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The proportional and derivative (PD) and proportional, integral, and derivative (PID) controllers have been used extensively in industry due to their simplicity and effectiveness. This paper aims to investigate whether simple PD and adaptive PD-based controllers work for a complex system consisting of a group of multiple autonomous underwater vehicles (AUVs). Simple control laws with exact and uncertain gravity compensation are proposed for shape control of multiple AUVs. The proposed adaptive PD-based controller, in the presence of gravity uncertainty, requires only the model of gravity and buoyancy regressor matrix and does not require any knowledge of the inertia matrix, Coriolis and centripetal force, hydrodynamic damping and the parameters of the gravity, and buoyancy forces of the AUVs. Hence, the proposed controllers have the advantages of simplicity and ease of implementation. A novel collision and obstacle avoidance strategy using multi-layer region control concept, which limit the unnecessary use of high control efforts that lead to oscillatory movements of AUVs, is discussed. Lyapunov-like functions are proposed for the stability analysis. Simulation studies on AUVs with 6 degrees-of-freedom are presented to demonstrate the effectiveness of the proposed controllers.
Date of Publication: Sept. 2011