• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.2
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• pp.213-220
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• 1989

This paper describes the application of the variable structure control(VSC) concept for the position control of an electro-hydraulic servomotor system. The basic philosopy of VSC is that the structure of the feedback control is altered as the state crosses discontinuity surfaces in the state space with the result that certain desirable properties are achieved. The switching of the control function yields total(or selective) invariance to system parameter variations and disturbances, and closed loop eigen value placement in time-varing and uncertain systems. The control scheme is derived, implemented and tested in the laboratory where analog controller have been used to control the representive servosystem. The control system schematics are given and simple results are shown for illustration. And the results of variable structure system for the electro-hydraulic servomotor were compared to that of the fixed structure system when load disturbance and system parameter variation exists.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10b
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• pp.1611-1616
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• 1991

A high power stewart platform is designed and manufactured to simulate the 6 degrees of freedom motion of moving vehicle. This paper describes the design of such a motion system including kinematic and kinetic analysis, real time servo control mechanical and hydraulic system configuration, and techniques of regeneration of test records. Discussions are also presented for an algorithm called remote parameter control, which has been developed to compensate the dynamic delay of the electro-hydraulic servo actuators and the nonlinearities of stewart platform.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.581-584
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• 1995

The frequency response of a electro-hydraulic servo(EHS) system is studied. The frequensy response characteristics of the EHS system obtained by linerization method, nonlinerar simulation method, and experimentation are compared ane another. It is found that the frequency response of the EHS is consistent when input signal applied is very small, but that is deviated as input signal becomes large.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.276-281
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• 1989

Comparison 3-port servo system with 4-port is made to obtain optimal design for heavy and unidirectional hydraulic system, It is concluded that 3-port servo system it more adequate than 4-port for the heavy load system which is usually operated at lower frequencies. High performance electro-hydraulic position controller is designed using 3-port servo valve. It includes dynamic pressure feedback as a inner loop and position feedback as a outer loop.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1576-1577
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• 2007

As a intelligent valve piezoelectric valve is to applied to various fields of application. Piezoelectric valves have fast response time and good linearity for pressure control but its hysteresis displacement by its stack actuator influences on pressure control in electro-hydraulic braking. Solenoid valves are traditional element to control hydraulic pressure but this paper proposes piezoelectric valve for brake pressure control with hysteresis compensation.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1002-1007
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• 2010

This study evaluates the electro-osmotic hydraulic conductivity for the clay specimen by applying the series of the voltage gradient simultaneously with different stress conditions. The test results shows that the shrinkage of voids corresponds to the linear decrease in the electro-osmotic seepage velocity, and the changes of electro-chemical characteristics in the specimen induces the gradual decrease of the electro-osmotic seepage velocity with the constant voltage gradient.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.8
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• pp.94-100
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• 2003

This paper presents the experiments on the approximation of a hydraulic servo system using a real time recurrent neural networks (RTRN) with time varying weights. In order to verify the effectiveness of the RTRN algorithm in hydraulic servo system, we design the experimental hydraulic system and implemented the real time approximation of system output. Experimental results show that approximated output of the RTRN well follows the position trajectory of the electro-hydraulic servo system. And also it is verified that the 2-D RNN can be implemented in sampling time even though high sampling frequency experimentally.

• Journal of Drive and Control
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• v.16 no.4
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• pp.1-8
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• 2019

The HPM (High-speed Power Matching) system is an electro-hydraulic control system. It directly controls the swash plate of the pump by selecting four-loop logic based on joystick signals, pump flow, and pressure signal to improve the efficiency and controllability of construction machines. In the NFC (Negative Flow Control) system, a typical pump control system using conventional open center type MCV, the loss is continuously generated by flow through the center bypass line even when the excavator is not in operation. Also, due to the slow response of the pump that indirectly controls the flow rate using the pressure regulator, peak pressure occurs at the start or stop of the operation. Conversely, the HPM system uses an MCV without center-by-pass flow path and the swash plate of a pump for the HPM is controlled by a high-speed proportional flow control valve. As a result, the HPM system minimizes energy loss in standby state of the excavator and enables peak pressure control through rapid electro-hydraulic control of a pump. In this paper, the concept of the HPM system algorithm is introduced and the hydraulic system efficiency is compared with the NFC system using the excavator SAT (System Analysis Tool).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.4
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• pp.316-322
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• 2007

The EHA(Electro-hydrostatic Actuator) reveals completely different characteristics from the conventional valve-controlled Electro-hydraulic actuators. In this paper, its mathematical model including nonlinear elements was derived to be verified by experiments. Based on this, a simulation program was developed for the EHAs consisting of an electric motor driven hydraulic pump, pipe lines and a cylinder. The influence of important design parameters such as peak motor torque and rotational inertia moment of the hydraulic pump on control performance was investigated, where the test condition was intentionally selected so that the motor torque was saturated during the transient phase. As a result, design requirements for improving the control accuracy under full speed operation conditions of the EHAs were investigated.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.1
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• pp.101-108
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• 2004

An electro-hydraulic manipulator using hydraulic actuators has many nonlinear elements, and its parameter fluctuations are greater than those of an electrically driven manipulator. So it is relatively difficult to obtain stable control performance. In this report, we applied disturbance estimation and compensation type robust control to all axes in a 3-link electro-hydraulic manipulator. From the results of experiment, it was confirmed that the performance of trajectory tracking and attitude regulating is greatly improved by the disturbance observer, which model is the same for each axis. On the other hand, for the autonomous assembly tasks, it is said that compliance control is one of the most available methods. Therefore we proposed compliance control which is based on the position control by disturbance observer for our manipulator system. To realize more stable contact work, the states in the compliance loop are feedback, where not only displacement but also velocity and acceleration are considered. And we applied this compliance control to Peg-in-Hole insertion task and analyzed mechanical relation between peg and hole. Also we proposed new method of shifting the position of end-effector periodically for the purpose of smooth insertion. As a result of using this method, it is experimentally confirmed that Peg-in-Hole insertion task with a clearance of 0.05［mm］can be achieved.