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차량의 롤-피치 거동 일체감 향상을 위한 차고 조절 시스템 제어로직 개발
조완기,길한별,유승한 한국자동차공학회 2023 한국 자동차공학회논문집 Vol.31 No.2
This paper describes a new control logic to improve the pitch and roll motion of a vehicle based on the vehicle’s height adjustment system. The proposed control logic consists of a vehicle observer to estimate vehicle states, a target vehicle motion, a vehicle controller, and an optimal distributor. The target vehicle motion determines the target roll angle and pitch angle. To achieve these target motions, the vehicle controller determines the roll and pitch angles to be added, respectively. These control inputs can be generated by the vehicle height adjustment system in the optimal distributor. To consider the performance limitation of the system and tunability, the optimal distributor is developed through an optimization method. Simulation tests were conducted to investigate the performance of the proposed control system in an asphalt road.
DYNAMICAL EVOLUTION OF SUPERNOVA REMNANTS BREAKING THROUGH MOLECULAR CLOUDS
조완기,김종수,구본철 한국천문학회 2015 Journal of The Korean Astronomical Society Vol.48 No.2
We carry out three-dimensional hydrodynamic simulations of the supernova remnants (SNRs) produced inside molecular clouds (MCs) near their surface using the HLL code \citep{har83}. We explore the dynamical evolution and the X-ray morphology of SNRs after breaking through the MC surface for ranges of the explosion depths below the surface and the density ratios of the clouds to the intercloud media (ICM). We find that if an SNR breaks out through an MC surface in its Sedov stage, the outermost dense shell of the remnant is divided into several layers. The divided layers are subject to the Rayleigh-Taylor instability and fragmented. On the other hand, if an SNR breaks through an MC after the remnant enters the snowplow phase, the radiative shell is not divided to layers. We also compare the predictions of previous analytic solutions for the expansion of SNRs in stratified media with our one-dimensional simulations. Moreover, we produce synthetic X-ray surface brightness in order to research the center-bright X-ray morphology shown in thermal composite SNRs. In the late stages, a breakout SNR shows the center-bright X-ray morphology inside an MC in our results. We apply our model to the observational results of the X-ray morphology of the thermal composite SNR 3C 391.
차량의 횡 안정성 제어를 위한 노면 마찰계수 추정에 관한 연구
조완기,유승진,유승한 한국자동차공학회 2023 한국 자동차공학회논문집 Vol.31 No.12
This paper describes a method of estimating the tire-road friction coefficient used in vehicle lateral stability control. The estimated tire-road friction coefficient is used to calculate a target yaw rate to maintain vehicle lateral stability control. The tire-road friction coefficient used for the target yaw rate should be estimated at a constant value, though there might be some errors, rather than accurately estimating the current road status. The estimation algorithm is developed by integrating two estimation methods: estimation based on the magnitude of the current lateral acceleration, and estimation applied with the Bayesian tracking method. To apply the Bayesian tracking method, the yaw rate calculated by the current lateral acceleration and the reference yaw rates for each tire-road friction coefficient are used. Simulation tests using Carmaker and Matlab/Simulink are then conducted to study the feasibility and performance of the proposed estimation algorithm under various road conditions.
조완기,나호용,전창준,유승한 대한기계학회 2022 大韓機械學會論文集A Vol.46 No.11
Recently, consumer demands for driving convenience and performance are gradually increasing in the off-road driving conditions of SUVs. However, because the mass-produced traction control system (TCS) and cruise control (CC) functions do not specifically consider rough road conditions, a lack of convenience and performance exists in current vehicles under the driving conditions. In the proposed study, a four-wheel independent longitudinal force integrated control was developed to control the vehicle speed to the driver’s set speed while minimizing wheel slips on the rough road with slope. The proposed logics consist of an estimation module such as a velocity estimation part and vehicle roll/pitch estimation part, driving/braking torque calculation part for speed control, and four-wheel driving/braking torque distribution part. The effectiveness of proposed control algorithms was verified through CARSIM simulation analysis, and the robustness against the vehicle mass variation was secured in the various rough road conditions. 최근 SUV 차량의 off-road 주행 조건에서 운전자 조작 편의성과 주행 성능에 대한 소비자 요구가 점차 높아지고 있다. 하지만, 기존의 TCS(traction control system), CC(cruise control) 기능들은 특별히 험로 경사 주행에 초점을 맞춰 개발되지 않았기 때문에 해당 주행 조건에서 다소 조작편의성 및 성능 상의 부족함이 존재한다. 제안 연구에서는 저속 험로 경사 주행 조건에 특화하여 차량이 운전자 설정 목표 속도로 휠 슬립을 최소화하며 자동으로 추종제어하도록 하는 4륜 독립 제동/구동력 통합제어를 개발하였다. 제안 기술은 속도 추정부, 롤/피치각 추정부 등의 추정부와 견실한 종방향 속도 제어를 위한 앞먹임/되먹임 토크 산출부, 4륜 제구동 토크 분배부로 구성된다. Carism 시뮬레이션 해석을 통해 제안 제어 로직의 효과가 검증되었고 다양한 기울기의 험로 경사 조건에서 차량 질량 변동에 대한 로직의 견실성도 확보되는 것을 확인하였다.