For both of these competitions, the mission the vessel must complete involves several tasks. Two required tasks are a thrust test, and a demonstration of navigation and control, which requires the vessel to navigate through two gates marked by a pair of colored buoys each. The mission tasks primarily include an obstacle detection and avoidance field, symbol recognition and automated docking, and underwater acoustic localization. The vessel also needs to be able to communicate with a server run by the judges to relay vital mission information, as well as to ensure normal operation for safety.
Villanova’s primary means of environmental sensing on the vessel is with a sensor fusion between a scanning LIDAR (a rotating laser sensor used to measure distances), and a video camera to capture color information. The LIDAR is a planar scanner, so it is gimbaled to provide a vertical field of view. The fusion is done through the use of a pin-hole camera model and coordinate transform, and allows for color information to be read from objects segmented by the depth field, or depth information to be read from objects segmented by color information.
The vessel needs to be able to process all the sensor data and make navigational decisions at a continuous dependable rate without delays to ensure the stability of the controller. A Speedgoat Mobile real-time target machine is used for this.
Without proper timing the control algorithm could easily overshoot or oscillate, or run commands that are not up to date with the current mission criteria. The target machine also has I/O for analog and digital signals, and several serial connections for the various sensors on the vessel, including inertial measurement unit, GPS, compass, and communicating with parallel processors such as Raspberry Pi’s and Arduinos.