While water is all around us in the form of oceans, lakes and rivers, only 2.5 percent of it is freshwater. Furthermore, only 1 percent of that freshwater is accessible, the rest being trapped in glaciers and ice caps. This small amount of water has the huge responsibility of meeting the needs of all living creatures on the planet. With freshwater supply quickly diminishing, it's more important than ever to ensure that the water that we do have is pure, clean, and available for human use. Clean water also affects many animals, whether they drink the water itself or live in it as a habitat. Identifying bodies of water that are polluted is an area of great importance as we go forward in securing our world’s water sources.
Remotely Operated Vehicles (ROVs) are the perfect robotic applications to detect marine pollution in hard-to-reach places in bodies of water. ROVs extend the capability of human divers and allow us to detect pollution and concentrate efforts where they’re needed. However, existing ROVs are either expensive, multi-million dollar scientific systems designed for deep sea navigation or cheap, inefficient systems that are ill-adapted for targeted pollutant detection. A lot of people would agree that underwater pollutants are a huge problem, but the state of current technology puts practical ROV systems that can tackle these problems out of reach for communities that need it the most.
Rogue Robotics aims to start a worldwide crowdsourcing campaign in utilizing low-cost, self-assembled ROVs to detect underwater pollution in local communities.
The World-Changing Underwater ROV
There are a few other low-cost ROV systems available for use, but Volturnus has a unique focus on underwater pollution and implementing cheap ways to detect it. Volturnus is designed with a philosophy of minimalism: Volturnus implements a few features but implements them well. Thus, Volturnus has the benefits of expensive ROVs, but also remains affordable. Not only does this result in an effective, uncluttered design, but it allows for users around the world to easily construct and modify their own devices. Volturnus may not be perfectly adapted to every single aquatic situation around the world, but by opening up the technology to any many people as possible, Volturnus has the potential to spark similar innovations across the globe.
- We began by researching various material types that can be used for the frame. Finding the best material requires finding an appropriate balance between performance and cost, as our goal is to develop an efficient apparatus accessible to the public. We summarized our research into a decision matrix.
Table 1. Decision matrix for frame material selection
Ease of Use
- After deciding on using PVC piping, we discussed the ideal frame shape and size. We wanted to keep dimensions and weight to a minimum, as a smaller vehicle maneuvers more easily through water. We also placed a high emphasis on simplicity because simple designs are easier to develop and troubleshoot. The mechanics team sketched the frame layout on graph paper, including locations of thrusters, cameras, and tether attachments. We ultimately decided on a simple four motor orthogonal structure that maximizes space within the frame.
- We then created a CAD model of our proposed frame in Autodesk Inventor. Creating a CAD model prior to construction allows us to visualize the design and confirm the idea is achievable. We first created individual Inventor parts, including 90 degree elbows, tee connectors, and PVC pipes of specific dimensions. We assembled the parts together based off of sketches, making sure to leave space for the gap between PVC pipes in connectors. Final dimensions did not exceed 12” x 12” x 18”.
- When we completed the CAD model, we created a list of parts to purchase for actual construction, including part name, quantity, and size. All PVC piping had 0.5” interior diameter to ensure consistency.
- After purchasing necessary components from Lowe’s, we worked on frame assembly. We marked a 10 ft. long PVC pipe with the appropriate dimensions and used a dremel to cut along our markings and smooth out the surfaces of uneven cuts. We joined the parts according to the CAD model, with elbow connectors to form corners and tee connectors to mount motors and cameras. Once we were sure that we could assemble the ROV in the time span that the PVC cement took to dry, PVC cement was applied to all connections to ensure a permanent bond.
Volturnus has three thrusters mounted orthogonally for three actuated degrees of freedom: surge, heave, and yaw. This gives it the necessary maneuverability for a versatile deployment strategy while maintaining mechanical simplicity for powerful movement. The minimalist design means that low-cost bilge pump motors with attached propellers are able to provide sufficient thrust for the ROV.
To keep electronics as simple, affordable, and accessible as possible, Volturnus’s electronic components are done entirely topside. This is made possible through a minimalist design and control scheme, allowing power to all the thrusters and claw to be delivered through cables inserted into a single lightweight tether.
The primary purpose of the electronics on our ROV is to take input from a program and use this input to control the motors. First, the Arduino microcontroller reads pulse width modulation (PWM) inputs from two joysticks that act as potentiometers. In addition, the orientation of the joysticks tells the motors whether to turn clockwise or counter-clockwise. The Arduino then sends data signals to L298n motor controllers. These serve two purposes. For one, they can be used as h-bridges which can output a negative and positive voltage so that the motors can turn both ways. Secondly, they take in a PWM signal ranging from 0 to 255 so that it can output any voltage from 0 to 12 volts. Initially problems arose as we tried to ensure that the motor controllers could handle the current drawn by the motors. We had to do calculations using Kirchhoff's Law to calculate the current drawn from and the voltage needed for the motors. We then had to measure these values in practice using a multi-meter. After this we tested our circuit and we found that it gave the robot the ability to turn and move forwards, backwards, and laterally at varied speeds.
The ROV uses a single IP68 waterproof car backup camera for underwater vision. ROV cameras are extremely important, as they are the primary and sometimes sole reference available to the pilot when navigating underwater. If multiple cameras are used or if a single camera is combined with a known reference or laser, it can additionally be used to take distance measurements underwater.
The car backup camera is connected to a USB video capture card, which is then plugged into the operator’s laptop. The operator then runs a Python script to reverse the camera feed (since the camera feed is inverted due to its design as a car backup camera) and displays the camera feed in a pygame window directly on the laptop.
Water Contamination Detection
Ultraviolet light is able to detect OBAs (Optical Brightening Agents), chemicals that are commonly used in cleaning products. OBAs are often swept into the environment when products containing these chemicals are disposed improperly (i.e. poured directly into the sink); such chemicals can cause widespread damage. By using a cost efficient absorbent material, like cotton, the ROV is able to collect samples of liquid from bodies of water that may be tested for concentrations of OBAs. The OBAs are best detected after the sampler absorbent material is dried, as the chemical would not be diluted by the presence of water and other substances.
Table 2. Budget for Volturnus ROV Materials
PVC (frame and tether waterproofing) + cement
(4) 500 GPH motors + propellers
110.00 (80.00 + 30.00)
Waterproof connectors (strain relief + tether waterproofing)
Backup Car Camera
L298N Motor controllers
Arduino - 11.00
L298N - 13.00
USB joystick / XBOX controller (re-used)