design and simulation of fuzzy sliding mode control of roll angular position of warship, in presence of structured uncertainties and external disturbances caused by sea waves

One way to stabilize a ship in the face of nonlinear movements in the direction of the roll is to control the fins. Due to the completely non-linear dynamics of the movement in the direction of the ship's roll angle, as well as considering the structural uncertainties and external disturbances caused by the sea waves, it is not easy to extract an accurate dynamic model. Therefore, it is difficult to design a system-based controller that, with optimal performance, applies the appropriate force as a control input to the fins and overcomes the stated structural and non-structural uncertainties. A common way to control such unreliable nonlinear systems is to use nonlinear resistant control. Control of the immersion model is one of the most widely used nonlinear resistive control methods that can overcome these uncertainties, but this control method in the practical implementation stage has disadvantages such as vibration at the control input. In this paper, in order to eliminate the undesirable phenomenon of control input vibration, the control of the immersion model is combined with the Takagi-Sugno-Kang fuzzy system. The controller of the obtained fuzzy immersion model has the advantages of controlling the immersive model and also in its implementation, there is no trace of the phenomenon of control input vibration. As a case study, in order to demonstrate the optimal performance of the proposed controllers, a favorable and challenging optimal path for the position of the roll angle has been considered and the controllers of the immersion model and fuzzy immersion model have been implemented and simulated on a warship.