Autonomous Underwater Vehicle Altitude Keeping to Variable Seabed with a Coupled Variable Ballast and Hydroplane Control System
The thesis objective is to develop a control approach that enables variable ballast systems (VBS) to be used in tandem with hydroplanes (HP) on an autonomous underwater vehicle (AUV). Methods to reduce power consumption of VBS are investigated and a AUV simulator is developed to explore where VBS proves beneficial. The VBS model includes capacity for free flow of seawater into and out of the ballast tank. This function combined air support allowed for four VBS control modes: static volume, expanded volume, high-pressure air assist and regenerative pressure assisted with the last mode requiring the least power. Using pitch and depth feedback as inputs to the HP and VBS controllers, HP responded before the VBS reacted making it ineffective. A new control was developed using HP deflection angle as inputs to the VBS with a low-pass filter. The simulations showed this control approach performed favorably in multiple scenarios.