Adaptive Consensus Control of Multiple Underactuated Marine Surface Vessels with Input Saturation and Severe Uncertainties

This paper is devoted to the consensus control of a networked system constituted by multiple underactuated marine surface vessels (MSVs) with input saturation. Compared with the related works on this topic, two remarkable features are involved in the system under investigation: (1) Input saturation of each follower MSV is considered in the paper but ignored in most of the related works. (2) More coarse information is allowed about the network since more severer uncertainties (external disturbance joint with unknown system parameters) are involved in each follower MSV, and moreover, the output of the leader MSV is not necessarily second-order continuously differentiable while its time derivatives are not necessarily available for feedback. The above two aspects lead to the incapability of the traditional control schemes on this topic. To solve the control problem, a novel adaptive control scheme is proposed by adaptive dynamic compensation technique combining with certain methods for the handling of saturation input and under-actuation. Specifically, a smooth function is introduced to approximate the saturation input, by which and a couple of state transformations, a new system is obtained with a skillful injection of an auxiliary input for the handling of under-actuation. Then, an iterative procedure is given to derive an adaptive controller which ensures that all the signals of the closed-loop system are bounded while the output of the follower MSVs practically tracks that of the leader. Finally, simulation results are provided to validate the effectiveness of the proposed theoretical results.