In the presence of unmeasurable velocities and system uncertainties, the distributed formation control problem is investigated in this paper for multiple vessels. A robust formation controller is proposed by incorporating an extended state observer (ESO) and finite-time prescribed performance function (FTPPF). Firstly, a nonlinear ESO is designed to estimate the unmeasurable velocities and system uncertainties. Subsequently, a novel FTPPF is designed to improve the dynamic performance of multi-vessel formation systems, where the upper bound of the convergence time and the constraint bounds can be set in advance based on the actual circumstances. Then, the proposed ESO and FTPPF are applied to the distributed formation controller design for multiple vessels. The proposed formation control scheme can maintain the multiple vessels in an expected formation with high tracking accuracy, a faster convergence speed, and smaller fluctuations. Finally, the performance of the proposed control method is verified by theory analysis and simulations.
Huang, X.L.; Ren, Y.T.; Zhang, J.A.; Wang, D., and Liu, J.P., 2020. Dynamic scheduling optimization of marine oil spill emergency resource. In: Qiu, Y.; Zhu, H., and Fang, X. (eds.), Current Advancements in Marine and Coastal Research for Technological and Sociological Applications. Journal of Coastal Research, Special Issue No. 107, pp. 437-442. Coconut Creek (Florida), ISSN 0749-0208.With the increasing development of marine resources development and marine transportation, oil spill has become one of the main threats to marine ecological environment. Considering that the oil film has the characteristics of drift, this paper studies the oil spill emergency material scheduling problem with multiple oil films. Firstly, the position of oil film drifting with time under the influence of sea condition is calculated. Secondly, aiming at the shortest scheduling time and the lowest cost, the dynamic scheduling optimization model of oil spill emergency materials is constructed. The maximum threshold of emergency dispatch time is introduced to transform the model, and MPSO algorithm is designed to solve the model. The results show that the emergency materials can be transported to the accident site within the prescribed time, thus preventing the continuous diffusion of pollution. At the same time, it can avoid unnecessary waste and reduce economic loss. And it can provide the theoretical support for the decision-maker to make the emergency material dispatch plan.
This paper presents a novel extended state observer (ESO)-based line-of-sight guidance law for path following of underactuated marine surface vehicles in the presence of time-varying sideslip angle. A reduced-order ESO is employed to identify the vehicle sideslip angle caused by constant ocean disturbances when following a curved path or time-varying ocean disturbances. This guarantees that the sideslip angle can be timely and exactly estimated, and thus contributes to following the desired path with higher accuracy regardless of external disturbances induced by wind, waves, and ocean currents. The input-to-state stability of the closed-loop system is established via cascade theory. It is proven that the transient learning process can be shorten by increasing the bandwidth of the ESO. Both simulation and experimental results are provided to validate the effectiveness of the method.
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