Adaptive fuzzy logic depth controller for variable buoyancy system of autonomous underwater vehicles

This paper presents an adaptive fuzzy logic controller for the variable buoyancy system (VBS) of an autonomous underwater vehicle (AUV). The control structure includes a fuzzy large range depth controller (LRDC) and a fuzzy small range depth controller (SRDC). The depth controllers bring the AUV to a desired depth by decreasing buoyancy, then descending to the desired depth and then restoring neutral buoyancy. Fuzzy rules adaptively determine the critical depth points for ballast adjustment based on a key parameter of the AUV dynamic model. This paper gives an explanation of the fuzzy rule base for the LRDC and presents preliminary simulation results of the LRDC