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부하외란이 가해지는 전기.유압서보계의 속도 제어에 관한 연구
하석홍,권기수,이진걸 한국마린엔지니어링학회 1993 한국마린엔지니어링학회지 Vol.17 No.1
The loads exerted on electro-hydraulic servo system are classified into inertial, viscous, and spring load. The additional load called disturbances is also exerted on system but is generally not modeled. To deal with these kinds of loads, it is necessary to maintain the continuous signal transfer, so we can construct compensator to satisfy control specifications using feedback signal such as displacement, velocity, acceleration and pressure known as state variables. In case of controlling the speed of hydraulic motor, we must keep up robust performance for the various loads and disturbances acted on the system. However, the load flow rate in the valve is characterized by nonlinearity so that traditional theory of linear control could not be expected to give the desired performance. In this paper, it is shown that speed controller of hydraulic motor gives a good command following and disturbance rejection performance by applying sliding mode theory as a way of robust control to the nonlinearity, variation of loads and disturbances.
PID 형 슬라이딩모우드에 의한 전기.유압서보계의 위치제어에 관한 연구
하석홍,Ha, Seok-Hong 한국정밀공학회 1992 한국정밀공학회지 Vol. No.
Up to now, there has been a lot of researches on the sliding mode control which has the insensitive characteristics to the variations of plant parameters, nonlinearities and external disturbances. One difficulty in applying the sliding mode control is the need for the knowledge of the full-state vector. The use of state observer is a natural step towards the relaxation of this condition. However, the exact plant-modeling is assumed to be known. Recently, there has been a remarkable advance in the microprocessor and one can construct the controller which could not realize due to hardware restriction in the past. Therefore in this paper, the PID sliding mode controller which has only one output feedback signal is suggested by means of microprocessor and the performance of electro-hydraulic servosystem compensated with this controller is proved.
박성환,하석홍,이진걸 대한기계학회 1995 대한기계학회논문집 Vol.19 No.4
The study deals with controlling the velocity of hydraulic motor with PI controller through the control of displacement pump which has higher efficiency than valve-controlled system. This was done as follows. First, we modified original displacement pump and designed this electrohydraulic puma system. Second, after experimenting static and dynamic characteristics, we identified system parameter of approximated model. Lastly, to control the velocity of hydraulic motor we controlled the angle of the swash plate of displacement pump. Test carried out in the laboratory shows that transient and steady state response could be improved by PI controller reducing power loss.
가변구조에 의한 편로드 실린더 서보계의 위치제어에 관한 연구
권기수,하석홍,허준영,이진걸 한국마린엔지니어링학회 1992 한국마린엔지니어링학회지 Vol.16 No.1
In eliminating the nonlinear characteristics such as piston displacement dift and difference in speeds of the reciprocating motion due to their nonsymetrical structure of single rod cylinder, the linear model can be given by equivalent outside disturbance, etc. The position control method of single rod cylinder servosystem using the sliding mode control of VSS was suggested and the good results without off-set are compared with PD control of fixed structure system.
굴삭기 엔진/펌프 시스템의 모델링 및 제어에 관한 연구
곽동훈,하석홍,조겸래,Kwak, Dong-Hoon,Ha, Sug-Hong,Cho, Kyeom-Ra 한국정밀공학회 1992 한국정밀공학회지 Vol. No.
According to the recent increase of demands for multi-function and economics on hydraulic excavator, it is required that excavator should have simple operation, higher and operational efficiency, however the modeling of engine/pump system of excavator is not prescribed by the paper. So, in this paper the modeling of engine/pump system of excavator is suggested by identification method from step response and verified effectiveness of identification system by comparing with experimental results which was conducted using PID controller. To improve the problem of parameter variation and modeling error in the system, sliding mode control was introduced and new switching surface was designed. This control algorithm was applied to a hydraulic excavator by simulation, and its effectiveness was verified, and the results of variable structure system for the excavator system using a output component was compared with that of full state feedback when load disturbances and system paramenter variation exist.