A method of multi-dimensional variable structure system synthesis for the control of autonomous underwater vehicle spatial motion is developed. The velocity controller based on the sliding mode properties is synthesised in order to compensate the arbitrary variations of control object parameters and dynamical coupling between the vehicle degrees of mobility. A special nonlinear correcting device is offered for the underwater vehicle position control. This device allows to compensate the kinematic correlations between its degrees of mobility. The efficiency of synthesised control system is confirmed by numerical simulation results.


Recently the development of underwater robotics is one of priority directions in the field of World ocean research. Requirements to autonomous underwater vehicles (AUV) control systems are increased in accordance with the complications of the tasks solved by these objects. So, the control system should provide precise AUV motion on a given spatial trajectory in order to execute composite manoeuvres in a working area. In other cases (at operation of manipulator, for example) the precise positioning of the underwater vehicle in a given point of space with compensation of all external perturbances is required. Numerous factors render essential influence on control system operation quality in the indicated modes, such as a prior uncertainty and significant changes of AUV inertia and hydrodynamic characteristics, a strong dynamical coupling and kinematic correlations between degrees of mobility and uncontrollable external perturbances of a viscous environment. All this factors connected with nonlinearity, nonstationarity and multiconnectivity of the underwater vehicle dynamic model. The traditional linear regulators do not provide given control quality in the given situation. Moreover system in whole frequently loses serviceability. It induces the investigators to access to principles and methods of the adaptive and robust control theory (Slotine and Li, 1991; Ramadorai and Tarn, 1993).

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