Our frame consist of aluminum angle bar linked together with custom corner brackets to create a cubic structure with plenty of space to mount the thrusters, cameras, and attachments.We are using re-bar weights and pool noodle foam to stabilize and balance the robot and keep it close to neutrally buoyant. The electronics canister houses all of our robot’s electronics and batteries.
The thrusters we selected are powered by a brushless DC motor which is inherently waterproof much unlike its counterpart the brushed DC motor. Being brushless, these motors require special motor controllers that convert constant DC voltage into the alternating signal that the motors are expecting. We are using blue robotics motor controllers.
The battery system consists of multiple custom Lithium Ion batteries with cells soldered together to meet the various current and voltage demands of the systems on the ROV. Each circuit is protected by a breaker that limits the power output of the battery to 1000W. In the case of a short circuit, the breaker will break the circuit to prevent hazardous current from leaving the battery.
Our camera system is composed of two cameras that work in parallax. One is aligned directly with the pitchfork, and one is centered to give us the best view when driving. The cameras send live video feed to the surface to allow the drivers to see what is happening underwater.
Onboard the robot, an Arduino Mega 2560 PRO seamlessly integrates peripherals into a unified code despite differing sensor protocols. The Arduino uses an ethernet module which connects to a router on the robot managing the PC to Arduino communication as well as two ethernet cameras.
To effectively operate and test our robot at the YMCA(5)we needed a compact system that could be transported easily and set up quickly. Blue robotics sells a tether and management spool for over $1000. We were able to recreate a similar spool and tether for around $60.
Our system to complete the rod task is composed of a pitchfork and arm. The pitchfork will skewer the rods and hold them to pull them out of the trashcan. Then the arm will grab the rods and pull them off the pitchfork to place them in their crate. The pitchfork is composed of three aluminum prongs and a 3D printed base piece. We designed the base to rest on top of the trashcan lid. This gives the robot stability in the vertical dimension. We also designed the pitchfork to have three prongs. If the robot tries to skewer a rod with the middle pitchfork prong, and we miss, the robot will skewer it with either the left or right prong.
The main arm has 3 degrees of freedom (two left-right joints and one rotating joint wrist joint).These joints are actuated with powerful servos.To waterproof them, we filled them with mineral oil and covered the seams with epoxy.The claw of the arm is designed to lock the rod into its grip. We used sandpaper to give our claw an incredible grip. The arm prototypes were made of standard PLA 3D print. However, for the final version, we are using waterproof resin print.
The sensor arm holds the temperature and ultrasonic distance sensor.The temperature sensor is housed in a cone to allow us to easily measure the temperature at the right depth and location.The ultrasonic sensor is mounted on the upper link so we can angle the sensor to point directly at the flag.This arm is made custom out of PLA 3D print and painted to be waterproof.
The canister is mounted on the robot using acrylic sheets cut to the curvature of the exterior, cradling it while two hose clamps wrap around the whole outside and loop over hooks mounted to the frame. The wires that exit the canister needed to be waterproof where they join the wall, at the connection points, and along the length of the wires. Special underwater connecters were ordered and tested and mounted to the back in this configuration(3). They are removable connection points so the canister’s location could be changed throughout the design process, but also water tight and secure so no damage to the electronics inside occurs.
Dr Kohl, who acted as our team’s technical advisor, was a huge help to us in figuring out how to do a lot of the work with the Arduino and the sensors. Dr George, who acted as our team’s official advisor, was very helpful in figuring out some of the waterproofing, and how to exist underwater, as well as all of the fundraising. Various other professors at Cedarville University(4), notably Dr Dewhurst and Fredette, were also a big help to our team in answering questions where their expertise lies. Dr. Fredette helped us print the arm out of resin.A special thank you to each of our sponsors, and to Jared’s grandmother, without whom we would not have been able to afford many of the components on our robot or competition travel cost.
Team Sponsors:
