A Full Hydrodynamic Consideration in Control System Performance Analysis for an Autonomous Underwater Vehicle

Abstract

Autonomous underwater vehicles (AUVs) have important applications in several areas such as data collection, geological survey and exploration in underwater environment. The hydrodynamic forces acting on AUVs are highly nonlinear and the higher-order hydrodynamic coefficients should be taken into account to represent these nonlinear behaviors. Therefore, developing a suitable dynamic model of the AUV and also an accurate knowledge about the hydrodynamic parameters are important for proper design of the navigation and control system. The main goal of the present paper is to investigate the role of proper dynamic model for an AUV which includes different hydrodynamic stability derivatives coefficients. Design of proper actuator is also significant for the global performance of the system and the expenses of the plan. It is tried in the present paper to investigate the effect of full hydrodynamic coefficients on the design of actuators and control system performance analysis for an AUV which was ignored in the previous works. For this purpose, the effect of these parameters on the open loop characteristics of the AUV, its role in the control system design and the interaction of control system and actuator dynamics are considered in nonlinear time domain and frequency domain. It is shown that in a full hydrodynamic consideration for design of the AUV, the effect of control gains, system bandwidth and damping can be different in comparison with the cases which are not fully considered them. Finally, the design of optimum actuator and the effect of actuator natural frequency on the flight performance in the presence of full hydrodynamic coefficients are studied.