadboards (also shown in Fig alongside an Arduino board) are simple tools used in circuit prototyping that allows you to quickly and easily change your circuit without the need for soldering.

For the ROV project, you will be given a circuit board that acts identically to the breadboard that your control circuits will be soldered to. This is your opportunity to experiment with the breadboard and understand how it works. Your IA and Justin will give an overview of the breadboard in the lab.

Take some time to experiment with an ohm-meter and discover where continuity lies within the board. To do so, turn the meter to the ohm position (Fig) and press the select button until a sound icon appears on the screen.

When the leads make contact you should hear an audible sound. Additionally, use several of the supplied jump wires to test out various configurations on the bread board and discover how to get continuity between circuits (Fig).

If the previous sentences make no sense to you, that’s okay! Ask lots of questions in lab, and Justin and your IA will explain everything.

Soldering Tips for Switches

Before you start wiring up the switch and button, review these tips for soldering:

• When soldering the switches, be very careful to avoid shorting out the many wires which end up in close proximity in the back of the switch. Shorting out means that two or more wires were accidentally soldered together when you didn’t want that.
• Attach all of the wires to the switch by creating a loop through the lug (see Fig). Make sure the wire is secure (not wiggly).
• Make sure that the wires are well twisted together, to help support the connection.
• Cut off any extra bare wire that is sticking out.
• Solder quickly, so that the wires do not get too hot, and melt their insulation.
• Do not use too much solder, which could stick out and touch other connections.

Part A: Soldering Leads to Switches

1. Obtain two push button switches and one toggle switch from the lab supplies.
2. Obtain a length of solder from the lab supplies.
3. Make sure the sponge in your soldering station is wet -- if not re-wet it in the sink.
4. Turn your soldering station on to approximately 625$^{\circ}$F.
5. When the green light blinks, the iron is ready to use. Clean the tip quickly on the wet sponge and apply some solder to the tip. Stow the iron in the holder with solder on the tip till you are ready to use it.
6. Cut four approximately 8" lengths of 22 gauge solid core wire.
7. Cut three approximately 7" lengths of 22 gauge solid core wire of a different color.
8. Strip 1/2" of the insulation off one end of each wire, strip 1/4" of insulation off the other ends.
9. Turn a 1/8" loop on the 1/4" stripped ends as shown in .

   

10. Place one of the switches in the vise at your workstation with the contacts up (don't over-tighten the vise on the switch!).
11. Take one of the 8" wires and hook the loop through either of the lugs on a push button switch, or through the center lug if you start with a toggle switch. Use small needle-nose pliers to crimp the wire loop down on the lug so it holds snug on the lug. STOP: At this point have your instructor check your progress. If they say you are ready, solder the connection. When you are done, you should have a lead soldered to your switch as shown in .

    

12. Take one (or two) of the shorter wires and repeat the procedure on the remaining lugs of the switch.
13. Your lab partner should now solder the wires onto the second switch in the same manner.
14. Either you or your lab partner should then solder the wires onto the third switch in the same manner. If one of you has less experience with soldering, then now is your chance to practice some more!
15. Check to see that your buttons and switch looks similar to the finished switch shown in .

    

Part B: Wiring the Arduino

1. Using either the sample on the display table OR the picture of the completed Arduino and breadboard shown in OR the wiring guide shown in OR the schematic shown in (if you have more electronics experience) as a guide, make the connections on the Arduino and breadboard. The jumpers will insert into the holes of the breadboard and/or the headers on the Arduino.
   1. NOTE -- both the breadboard and the Arduino may be mounted on your unit base in either direction. If yours does not match the sample or the figure you will have to figure out how to wire it in the orientation it happens to be in.

ASK QUESTIONS if you are interested in understanding more about the circuit!

When you are all done, your test circuit should look like what is shown in Fig.

Part C: Testing the Circuit

1. When you think your Arduino is ready to be tested, bring it to the instructor and have the control program loaded into it.
2. Connect a 7.2V battery to your board.
3. Operate your push-buttons and toggle switch and verify that the ROV payload responds correctly through the radio link (see Fig for the buttons and Fig for the toggle).

Part D: Cleanup

1. Unwire your Arduino and leave it at your workstation.
2. Discard cut wire.
3. Clean up wire stripping residue.
4. Make sure your soldering station is shut down.
5. If you have done a good job soldering your switches and the leads are long enough, keep them for possible use on your ROV controller.

Lab 3: Hydrodynamics

Checklist

Overview

This lab will give you hands-on experience with some hydrodynamics concepts. Remember that hydrodynamics is a very complex area of knowledge, and we do not expect you to understand and document the math behind these experiments! But you should be able to describe at a high-level how these general hydrodynamics concepts informed your design decisions later on in the ROV project.

There are three different experiments you will do today:

1. Drop tests to understand how an object’s shape and orientation affects how it moves through water
2. ROV thruster moment balancing to understand how the placement of your thrusters will impact how your ROV will move through the water
3. Calibration of a load cell to understand how you will be able to measure the thrust of your ROV’s thrusters

We will be rotating groups around the lab to get all these experiments done, so listen to your IA as they tell you which experiment to start with.

Drop Tests (40 min)

A drop test is when you drop an object through a fluid and observe how it moves. We have four different underwater vessels for you to perform drop tests on. For each vessel:

1. Attach ping pong balls in different spots (including at CG)
2. Take a picture of the vessel and add picture to your notes; note orientation of frame, ping pong balls, surfaces
3. Predict what will happen before you drop the vessel
4. Drop vessel in tall tanks
5. Record time to drop
6. Note stability:
   1. Does it tumble?
   2. Does it rotate?
   3. Does it veer sideways?
   4. Does it drop straight?

ROV Thruster Moment Balancing (40 minutes)

Your ROV has the ability to use up to four thrusters. During the lab, you will be called over by your IA to perform the following experiments using the demo ROV:

1. Determine where to mount two of the thrusters such that the ROV does not pitch up or down when it travels forward
2. Measure and then compare the rates of yaw when the side thrusters are inside the frame vs. when they are outside the frame
3. Compare the vertical maneuverability of the ROV when the ROV can move purely in heave vs. when the ROV must pitch upwards/downwards to move vertically
4. Measure and compare the rate of vertical ascent and descent with the vertical thruster pointing up vs. when it is pointing down

Take notes on these experiments. You will need them to answer questions on the assignment for this lab and to refer back to when designing your own ROV.

Calibration of the Load Cell (30 min)

When the ROV project starts in earnest, you will learn how to measure the thrust produced by a thruster. To measure the thrust, you use something called a load cell. A load cell is a transducer that converts a force to a voltage. This lab will get you experience working with a load cell by calibrating a beam-type load cell. These load cells have a built-in amplifier, so the output is in the range of 0.5-9.0 V. A multimeter is a device that is capable of measuring voltage, current, or resistance (hence the multi- in its name). We will be using multimeters to measure the voltage output from the load cell, so they will be acting as voltmeters. Fig shows the setup you will create to calibrate the load cell.

Calibrating the load cell involves figuring out what voltage means in terms of mass (and hence force).

1. Make sure everything is disconnected.
2. Remove any weights that may be hanging from the wire attached to the load cell
3. We will use Virtual Bench to power the load cell and read its output.
4. Connect the black wire and braided wire to the ground lug of the +25V supply and the red (power) wire to the +25V lug.
5. Connect the green and white wires to the DVM (voltmeter) input of the virtual bench
   
6. Set the power supply to 12 Volts, 0.5 Amps in the Virtual Bench software suite
7. Read the load cell output on the Virtual Bench voltmeter
8. Record what voltage the multimeter shows. This will be the offset in your calibration.
9. Add the 50 g mass
10. Record the total mass
11. Record the voltage output of the transducer
12. Add a 20 g mass
13. Record the total mass
14. Convert mass to kilograms and multiply the total mass by gravity (9.8 m/sec$^2$) to get a force
15. Record the voltage output of the transducer
16. Repeat Steps 12—15 until there is 250 g of mass hanging from the load cell
17. Borrow additional full 250 g sets of weights from your labmates to get data points at 500 g, 750 g, and 1000 g
18. Redo a couple of points (your choice) in decreasing mass order to check for error
19. Remove all the weight from the wire
20. Turn off the power supply

Create the Calibration Graph

Now, make a nicely-formatted graph with your calibration data. There are many ways to do this; the imporant part is to make sure you have all the pieces of a calibration graph:

• data points plotted with voltage on the x-axis and force on the y-axis
• linear trend line applied to the data
• show the trend line equation on the graph
• annotate the graph so it can be easily used (axis labels, font size is large enough to read, lines are easy to see, includes grid lines, etc.)

Here is an example of making a calibration graph using MATLAB; you can adapt this approach to use the data that you just gathered. If you do not want to use MATLAB, you can use something else (spreadsheet or other plotting program), but make sure to do the same steps so that you create a useful engineering graphic.

First, save your calibration data to an .xlsx file, like this:

Next, create a MATLAB script that does the following:

1. Import your data to MATLAB using the readtable function.
2. Pull out the vectors of mass and voltage
3. Calculate a parallel vector to be the corresponding force (watch your units!)
4. Create a scatter plot of force vs. voltage, with voltage on the x-axis
5. Add a linear trend line to the data and display the equation for the trend line
6. Annotate and improve the graph:
   • Add x-axis and y-axis labels
   • Increase the font size for everything so it is readable
   • Add grid lines
   • Increase the size of the data points so that it is easier to see the individual points
   • Increase the thickness of the trend line so that it is easier to see
   • Add a trend line and display the equation
   • Lots of other things to make this be a good graph!

This MakeCalibrationGraph.m script implements these steps for the sample data set shown above:

clear
close all


% read in the data
data = readtable("calibration_data.xlsx");

% pull out the mass (g)
mass_data = data{:,1}; % use curly braces to get the numerical values

% pull out the voltage (mV)
voltage_data = data{:,2}; % use curly braces to get the numerical values

% calculate the force (N), don't forget to convert from grams to kg!
force_data = mass_data .* 9.81 ./ 1000;

% make a scatter plot of the force vs. voltage
s = scatter(voltage_data,force_data);
s.SizeData = 70;
s.LineWidth = 3;
s.MarkerEdgeColor = "#0072BD"; % this is the pretty blue that MATLAB uses
s.Marker = "o";

% create a linear trend line
p = polyfit(voltage_data,force_data,1); % this gets the coefficients 
lineFit_xValues = [0 1000];
lineFit_yValues = polyval(p,lineFit_xValues); % this makes data points to plot.

% add the linear trend line to the plot
hold on;
linefit = plot(lineFit_xValues,lineFit_yValues);
linefit.LineWidth = 3; 
linefit.Color = "#0072BD";

% add the equation for the line fit to the plot
xCoordCaption = 50;
yCoordCaption = 9;
caption = sprintf('y = %f * x + %f', p(1), p(2));
text(xCoordCaption, yCoordCaption, caption, 'FontSize', 16, ...
    'Color', '#0072BD', 'FontWeight', 'bold','BackgroundColor','white');

% add arrow from equation to line
xa = [.4 .5]; % these are not coordinates, these are the positions across the whole graph
ya = [.68 .55]; % these are not coordinates, these are the positions across the whole graph
ar = annotation('arrow',xa,ya);
ar.Color = '#0072BD';
ar.LineWidth = 2;
ar.HeadWidth = 20;
ar.HeadLength = 20;

hold off;

% Improve the graph so it is easier to read and understand
grid on;
ax = gca;
ax.LineWidth = 2;
ax.FontSize = 16;
xlabel('voltage (mV)');
ylabel('force (N)');
ax.XLim = [0 800];
ax.YLim = [0 12];


% Save the plot to a .png file
print('sampleCalibrationGraph','-dpng');

To see this work, download the calibration_data.xlsx and the MakeCalibrationGraph.m files and put them in the same folder on your computer. Open MATLAB and set the current folder to be the folder that has these two files in it. Then, run the MATLAB script by typing the name of the script in the Command Window:

>> MakeCalibrationGraph

The script will create this sample calibration graph and save it as sampleCalibrationGraph.png:

You will need to record your actual data measurements in a new .xlsx file and then change the MATLAB script to read in that .xslx file instead of the sample version.

Whether you use MATLAB or another program, create the calibration graph for the load cell and save it as a .png file named LoadCellCalibrationGraph.png. You will turn in this file as part of the post-lab assignment.

Lab 4: 3D Modeling

Checklist

Overview

During the course of this lab, you will create a box like frame with a Payload for an ROV (Fig) to practice creating a 3D model with the SolidWorks CAD program.

You will learn how to mate pieces together to make an assembly. Once complete, save renderings of this model as directed for the post-lab assignment. Then proceed to making your own conceptual design for next week’s lab.

Launch & Start SolidWorks

1. Start CAEN Computer and login using your uniqname and password. Note some monitors in the lab may have several different computers attached to them for different purposes. If your computer does not behave properly on startup, let your IA know
2. A Google Chrome window will appear upon login with a library of programs that Michigan Engineering Students have access to. If you don’t see it, there should be a shortcut on the desktop called CAEN software leading to appsanywhere.engin.umich.edu
3. Search for SolidWorks in the search box of this page
4. Select the SolidWorks 2024 Student Instructional Version: Red Cube with a S W and Blue I
5. Then select the blue Launch button
6. The Cloudpaging Player window should open up (it might be in the background)
7. Wait for SolidWorks to initialize fully until the status shows Ready
8. Once Ready appears, you can select Solidworks and then the Green Launch button – this will start Solidworks
9. Accept the License Agreement if prompted
10. Solidworks should now fully display on your computer with a gray background and its logo

Create a PVC Pipe

1. In SolidWorks, create a new part by clicking on the part icon
2. Verify that your units are set to IPS (inch, pound, second), and click OK
3. Save (ctrl + S) the file; use a good descriptive filename of your choice. Save the file periodically throughout the process. We recommend creating a folder somewhere to keep all your 3D printing documents for this class in particular, because you may choose to go down a route that requires more printing in the future
4. Select Front Plane on left-hand menu (this is called the feature tree)
5. Create a new sketch from the the horizontal toolbar at the top of the screen. This toolbar is called the tool ribbon. Go to the sketch tab and click sketch
6. Choose the Circle sketch tool. Click the origin (where the red axes intersect at a right angle) to begin drawing a circle. Click anywhere to complete the circle. The size of the circle is not relevant
7. Draw another circle, again centered at the origin.
8. Click Smart Dimension from the ribbon. Click on the outer circle, then click in empty space. Type in 0.84 and hit enter. Note, that since we set our units to IPS, this dimension is in inches.
9. We can not only dimension a shape in absolute terms, but we can also dimension a shape in reference to another. Click on the outer circle, then the inner circle, and type in 0.12. Now, regardless of the diameter of the outer circle, we’ll have a pipe with a thickness of 0.12.
10. Hit escape to exit the sketch.
11. Go to the Features tab in the tool ribbon and select Extruded Boss/Base
12. The left-hand menu which will have switched to “Boss-Extrude.” Change the D1 dimension to 11.5-inch. Click the Green Check Mark to finish the dimension change
13. Hit the F key on your keyboard to “fit” the cylinder onto the screen. Try out the following techniques to move the model around:
    • Use the scroll wheel to zoom
    • Hold shift and the scroll wheel and move the mouse up and down to zoom with respect to the center of the screen
    • Hit the space bar and select a face to go a particular view (front, top, left, isometrics, etc)
    • Use the arrow keys to rotate the model
    • Press the scroll wheel and drag the mouse to rotate the model
    • Hold alt and the scroll wheel and drag the mouse to roll the model (rotates in 2D)
    • Hold ctrl and the scroll wheel and drag the mouse to pan the view
14. Select the Top Plane from the Feature Tree and create a new sketch
15. Create a circle anywhere and of any size.
16. Use smart dimension and dimension the circle to 0.266in.
17. Hold down ctrl and click the centerpoint of the circle (not the actual circle itself) and select the origin as well. Release ctrl. There will be a new menu on the left with a section called relations. Select Vertical.
18. Using smart dimension, click on the circle you made and then click on the bottom of the pipe. Then type in 2.5 and hit enter.
19. Exit smart dimension tool with esc.
20. Next, select Extruded Cut under the Features tab in the tool ribbon
21. On the left-hand menu, select Through All-Both under Direction 1. Click the green check mark. There should now be a hole all the way through the pipe
22. Select Cut-Extrude 1 from the feature tree. Then click linear pattern in the tool ribbon under the features tab
23. Click the box under Direction 1 and then click on the pipe.
24. Select the Spacing and Iterations option under Dimension 1. Type 1” in the spacing box and 8 in the instances box. You should see a series of yellow circles. If they are not over the pipe, click the double arrow box right below Dimension 1 to change the direction of the linear pattern. Click the green check mark
25. Right click on Material <not specified> in the feature manager. Click edit material. Search for PVC Rigid. Your pipe should now look white
26. Save (ctrl + S)

Congratulations! You have just made your first CAD part for the ROV frame. The rest of the parts for this exercise are located in the ROV SolidWorks Parts Library linked on the course website.

Creating the ROV Box Frame Assembly

The bottom part of a simple box frame is assembled in a file that we provide to you. Your task is to complete the frame and add the Payload by using parts given in the Parts Library.

Download the Parts Library

1. Now go back to Chrome and go to the course website
2. Scroll down to the The ROV Project section and click on the SolidWorks Parts Library card
3. Download the SolidWorks files from within the parts library folder and place them in your Documents folder, or wherever you are putting your ENGR 100-600 files. Note: if it downloads as a .zip file you need to extract the files before you can use them
4. Go back to SolidWorks: Hover over the SolidWorks icon at the top left. A toolbar should appear. Go to File, then folder icon with a green arrow, called Open
5. Navigate to your Documents Folder and the Parts Library you downloaded from the Google Drive
6. Within the Parts Library, select the file LAB-Frame-Base to open the partially complete frame assembly.
7. If the file opens but cannot locate the parts, click Browse for file and locate the part in parts library. If it asks you to rebuild the file, click yes. Should it give you errors, let your IA know.

Adding the vertical PVC pieces

1. Select Insert Components from the top left tool bar under the Assembly tab
2. Browse to the given Parts Library for this lab (should be in your documents folder where you saved it earlier)
3. Select PVC .5x5-inch and place it in the workspace by clicking in the design area next to the model

4. Choose Mate from the top left tool bar

   Note: There are 5 different types of standard “mates” or ways to lock pieces together in Solidworks:

   An “attachment,” “glue,” “bond,” or however you imagine the invisible force connecting two pieces together in 3D modeling is made up of one or more mates. However, it is best to think of a mate as a type of restriction or limitation on how two objects act in relation to each other. The names of the standard mates are logical, but how to use them can be a bit unintuitive. A part being assembled will have a series of limitations, or mates, that will define the location and orientation of that part in relation to other parts.

   • Coincident limits two things to the same plane
   • Parallel limits two things to parallel axes
   • Perpendicular limits two things to axes at right angles from each other
   • Tangent limits two things to connecting on the plane tangent to one object’s surface
   • Concentric limits two things to existing along the same axis
   • Lock means an object is immovable in both location and orientation
   • Mate Alignment allows for an object to be flipped in orientation while defining a mate

   When you make a mate, the second object you select will move to match the mate requirement with respect to the first object’s original position, keeping the first object stationary.

   Oftentimes, if not careful, you can overdefine an object. This is when you provide too much information about a dimension, at which point, some things may become contradictory. If you get a window offering to have you overdefine something, or break mates to satisfy the newest mate, figure out what is wrong or ask your IA.

   For more information please reference: the introduction video on Standard Mates and the SolidWorks help center.

   We will be forming mates with the PVC ends not entering the PVC joints; therefore the distance between two joints is the length of the PVC pipe in the model. This could be talked about as a source of error in later reports/discussions. To calculate the actual length of pipe you need to cut, add 0.75-inch for each joint the pipe is in.

5. We want to attach the 5-inch piece vertically on top of a tri-corner connector. In order to make this attachment, we need to define two mates. First, select the outer rim surface of the 5-inch pipe. It should glow as an orange circle when you hover over it and turn blue when you click on it.
6. Next, select the outer rim surface of the tri-corner. Solidworks will usually automatically move your 5-inch piece and assume a Coincident mate, but double check that on the lefthand control box Coincident is selected.
7. Use the Mate alignment to flip the 5-inch PVC piece if necessary
8. Right-click, or select the green check mark to form the mate
9. Now that the pipe is aligned with the surface to which it will be attached, we need to center the pipe in the hole using the Concentric mate.
10. Select the outer edge of the 5-inch PVC (might have to rotate) and the outer edge of the tri-corner, while still in the mate command window (if you do not see the standard mates list on the left, click Mate from the top tool bar to re-open the command window)
11. Make sure that the Concentric mate is selected on the left command window
12. Right-click, or select the green check mark to form the mate
13. You have now limited the axis and the planar surface on which the 5-inch PVC can exist on. The only non-limited part of the piece is that is can still currently rotate, which is fine!
14. Repeat steps 1-13, three more times to finish adding the vertical 5-inch PVC pieces for forming the box frame
15. Save (ctrl + S). If you get a dialogue box asking to overwrite the file, click SAVE.
16. Select Insert Components from the top left tool bar
17. Navigate to the given Parts Library for this lab
18. Select PVC tri-corner and place it in the workspace by clicking in the design area next to the model
19. Like before, we need to use two mates to attach these corners to the vertical PVC pipes

20. Make a Concentric mate between the inner tri-corner edge and the 5 in PVC piece’s outer edge

    Tip! Remember to use the Mate alignment feature to flip alignment as necessary.

21. Next make a Coincident mate between the tri-corner’s outer rim surface and the 5-inch PVC piece’s outer rim surface

    Note: You should now be seeing a pattern of how to assemble PVC components together in Solidworks using two types of mates: Concentric & Coincident

22. Repeat steps 16-21, three more times to make all the top corners

    Note: Rotational orientation of the top tri-corners does not matter at this point, because we are able to define the rotational orientation by placing PVC pipe in between all four of the top tri-corners.

23. Now that you have some intuition as to mate objects, insert two 11.5-inch PVC pieces and mate them between the corners. Think about what type of mates you need and then what to select to make the mates. Look back at previous steps and if you are stuck – ask for help!

24. Add two 3.5-inch PVC pieces and mate them into the assembly to finish the box frame

25. Save (ctrl + S).

Adding the Payload

This is a more difficult mating process, but the concepts are the same!

1. Insert the Payload part from the parts library; it is already pre-drilled with holes that align with the 11.5-inch PVC pipe in the base of the box frame. It’s ok if the payload is not oriented properly. The mating process will fix this.
2. Line up the holes in the flanges of the payload with the holes in the 11.5-inch pipe. Use two concentric mates between the inner surface of the holes in the Payload and and the inner surface of one hole on each pipe. Note, we haven’t locked its vertical location in the payload yet. Refer to Fig to ensure you have the Payload oriented correctly. You may have to change the mate orientation, depending on the pair of holes you choose.
3. After you have the holes lined up, mate the one flat of the can to the 11.5-inch pipes. You might consider using a Tangent mate
4. Repeat Steps 1 – 4 with the battery payload
5. Save (ctrl + S).
6. Insert one Bolts
7. Mate this bolt with the proper hole that aligns with the Payload by using a Concentric mate, such that the head is on the inside of the frame, using the flip alignment button if necessary
8. Make the top of the bolt flush with the Payload by using Coincident mate between the flat underside of the head of the bolt and the flat wing of the Payload that has the holes drilled into it
9. Insert a Wingnut piece
10. Mate the Wingnut with the bolt by using a Concentric mate and with the payload by using a Coincident mate
11. Select the Wingnut you just mated and right click. On the dropdown menu, select Copy with mates
12. Select the bolt. Once both the bolt and the wingnut are selected, hit the right arrow in the circle (next) to move to the part that will match the bolt’s and nut’s existing mates with the ones we want to copy it to.
13. Determine which mate on the original bolt/nut corresponds to the mate where we will copy the bolt/nut to, and select each accordingly. You may have to use the flip alignment button.
14. Do step 13 six more times. You will not need to exit the Copy with mates window—it will automatically move you onto the next one. Once you’ve made all seven, click the red × next to the checkmark to exit the copy with mates window.
15. Make the wingnuts flush with the PVC by using Tangent mates between the pipe’s outer cylindrical surface and the flat base of the wingnut
16. Save (ctrl + S).

Note: This design is not suitable for your actual ROV because the Payload falls outside of the frame! You will also need to add other features (e.g. thrusters, camera, buoyancy, ballast, etc.) for your final design.

Well Done! You now have a solid intro to SolidWorks for assembling your ROV models. However, the real power of SolidWorks and CAD modeling software in general is in being able to run analyses on your model. For this class, Center of Gravity and Center of Buoyancy are very important things you can calculate via Solidworks.

Examining Center of Gravity and Center of Buoyancy

The individual pieces have material properties already applied. SolidWorks can calculate the Center of Gravity automatically from these properties. The Center of Buoyancy can be found by making every object have equivalent density. This is an important concept… think about how this is true!

1. Go up to the lower of the two upper horizontal tool bars. Select Evaluate, next to Sketch
2. The horizontal ribbon above this tool bar will change and now select Mass Properties
3. Solidworks has made all the calculations for you! Record the center of mass (it is your Center of Gravity)
4. To calculate Center of Buoyancy, we need to save a copy of the file.
5. Go to Save As in the drop-down menu next to the save button
6. Re-name the file to your original filename and denote this as the Center of Buoyancy copy (e.g. filename_COB)
7. Under the filename, change the Save as type from Assembly to Part (.sldprt)
8. Now select Save
9. Now open the file you just saved; it will not automatically open
10. If a feature recognition text box appears, you can ignore it as you want the object to stay as one piece.
11. Change the units to IPS (tools > options > document properties > units)
12. Now on the left-hand toolbox, immediately above the planes is the Material button, right-click on it
13. After right-clicking on it, choose Edit Material
14. Select any material of your fancy
15. Repeat steps 1-3 to Calculate Center of Buoyancy by taking the readings of Center of Mass (And think about why taking the Center of Mass of this object be the same as finding the Center of Buoyancy of the assembly, the original version of the ROV with all the correct materials for the parts.)
16. Select any other material of your fancy
17. Repeat steps 1-3 to Calculate Center of Buoyancy by taking the readings of Center of Mass
18. These two readings should be the same! Why?

Taking Screenshots of Different Views

Tip! In SolidWorks right-click in the free space of the model and drag your mouse up, down, left, right in order to change views of the model.

Use the Windows Snipping Tool (⊞ WIN + shift + S) to take a screen clipping of the following views:

• Profile View: the side view of an object, as accepted practice in Naval Architecture the stern (rear end) of a vessel is on the left side of this view, hence sometimes this view being called the Right View
• Top View: the view from above the vessel in a direct birds-eye-view
• Perspective View: the angled view of the vessel that produces a 3D rendering of the vessel and is usually positioned to give the viewer the best grasp of the vessel

Save these images of your sample ROV with these filenames so that you can upload them in the post-lab assignment:

• SampleROV_ProfileView.png
• SampleROV_TopView.png
• SampleROV_PerspectiveView.png

POST-LAB: Creating an ROV concept vessel

You will now practice these SolidWorks skills by creating a “concept vessel”. This concept vessel has nothing to do with the ROV that you are going to build in this course other than as a mechanism to practice 3D modeling and to learn about some construction techniques in the next lab.

Your ROV concept vessel has the following design constraints:

• Minimum of 2 three-way fittings
• Minimum of 2 elbows
• Minimum of 3 tees
• All fitting joints must have a pipe inserted (i.e. you can’t have a tee fitting that only connects two pieces of pipe)
• Minimum dimension in any direction of 4 inches (overall length, width, height)
• Maximum width and length of 11 inches
• Maximum height of 16 inches
• Minimum of 16 straight pieces of pipe
• Maximum of 10 total feet of straight pipe

Make your concept vessel in SolidWorks using the ROV parts library and the skills you gained in this lab. Take screenshots (just like you did with the ROV you made in lab) and create a parts list that includes the types and number of joints and the number and lengths of pipes. Also note the overall dimensions of your concept vessel (length, width, height).

Lab 5: Preliminary Design Review & Construction Techniques

Checklist

Overview

In this lab, you will learn how to work with the basic construction materials for your ROV project. These materials are Commercial Off-the-Shelf (COTS) equipment. There are pros and cons to working with COTS equipment: they are readily available and relatively inexpensive, however you are limited by what shapes, colors, and materials you can buy. So, when you find yourself frustrated because you can’t build what you want to with the provided equipment, think about what kind of piece you need and how you might be able to produce that through 3D printing, laser cutting, CNC-machining, etc.

Power Tool Training (20 min)

At some point during the lab, Justin will bring your team over to the power tools to train each of you on the different machines that we have. Everyone will use the drill press to drill a hole in a piece of PVC pipe and cut piece of wood on the band saw. This way, everyone can get a feel for how our particular power tools work.

Preliminary Design Review (30 min)

At some point during lab, your team will be pulled out for your Preliminary Design Review.

Constructing an ROV Concept Vessel (120 min)

To make sure that your ROV design will be able to meet its design objectives and constraints, your team needs to make sure everyone understands that there are differences between what you design in a 3D model and what can actually be built in the real world. Get some experience with building things in the real world by constructing one of the ROV concept vessels that your team submitted to last lab’s Post-Lab assignment:

1. Get in your ROV team.
2. Have everyone bring up their documents that they submitted for the previous lab’s Post-Lab assignment – the documents that described their ROV concept vessel.
3. Compare everyone’s designs and come to a consensus on which design is most promising to build in this lab (remember: this is NOT the ROV you are going to build for the project… this is just for build practice; so if your ROV concept vessel is not chosen don’t take it personally!).
4. Generate a parts list for this ROV concept vessel based on the SolidWorks model.
5. Complete your team’s pre-build checklist:
   • Straight pipe on SolidWorks will have different lengths than what you actually need to cut because of the overlap inside the PVC fittings. Update your parts list accordingly.
   • Determine the order of assembly (i.e. what order do you need to put stuff together in order to cement it together)
   • Determine how you are going to ensure that when you cement pieces of PVC together they are aligned correctly (e.g. connectors on either end of a pipe are straight, etc.).
6. STOP. Get approval from your IA on your parts list and pre-build checklist.
7. After you get approval, note your ROV concept vessel’s overall height, length, and width.
8. Determine who is going to make/obtain what parts. Make sure everyone will get a chance to do all the different types of build actions (cutting, cementing, aligning, etc.).
9. Make/obtain parts; you do NOT need to drill holes in the PVC for this vessel.
10. Dry fit components; make changes if needed.
11. Assemble ROV concept vessel using PVC cement.
12. Measure the overall height, length, and width of your assembled ROV concept vessel. Compare to the dimensions of your design that you started with.
13. Take a picture of the ROV concept vessel (always document your work!); share it with the team.
14. Someone can take the ROV concept vessel home.

POST-LAB

Reflect on these questions and be ready to answer them on the Post-Lab assignment:

• What was the most problematic aspect of the ROV concept vessel, in terms of building it?
• How would you revise this design, now that you have information on how it can be built?
• What aspects of this ROV concept vessel might you incorporate into your team’s ROV design?
• As you designed and built your ROV Concept Vessel, you may have been unable to construct your ideal design due to limitations of the provided parts. You will have the same challenge with your ROV. Look at your Preliminary Designs. What are some potential challenges that you will have in constructing this ROV? Where does an innovative, custom part make sense?

Lab 6: ROV Plan & Prep

Checklist

Overview

Now that we have started the ROV project, there are no formal lab instructions for the rest of the semester. Instead, we’ll list some guidelines for each of the ROV labs so that you can compare your team’s progress with where you generally should be each week.

These are guidelines, not rules. If your team is running a little bit ahead or behind these checkpoints/suggested actions, that is totally fine. However, if you find that you’re consistently behind or behind by more than a week, get to Open Lab and get caught up!

• Major goals
  • Get your ROV Plan approved by Justin
  • Start building your ROV
• What to do
  • Go through your ROV Plan Checklist (below) with Justin and your IA
  • Answer questions
  • Make plan revisions based on feedback from Justin/IA
  • Repeat until plan is approved
  • Once plan is approved, start building!

ROV Plan Checklist

To get approval to build your ROV, your team needs to pass this checklist and get approval from Justin and your IA.

• Vehicle design
  • Start by just highlighting the overall design: What are three adjectives that describe your vision?
  • Frame
    • Dimensions: ROV will fit in bin
    • Lengths of all PVC pieces specified
    • # fittings, of what types
    • # fasteners, types (zip-ties, bolts, etc.)
    • Are your holes drilled such that the ROV can vent its air at the highest point?
    • How is the payload mounted/supported? Is there room for the wires to be fixed back without being pulled tight?
  • Thrusters
    • placement specified (and enough flow around them)
    • Protection
    • Mounting is sufficient:
      • Can you attach the thruster the way your model says?
      • If so, will the attachment be of sufficient strength?
      • Can you get the thruster back off at the end of the project?
  • Cable management
    • Wires have slack/are not pulled tight
  • Camera
    • How is the camera protected?
    • Can you get the camera back off at the end of the project?
    • How does your camera placement support how you are going to drive your ROV?
  • Buoyancy
    • What material(s) are you using?
    • How are you attaching it?
    • Where is your buoyancy flexibility/adjustment? (placement and amount)
• Control box design
  • Start by just highlighing the overall design: What are three adjectives that describe your vision?
  • Hardware
    • Number of buttons/switches
    • Buttons/switches will fit where they are intended to go
    • Are you using something other than buttons/switches? If so,
      • What are you using?
      • Do you understand the interface? (this is your job!)
  • Software
    • Are you using stock code or custom?
    • For custom code
      • What are your algorithms?
      • How will you implement and test this code?
      • What happens if you can’t get your code to work? What are your backup plans?
• Order of assembly
  • What is the largest # of joints you’ll have to make simultaneously to put this together?
• Custom parts (OPTIONAL)
  • What are the strength requirements? (Does it carry a load? If so, how will you test this?)
• Deployment
  • Can you get in and out of the water in less than 5 minutes?
  • What’s pre-assembled in the box, and what do you have to do for deployment? (is there a specific order those things have to be done in?)
  • How many fasteners/what type will be added in those 5 min?
• Servos (OPTIONAL)
  • All thrust/structural loads must be supported by ROV chassis, not the servo. (Are yours?)
  • How are you going to isolate these loads?
  • What’s your plan if the servo fails?

Lab 7: ROV Build

Checklist

Overview

• Major goals
  • Complete thruster testing
  • Continue on frame
  • Continue on control box
  • Continue on controller code
  • Develop back up plans for if any of your subsystems don’t work at the MHL (custom thruster protection fails, etc.)
  • Develop back up plans for if any of your subsystems don’t work at the MHL (servo fails, custom thruster protection fails, etc.)
• What to do
  • Make significant progress on your ROV’s frame
  • Make significant progress on your ROV’s control box
  • Make significant progress on your custom code (if you are using any… you don’t have to)
• Things to remember
  • It is a lot easier to document your ROV as you go along. For example, get the masses of your individual components BEFORE you cement them together!
  • Rotate people through both the actual build roles and the documentation/verification roles.
  • Update your CAD model as you go along so that the final CAD model matches what you actually built.
• With 15 minutes left in lab
  • Put away all tools and material
  • Reconvene team
  • Make sure each person knows when the team is meeting next and what action items they need to have done by then

Measuring the Thrust Provided By Your Thrusters

A thrust stand is set up at the testing tank in lab. This stand will allow you to test each of your ROV thrusters in both the forward and backward direction to get their actual measured thrust. You can then use these measurements to help you decide where to place your thrusters on your ROV.

Equipment:

1. Power supply set to exactly 12.00V to power load cell
2. Load cell
3. 12V SLA battery
4. 3 DVMs, one for battery voltage, one for batter current, one to read load cell. 5 – Lever arm with bearing
5. Optical table and hardware to mount load cell
6. Wire for tension hookup
7. Clamp for thrust arm bearing.

Fig and Fig show what the thrust stand looks like.

Follow these directions to measure the thrust of one of your thrusters:

1. Attach a thruster to the metal end of the arm with a cable tie through the marked holes.

   

2. Install the thrust arm on the bearing. Make sure bearing is lubricated.

   

   

   

3. Plug the thruster in and connect the battery to power the thruster, read load cell voltage, battery voltage and battery current.
4. To read reverse thrust, remove and reverse thrust arm, connect battery with leads reversed to reverse direction of motor rotation and read voltages and current.

   

   

For Fall 2019, the load cell calibration equation is:

$N$ = -57.1354 + 52.84 $V$

where $N$ = newtons and V = volts (not millivolts!)

Lever arm length pivot to thruster = 37.8 cm
Lever arm length pivot to load cell = 12.7 cm

Note that the thruster is producing a thrust which is the load cell force times the ratio of upper lever arm to the lower level arm.

Lab 8: Critical Design Review

Checklist

Overview

• Major goals
  • Conduct Critical Design Review
  • Complete ROV, including frame, control box, and code
• What to do
  • Continue executing your ROV plan!
  • This is the last official lab that we have before going to the MHL to do a performance evaluation of your ROV.
  • Finish up anything you need to do to make sure that your ROV is fully complete and operational by the end of lab.
• Things to remember
  • Continue to document your ROV and update your CAD model, if necessary
  • If you have downtime, like while you are waiting for PVC cement to fully harden, work on your ROV calculations.
• With 15 minutes left in lab
  • Put away all tools and material
  • Reconvene team
  • Make sure each person knows when the team is meeting next and what action items they need to have done by then

Critical Design Review (30 min)

At some point during lab, your team will be pulled out for your Critical Design Review.

ROV Build and Test (120 min)

This is your last big chunk of lab time to work on your ROV and make sure it’s ready for the performance evaluation next week at the MHL. There will NOT be time to work on your ROV at the MHL, so ideally, you want your ROV to be completely functional by the end of lab. We will have some open lab time before we have to take the ROVs to the MHL, but you should think of those as absolute emergency times to fix something that catastrophically broke.

Lab 9: ROV Performance Evaluation at MHL

Checklist

Overview

• Major goals
  • Test ROV in deep water
  • Verify that all systems work as intended
  • Practice driving the ROV in deep water
  • Measure speed in 2-3 different directions of travel
  • Practice inspection task simulation
  • Conduct inspection task simulation
• What to do
  • This lab is on Central Campus!
  • Follow the Performance Evaluation Procedures.
• Things to remember
  • The MHL is a working laboratory! Be careful where you step, move slowly, and watch out for each other at all times
  • There is absolutely NO jumping around on the carriage or sub-carriage.
  • Laura has the right and the responsibility to kick you out of the MHL if you are behaving in an unsafe manner. Please do not make her do this.
  • You have a lot to cover in this lab, and we will enforce time limits for each part of the lab so everything keeps moving along. Make sure your team has a plan in place for how to stay organized and on-time!
• With 15 minutes left in your lab session
  • Take your ROV out of the water
  • Remove the payload and camera
  • Put your ROV back in its bin but leave the lid off so it can dry out
  • Put away all tools and material
  • Reconvene team
  • Make sure each person knows when the team is meeting next and what action items they need to have done by then
  • You can leave when your IA has inspected your station and says you can leave

Lab 10: Post-Performance Evaluation Data Gathering

Checklist

Overview

• Major goals
  • Gather all additional data and video that you need to complete your ROV’s final deliverables: final presentation, final report, and innovation video
• What to do
  • Your team should have a list of all the information you need about your ROV to complete the remaining deliverables.
  • This lab is your chance to gather any additional information you need, perform additional tests, and do anything else you found out you were missing
• With 15 minutes left in lab
  • Put away all tools and material
  • Reconvene team
  • Make sure each person knows when the team is meeting next and what action items they need to have done by then

Lab 11: Dress Rehearsal for Prototype Review Presentation to Client

Checklist

Overview

• Major goals
  • Practice final presentation and get feedback
  • Make progress with all remaining project deliverables
• What to do
  • Practice your final presentation
  • Provide feedback to another team on their presentation
  • Gather any additional pictures or data you need from your ROV
  • Work on remaining ROV deliverables
• With 15 minutes left in your lab session
  • Make sure each person knows when the team is meeting next and what action items they need to have done by then
  • You can leave when your IA has inspected your station and says you can leave

A dress rehearsal is a performance that is the “real thing” except that the expected audience isn’t there. It’s a chance for the performers to practice everything ahead of time and build confidence for the actual performance. A dress rehearsal might have no audience at all, or the audience might be a group of people who have no expectations of quality so that the performers can be in front of people but not be stressed about the audience’s reaction. For example, a local high school’s theater group invites students from the nearby elementary school to their dress rehearsals. The elementary school kids get to see a free play, and the high school students get to practice in front of a bunch of people knowing that the little kids will be happy no matter what happens!

A team presentation, as you’ve experienced in this class, is absolutely a performance. We want all of you to feel as confident as you can going into your final presentation. This dress rehearsal will also serve as an internal deadline for your team so that you have your final presentation slides done with enough time to get feedback on your presentation and make revisions before you do the “real thing”.

We also want you all to continue getting experience giving useful feedback to your peers; this is a crucial engineering skill. So, each team will give their presentation and also watch another presentation.

We will bring two teams at a time to do their dress rehearsals for the final presentation. Each team will give their presentation and provide feedback on the other team’s presentation.

The remainder of the time in lab is yours to use as needed so that you can complete your project deliverables on time.

Lab 12: ROV Tear Down & Finish Documentation

Checklist

Overview

• Major goals
  • Get any final pictures or video that you need for your final report and innovation video
  • Go through the cost audit
  • Tear down ROV and return all reusable parts to their proper bin
  • Clean out your ROV bin
  • Work on ROV Prototype Report to Executive Team and Innovation Video
• What to do
  • Check your shot list/storyboards/script for your innovation video; identify what shots you still need to get with your ROV
  • Take pictures and/or video that you need
  • When you are done, tell your IA that you are ready for your cost audit. They will compare your ROV to the cost worksheet you submitted to Canvas.
  • Gently detach all reusable parts of your ROV, including but not limited to: the thrusters, hose clamps, bolts, floats, foam, mesh, etc.
  • You can take the PVC frame with you if you want to (otherwise, we will just throw it away)
  • Clean out your ROV’s bin, sorting items into reusable, recyclable, and trash
  • Spend the rest of the time working on your ROV Prototype Report to Executive Team and Innovation Video

Lab 13: Work Time for Final Deliverables

Checklist

Overview

This time is yours to work with your team to finish up the remaining ROV project assignments.