The main goal here is to design a proper and efficient controller for a ship autopilot based on the sliding mode control method. A hydrodynamic numerical model of CyberShip II including wave effects is applied to simulate the ship autopilot system by using time domain analysis. To compare the results similar research was conducted with the PD controller, which was adapted to the autopilot system. The differences in simulation results between two controllers are analyzed by a cost function composed of a heading angle error and rudder deflection either in calm water or in waves. Simulation results show the effectiveness of the method in the presence of nonlinearities and disturbances, and high performance of the proposed controller.
This paper presents the designs of two observers, which are: the extended Kalman filterand the nonlinear passive observer. Based on the measured values of ship position andheading, the observers estimate the surge, sway and yaw velocities of the ship motion.The observers make use of the simplified nonlinear mathematical model of ship motion inwhich the neglected ship dynamics and disturbances are modelled using bias. The designedobservers firstly have been simulated on a computer model where their parameters werecalibrated, and then were implemented on the physical model of the training ship “BlueLady” in the ship handling centre in Ilawa-Kamionka. The comparative analysis wasdone with respect to the estimated variables describing the ship motion in three directions: surge, swayand yaw
The dynamical positioning system is a complex control consisting of a number ofcomponents, including: filters, observers, controllers, and propeller allocation systems.The design and preliminary analysis of operational quality of system operation are usuallydone based on numerical simulations performed with the aid of the mathematical modelof the ship. The article presents a concept of the dynamic positioning system applied tosteering the training ship Blue Lady used for training captains in the ship handling researchand training centre owned by the Foundation for Safety of Navigation and EnvironmentProtection in Ilawa/Kamionka. The simulation tests performed in the numerical environmentof Matlab/Simulink have proved the usability of the designed system for steering a ship at low speed.
In cases when the navigational space of the manoeuvre performed by the ship is severely limited, the procedures making use of the rudder blade, propeller screw, and thrusters are very complicated. Such situations take place when the ship manoeuvres inside the harbour area and in those cases the structure of the control system is very complex. Te article describes the algorithm of multivariable control of ship motion over the water surface, which makes use of the state vector consisting of 6 variables. Tree of them, which are the position coordinates (x, y) measured by the DGPS system and the ship heading y measured by gyro-compass, were obtained experimentally. Te three remaining variables, which are the velocities in surge u, sway v, and yaw r directions, were estimated by Kalman filter, Kalman-Bucy filter and extended Kalman flter, respectively.
The control algorithms making use of these observers were examined using the training ship “Blue Lady” which was navigated on the lake Silm in Ilawa/Kamionka in the Ship Handling Research and Training Centre owned by the Foundation for Safety of Navigation and Environment Protection. Te experimental results obtained using control systems with three observers were finally compared between each other.
The paper presents the design of a hybrid controller used to control the movement of a ship in different operating modes, thereby improving the performance of basic maneuvers. This task requires integrating several operating modes, such as maneuvering the ship at low speeds, steering the ship at different speeds in the course or along the trajectory, and stopping the ship on the route. These modes are executed by five component controllers switched on and off by the supervisor depending on the type of operation performed. The desired route, containing the coordinates of waypoints and tasks performed along consecutive segments of the reference trajectory, is obtained by the supervisory system from the system operator. The former supports switching between component controllers and provides them with new set-points after each change in the reference trajectory segment, thereby ensuring stable operation of the entire hybrid switching controller.
The study also presents designs of all controller components, which are done using a complex mathematical model of the selected ship, after its simplification depending on the type of controller. The developed control system was tested on the training ship Blue Lady and used to train captains at the Ship Handling Research and Training Center near Iława in Poland.
The conducted research involved an automatic movement of the ship from one port to another. The performed transit route required the ship to leave the port, pass the water area, and berth at the port of destination. The study revealed good quality of the designed hybrid controller.
Anna Witkowska, Miroslaw Tomera and Roman Śmierzchalski
A Backstepping Approach to Ship Course Control
As an object of course control, the ship is characterised by a nonlinear function describing static manoeuvring characteristics that reflect the steady-state relation between the rudder deflection and the rate of turn of the hull. One of the methods which can be used for designing a nonlinear ship course controller is the backstepping method. It is used here for designing two configurations of nonlinear controllers, which are then applied to ship course control. The parameters of the obtained nonlinear control structures are tuned to optimise the operation of the control system. The optimisation is performed using genetic algorithms. The quality of operation of the designed control algorithms is checked in simulation tests performed on the mathematical model of a tanker. In order to obtain reference results to be used for comparison with those recorded for nonlinear controllers designed using the backstepping method, a control system with the PD controller is examined as well.