Modelling and simulation of a robust energy efficient AUV controller

Limited on-board energy resources of autonomous underwater vehicles (AUVs) demand design of an appropriate controller to achieve optimal energy consumption while tracking a commanded path accurately for some envisaged applications. The unstructured oceanic environment calls for a robust control law which is capable of handling parametric uncertainties and environmental disturbances. Though switching surface control has been proven to be an effective strategy for underwater operations, it provides no scope for energy optimization. For an energy critical mission, it is desirable to minimize the net control effort through advanced mathematical modelling, even at the cost of compromising accuracy within a reasonable bound. With this aspect in mind, the present work addresses these two issues (i.e. energy and accuracy) together through design of a novel controller based on sliding mode control in association with Euler–Lagrange based classical optimal control. Mathematical modelling and simulation results are presented to demonstrate the effectiveness of the proposed controller with real life parameters of an experimentally validated AUV, designed and developed for 150 m depth of operation at sea.