Robust ¥ H and μ -Synthesis Controller Design for an Underwater Unmanned Vehicle

The ever-developing trend of Underwater Unmanned Vehicles’ applications for operations such as environmental data gathering as well as inspection and assembly of underwater structures has arisen a major need and has recently received a great deal of attention by control designers. Highly nonlinear dynamics and enormous uncertainties as a result of poor knowledge of hydrodynamic coefficients as well as the effect of unmeasurable disturbances like underwater ocean currents has challenged the designers in devising a suitable controller for these vehicles. In this paper the objective is to design a controller for the linearized model having an acceptable performance despite the disturbance caused by the ocean current and also being capable of robustly stabilizing the closed-loop system in the presence of uncertainty due to unmodelled dynamics. To achieve this goal two controllers using Hinfinity and Mu-synthesis approaches have been designed. Finally by implementing the designedcontrollers to the nonlinear model, they have been evaluated and compared in the presence of disturbance. Simulations confirmed the efficiency of the designed controllers. Both controllers exhibited a good performance and an acceptable speed of response for a typical ROV mission.

Keywords:

H-Infinity , Mu-Synthesis , Remotely operated Vehicle