PROJECT N 36 Low cost underwater exploration vehicle David O Brien-Møller European School Brussels III Boulevard du Triomphe 135, 1050 Ixelles, Belgique S6 ENA Abstract Key words: Under Water robot, independent researchers The purpose of my project is to construct a low cost underwater exploration vehicle. Using joysticks as controls the operator on land can manoeuvre the vehicle through the water while receiving a live feed hfrom a camera mounted within it. This project will be Open-Source, all the files, such as the 3D printing files for parts, will be published letting any researcher anywhere construct their own robot, since it uses low cost easily available components. It will cost 200 euros in comparison to the cheapest similar robot which costs 899 dollars. It can be used for observing wildlife, and gather temperature data. The robot can have a small waterproof camera mounted on it to take good pictures and can support sensors such as temperature sensors to gather data. The robot unlike other ROVs allows for easy modification of form and function as is later discussed. The vehicle is easily converted to other uses, as it s body is positioned on threaded rods, which allow for fast and simple shape changes and for easy swapping of any attachments the researcher wishes to add or remove from their robot. The attachment that I will construct for the robot is a grabbing tool that can be used to collect scientific samples or rubbish. My robot is ideally suited to these tasks as it is small (30cm width by 25 cm length by 15 cm height), in its current form, and can access places inaccessible to divers or larger submersibles. This robot is more a platform that allows anybody to modulate and change to suit their desires. 1
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1. Introduction Humans have explored less the 5% of the oceans floor, in the words of Robert D. Ballard, the discoverer of the Titanic wreck, Only a tiny percentage of the ocean floor has been carefully mapped, which means we know less about 71 percent of the Earth s landscape than about the far side of the Moon This means that the ocean is the last big unknown for the human race here on earth, the last place waiting for us to explore. I believe that all of us should have the opportunity to be able to do that exploration, it shouldn t just be the role of organisations, small researches should also be allowed to advance the knowledge of the human race. Therefore, I am in the process at the moment of creating a new underwater drone that anyone can build. It is designed with it being open to everyone in mind, this means that most of the pieces are 3D printed, as now almost everyone can have access to such a machine, and all other components have an extremely low cost, which allows the entire construction to cost less than 200 euros. This democratization is happening in every sector of scientific research, even in space exploration, and now with tools such as 3D printing and easy to use microcontrollers such as the Arduino, which allow everyone to relatively easily create their own custom data collection tools, that if they are open source can be improved upon by everyone. Even space research is becoming easier to access by citizens. 2. Materials For this project, I am using: 30M of Ethernet wire to carry video signal from the webcam on board the robot to the surface 3
Joysticks 30M of speaker wire to carry I2c communications from the surface to the robot An Arduino in the robot to acquire incoming data and control the robot from that 4
A PyBoard on the surface to send information from joysticks to the Arduino in the water PVC tube to provide a waterproof hull to store the electronics An Ethernet to USB converter, to send the USB webcam signals through the Ethernet 5
An LED ring to provide light A lipo battery to provide the power A plexiglass circle to allow the robot s camera to see through the front of it 6
4 Converted bilge pumps to thrusters Waterproof seals Voltage regulators 7
Temperature Sensor SD card shield for Arduino Threaded steel bars Nuts and bolts 8
Many miscellaneous 3D printed parts A webcam Motor controllers A waterproof servo motor 9
3. Method My method consists of trying and testing, seeing what works and what doesn t so it has followed this order: 1) Designed the Computer aided model for the robot 2) Designed the circuit 3) 3D printed the parts 4) Assembled the parts into a rough prototype 5) Assembled the electronics 6) Program the electronics 7) Final completely waterproof assembly 8) Publish files on the internet 4. Results The results so far are a primary stage prototype of what the final machine will look like. To date, all the necessary files have been designed and 3D printed, the Arduino code and python code has been developed, but still isn t functioning with 30M cable, but works perfectly with jumper wires connecting the two. The wooden side panels in the pictures are only temporary as they allowed me to visualise how the robot will look and accurately design the side panels that will be lasercut out of acrylic. How does it work? The robot has two microcontrollers, one on the surface, one in the actual robot. The role of the microcontroller on the surface is to take messages from the human controller to the microcontroller in the robot who executes tasks depending on these signals. The PyBoard will be the microcontroller on the surface and is connected to two joysticks, these joysticks will control the forward/backward turn left/turn right and up/down movement of the robot. The Arduino Uno inside the robot receives a number from the PyBoard and executes the function which corresponds to the number. For example, if I were to send 1 through the I2c communication, the Arduino would turn the LED ring on. These packets of information should be send 100 times a second, and have a starting number and a stopping number so the Arduino can store the commands in an array and execute them and then only start refreshing the array when it receives the starting number. 10
At the same time the Arduino also writes temperature data to the SD card connected to it by the SD card reader, this is done independently of the PyBoard and it write the data once ever loop. The motors are connected to the Arduino through motor controller circuits, that allow for easy reversal of direction. Each motor draws approximately 2 Amps of current going at full speed, which is why I will use PWM to slow them down and hopefully make them draw less current. The robot can turn in the water by counter rotating the two propellers on the end of it, can advance by turning them both on to turn the same direction, and can go up or down by rotating the propellers on the vertical axis in a certain direction. The grabber tool is simply a 3D printed attachment to a waterproof servo motor that can open or close depending what is sent through the PyBoard. The webcam s video is transmitted through the 30M of Ethernet cable after passing through the Ethernet to USB converter. The robot should have a final functional operational depth of approximately 5M but this can be improved by changing the material of the hull. 11
5. Discussion The work that is needed to put into the project is more than I anticipated, which accounts for the fact that there is only a prototype available now. But soon hopefully the entire project should be finished and all the files will be available for anyone to use and improve upon. The software is still proving a problem, especially trying to get communication through 30M of wire. The solutions I have come up to overcome this problem is changing the frequency of the I^2C signal, as the lower the frequency of the clock the better the signal should in theory transmit. If this fails I 12
might replace the Arduino with another python driven device as this allows for quicker troubleshooting in my opinion. If there is still a problem with the communication I will possibly try other solutions such as using SPI communication, but I will be forced to redesign major parts of my project. Even though the robot does require expensive tools to construct, these are becoming more and more available as time progresses, and even people without a 3D printer can order the parts from 3D printing services at a low price. The robot I believe is truly open to anyone willing to invest a bit of time into learning the Arduino C and python programming languages, and they are intuitive to use and hopefully my code should make it clear how to modify parts to suit your needs. The beauty of the design is that it can almost do anything, it has a 30M long length range, has a relatively high velocity due to the power and size of the motors, can be made extremely small, has a 5M depth rating and is modular, so anyone can add their own tools, edit the code and use the robot for their own scientific research in any water bodies, such as under ice for example, or inspecting the bottom of boats, or as I intend to use mine, monitoring marine life in Skagen harbour in Denmark where swimming is of course forbidden. The possibilities for it are practically endless and I would hope that at least one person would find my work useful or be inspired to build their own version of the ROV. Conclusion So far, I have stayed within the 200-euro budget, and I do not see myself overspending it. The project is in progress to be finished in an extremely short period and should function as expected. 6. Acknowledgements I would like to thank Mrs Schallhorn and of course Mr Theocharopoulos for their guidance and push to participate in the competition. I would also like to thank the community at the Brussels Fablab for their advice and help in using the machines available there. 7. References https://store.openrov.com/collections/openrov/products/openrov-v2-8-kit price of Open ROV accessed on the 15/02/2017 http://www.openspaceagency.com/ Open space agency website, accessed on the 15/02/2017 http://www.smithsonianmag.com/science-nature/why-we-must-explore-sea-180952763/ Article on the need to explore the sea, written by Robert D. Ballard, accessed on the 15/02/2017 13