Adatpive LQR control system for the nonlinear 4-DoF model of a container vessel

In the paper an adaptive Linear-Quadratic (LQR) control system for Multi-Input, Multi-Output (MIMO) nonlinear dynamic plants is presented. A nonlinear four-Degrees-of-Freedom (4-DoF) mathematical model of a singlescrew, high-speed container vessel is used as a MIMO plant. The main task of the proposed system is control the course angle and forward speed of the ship according to the changing hydrodynamic operating conditions. Due to the strongly nonlinear nature of the equations of the ship motions adaptive LQR controller is tuned according to the current operating point of the ship. The system synthesis is carried out by linearization of the nonlinear model of the ship at its nominal operating points in the steady-state. The final part of the paper includes results of simulation tests of the proposed control system carried out in the MATLAB/Simulink environment.