Abstract
Unexpected severe hull deformation caused by the wave loads would significantly influence the dynamical behaviours of the propulsion system in large scale ships, resulting in degradation of the ship control performance. A new global sliding model control (GSMC) for marine water-hull-propulsion unit systems is proposed to obtain more accurate control performance in this paper. The GSMC was firstly employed to establish the marine propulsion control model with nonlinear uncertainties. In the GSMC model, the saturation function method is applied to eliminate chattering on the sliding surface. Then the Lyapunov stability criterion is adopted to confirm the stability of the control system. Following, for the first time, the boundary problem of the nonlinear model uncertainties were investigated quantitatively. The bounded nonlinear model uncertainties required in the proposed GSMC model, involving engine torque loss / variations, power transfer for various load conditions and shaft rotational speeds, were derived based on the experiments carried out on a marine shaft-line test-bed of the integrated propulsion system as well as a sea trial implemented for a running bulk carrier. An upper boundary of 1,85 % for the model uncertainty has been obtained, which would be introduced into the GSMC for the integrated marine propulsion system to derive the total control law realising the robust control of the system
Highlights
The control of marine propulsion systems considering hull deformations has attracted a great attention due to the important effects of the propulsion system – hull interactions on the dynamic characteristic of the propulsion unit
There are many difficulties for a traditional Proportional Integral Derivative (PID) controller to obtain the desired performance of marine propulsion systems [1, 3] while involving some inevitable uncertainties caused by the complex water – propeller – hull interactions
In order to develop a practicable tool for a high performance control of the marine propulsion system, it is crucial to investigate the boundaries of the model uncertainties of the marine propulsion system caused by interactions between the water, hull and propulsion unit, from which a good estimation of the upper boundary of the system uncertainties can be obtained to design a stable and effective sliding mode control (SMC) controller for the robust control of the marine propulsion system
Summary
The control of marine propulsion systems considering hull deformations has attracted a great attention due to the important effects of the propulsion system – hull interactions on the dynamic characteristic of the propulsion unit. In order to develop a practicable tool for a high performance control of the marine propulsion system, it is crucial to investigate the boundaries of the model uncertainties of the marine propulsion system caused by interactions between the water, hull and propulsion unit, from which a good estimation of the upper boundary of the system uncertainties can be obtained to design a stable and effective SMC controller for the robust control of the marine propulsion system. The parameters ks and ζ are determined by the wave loads outside the ship, which means all the variations and uncertainties of the propulsion system are caused or induced by the external stochastic excitations, through the interaction of the water, ship hull and propulsion system This coupled effect between the water, ship hull and propulsion system attributes to the particular operation environment of the ship in the sea. ∂ζ [21], we firstly rewrite (1) into the following form:
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