Ship track-keeping: experiments with a physical tanker model

doi:10.1016/S0967-0661(98)00082-3

Control Engineering Practice

Volume 6, Issue 6, 1 June 1998, Pages 763-769

https://doi.org/10.1016/S0967-0661(98)00082-3 Get rights and content

Abstract

Two autopilots for ship track-keeping along a given trajectory are presented, namely a linear quadratic output feedback controller and a robust cascade controller. In both of them, the rudder is used as the only control actuator. The paper presents the mathematical foundation of the problem, the filtering techniques applied in its solution, and selected results of the simulations carried out on a physical ship model on the Silm Lake.

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Cited by (39)

Collision avoidance for autonomous surface vessels using novel artificial potential fields
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As the demand for transportation through waterways continues to rise, the number of vessels plying the waters has correspondingly increased. This has resulted in a greater number of accidents and collisions between ships, some of which lead to significant loss of life and financial losses. Research has shown that human error is a major factor responsible for such incidents. The maritime industry is constantly exploring newer approaches to autonomy to mitigate this issue. This study presents the use of novel Artificial Potential Fields (APFs) to perform obstacle and collision avoidance in marine environments. This study highlights the advantage of harmonic functions over traditional functions in modeling potential fields. With a modification, the method is extended to effectively avoid dynamic obstacles while adhering to COLREGs. Improved performance is observed as compared to the traditional potential fields and also against the popular velocity obstacle approach. A comprehensive statistical analysis is also performed through Monte Carlo simulations in different congested environments that emulate real traffic conditions to demonstrate robustness of the approach.
Experimental investigation of practical autopilots for maritime autonomous surface ships in shallow water
2020, Ocean Engineering
To evaluate the performance of autopilots in real scenarios for maritime autonomous surface ships (MASS), this article investigates four autopilots via the experimental study instead of the theoretical analysis and discusses their application capabilities. Free running model tests with four autopilot algorithms were performed using a scale model of a Liquefied Natural Gas (LNG) carrier in the towing tank at Flanders Hydraulics Research (FHR), and they were tested at different forward speeds and Under Keel Clearances (UKCs) focusing on the autopilot performance in shallow water. Furthermore, an innovative method combining the model evaluation mechanism and the grey relational decision-making theory was proposed to comprehensively evaluate the performance of autopilots. Finally, we discussed the application potential of the autopilots for controlling a surface ship in shallow water and presented shallow water effects on autopilots’ performance. The four autopilots presented in this research could successfully follow the desired trajectories with satisfactory control effects in shallow water, but their performance varied in different scenarios. Our results indicate the tested controllers can be applied in the towing tank, but for optimum selection of autopilot algorithms, we should take into consideration multiple factors including controller parameters, trajectory, and test condition, etc.
Experimental and numerical study of autopilot using Extended Kalman Filter trained neural networks for surface vessels
2020, International Journal of Naval Architecture and Ocean Engineering
Citation Excerpt :
The physical model is a 1:100 scaled replica of the ‘M/V Nedlloyd: Hoorn’ (the main characteristics are outlined in Table 1), whose hydrodynamic design and loading condition follow the properties of the full scale ship. The geometric, kinetic and dynamic similarity principles were preserved to guarantee that experiments results can be further referred to real objects (Morawski and Pomirski, 1998). In this section, the configurations of the ship and the four Degree of Freedom (DOF) motion equations are presented.
Due to the nonlinearity and environmental uncertainties, the design of the ship's steering controller is a long-term challenge. The purpose of this study is to design an intelligent autopilot based on Extended Kalman Filter (EKF) trained Radial Basis Function Neural Network (RBFNN) control algorithm. The newly developed free running model scaled surface vessel was employed to execute the motion control experiments. After describing the design of the EKF trained RBFNN autopilot, the performances of the proposed control system were investigated by conducting experiments using the physical model on lake and simulations using the corresponding mathematical model. The results demonstrate that the developed control system is feasible to be used for the ship's motion control in the presences of environmental disturbances. Moreover, in comparison with the Back-Propagation (BP) neural networks and Proportional-Derivative (PD) based control methods, the EKF RBFNN based control method shows better performance regarding course keeping and trajectory tracking.
Unscented Kalman Filter trained neural network control design for ship autopilot with experimental and numerical approaches
2019, Applied Ocean Research
Citation Excerpt :
The hull was constructed of fabric glass with the geometric, kinetic and hydrodynamic similarity principles fully preserved. Thus, the results of hydrodynamic and control investigations can be recalculated to refer to real objects using the known relations [33]. The main particulars of the scaled model are outlined in Table 1.
In the recent decades, the application and research of unmanned surface vessels are experiencing considerable growth, which have caused the demands of intelligent autopilots to grow along with the ever-growing requirements. In this study, the design of an autopilot based on Unscented Kalman Filter (UKF) trained Radial Basis Function Neural Networks (RBFNN) was presented. In particular, in order to provide satisfactory control performance for surface vessels with random external disturbances, the modified UKF was utilised as the weights training mechanism for the RBFNN based controller. The configurations of the newly developed free running scaled model, as well as the online signal processing method, were introduced to enable the experimental studies. The experimental and numerical tests were carried out through using the physical scaled model and corresponding mathematical model to validate the capability of the designed control system under various sailing conditions. The results indicated that the UKF RBFNN based autopilot satisfied the functionalities of course keeping, course changing and trajectory tracking only using the rudder as the actuator. It was concluded that the developed control scheme was effective to track the desired states and robust against unpredictable external disturbances. Moreover, in comparison with Back-Propagation (BP) RBFNN and Proportional-Derivative (PD) based autopilots, the UKF RBFNN based autopilot has the comparable capability in the aspects of providing smooth and effective control laws.
Iterative lead compensation control of nonlinear marine vessels manoeuvring models
2014, Applied Ocean Research
Citation Excerpt :
However, for high speed applications, tight turns, large sideslip angles or in the presence of currents, nonlinear effects become pronounced and thus neglecting them may degrade the controller's performance and robustness. On the other hand, different nonlinear methods [10] have been presented for course-keeping autopilot's design such as state feedback linearization [12], nonlinear backstepping [2,38], sliding mode control [20], output feedback [21], H∞-control [16], particle swarm optimization [31], genetic algorithms [20], fuzzy logic methods [5], etc. For most of these type of applications, nonlinear manoeuvring models in 1 degree of freedom (DOF) are considered, see [25] or [3] as example, still in these contributions, the coupling existing between the various variables is obviously not taken into account.
This paper addresses the problem of control design and implementation for a nonlinear marine vessel manoeuvring model. The authors consider a highly nonlinear vessel 4 DOF model as the basis of this work. The control algorithm here proposed consists of a combination of two methodologies: (i) an iteration technique that approximates the original nonlinear model by a sequence of linear time varying equations whose solution converge to the solution of the original nonlinear problem and (ii) a lead compensation design in which for each of the iterated linear time varying system generated, the controller is optimized at each time on the interval for better tracking performance. The control designed for the last iteration is then applied to the original nonlinear problem.
Simulations and results here presented show a good performance of the approximation methodology and also an accurate tracking for certain manoeuvring cases under the control of the designed lead controller. The main characteristic of the nonlinear system's response is the reduction of the settling time and the elimination of the steady state error and overshoot.
Experiment on track-keeping performance using free running model ship
2013, IFAC Proceedings Volumes (IFAC-PapersOnline)
This research presents an analysis of algorithm for ship track-keeping along a given trajectory. The maneuver of a free running model ship guiding through a simple path are presented. In order to solve the problem above, a desired trajectory is usually determined by GPS points in a pre-fixed place then these points are set in a pre-programmed navigation so that the ship would be automatically tracked. Proportional-Derivative (PD) control which is useful for fast response controllers was used in this program as a course keeping system. A high accuracy GPS receiver was installed on the model ship that could provide positions frequently, the system will compare and give out the remaining distance and heading to the target way-point. The results of ship auto track-keeping experiment will be explained in order to illustrate the adjustment in controlling parameters. These results can be utilized as a step to carry out the experiment of ship collision avoidance system and automatic berthing in the future.

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