A nonlinear H-∞ controller for autonomous underwater vehicles

This paper presents a six degree-of-freedom nonlinear H-_∞ controller for autonomous underwater vehicles. The controller makes use of Euler parameters, or unit quaternion, which have been used extensively with spacecraft and aircraft as opposed to the more popular Euler angle representation. Euler angles suffer as with other 3-parameter representations from singular points. One of the main challenges associated with designing an underwater control is the unknowns of the model. The nonlinear H-_∞ controller attempts to address this problem such that the closed loop system has L₂ - gain ≤ γ from torque disturbances to a penalty variable for a fixed positive constant γ.