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장효환,전윤식,Chang, Hyo-Whan,Jun, Yoon-Sik 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.3
Shift quality of an automatic transmission in a vehicle is mainly affected by transient pressures in the hydraulic system during shifting. In this study, dynamic modelings of the hydraulic system and the power train of an automatic transmission are made systematically by a bond-graph method. The dynamic characteristics of the line pressures and clutch/brake pressures during shiftings are investigated by simulations and verified by experiments. The effects of clutch/brake pressures on the shift torque are also investigated through driving simulation.
가스보조식 이중행정 유압브레이커의 민감도 해석에 의한 성능 향상
류택직(Taek Jik Ryoo),장효환(Hyo Whan Chang) 유공압건설기계학회 2009 유공압건설기계학회 학술대회논문집 Vol.2009 No.11
A gas-assisted hydraulic breaker uses both hydraulic and pneumatic energies and an appropriate balance between two energies mostly effects its performance. Mathematical modeling of the breaker is established and verified by experiment. Through sensitivity analysis using AMESim, the key design parameters are selected and nearly optimized to maximize the output power as well as the impact energy for long and short strokes. As the results, the impact energy and output power are increased significantly compared with the current design. The dynamic characteristic of the piston displacement is also improved by the design change.
시뮬레이션에 기초한 엔진/브레이크 통합 TCS 제어 로직의 개발
장효환(Hyo-Whan Chang),송재복(Jae-Bok Song),김병철(Byong-Cheol Kim),김세윤(Sei-Yoon Kim) 한국자동차공학회 1999 한국 자동차공학회논문집 Vol.7 No.4
A traction control system (TCS) is the active safety system used to prevent the wheel slipping and thus improve acceleration performance, stability and steerability on slippery roads through the engine torque and/or brake torque control. While most TCS-equipped vehicles have either the engine-based TCS or the brake-based TCS, the engine/brake integrated TCS logic is developed mainly on a simulation basis in this research. The simul-ation involves not only the actual experimental data on the engine, powertrain and brake systems but also 7-DOF vehicle dynamics along with the nonlinear tire model and driver model. In order to compare the performance of 3 approaches of the TCS, various simulations have been carried out for the quick start-off conditions on both the uniform and split roads. The simulation results show that the engine/brake integrated TCS has better acceleration performance than the engine-based TCS and better steerability than the brake-based TCS.<br/>
ANFIS 기반 경로추종 운동제어에 의한 모형차량의 자동주차
장효환(Hyo Whan Chang),김창환(Chang Hwan Kim) Korean Society for Precision Engineering 2009 한국정밀공학회지 Vol.26 No.12
In this study an ANFIS-based trajectory tracking motion control algorithm is proposed for autonomous garage and parallel parking of a model car. The ANFIS controller is trained off-line using data set which obtained by Mandani fuzzy inference system and thereby the processing time decreases almost in half. The controller with a steering delay compensator is tuned through simulations performed under MATLAB/Simulink environment. Experiments are carried out with the model car for garage and parallel parking. The experimental results show that the trajectory tracking performance is satisfactory under various initial and road conditions.
전윤식,장효환,Jun, Yoon-Sik,Chang, Hyo-Whan 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.3
Most of feedback shift controllers developed in the past have fixed control parameters tuned by experts using a trial and error method. Therefore, those controllers cannot satisfy the best control performance under various driving conditions. To improve the shift quality under various driving conditions, a new self-organizing controller(SOC) that has an optimal control performance through self-learning of driving conditions and driver's pattern is designed in this study. The proposed SOC algorithm for the shift controller uses simple descent method and has less calculation time than complex fuzzy relation, thus makes real-time control passible. PCSV (Pressure Control Solenoid Valve) control current is used as a control input, and turbine speed of the torque converter is used indirectly to monitor the transient torque as a feedback signal, which is more convenient to use and economic than the torque signal measured directoly by a torque sensor. The results of computer simulations show that an apparent reduction of shift-transient torque is obtained through the process of each run without initial fuzzy rules and a good control performance in the shift-transient torque is also obtained.
퍼지 추론을 이용한 주차지원 시스템의 경로추종 운동제어
김승기(Seungki Kim),장효환(Hyo Whan Chang),김창환(Changhwan Kim) 한국자동차공학회 2009 한국 자동차공학회논문집 Vol.17 No.2
A parking-assist system is defined that a driver adjusts vehicle velocity through brake pedal operation and parking-assist system controls the motion of the vehicle to follow a collision-free path. In this study, a motion control algorithm using Fuzzy inference is proposed to track a maneuvering clothoid parallel path. Simulations are performed under SIMULINK environments using MATLAB and CarSim for a vehicle model. As the vehicle model in MATLAB a bicycle model is used including lateral dynamics. The simulation results show that the path tracking performance is satisfactory under various driving and initial conditions.
고층건물 시공자동화를 위한 다중 클라이밍 유압로봇의 운동 동기제어
홍윤석(Yun Suk Hong),장효환(Hyo Whan Chang) Korean Society for Precision Engineering 2009 한국정밀공학회지 Vol.26 No.9
Multi-climbing hydraulic robots are used to lift construction factory (CF) synchronously for applications in the automation of a high-rise building construction. In this study, synchronous motion controller is proposed for the hydraulic robots, whose strategy is not only to make each robot follow the reference path basically by sliding-mode control, but also to synchronize motions of two adjacent robots consecutively by cross-coupled control technique. Simulations are performed by using SIMULINK for a system similar to a practical application that includes unbalance in CF and wind disturbance. The results show that the proposed controller significantly reduces synchronous errors, compared to the individual controller for each hydraulic robot.