A self-tuning guidance and control system for marine surface vessels
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O R I G I N A L PA P E R
A self-tuning guidance and control system for marine surface vessels Nassim Khaled · Nabil G. Chalhoub
Received: 25 November 2012 / Accepted: 18 February 2013 / Published online: 8 March 2013 © Springer Science+Business Media Dordrecht 2013
Abstract An integrated guidance and control system has been developed to enable underactuated marine surface vessels to operate autonomously and yield robust tracking performance in spite of significant external disturbances and modeling imprecision. A nonlinear ship model, accounting for all six degrees-offreedom of the ship, has been used as a test bed to assess the performance of the proposed scheme. The controller combines the advantages of the variable structure systems (VSS) theory with the self-tuning fuzzy logic scheme. It does not require an accurate dynamic model of the ship or the construction of a rulebased expert system. Its asymptotic stability is ensured by knowing the upper bounds on modeling imprecision and external disturbances and by forcing the tuning parameters to satisfy the sliding conditions. The guidance system is based on the concepts of the variable radius line-of-sight (LOS) and the acceptance circle around the waypoints. The current system varies the LOS radius exponentially with the cross track error in order to achieve a fast convergence rate of the ship to its desired trajectory. The simulation results demonstrate the robust tracking characteristic of the integrated guidance and control system in spite of sig-
N. Khaled () · N.G. Chalhoub Department of Mechanical Engineering, Wayne State University, 5050 Anthony Wayne Dr., Detroit, MI 48202, USA e-mail: [email protected]
nificant modeling uncertainties and environmental disturbances. Keywords Ship guidance system · Ship dynamics · Ship maneuvering and seakeeping · Robust nonlinear controller · Self-tuning controller · Fuzzy controller
1 Introduction Autonomous operation and robust performance of marine surface vessels are essential for minimizing human errors in ship navigation and control as well as for efficient operation of marine vessels under different sea states and harsh environmental conditions. This goal presents a formidable task due to the inherent nonlinearities of ship dynamics, modeling imprecision, underactuated ship configuration along with considerable and unpredictable environmental disturbances. In pursuing a specified trajectory, the surge, X, and sway, Y , displacements along with the heading angle, ψ, of the ship must accurately track their desired values (see Fig. 1). The challenge brought about by the underactuated configuration of the ship stems from the fact that only two actuators are available for controlling these three degrees-of-freedom. The propeller thrust is commonly used for controlling the surge speed of the ship. This will require the rudder action to control both the sway displacement and the heading angle. A plausible approach for empowering
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Fig. 1 Ship schematic
the rudder to simultaneously compensate for the sway
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