The autonomous underwater vehicle developed in this research had an overarching goal of being significantly less expensive than other research and commercial platforms (less than AUS$10,000). It was also required to be small enough to be deployed from small boats, jetties or from the foreshore so to increase the ratio of operated vehicles to human operators to be greater than one.
The vehicle must be capable of autonomously performing the environmental monitoring tasks required by the reef monitoring organisations . The primary tasks to be performed are video transect surveys and water quality measurements. In order to achieve these tasks, the vehicle must be capable of navigating over highly unstructured surfaces at fixed altitudes (down to 300mm from sea floor) at depths in excess of 100m in cross currents of 2 knots. The required positional accuracy in linear transects must be less than 5% of total distance travelled to ensure repeatable transects.
In order to effectively navigate around this environment, the physical properties of the AUV must decrease in size and increase in manoeuvrability. Additionally, the size and power requirements of the sensor suite must decrease whilst still providing a speedy and efficient monitoring platform. It is also considered essential that the vehicle be untethered to reduce risk of entanglement, the need for support vessels and reducing drag imposed on the vehicle during strong currents.
Fig. The “Starbug” Autonomous Underwater Vehicle.
The vehicle design is a compromise between endurance, manoeuvrability and functionality. Endurance is best achieved with a streamlined torpedo style vehicle, however, this requires the vehicle to have longitudinal motion to obtain any control authority. Manoeuvrability is best achieved with the well actuated “crate” style vehicles typical of most deep sea and research platforms. These generally have control authority in multiple directions to allow station keeping although they are power hungry and consequently usually tethered. Both these style of vehicles have limited functionality away from research purposes.
The “Starbug” vehicle is a hybrid of these two concepts with extra design features added to increase the functionality of the platform through provisions for manipulators and scientific payloads.