• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1986년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 17-18 Oct. 1986
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• pp.673-677
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• 1986

This paper deals with the state observer-controller which observes unmeasurable state variables of the system and then uses the estimated values as feedback signals. The linearized model is deduced from the nonlinear electrohydraulic servo system. The 4th order analog linear observer-controller and the 2nd order digital one are modelled and implemented using OP amplifiers and IBM PC/XT, respectively. The two observer are experimentally used in the control of an electrohydraulic system. The results are satisfactory in estimation performance and in tracking performance to command signal.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.69-69
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• 2000

Control systems using a hydraulic cylinder as an actuator are modeled to a nonlinear system owing to varying of moments and nonlinearities of hydraulic itself. In this paper, we want to control nonlinear hydraulic systems by adopting the fuzzy PID control technique which include nonlinear time varying control parameters. To do this, we propose the design method of fuzzy Pm controller and in order to assure effectiveness of fuzzy PID controller, computer simulations were executed for the control system.

• 유공압시스템학회논문집
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• 제2권4호
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• pp.7-13
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• 2005

This paper presents modeling and ostimator/controller design for the hydraulic system in Vehicle Stability Control(VSC) system. A nonlinear mathematical model of the VSC hydraulic system is proposed and its accuracy is experimentally verified. A brake pressure estimator is then designed based on the derived mathematical model of VSC hydraulic system. And a disturbance observer, which compensates the estimation error between the brake pressure and the computed brake pressure is also designed to enhance the accuracy of the estimator. The proposed controller has the form of a feedback controller and determines explicitly the on/off ratio of valves' driving PWM signals by means of making use of the simplified mathematical model in the VSC hydraulic system. The performance of the designed controller whose feedback signal is generated by the brake pressure estimator is validated through experimental results.

• Journal of Biosystems Engineering
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• 제24권5호
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• pp.383-390
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• 1999

When a tractor travels slope lands, problems of operator safety and the reduction of job efficiency usually occur. Therefore, maintaining the tractor body being horizontal is critical to improve the security of traveling and the job performance. An experiment was made in a soil bin using the experimental model system built and equipped with a leveling control system. Adaptability of the control system was tested and investigated by analyzing system response in time and frequency domains. Control response time of hydraulic cylinder with 10lpm flow rate on a step input of 10$^{\circ}$slope was about 0.42sec. And it showed a linearly increasing trend without any hunching state. A steady state error of 0.6$^{\circ}$occurred but it was negligible. The hydraulic control system showed a little phase differences within the range of 0.4Hz input frequency. The experimental model showed that implementation of the proposed tractor control system to on slope lands tractor was feasible.

• 한국정밀공학회지
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• 제33권10호
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• pp.837-843
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• 2016

This paper presents a position control strategy for a pump-controlled electro-hydrostatic actuator (EHA) using feedforward control with disturbance compensation. As the disturbance observer is used to estimate nonlinear dynamics of EHA, which has valve-opening conditionals, as well as external disturbances, an additional feedforward control is adopted to achieve rapid response. The effectiveness of the proposed control strategy is verified through experiment using an EHA test bench. The proposed controller shows better tracking performance compared with a conventional PID controller.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.585-588
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• 1995

In this study, the analysis of the static and dynamic characteristics of the load-sensitive hydraulic pump control system used in the hydraulic excavator was performed by hydraulic circuit ananlysis program. Thess results was verified by the experimental data of the hydraulic excavtor system. The responses on effective parameters of system at the controllable region and the pressure variation of the pump used in hydraulic excavator system was studied to enhance the static performace of the system. the parameter enhance dynamic sharacteristics was considerd.

• 한국공작기계학회논문집
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• 제12권6호
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• pp.77-83
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• 2003

This paper deals with a position control problem of a hydraulic proportional position control system using a nonlinear friction compensation control. As nonlinear friction, stiction and coulomb friction forces are considered and modeled as deadzone and external disturbance respectively. In order to compensate this nonlinearities, we designed the controller which is the adaptive friction compensator using discrete time Model Reference Adaptive Control method in this paper. Digital Signal Processing board is employed for data acquisition and manipulation. The experimental results show that response is slow and steady-state error cannot be compensated properly without friction compensation but this compensator is effective to obtain fast response and good steady-state response.

• 대한기계학회논문집A
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• 제31권9호
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• pp.934-942
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• 2007

In this study, the characteristics of the load-sensitive hydraulic control system for closed center type of a wheel loader were analyzed using developed analysis program based on Amesim tool. From the parametric analysis, the effects of each factor were revealed. Through the simulation with varying parameters, the system parameter effects on the controllable region and the pump pressure and load pressure variations were studied. The results were compared with the experimental ones. The results and discussions of the present paper could aid in the design of a load-sensitive hydraulic control system for closed center type.

• 대한기계학회논문집A
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• 제32권2호
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• pp.119-126
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• 2008

In this study, the characteristics of the hydraulic control system with bleed-off center type of a compact excavator were analyzed using developed analysis program. From the parametric analysis, the effects of each factor were revealed. Through the simulation with varying parameters, the system parameter effects on the controllable region and the pump pressure and load pressure variations were studied. The results were compared with the experimental ones. The results and discussions of the present paper could aid in the performance improvement of a hydraulic control system of a compact excavator.

• 유공압시스템학회논문집
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• 제1권1호
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• pp.23-30
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• 2004

This paper deals with the issue of trajectory tracking control of a hydraulic excavator using disturbance observer in order to compensate external disturbances occuring from coupling between attachment, asymmetry of a single rod cylinder, and deadzone of main control valve. Disturbance compensation control system with disturbance observer has been constructed for the boom and arm respectively. Simulation results were compared with experimental results to validate the computer simulation system of hydraulic excavator itself. Computer simulation shows that disturbance compensation control is effective for compensating system nonlinearity and thus improves positioning accuracy and trajectory tracking performance. Steady state error has been decreased by adding PI controller to this control scheme.