North Carolina State University
2023-2024 Welcome to PEP: Slide deck
This strong team of engineering students described their journey best in this After-Action report:
At North Carolina State University, our goal for our first season in Promoting Electric Propulsion was to create a boat capable of competing in the competition while developing a strong foundation for future teams. To do this we split the project into separate subsystems for each operation in the boat. The major systems were power, controls, hull, and propulsion. Each system had at least a leader and support assigned to them and together we worked as a team to put our subsystems together to make a functioning RC boat.
The power system is made up of two lithium ion batteries in parallel, operating at 25V. There are three primary cutoff switches. There are two physical switches on the boat. The first cuts power to everything on the boat. The second switch cuts power output from the flight controller to the gate of our MOSFETs. The third switch is a remote cutoff that turns off that same flight controller power output. All three switches must be turned on in order for the motors to receive power. This redundancy allows us to turn on the controller and ensure it is connected while being able to safely put the boat in the water with no risk of the motors turning on.
Our controller system is an SIYI MK15 remote control with a Kakute H7V2 flight controller. The remote control was chosen because it came with a compatible camera and receiver setup. It was long range to ensure we would not lose connection and was easily configurable from the controller itself. The flight controller was chosen because of its compatibility with Ardupilot Mission Planner and its controllable output port. We wanted to use Mission Planner because of our professor's recommendation and if we got ahead during the semester, we intended to make the boat autonomous.The flight controller had a 9V 3A output port and could take in power directly from the batteries we were using. Since this port was able to be turned off from the controller we used it as a cut off for high risk systems, like the motors and water cooling.
Our boat has a fiberglass hull (52" x 15") and is in the semi-deep Vee shape. There are two internal bulkheads (made from Lauan Plywood Underlayment) that divide the boat interior into three sections. The front section houses the pumps and reservoir for the cooling system; the larger, middle section houses the batteries and electronics (flight controller, batteries/BMS, receiver, etc); the rear section houses the ESCs, motors, servos (controlling rudders). The top cover that seals the boat is also made from Lauan Plywood Underlayment. The top side of the cover is triple coated with marine grade epoxy while the bottom side is only single coated. The top cover is secured to the hull via fiberglass cloth tape soaked in marine grade epoxy. There are three waterproof inspection hatches (one for each section) for accessing internal components. Lastly, we have a custom built, carbon fiber antenna mast for mounting the antennas.
Propulsion and Rudder System:
- Two Turnigy XK2674-2200KV 1750w Brushless DC Inrunner RC Boat Motors (centrally located at the stern) mounted with marine epoxy.
- Two 120A Turnigy Marine ESCs mounted to the rear bulkhead in close proximity to the motors.
- Two aluminum rudders (110mm) mounted on the outside of the motors.
- Two waterproof 20KG Digital Servos (internally located at the stern) for controlling rudders position.
Throughout our year-long project, we were only able to test on the water towards the end a week before the race. Despite our many attempts to get the boat out in the water earlier, we kept facing breakages in the power system, the water proofing, as well as unfortunate weather conditions. We were able to test, run, and troubleshoot all of the systems alone and together throughout the year, although not in the water. From an electrical standpoint, we expected the boat to go all five miles. We had never experienced any issues with the current batteries and had built the batteries to supply full power to the system for the 30 minutes. From our propulsion calculations we expected to be able to finish the race in around 20 minutes. Also from our testing, we expected all the electronics to be safe from water because we had tested the waterproofing extensively. Given there were no mechanicals failures, we were hopeful for race day. During our testing we did encounter issues with some screws being loose, primarily the ones attaching the propellers to the drive shaft and holding the rudders in place. We tightened these up, but unfortunately during the race some of the screws inside the boat, attaching the motor to the drive shaft came loose. This ultimately resulted in the motor disconnecting and we could only spin the right motor around half a mile. Although not the result we were hoping for, we were able to keep all parts and electronics intact, there was no water damage to any of the components, and we can pass everything on to the next team.
Congratulations on a year of strong design, great teamwork, and careful integration!
NC State at PEP 23
Visit to NC State on April 14