• Journal of the Korean Society for Precision Engineering
• /
• v.17 no.11
• /
• pp.115-121
• /
• 2000

In this paper, track tension estimation methods are developed for tracked vehicles which are subject to various maneuvering tasks such as turning and pivoting on flat road. The information of the track tension is very important for the tracked vehicles because the track tension is closely related to the maneuverability and the durability of the tracked vehicles. Kinetic models for the six road-wheels are obtained and used for calculating the track tension around the sprocket. This method does not require the tuning of the turning resistance, which makes it difficult to estimate the track tension in turning. The tension estimation performance of the proposed methods is verified through the simulation of the Multi-body Dynamics tool. The simulation results demonstrate the effectiveness of the proposed method under steering and pivoting of the tracked vehicles.

• Journal of Institute of Control, Robotics and Systems
• /
• v.2 no.2
• /
• pp.121-126
• /
• 1996

The hydrodynamic coefficients estimation (HCE) is important to design the autopilot and to predict the maneuverability of an underwater vehicle. In this paper, a system identification is proposed for an HCE of an underwater vehicle. First, we attempt to design the HCE algorithm which is insensitive to initial conditions and has good convergence, and which enables the estimation of the coefficents by using measured displacements only. Second, the sensor and measurement system which gauges the data from the full scale trials is constructed and the data smoothing algorithm is also designed to filter the noise due to irregular fluid flow without changing the data characteristics itself. Lastly the hydrodynamic coefficients are estimated by applying the measured data of full scale trials to the developed algorithm, and the estimated coefficients are verified by full scale trials.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.59 no.3
• /
• pp.261-263
• /
• 2023

Recently, universities of fisheries and institutions related to fisheries are actively carrying out a project to build new fisheries training ships. These new fisheries training ships are significantly larger in size and longer in length than the previous ships. In addition, these new ships basically have space that can accommodate more than 100 crew and passenger. On the other hand, they are excluded from IMO maneuverability evaluation since the size of these ships are still less than 100 m in length (LBP). These results have had an impact on the study of maneuverability of fishing vessels including the fisheries training ships. Against these backgrounds, the authors conducted a study to estimate the maneuvering characteristics of fisheries training ship Baek-Kyung according to depth in order to prepare a maneuvering characteristic index that enables the large fisheries training ships to navigate more safely using a modified empirical formula. It was confirmed that the maneuvering characteristics of Baek-Kyung changed significantly as the values of the hydrodynamic force coefficients changed as the water depth gradually decreased from around 1.5 (approx. 8 m in depth) of the ratio of the water depth to the ship draft. The results of this study will not only help navigators understand the maneuvering characteristics of Baek-Kyung, but also serve as an indicator when navigating in shallow water. In addition, the accumulation of these results will serve as a basis for future study on maneuverability of fishing vessel types.

• Journal of Ocean Engineering and Technology
• /
• v.32 no.5
• /
• pp.386-392
• /
• 2018

It is necessary to predict hydrodynamic derivatives when assessing the maneuverability of a submarine. The force and moment acting on the vehicle may affect its motion in various modes. Conventionally, the derivatives are determined by performing captive model tests in a towing tank or applying a system identification method to the free running model test. However, a computational fluid dynamics (CFD) method has also become a possible tool to predict the hydrodynamics. In this study, virtual captive model tests for a full-scale submarine were conducted by utilizing a Reynolds-averaged Navier-Stokes solver in ANSYS FLUENT version 18.2. The simulations were carried out at design speed for various modes of motion such as straight forward, drift, angle of attack, deflection of the rudder, circular, and combined motion. The hydrodynamic force and moment acting on the submarine appended rudders and stern stabilizers were then obtained. Finally, hydrodynamic derivatives were determined, and these could be used for evaluating the maneuvering characteristics of the submarine in a further study.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• v.5 no.4
• /
• pp.316-321
• /
• 2005

We designed and implemented fish robots for various purposes such as autonomous navigation, maneuverability control, posture balancing and improvement of quick turns in a tank of 120 X 120 X 180cm size. Typically, fish robots have 30-50 X 15-25 X 10-20cm dimensions; length, width and height, respectively. It is essential to have the ability of quick and smooth turning to avoid collision with obstacles or walls of the water pool at a close distance. Infrared distance sensors are used to detect obstacles, magneto-resistive sensors are used to read direction information, and a two-axis accelerometer is mounted to compensate output of direction sensors. Because of the swing action of its head due to the tail fin movement, the outputs of an infrared distance sensor contain a huge amount of noise around true distances. With the information from accelerometers and e-compass, much improved distance data can be obtained by fuzzy logic based estimation. Successful swimming and smooth turns without collision demonstrated the effectiveness of the distance estimation.

• Journal of the Society of Naval Architects of Korea
• /
• v.57 no.5
• /
• pp.287-296
• /
• 2020

The present study aims to improve the accuracy of the maneuvering simulations based on captive model test results. To derive the hydrodynamic coefficients in a self-propelled condition, a mathematical maneuvering model using a whole vehicle model was established. Captive model tests were carried out using the Vertical Planar Motion Mechanism (VPMM) equipment. A motor controller was used to control the constant propeller revolution rate during pure motion tests. The resistance tests, self-propulsion tests, static drift tests, and VPMM tests were performed in the towing tank of Seoul National University. When the vertical drift angle changes, the gravity load on the sensors were changed. The hydrodynamic forces were deduced by subtracting the gravity load from the measured forces. The hydrodynamic coefficients were calculated using the least-square method. The simulation of the turning circle test was compared with the free-running model test result, and the error of the turning radius was 8.3 % compared to the free-running model test.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.8 no.4
• /
• pp.169-176
• /
• 2000

Longitudinal and lateral forces acting on tires are known to be closely related to the tract-ability braking characteristics handling stability and maneuverability of ground vehicles. In thie paper in order to develop tire force monitoring systems a monitoring model is proposed utilizing not only the vehicle dynamics but also the roll motion. Based on the monitoring model three monitoring systems are developed to estimate the tire force acting on each tire. Two monitoring systems are designed utilizing the conventional estimation techniques such as SMO(Sliding Mode Observer) and EKF(Extended Kalman Filter). An additional monitoring system is designed based on a new SKFMEC(Scaled Kalman Filter with Model Error Compensator) technique which is developed to improve the performance of EKF method. Tire force estimation performance of the three monitoring systems is compared in the Matlab simulations where true tire force data is generated from a 14 DOF vehicle model with the combined-slip Magic Formula tire model. The built in our Lab. simulation results show that the SKFMEC method gives the best performance when the driving and road conditions are perturbed.

• 한국기계연구소 소보
• /
• s.10
• /
• pp.35-48
• /
• 1983

When the hydrodynamic coefficients of the ship maneuvering equation are estimated by captive model test, it is difficult to take account of the scale effect between model and full scale ship. This scale effect problem can be overcome by processing the sea trial data with system identification. Extended Kalman filter is used as a system identification technique for the modification of the simulation equation as well as the estimation of hydrodynamic coefficients. The phenomena of simultaneous drifting of linear coefficients occur. It is confirmed that two coefficients in each pair-($Y_v$', $Y_r$' -m' u'), ($N_v$', $N_r$' )-are simultaneously drifting and all 4 coefficients are simultaneously drifting together. Particularly simultaneous drifting of 2 coefficients in each pair is more significant. It is also shown that the simultaneous drifting of 4 coefficients can be reduced by choosing the input data which have the random v'/r' curve and 4 coefficients are estimated within 2-4% error, which may be noise level. So, it is recommended to operate the rudder randomly in sea trial or model test for the application of system identification technique.

• Journal of the Society of Naval Architects of Korea
• /
• v.43 no.1 s.145
• /
• pp.50-58
• /
• 2006

Free running model tests gives us only maneuvering indices not hydrodynamic derivatives. For this reason, system identification method has been applied to the measured data to identify mathematical model describing hydrodynamic force. However It is difficult to obtain complete set of maneuvering derivatives because of strong correlation of sway velocity and yaw rate. Therefore, in this paper, we assumed that sway velocity related coefficients would be obtained by oblique towing test. and then proposed new procedure to estimate yaw related coefficients. To do this, correlation and regression analyses were carried out to establish modified model and estimate maneuvering derivatives. Also D-optimal rudder input scenario was found based on the modified model and confirmed the validity of its sufficient richness as a input scenario.

• Journal of Navigation and Port Research
• /
• v.38 no.1
• /
• pp.11-18
• /
• 2014

To confirm whether the square tank at Changwon National University (CWNU) can be used for estimation of maneuverability, planar motion mechanism (PMM) test and circular motion (CM) test were performed for various conditions. PMM test can be implemented using an XY carriage and a yaw table in the square tank. However, sometimes test section is insufficient for PMM test owing to low length-breadth ratio of the tank. In addition, the speed of a towing carriage is also quite limited. Therefore, it would be useful if PMM test could be effectively performed diagonally, by establishing coupled control logic to drive three servomotors. In addition, Froude number dependency on the estimated hydrodynamic coefficients was checked. Furthermore, CM tests, which cannot be completed in a conventional linear towing tank, were performed, and its results were compared with the results of PMM test. The results of the PMM tests in the diagonal direction were consistent with the results of the test performed in the direction parallel to the sidewall. However, the results of the CM test were greater than those of the PMM test. This tendency was also observed in the results published at Ulsan University.