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김도태(Dotae Kim),장중걸(Zhong Jie Zhang) 한국자동차공학회 2013 한국 자동차공학회논문집 Vol.21 No.6
This paper studies the comparative analysis on two different internal cushion devices (the types of needle and relief valve) used to absorb the energy which is generated when the pneumatic cylinder moves with the load at meter-out speed control system. The effect at varying the piston velocity under same driving condition is mainly investigated. The simulation results on pressure in the cushion chamber and the dynamic behavior of the relief valve type cushion device are compared with the needle valve type. Design and performance are improved with the cushion configuration of better quality at high-speed pneumatic cylinder. Based on the relation between absorbed energy and impact energy at cushion process, cushion performance at pneumatic cylinder is evaluated.
김도태(Dotae Kim) 한국자동차공학회 2007 한국 자동차공학회논문집 Vol.15 No.6
In this paper, automotive hydraulic pipeline systems are modeled in which a straight blocked pipe, two pipes with sudden expansion or contraction are connected in series and terminated with a chamber. The frequency response characteristics of these composite pipeline systems are investigated experimentally. The theoretical analysis for various pipe configurations is base on transfer matrix method with frequency dependent viscous friction distributed parameter pipeline model. The gain and phase of transfer functions are included for comparison with experimental results. There is close agreement between the results of experimental and theoretical determination of pressure response in automotive hydraulic pipeline systems.
고속 공기압 실린더용 릴리프밸브형 쿠션기구의 특성 해석
김도태(Dotae Kim),장중걸(Zhong Jie Zhang) 한국자동차공학회 2010 한국 자동차공학회논문집 Vol.18 No.3
This paper presents a simulation model of a double-acting high-speed pneumatic cylinder with a relief valve type cushion mechanism. The model predicts piston motion, mass flow rate, pressure and temperature time histories of cushion chamber. Of interest here is to investigate the cushioning effect of varying the piston and piston-rod diameter, cushion ring diameter and length, and stoke in cushion mechanism. As a result, this cushion mechanism is found to be adequate under high-speed driving of pneumatic cylinders. The simulation model proposed here will be very useful to analyze the dynamic characteristics and to improve or design the better cushion mechanism in high-speed pneumatic cushion cylinders.
김도태(Dotae Kim),장중걸(Zhong Jie Jang) 한국자동차공학회 2017 한국 자동차공학회논문집 Vol.25 No.6
This paper presents a robust control scheme applied to a pneumatic cylinder positioning servo system. The use of a pneumatic system is associated with the highly nonlinear dynamics that makes conventional control strategies such as PID ineffective. In order to improve position control performance in a pneumatic servo system, a nonlinear mathematical model is developed and a robust controller is designed based on the H<SUB>∞</SUB> theory. The simulation results show better control performance and disturbance rejection as well as much faster response than PID control. Finally, the simulated results are compared with the experimental data under various conditions. The results show a good agreement between the simulation and experiment in terms of pressure wave forms in cylinder chambers and piston displacements. The availability and effectiveness of a robust H∞ controller are verified through the results of varying supply pressure, load, and piston velocity in closed loop position control of pneumatic cylinders.
김도태(Dotae Kim),김진(Jin Kim) 한국자동차공학회 2000 한국 자동차공학회논문집 Vol.8 No.6
A balanced vane pump for the use of automotive power steering systems generates a flow ripple which is imposed upon the mean flow rate. The flow ripple interacts with the characteristics of the connected pipes, valves and steering gear in a complex manner to produce a pressure ripple, also known as fluid-borne noise. In order to reduce vibration level and produce quieter and more reliable power steering systems, it is important to measure the flow ripple produced by a pump with high accuracy and fast response.<br/> In this paper, the flow ripple generated by a vane pump in automotive power steering systems is measured by the remote instantaneous flow rate measurement method (RIFM) using hydraulic pipeline dynamics. In experiment, flow and pressure ripple wave forms are measured under various operating conditions. Also, the parameters affected upon the flow and pressure ripple are investigated by the frequency analysis.<br/>
ER밸브 개발을 위한 3포트 4각 튜브내에서 ER유체의 유동가시화에 관한 연구
장문제(Munjey Jang),장성철(Sungcheol Jang),염만오(Manoh Yum),김도태(Dotae Kim),김기홍(Kihong Kim) 한국자동차공학회 2005 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-
The purpose of this study is to visualize the characteristics of ER fluids as preceding step of developing 3 port ER valves. ER fluids are made with silicone oil and 3 weight percent starch having hydrous particles. The flow visualization of ER fluids flow is obtained by CCD camera with changing the strength of electric field to ER fluids flow. As the strength of the electric field increases, more clustors in flow are made and these clusters are thought to be the reasons of the load flow rate being increaed and the outlet flow rate being decreased.