The semi-pelagic trawl is a relatively advanced trawl system which is mainly adopted to catch demersal fish such as squid and butterfish. Now aiming at improving its security in a complex working environment, this paper proposes a three-dimensional tracking control system for the guidance of a semi-pelagic trawl on a complicated trajectory. A new simplified mass-spring-barmodel is presented and the movement of the trawl system can be described by a group of state space equations. Then, a hierarchical backstepping controller is designed for the trajectory tracking of the trawl net and two otter boards. To obtain the control instruction of the whole system, the state space model is divided into six subsystems. The principle of system division is that the lower-order subsystem stabilization is rely on the next higher-order subsystem. However, high-order state variables caused by the non-strict feedback characteristic of the trawl system appear frequently in recursive processes. Hence, a control algorithm based on the Sigmoid function is applied to construct the control outputs of these high-order variables. This method is called as "S-plane control" ,which partly embodies the idea of fuzzy control.And its essential similarities of PD control can effectively ensure the effect of motion control.The stability of the proposed hybrid control method is analyzed based on the Lyapunov theorem when interference with an unknown upper limit occurs. Finally, the simulation results show the superiority and effectiveness of the proposed control approach.
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Reference: Yan, Z.; et al (2016). A Parallel Hybrid Controller based on the Backstepping Method and S-plane Control for Three-dimensional Tracking of a Semi-pelagic Trawl System. The Open Cybernetics & Systemics Journal., DOI: 10.2174/1874110X01610010180
Faizan ul Haq
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