6.20.2015
Choosing a Camera – Update
The search for a camera to use in our robot has been long and involved. Throughout the process, we have worked toward finding a camera that satisfied a basic set of requirements. Our camera needs to be capable of outputting high quality video, interfacing with C++ or Java through the Beaglebone black, and be capable of stereoscopic imaging. We believe we have finally found a camera that can satisfy all of those requirements: the DUO MLX.
This camera, while expensive, boasts an impressive array of features and capabilities. It stereoscopic and infrared, allowing it to judge depth in low light environments. It comes equipped with a small array of programmable infrared LEDs and an on-board 9-DOF freedom IMU, allowing it to sense its orientation with a high degree of accuracy. Finally, it comes with a SDK which, just recently, allows it to interface with ARM based micro-controllers like the Beaglebone - although access to this capability requires subscription to DUO's developer program. This SDK is compatible with C++ and C, as well as Java through the Java Native Interface. Another distinct advantage of this camera is its form factor. It is very small, being only 52mm long. This will allow us to fit many more design features into the front portion of the submersible.
6.17.2015
Small Thrusters v2.0 – CAD Model
We recently finished the final CAD model for the small thrusters we're using in our submersible. Four of these thrusters, two vertical and two horizontal, helps our submersible attain 4 of our submersibles 5 degrees of freedom.
The design of the small thrusters was focused around designs that were both easy to build and easy to install. We decided to work off of last years design, keeping the same idea, but tweaking it to fit in the new form factor of the sub. Each thruster assembly has only 5 total parts (excluding the motor and prop) making it an easy part to build and assemble. An image of the finished thruster is below:
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| Thruster Assembly |
This design consists of four main parts: the thruster grill, motor mount, PVC mount, and the PVC piping. In the image above the PVC is transparent, the grills are black and both the motor and PVC mounts are green. The thruster is assembled by sliding the PVC mount into the three slots cut in the PVC pipe and then epoxying it place. The motor and motor mount are then able to slide freely into the six slots cut on the opposite side of the PVC pipe. This side is not epoxied and allows us to easily remove the motor by removing three bolts on either side of the thruster and sliding out the PVC pipe, PCV mount, and motor mount all together.
The bolts we are using are 16mm long, 4M bolts that are threaded into tapped Delrin plastic (green). These bolts mostly have to deal with torque and therefore are suitable for the size and power of motor and prop combination we're using. This is also nice because it means the thruster is mounted directly to the aluminum body and the PVC acts only to direct the flow of water. Three of the parts are pictured below:
The bolts we are using are 16mm long, 4M bolts that are threaded into tapped Delrin plastic (green). These bolts mostly have to deal with torque and therefore are suitable for the size and power of motor and prop combination we're using. This is also nice because it means the thruster is mounted directly to the aluminum body and the PVC acts only to direct the flow of water. Three of the parts are pictured below:
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| Thruster Mount |
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| PVC Mount |
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| PVC Pipe |
Finally we created the grill for our thrusters. The main purpose of these pieces are to keep any large pieces of material from interfering with the performance of our thrusters. They do, however, also help with the aesthetics of the sub. By using these pieces to slide into the holes cut in the aluminum body we are able to keep a relatively smooth form factor which is important in reducing the drag of the sub. There are also three bolts on either side in order to mount the thruster firmly in the sub.
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| Grill |
Both the vertical and horizontal thrusters will be mounted close together and as far from the center of the sub as possible. This gives us finer control over the submersible due to mechanical advantage. An image of the two thrusters mounted in the aluminum body is below:
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| Mounted Thrusters |
6.16.2015
Rear Thruster v2.0 – CAD Model
We recently finished the CAD model for our large rear thruster. The thruster from our first version actually worked pretty well, so we kept many of the elements from it and changed only what was necessary.
We started by coming up with a cone to guide water-flow from the rear edge of the submersible to the propeller. The first idea was to have the end near the submersible be square (to make it look like a continuous piece) and have only the end near the propeller be a circle.
This shape had two advantages over a circle to circle cone. First, it is more streamline with the rest of the submersible - this helps some with the water flow but is mostly for visual appeal. Second, it would allow us to use the flat part of the surface to bolt fins onto for the thruster nozzle. We would probably have used this design if it did not require remaking the nozzle.
Instead we switched to a circle to circle cone so that we could use the same nozzle as last year.
By using a circular cone and last years nozzle we are able to cut down on the number of pieces we need. The fins that connect the cone to the nozzle are 1/8" plastic and will be epoxied into the grooves that can be found in each piece. While the cone itself is circular we did leave a square part on the larger end allowing for an easy connection with the square submersible.
Once we had the external portion completed we moved on to the inner parts. First cutting a hole for the shaft and motor so that they can be set into the rear cone and not take any space from the submersible. We then created a mounting bracket for the large thruster motor which would suspend it inside of the thruster cone.
We started by coming up with a cone to guide water-flow from the rear edge of the submersible to the propeller. The first idea was to have the end near the submersible be square (to make it look like a continuous piece) and have only the end near the propeller be a circle.
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| Square to Circle Thruster Cone |
This shape had two advantages over a circle to circle cone. First, it is more streamline with the rest of the submersible - this helps some with the water flow but is mostly for visual appeal. Second, it would allow us to use the flat part of the surface to bolt fins onto for the thruster nozzle. We would probably have used this design if it did not require remaking the nozzle.
Instead we switched to a circle to circle cone so that we could use the same nozzle as last year.
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| Circle to Circle Thruster Cone |
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| Nozzle |
By using a circular cone and last years nozzle we are able to cut down on the number of pieces we need. The fins that connect the cone to the nozzle are 1/8" plastic and will be epoxied into the grooves that can be found in each piece. While the cone itself is circular we did leave a square part on the larger end allowing for an easy connection with the square submersible.
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| Cone and Nozzle |
Once we had the external portion completed we moved on to the inner parts. First cutting a hole for the shaft and motor so that they can be set into the rear cone and not take any space from the submersible. We then created a mounting bracket for the large thruster motor which would suspend it inside of the thruster cone.
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| Thruster Cutout |
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| Motor and Bracket |
When all of the pieces are put together the result is a pretty weird looking, but highly functional piece of our submersible. For information about the coloring see the general CAD post.
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UPDATE (7/13/2015): A New Cone Design
In our first attempt at creating the cone piece we tried to cut a large block of plastic on a 3-axis router – it did not work well for a couple reasons. Thus we decided to 3D print the piece instead. Although we were skeptical at first, this method turned out to work well. The design however, was changed in a few ways to make printing easier.
1) The first change we made actually didn't have anything to do with printing: we decided to return the the square to circle lofted cone. This is because it gives us a much better form factor and looks better when attached to the body of the sub. The only down side is that there are three fins going into a four sided object, which just means that we have to make a custom fin for each slot as they are not the same due to a lack of symmetry.
2) Another important change we made is the use of threaded inserts (discussed in this post). Without these inserts a printed cone would not work with out current mounting design because threads do not hold well in printed plastics.
3) A final change came in the form of moving the mounting bolts. While this may not seem related to printing the cone it is a change that has only come about because we can make multiple versions easier and cheaper using this rapid prototyping method.
We decided that we want to make as many of the external bolts in one line so that we have the smallest impact on our coefficient of drag. This type of modularity also allows us to mix and match the different sections of the submersible. We decided to move moved the bolts so that all four are on the sides, rather than having one on each of the four sides.
Below is a picture of the final design:
6.14.2015
RoboGoby II – General CAD
After deciding to continue with Project RoboGoby this summer we decided that having an in-depth CAD, or Computer Aided Design, of the submersible was the best way to plan Version II. This post, which is about the initial CAD of sub, allowed us to flush out all of our ideas and not worry about specifics. This gives us the freedom of designing the submersible how we want to and then thinking more about specifics later on. The second round of CAD (which will be done for each of the major pieces) will focus on the specifics before machining parts.
As part of the initial design phase we broke the submersible up into three distinct pieces — the front section, the middle, and the rear section. Each of the sections are important to the overall design yet still describe the general ideas for the finished sub. Below each of the sections are quickly explained and an images of each section is provided.
We also used the coloring scheme in CAD to color different parts in our design to easily tell what material each piece is going to be made out of. This key will help you in understanding all of our CAD designs for RoboGoby II.
CAD Key
Printed PLA ----------> Black
Delrin -----------------> Green
PVC -------------------> White
Aluminum--------------> Grey
Polyethylene -----------> Pink
Tapped Holes --------> Yellow
Paint----------------------> Red
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UPDATE (7/13/2015): Threaded Inserts
We will also be using RED to represent the holes we are using threaded inserts in. The threaded inserts look like this:
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| 6mm Threaded Insert |
And the CAD'ed plastic holes will look like this:
It is designed to be pressed into wood/thermoplastics and is perfect for using in common 3D printed plastics to make use of bolts as printer plastic is notoriously hard to tap. We will be using these in most if not all of the future 3D printed pieces.
It is designed to be pressed into wood/thermoplastics and is perfect for using in common 3D printed plastics to make use of bolts as printer plastic is notoriously hard to tap. We will be using these in most if not all of the future 3D printed pieces.
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Front
The front section houses our camera, lights, sensors, and two of the side thrusters. This section was therefore one of the more complicated of the sections to design as it includes many different components. Below is a transparent image of the front section of the submersible. You can see the horizontal and vertical thrusters which are placed behind the variable pitch camera and lighting system. |
| Front Section |
Middle
The middle section of the submersible houses most of our electronics and all of our electronic controllers. This section has been designed to be waterproof in pressure exceeding 150 PSI. Much of the complicated work in this section will be done when mounting our electronics and connectors on the inside. For now the main part of this section is the double o-ring plug you can see in the transparent part of the image below. This plug ensures that everything stays waterproofed while still giving is easy access to the electronics inside.
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| Middle Section |
Rear
The rear section is almost completely thrusters (in the future it will have a power connector). Currently it contains side thrusters symmetric to those in the front (vertical and horizontal), but also has our large rear thruster, cone, and nozzle which are extremely important to the submersible.
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| Rear Section |
Stay tuned for future posts with more detail explanations about the design of the components of each of the sections.
9.28.2014
RoboGoby Version 1 and the Plan for Version 2
It has been quite a summer for Project RoboGoby. Near the deadline for most of the Limbeck crew's college departures, we held an official launch for the first generation of the RoboGoby submersible. The design outperformed our hopes for the alpha version, bringing a favorable close to the first chapter of the Limbeck Engineering story. Below is some footage of the launch event, edited together from the various videos taken:
Full Promotion:
Just Footage of the Robot at Work
However, Project RoboGoby is not over. This year, the project will be moved to Baxter Academy in Portland, where Limbeck Engineering will work to both create a production-ready beta type of the robot and to teach and manage a group of students at Baxter as they help work on the project. Of course, this means that Limbeck Engineering will again be reaching into their own pockets and out into the community for support.
On Friday, Josef - the member of our team still at Freeport High School - attended the Envision Maine Summit in Freeport. The summit's purpose was to help build an innovative and entrepreneurial community in Maine. We at Limbeck Engineering would like to thank everyone at the summit for showing enormous support for our project. Specifically, we would like to thank Coffee by Design for their generous support and sponsorship in kicking off the fundraising for gen 2 of RoboGoby. Here is a video of our Josef's speech at the event:
http://www.youtube.com/watch?
In the coming months, we will continue to update the blog on our progress with the students at Baxter Academy - though we won't begin working with the students until their second trimester starts. In the meantime, we will begin building a business plan for the second phase of the project, including our technical goals, our financial requirements and our fundraising plans.
Full Promotion:
Just Footage of the Robot at Work
However, Project RoboGoby is not over. This year, the project will be moved to Baxter Academy in Portland, where Limbeck Engineering will work to both create a production-ready beta type of the robot and to teach and manage a group of students at Baxter as they help work on the project. Of course, this means that Limbeck Engineering will again be reaching into their own pockets and out into the community for support.
On Friday, Josef - the member of our team still at Freeport High School - attended the Envision Maine Summit in Freeport. The summit's purpose was to help build an innovative and entrepreneurial community in Maine. We at Limbeck Engineering would like to thank everyone at the summit for showing enormous support for our project. Specifically, we would like to thank Coffee by Design for their generous support and sponsorship in kicking off the fundraising for gen 2 of RoboGoby. Here is a video of our Josef's speech at the event:
http://www.youtube.com/watch?
In the coming months, we will continue to update the blog on our progress with the students at Baxter Academy - though we won't begin working with the students until their second trimester starts. In the meantime, we will begin building a business plan for the second phase of the project, including our technical goals, our financial requirements and our fundraising plans.
7.13.2014
Camera and Embedded Linux Pots (and shelves)
For the last could of days we have been working on fitting the LEDs, their heat-sinks, and all three cameras into the dome port. This was a very tedious process but it is now complete.
In the process of fitting the cameras into the front of the sub we had to take into account that they would be in boxes that we 3D print. The boxes will hold the cameras' control boards and will then be filled with epoxy. Putting them in epoxy makes them waterproof and thus allows us to flood the whole submersible. We created a box that had three separate compartments, two for the Raspberry Pi cameras and one for the webcam. On the back of the box there is a mount for the rod on the servo to attach to. It is impossible for this part to be printed in one piece so we broke it up into three separate pieces for printing. An image of the final potted camera setup is below:
We then moved on to printing the boxes for the embedded Linux microcomputers. We have two boxes, two for our Raspberry Pi's and one for the BeagleBone Black. Both containers are going to be filled with thermally conductive epoxy in order to keep out electronics cool. We decided to place the BeagleBone/shield combination face-up in the container while we put Raspberry Pi's upside down. This made the 3D printing a lot easier although it did add to the amount of epoxy we needed to use. An image of all three potted computers is below:
After creating the boxes we also needed to make a way to hold them in place. In the end we created three shelves we put the two RPi's on the top and bottom of the middle section and put the BeagleBone in the middle of the front section. We are also going to put the IMU on top of the BeagleBone so it doesn't need its own space.
In the process of fitting the cameras into the front of the sub we had to take into account that they would be in boxes that we 3D print. The boxes will hold the cameras' control boards and will then be filled with epoxy. Putting them in epoxy makes them waterproof and thus allows us to flood the whole submersible. We created a box that had three separate compartments, two for the Raspberry Pi cameras and one for the webcam. On the back of the box there is a mount for the rod on the servo to attach to. It is impossible for this part to be printed in one piece so we broke it up into three separate pieces for printing. An image of the final potted camera setup is below:
We then moved on to printing the boxes for the embedded Linux microcomputers. We have two boxes, two for our Raspberry Pi's and one for the BeagleBone Black. Both containers are going to be filled with thermally conductive epoxy in order to keep out electronics cool. We decided to place the BeagleBone/shield combination face-up in the container while we put Raspberry Pi's upside down. This made the 3D printing a lot easier although it did add to the amount of epoxy we needed to use. An image of all three potted computers is below:
After creating the boxes we also needed to make a way to hold them in place. In the end we created three shelves we put the two RPi's on the top and bottom of the middle section and put the BeagleBone in the middle of the front section. We are also going to put the IMU on top of the BeagleBone so it doesn't need its own space.
6.13.2014
BeagleBone Capes
After choosing the sensors and getting the software complete, we needed to create the sensor Capes for both BeagleBone Blacks (one on the float and one in the sub). For the BeagleBone Black on the float we attached the connectors for the stepper motors, the GPS module, a compass, a temperature probe, and a battery measurement circuit. The actual making of this cape took an unexpectedly long time, although it turned out very nicely:
The BeagleBone on the float has to be supplied with 5v. To do this we decided to use voltage dividers. This task took longer than expected as dropping the 25.6v from the battery had a few different issues. Originally we were going to use the LM317. This variable voltage regulator should have given us a constant voltage supply by choosing the right resistors (based on the formula). Sadly as the voltage supply to the LM317 dropped, so did the voltage output.
The BeagleBone on the float has to be supplied with 5v. To do this we decided to use voltage dividers. This task took longer than expected as dropping the 25.6v from the battery had a few different issues. Originally we were going to use the LM317. This variable voltage regulator should have given us a constant voltage supply by choosing the right resistors (based on the formula). Sadly as the voltage supply to the LM317 dropped, so did the voltage output.
We then moved on and chose to use the simple UA7805 5v regulator. This chip can talk up to 24v and regulate it to 5v. As the rating on the 7805 was only 24v we decided to first step own the voltage using the LM317s we already had and then using the 7805 to get the exact 5v we required. Our float also needed a second 5v 1A power supply so we decided to create two of these circuits in parallel (as the chips can only handle a certain amperage). An image of the final regulator is below:
The second BeagleBone Cape we made is for the sub. This Cape is also fairly simple. It contains the MOSFET controllers for varying our LED brightness, the IMU, the depth sensors, the temperature sensor, and a few extra pin-outs for any future sensors. An image of the Cape for the submersible is below:
6.10.2014
Choosing a Camera
For the last few week we have been trying to make a final decision about what will be in the dome of the submersible, especially which cameras we will use. Originally we just had two pi cameras on a rod so they could be tilted up and down.
We then moved on to have the LEDs inside the submersible, putting them in between the two cameras. This worked well while we were planning on a 6" diameter submersible as the pi cameras were small enough, but once we changed to a 4" it didn't fit well.
Thirdly we decided to have either two pi camera's or two webcams and no LEDs. The pi cameras fit more easily but didn't stream as nicely, so we thought about using webcams. Because most webcams are fairly long in one dimension they were going to have to stand up and would take most of the room. We then decided to buy a nice webcam and see how it fit. When it arrived we found that it was much bigger than the other (being about 3.25" long).
With the new cameras and the decision to try and move the LEDs back inside the dome with the cameras we changed our plan entirely. We decided to have one nice webcam for streaming video, and having two pi cameras on board to do stereoscopic vision.
Another factor in choosing our cameras has been the video quality. After testing various different streaming methods (all can be found here) we settled on using a combination of cameras. For the live video feed we settled on using MJPG-Streamer on the BeagleBone with Logitech's C920. For the stereoscopic vision we decided to use two Raspi-Cameras. Both can be seen in the CAD images above (RPi are the small square ones, the C920 is the long one). While driving, the user will only be using the C920. The RPi cameras will only be used to take images and record video (and are specifically placed where they are for stereoscopic vision. An image of the C920 out of it's case is below:
MJPG-Streamer was chosen out of the various different streaming methods (GStreamer, Motion, FFMPEG, MPlayer w/ Netcat) because of its speed and compatibility. Not only can it handle 30 fps, but the stream can be picked up by OpenCV running on the OCU.
The last step with the cameras was potting them. We 3-D printed boxes for the cameras to fit inside of, as well as a place for a rod to go through the system so it could be tilted. The picture below is of the cameras epoxied into their boxes, and below that is a CAD model of the entire system in place.
We then moved on to have the LEDs inside the submersible, putting them in between the two cameras. This worked well while we were planning on a 6" diameter submersible as the pi cameras were small enough, but once we changed to a 4" it didn't fit well.
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| Vertical LEDs between cameras |
Thirdly we decided to have either two pi camera's or two webcams and no LEDs. The pi cameras fit more easily but didn't stream as nicely, so we thought about using webcams. Because most webcams are fairly long in one dimension they were going to have to stand up and would take most of the room. We then decided to buy a nice webcam and see how it fit. When it arrived we found that it was much bigger than the other (being about 3.25" long).
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| LED modules with two Pi-Cameras |
With the new cameras and the decision to try and move the LEDs back inside the dome with the cameras we changed our plan entirely. We decided to have one nice webcam for streaming video, and having two pi cameras on board to do stereoscopic vision.
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| 3 Cameras with LED strip |
Another factor in choosing our cameras has been the video quality. After testing various different streaming methods (all can be found here) we settled on using a combination of cameras. For the live video feed we settled on using MJPG-Streamer on the BeagleBone with Logitech's C920. For the stereoscopic vision we decided to use two Raspi-Cameras. Both can be seen in the CAD images above (RPi are the small square ones, the C920 is the long one). While driving, the user will only be using the C920. The RPi cameras will only be used to take images and record video (and are specifically placed where they are for stereoscopic vision. An image of the C920 out of it's case is below:
MJPG-Streamer was chosen out of the various different streaming methods (GStreamer, Motion, FFMPEG, MPlayer w/ Netcat) because of its speed and compatibility. Not only can it handle 30 fps, but the stream can be picked up by OpenCV running on the OCU.
The last step with the cameras was potting them. We 3-D printed boxes for the cameras to fit inside of, as well as a place for a rod to go through the system so it could be tilted. The picture below is of the cameras epoxied into their boxes, and below that is a CAD model of the entire system in place.
6.08.2014
Finishing the LEDs
After spending many hours designing a various different heat-sinks for the LEDs, we settled on putting the LEDs on the outside of the acrylic dome to minimize the reflection and interference with our cameras. Space has also been another huge issue for our LED setup. To minimize the space used by these LEDs, we have decided to put them into a 12mm pipe (10mm ID) attached to a 10mm rod.
The LEDs will be glued onto a copper strip and then onto a 10mm aluminum rod. This unit will then slide into the larger 12mm rod. The lens will be glued into the end of the pipe and the wires will come our via slots in the aluminum piping.
After routing out the aluminum pieces (shown below) we glued the LEDs to the copper strips, soldered on the power and ground wires, and covered the wire leads in order to ensure that electrical jumping did not occur. We then attached the copper to a 10mm rod and were done building the heat-sinks!
In order to have the lights on outside of the water and at variable brightnesses in the water we are using pulse width modulation (PWM) to control them. By wiring the LEDs to our 12v power supply on the sub and then using a MOSFET (metal-oxide-semiconductor field-effect transistor) we were able to translate the variable pulses to variable brightness on the LED. The MOSFET can be attached by sending DATA to the gate pin, attaching the GROUND of your LED to the drain pin, and finally attaching the GROUND of your power source to the source pin.
The LEDs will be glued onto a copper strip and then onto a 10mm aluminum rod. This unit will then slide into the larger 12mm rod. The lens will be glued into the end of the pipe and the wires will come our via slots in the aluminum piping.
After routing out the aluminum pieces (shown below) we glued the LEDs to the copper strips, soldered on the power and ground wires, and covered the wire leads in order to ensure that electrical jumping did not occur. We then attached the copper to a 10mm rod and were done building the heat-sinks!
In order to have the lights on outside of the water and at variable brightnesses in the water we are using pulse width modulation (PWM) to control them. By wiring the LEDs to our 12v power supply on the sub and then using a MOSFET (metal-oxide-semiconductor field-effect transistor) we were able to translate the variable pulses to variable brightness on the LED. The MOSFET can be attached by sending DATA to the gate pin, attaching the GROUND of your LED to the drain pin, and finally attaching the GROUND of your power source to the source pin.
After wiring up the MOSFET you can easily control is using the RPi.GPIO library on your Raspberry Pi. Read this post to get a handle on the basic concepts of PWM control. By simply sending varied duty cycles to the gate pin, you will get a variable brightness LED. Below is a small clip of the LED pulsing using the MOSFET and RPi.GPIO:
6.05.2014
Finishing the Spool
After another round of testing, we were able to finalize the design for the spool on the float.
After receiving 230 feet of 10 gauge wire from Matt Anderson in December, we twisted and coiled the two wires together. We did this thinking that in the future we could easily add some flotation and be done with the tether.
A few months later, we decided to finally finish the tether. We measured the density of the wire, and then purchased 250 feet of 1/4" foam cord for flotation. To cover the wires and foam cord we purchased an expandable polyester sleeving. After uncoiling and then untwisting the wire, we tapped on the foam cord and then spend a few hours pushing on the expandable sleeving. Below is an image of the wire, foam, and polyester sleeving combination.
After receiving 230 feet of 10 gauge wire from Matt Anderson in December, we twisted and coiled the two wires together. We did this thinking that in the future we could easily add some flotation and be done with the tether.
A few months later, we decided to finally finish the tether. We measured the density of the wire, and then purchased 250 feet of 1/4" foam cord for flotation. To cover the wires and foam cord we purchased an expandable polyester sleeving. After uncoiling and then untwisting the wire, we tapped on the foam cord and then spend a few hours pushing on the expandable sleeving. Below is an image of the wire, foam, and polyester sleeving combination.
We also took a time-lapse video of the processes:
After finishing with the tether, we also finalized the power transfer on the float. We had tried a few different ways of transferring the power from the battery to the spool. At first, we tried to transfer electricity through the ball bearings we are using on the spool. Unfortunately those provided too much resistance as the contact points between the balls and the metal rings were extremely small. We looked into a few other options and final decided to use a brushed system to transfer power from the batteries to the tether on the spool.
The final design of the spool consists of the brushed system you see below. The brush is made using a threaded copper rod and copper tubing. The threaded rod is inserted into our support braces and attached to the power coming from the battery. The rub is soldered onto the rod leaving just enough room for the brush. After reaching the rod, the power is transferred into the tube and then through the brush onto the metal plate shown below. This plate is wired into the tether and thus provides the submersible with power. An image of the final brushed system is below:
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