Contents I. Introduction
In recent years, there has been a growing interest in the development of advanced autonomous vehicles (AUVs) for operations at sea. Autonomous ocean vehicles allow access to otherwise unreachable regions and can, in principle, simplify the task of acquiring ocean data fast and cost effectively without placing human lives at risk. Envisioned missions include environmental monitoring, underwater inspection of estuaries and harbors, pipeline inspections, geological and biological surveys, marine habitat mapping, military applications, etc. Underwater vehicles performing coupled maneuvers at some speed are known to be highly nonlinear in their dynamics and kinematics [1]. In such cases, autopilots based on linear control theory can yield poor performance. It is a common assumption that linear control design is much simpler than its nonlinear counterpart. However, exploiting the structure of the nonlinear equations of motion often yields a relatively simple and intuitive nonlinear autopilot design. The approach used in this paper is based on the linear quadratic optimal design. This will involve the design of a control system for depth and course control in presence of waves.
