• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.32 no.2
• /
• pp.126-131
• /
• 2010

Objectives: This study is aimed to determine any differences in the postoperative stability between absorbable and titanium plate systems for fixation in orthognathic surgery with simultaneous maxillomandibular procedures especially including maxillary posterior impaction and advancement. Study Design: Forty patients with dentofacial deformities were randomly assigned into titanium (4 males and 6 females) and absorbable (17 males and 13 females) fixation group. All patients had undergone surgical alterations of maxilla with posterior impaction and advancement. A comparison study of the change in the maxillary position after the simultaneous surgery was performed with 1-day, 6-months postoperative lateral cephalograms compared to preoperative lateral cephalogram by tracing. Wilcoxon rank sum test was used for statistical analysis. Result: The position of the maxilla was stable after surgery and was not changed significantly from 1 day to 6 month after the simultaneous maxillomandibular surgery both in the experimental (absorbable plates) and control (titanium plates). Conclusion: This study suggests that application of absorable plating system in the fixation of maxillary segment in the simultaneous maxillomandibular procedures, leads to a predictable short-term postoperative skeletal stability comparable to the titanium plating system. Long term follow-up and further studies will be needed.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.10a
• /
• pp.1157-1166
• /
• 2008

Critical surcharge value of silt ground polluted with garbage leachate to the dyes $q_{cr}=3.73c_u$ and ultimate bearing capacity value $q_{ult}=8.60c_u$. Lateral flow pressure at polluted silt ground was about $P_{max}$/3 and depth of maximum lateral flow pressure was found at that of H/3 of soft layer thickness(H). Expression of polluted silt ground of fracture baseline at stability control charge by Matsuo Kawamura is $S_v=3.56\exp\{0.51(Y_m/S_v)\}$.

• Journal of Mechanical Science and Technology
• /
• v.17 no.5
• /
• pp.654-667
• /
• 2003

This paper presents a consequence of the systematic approach to identify the aerodynamic parameters of an unmanned aerial vehicle (UAV) equipped with the automatic flight control system. A 3-2-1-1 excitation is applied for the longitudinal mode while a multi-step input is applied for lateral/directional excitation. Optimal time step for excitation is sought to provide the broad input bandwidth. A fully automated programmed flight test method provides high-quality flight data for system identification using the flight control computer with longitudinal and lateral/directional autopilots, which enable the separation of each motion during the flight test. The accuracy of the longitudinal system identification is improved by an additional use of the closed-loop flight test data. A constrained optimization scheme is applied to estimate the aerodynamic coefficients that best describe the time response of the vehicle. An appropriate weighting function is introduced to balance the flight modes. As a result, concurrent system models are obtained for a wide envelope of both longitudinal and lateral/directional flight maneuvers while maintaining the physical meanings of each parameter.

• International Journal of Aeronautical and Space Sciences
• /
• v.15 no.4
• /
• pp.412-418
• /
• 2014

This paper describes the development of variable stability system (VSS) control laws for the KFA-i to simulate the dynamics of KFA-m aircraft. The KFA-i is a single engine, Class IV aircraft and was selected as an in-flight simulator (IFS) aircraft, whereas the KFA-m is a simulated aircraft that is based on the F-16 aircraft. A 6-DoF math model of KFA-i aircraft was developed, linearized, and separated into longitudinal and lateral motion for VSS control law synthesis. The KFA-i aircraft has five primary control surfaces: two flaperons, two all movable horizontal tails, and one rudder. Flaperons are used for load control, the horizontal tails are used for pitch and roll rate control, and the rudder is used for yaw rate control. The developed VSS control law can simulate four parameters of the KFA-m aircraft simultaneously, such as pitch, roll, yaw rates, and load. The simulation results show that KFA-i follows the responses of KFA-m with high accuracy.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.03a
• /
• pp.1094-1103
• /
• 2010

The safety of pile foundation is getting declined when the pile foundation acting on lateral load is exposed by dredging. So appropriate reinforcement is needed for stability secure. Thus, in this study, the stability variation and reinforcement range caused by dredging is estimated on the basis of down scale test. The scale effect is determined by real scale numerical analysis. the behavior of pile by dredging stages is estimated by load control type. The credibility is verified through the comparison between down scale model test and numerical analysis.

• ETRI Journal
• /
• v.37 no.3
• /
• pp.617-625
• /
• 2015

In this paper, a steering control system for the path tracking of autonomous vehicles is described. The steering control system consists of a path tracker and primitive driver. The path tracker generates the desired steering angle by using the look-ahead distance, vehicle heading, and a lateral offset. A method for applying an autonomous vehicle to path tracking is an advanced pure pursuit method that can reduce cutting corners, which is a weakness of the pure pursuit method. The steering controller controls the steering actuator to follow the desired steering angle. A servo motor is installed to control the steering handle, and it can transmit the steering force using a belt and pulley. We designed a steering controller that is applied to a proportional integral differential controller. However, because of a dead band, the path tracking performance and stability of autonomous vehicles are reduced. To overcome the dead band, a dead band compensator was developed. As a result of the compensator, the path tracking performance and stability are improved.

• 제어로봇시스템학회:학술대회논문집
• /
• 1989.10a
• /
• pp.499-502
• /
• 1989

This paper is concerned with the stability analysis and the design of an auto pilot using direct model reference adaptive control for BTT missile with unknown dynamics when subjected to the longitudinal and lateral gusts. A motion of BTT missile can be separated into the longtudinal and lateral motione. The proposed algorithm is introduced different leakage terms about each motion into adaptation so as to prevent drift of the adaptive gain and alleviate gust effects and cross-coupling. The algorithm is applied to the 6DOF motion of an EMRAAT missile.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.14 no.4
• /
• pp.174-180
• /
• 2006

The wheel slip control systems are able to control the braking force more accurately and can be adapted to different vehicles more easily than conventional braking control systems. In order to achieve the superior braking performance through the wheel slip control, real-time information such as the tire braking force at each wheel is required. In addition, the optimal target slip values need to be determined depending on the braking objectives such as minimum braking distance, stability enhancement, etc. In this paper, a wheel slip control system is developed for maintaining the vehicle stability based on the braking monitor, wheel slip controller and optimal target slip assignment algorithm. The braking monitor estimates the tire braking force, lateral tire force and brake disk-pad friction coefficient utilizing the extended Kalman filter. The wheel slip controller is designed based on the sliding mode control method. The target slip assignment algorithm is proposed to maintain the vehicle stability based on the direct yaw moment controller and fuzzy logic. The performance of the proposed wheel slip control system is verified in simulations and demonstrates the effectiveness of the wheel slip control in various road conditions.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.167.1-167
• /
• 2001

Although computational-fluid-dynamic methods and wind-tunnel testing can provide data about the aerodynamic characteristics of an aircraft, the determination of these and other characteristics from flight data plays and important role. The object of this study is the verification of overall aircraft system performance to improve the stability of vehicle. We have test the Velocity-173, canard-type airplane to obtain the stability data. We adopt the two identifications method, EKF and MLE, for the parameter estimation. The results are compared with those of conventional type airplane.

• Journal of the Korean Society for Railway
• /
• v.4 no.1
• /
• pp.1-8
• /
• 2001

In this paper, the dynamics and stability of the automated guideway transit (AGT) vehicles with rubber tires are investigated. Two types of AGT systems are considered: the bogie-type and steering-type systems. The critical speeds for the dynamic instability of lateral and yawing motions are investigated by use of the Routh-Hurwitz's stability criterion. It is shown that the bogie-type AGT vehicles are likely to be stable within the range of practical operating speed, whereas it is not true for the steering-type AGT vehicles. It is also shown that the control performance of steering-type AGT vehicles can be improved by choosing proper steering gains of the closed-loop steering control system.