A Comparison of Optimization Algorithms: An Assessment of Hydrodynamic Coefficients

Daewon Kim 해양환경안전학회 2018 해양환경안전학회지 Vol.24 No.3

This study compares optimization algorithms for efficient estimations of ship's hydrodynamic coefficients. Two constrained algorithms, the interior point and the sequential quadratic programming, are compared for the estimation. Mathematical optimization is designed to get optimal hydrodynamic coefficients for modelling a ship, and benchmark data are collected from sea trials of a training ship. A calibration for environmental influence and a sensitivity analysis for efficiency are carried out prior to implementing the optimization. The optimization is composed of three steps considering correlation between coefficients and manoeuvre characteristics. Manoeuvre characteristics of simulation results for both sets of optimized coefficients are close to each other, and they are also fit to the benchmark data. However, this similarity interferes with the comparison, and it is supposed that optimization conditions, such as designed variables and constraints, are not sufficient to compare them strictly. An enhanced optimization with additional sea trial measurement data should be carried out in future studies.

Estimating Hydrodynamic Coefficients of Real Ships Using AIS Data and Support Vector Regression

VU HOANG THIEN,박종열,윤현규 한국해양공학회 2023 韓國海洋工學會誌 Vol.37 No.5

In response to the complexity and time demands of conventional methods for estimating the hydrodynamic coefficients, this study aims to revolutionize ship maneuvering analysis by utilizing automatic identification system (AIS) data and the Support Vector Regression (SVR) algorithm. The AIS data were collected and processed to remove outliers and impute missing values. The rate of turn (ROT), speed over ground (SOG), course over ground (COG) and heading (HDG) in AIS data were used to calculate the rudder angle and ship velocity components, which were then used as training data for a regression model. The accuracy and efficiency of the algorithm were validated by comparing SVR-based estimated hydrodynamic coefficients and the original hydrodynamic coefficients of the Mariner class vessel. The validated SVR algorithm was then applied to estimate the hydrodynamic coefficients for real ships using AIS data. The turning circle test was simulated from calculated hydrodynamic coefficients and compared with the AIS data. The research results demonstrate the effectiveness of the SVR model in accurately estimating the hydrodynamic coefficients from the AIS data. In conclusion, this study proposes the viability of employing SVR model and AIS data for accurately estimating the hydrodynamic coefficients. It offers a practical approach to ship maneuvering prediction and control in the maritime industry.

Analysis on Hydrodynamic Force Acting on a Catamaran at Low Speed Using RANS Numerical Method

Thi Loan Mai,Tien Thua Nguyen,Myungjun Jeon,Hyeon Kyu Yoon 한국항해항만학회 2020 한국항해항만학회지 Vol.44 No.2

This paper discusses the hydrodynamic characteristics of a catamaran at low speed. In this study, the Delft 372 catamaran model was selected as the target hull to analyze the hydrodynamic characteristics by using the RANS (Reynold-Averaged Navier-Stokes) numerical method. First, the turbulence study and mesh independent study were conducted to select the appropriate method for numerical calculation. The numerical method for the CFD (Computational Fluid Dynamic) calculation was verified by comparing the hydrodynamic force with that obtained experimentally at high speed condition and it rendered a good agreement. Second, the virtual captive model test for a catamaran at low speed was conducted using the verified method. The drift test with drift angle 0-180 degrees was performed and the resulting hydrodynamic forces were compared with the trends of other ship types. Also, the pure rotating test and yaw rotating test proposed by Takashina, (1986) were conducted. The Fourier coefficients obtained from the measured hydrodynamic force were compared with those of other ship types. Conversely, pure sway test and pure yaw test also were simulated to obtain added mass coefficients. By analyzing these results, the hydrodynamic coefficients of the catamaran at low speed were estimated. Finally, the maneuvering simulation in low speed conditions was performed by using the estimated hydrodynamic coefficients.

A Comparison of Optimization Algorithms: An Assessment of Hydrodynamic Coefficients

Kim, Daewon The Korean Society of Marine Environment and safet 2018 海洋環境安全學會誌 Vol.24 No.3

This study compares optimization algorithms for efficient estimations of ship's hydrodynamic coefficients. Two constrained algorithms, the interior point and the sequential quadratic programming, are compared for the estimation. Mathematical optimization is designed to get optimal hydrodynamic coefficients for modelling a ship, and benchmark data are collected from sea trials of a training ship. A calibration for environmental influence and a sensitivity analysis for efficiency are carried out prior to implementing the optimization. The optimization is composed of three steps considering correlation between coefficients and manoeuvre characteristics. Manoeuvre characteristics of simulation results for both sets of optimized coefficients are close to each other, and they are also fit to the benchmark data. However, this similarity interferes with the comparison, and it is supposed that optimization conditions, such as designed variables and constraints, are not sufficient to compare them strictly. An enhanced optimization with additional sea trial measurement data should be carried out in future studies.

A Comparison of Optimization Algorithms: An Assessment of Hydrodynamic Coefficients

김대원 해양환경안전학회 2018 해양환경안전학회지 Vol.24 No.3

This study compares optimization algorithms for efficient estimations of ship's hydrodynamic coefficients. Two constrained algorithms, the interior point and the sequential quadratic programming, are compared for the estimation. Mathematical optimization is designed to get optimal hydrodynamic coefficients for modelling a ship, and benchmark data are collected from sea trials of a training ship. A calibration for environmental influence and a sensitivity analysis for efficiency are carried out prior to implementing the optimization. The optimization is composed of three steps considering correlation between coefficients and manoeuvre characteristics. Manoeuvre characteristics of simulation results for both sets of optimized coefficients are close to each other, and they are also fit to the benchmark data. However, this similarity interferes with the comparison, and it is supposed that optimization conditions, such as designed variables and constraints, are not sufficient to compare them strictly. An enhanced optimization with additional sea trial measurement data should be carried out in future studies.

Disc-type Underwater Glider Modeling and Analysis for Omnidirectional and Steering Motion Characteristics

Han Zhou,Tianlin Wang,Li Sun,Xiang Jin 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.1

A disc-type underwater glider (DTUG) has a highly symmetrical full-wing shape that allows it to moveomnidirectionally and have the same hydrodynamic characteristics in all directions in the horizontal plane. Thesecharacteristics make the viscous hydrodynamic coefficients measured by conventional methods unsuitable for simulating the omnidirectional and steering motions of the DTUG. To further reveal the omnidirectional and steeringmotion characteristics of the DTUG, this paper proposes a new theoretical method for calculating the DTUG motion control equations in the velocity frame rather than the body frame. Based on the structural characteristics ofthe DTUG, the motion control equations are derived and then solved using the fourth-order Runge-Kutta method. The omnidirectional and steering motions of the DTUG are simulated in the velocity frame and compared withthe results calculated in the body frame. The results show that the viscous hydrodynamic coefficients obtained byconventional methods are not suitable for analyzing the omnidirectional motion of the DTUG, and the method ofcalculating the motion control equations in the body frame has limitations in studying the steering motion. The newmethod proposed in this paper solves these limitations well and can more accurately reveal the motion characteristics of the DTUG without recalculating the hydrodynamic coefficients. The results also show that the DTUG canchange the heading angle more easily than a torpedo-type underwater glider (TTUG), and the steering radius ismuch smaller, which means that the DTUG has greater flexibility in a small body of water. The DTUG can remainstable when the control variables are within the control range and the new method is adopted.

Controller design for an autonomous underwater vehicle using nonlinear observers

Negahdaripour, Shahriar,Cho, So-Hyung,Kim, Joon-Young Korean Society of Ocean Engineers 2011 International journal of ocean system engineering Vol.1 No.1

The depth and heading control of an autonomous underwater vehicle (AUV) are considered to follow the predetermined depth and heading angle. The proposed control algorithm was based on a sliding mode control, using estimated hydrodynamic coefficients. The hydrodynamic coefficients were estimated employing conventional nonlinear observer techniques, such as sliding mode observer and extended Kalman filter. Using the estimated coefficients, a sliding mode controller was constructed for a combined diving and steering maneuver. The simulated results of the proposed control system were compared with those of a control system that employed true coefficients. This paper demonstrated the proposed control system, and discusses the mechanisms that make the system stable and accurately follow the desired depth and heading angle in the presence of parameter uncertainty.

Hydroelastic Response of VLFS with Submerged-Plate Using Modified Hydrodynamic Coefficients

Sang-Min Lee 한국항해항만학회 2007 한국항해항만학회지 Vol.31 No.7

The primary objective of this study is to present a modified method of hydroelastic analysis and application of it to the VLFS with submerged plate. The modal analysis method is applied to the VLFS with the submerged plate using the modified hydrodynamic coefficients. Namely, the wave exciting forces are modified by the transmission wave coefficients, while the interaction factor is used for the modification of radiation forces. To validate the proposed method, comparisons between the numerical calculations and experimental data taoe been carried out for the deflections of VLFS, and it shows good agreement between the calculation and experiment. The results presented in this study demonstrate that the elastic response of the VLFS is strongly affected by the hydrodynamic interaction induced by the submerged plate. As a result, we can confirm that the submerged plate is useful for reducing the hydroelastic deflection of VLFS, and the proposed method is valuable for predicting the elastic response of VLFS with attached the submerged plate.

Controller Design for an Autonomous Underwater Vehicle Using Estimated Hydrodynamic Coefficients

JOON-YOUNG KIM 한국해양공학회 2006 韓國海洋工學會誌 Vol.20 No.6

Depth and heading control of an AUV are considered to follow the predetermined depth and heading angle. The proposed control algorithm is designed. based on a sliding mode control using estimated hydrodynamic coefficients. The hydrodynamic coefficients are estimated with conventional nonlinear observer techniques, such as sliding mode observer and extended Kalman filter. By using the estimated coefficients, a sliding mode controller is constructed for the combined diving and steering maneuver. The simulation results of the proposed control system are compared with those of control system with true coefficients. This paper demonstrates the proposed control system, discusses the mechanisms that make the system stable and follows the desired depth and heading angle, accurately, in the presence of parameter uncertainty.

Hydroelastic Response of VLFS with Submerged-Plate Using Modified Hydrodynamic Coefficients

Lee, Sang-Min Korean Institute of Navigation and Port Research 2007 한국항해항만학회지 Vol.31 No.7

The primary objective of this study is to present a modified method of hydroelastic analysis and application of it to the VLFS with submerged plate. The modal analysis method is applied to the VLFS with the submerged plate using the modified hydrodynamic coefficients. Namely, the wave exciting forces are modified by the transmission wave coefficients, while the interaction factor is used for the modification of radiation forces. To validate the proposed method, comparisons between the numerical calculations and experimental data have been carried out for the deflections of VLFS, and it shows good agreement between the calculation and experiment. The results presented in this study demonstrate that the elastic response of the VLFS is strongly affected by the hydrodynamic interaction induced by the submerged plate. As a result, we can confirm that the submerged plate is useful for reducing the hydroelastic deflection of VLFS, and the proposed method is valuable for predicting the elastic response of VLFS with attached the submerged plate.