• Journal of Drive and Control
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• v.14 no.1
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• pp.14-22
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• 2017

Flow force is the additional unbalanced force acting on the valve spool by fluid flow, excluding the static pressure force that is offset on the spool land wall at the same magnitude. When designing the valve spool, it is assumed that the same average value of static pressure is applied to the inlet and outlet spool land wall in one chamber. However, the high velocity of the fluid flow by the inlet or outlet metering orifice creates unbalanced pressure distribution and generates additional force in the opposite direction to that of the solenoid attraction force. This flow force has a negative effect on the control performance of the EPPR valve, which needs to develop uniform output pressure along the entire spool control range. In this study, we developed a 3D model of the EPPR valve and conducted flow force characteristic analysis using CFD S/W (ANSYS FLUENT). The alleviated flow force model was derived by adjusting the design parameters of the spool notch.

• Journal of Drive and Control
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• v.17 no.1
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• pp.51-60
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• 2020

This study addresses the modeling of a bi-directional outlet variable swash plate type axial piston pump with two EPPR valves and an analysis of the response characteristics to the angle control of that pump. In this paper, the combination of the EPPR valve and double rod type piston is referred to as the EPPR regulator. The EPPR regulator is compact and inexpensive, and has good responsiveness. Under actual pump operating conditions, because of the various external conditions of the pump, inertia is applied to the swash plate, generating the tilting torque. Also, the tilting torque can delay or shorten the response characteristics of the regulator. So we validated them through the analysis using SimulationX and these results allow users to freely integrate the EPPR regulator into the desired system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1109-1110
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• 2010

• Journal of Drive and Control
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• v.13 no.2
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• pp.34-41
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• 2016

Unlike the commonly used On/Off solenoid, constant attraction force which is independent of plunger displacement is a considerably important characteristic to proportional solenoid of the EPPR Valve. Attraction force uniformity is mainly affected by the internal shape design parameters. Due to a number of shape design parameters, the optimal parameter values are very complex and time consuming to find by trial and error method. Much research has been conducted or are still in progress to find the optimal parameter values by applying various optimization techniques like Genetic Algorithm, Evolution Strategy, Simulated Annealing, or the Taguchi method. In this paper, the design parameters which have primary effects on the attraction force uniformity and the average attraction force are decided by main effects analysis of Design of Experiments. Optimal parameter values are derived using finite-element analysis and a neural network model.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.160-170
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• 2006

If hydraulic pump controlled by mechanical type regulator has more than one control function, the construction of regulator will be very complicated and control performance falls drastically. It is difficult to have more than one control function for hydraulic pump controlled by electronic type hydraulic valve due to the inconsistency of controllers. This paper proposes a multi-function control technique which controls continuously flow, pressure and power by using EPPR(Electronic Proportional Pressure Reducing) valve in swash plate type axial piston pump. Nonlinear mathematical model is developed from the continuity equation for the pressurized control volume and the torque balance for the swash plate motion. To simplify the model we make the linear state equation by differentiating the nonlinear model. A reaction spring is installed in servo cylinder to secure the stability of the control system. We analyze the stability and disturbance by using the state variable model. Finally, we review the control performances of flow, pressure and power by tests using PID controller.

• Transactions of The Korea Fluid Power Systems Society
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• v.5 no.4
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• pp.32-37
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• 2008

For the bucket tip position control of the excavator, a traditional hydraulic excavator system was exchanged into an electro-hydraulic one. EPPR valves are attached to the traditional MCV and hydraulic joysticks are replaced by electronic ones to develop the electro-hydraulic system. To control the electronic pump with a good performance, the control logic for the pump is deduced from the AMESim simulation and the experimental method on the test bench. To get a good position control performance of the excavator bucket tip, PI+AntiWindup controller is selected as a position controller. The experimental results showed the good controllability for the electro-hydraulic excavator system on the test bench.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.481-486
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• 2002

Automation of Field Robot has many advantages for efficiency and convenience. In this paper, mathematical equation of field robot is established and automation system is constructed. Hydraulic and Dynamic equation of field robot are constructed in this paper. Inputs of system are angle data from each link (boom, arm, bucket, swing) and pressure data from in, out port of each cylinder. Outputs of system are voltage into electo-proportional valve.

• Journal of Drive and Control
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• v.12 no.4
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• pp.28-34
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• 2015

Because heavy-duty construction vehicles such as excavators are required for good engine-room cooling capacity, a hydraulic gear motor is adopted in the cooling fan drive mechanism to actively control the output speed, instead of adopting the conventional ON/OFF type belt drive. While gear motors are normally limited to 140bars of operating pressure, those for the cooling fan are capable of operating at continuous pressures of up to 220bars. After assembly, all gear motors for high pressure must pass an aging test which is a kind of the wearing process between the gear teeth and motor housing. During the aging process with gradual pressure increments, gear sticking sometimes occurs due to abnormal wear, resulting in defects. This paper focuses on a gear-sticking free aging test controller that is designed together with the knowledge of an experienced operator and the analysis results of experimental data of the gear jamming phenomenon. From the aging experiment, it is demonstrated that the developed controller that can alter the setting pressure of the load pump is effective for stabilizing the abrupt increase in the motor input pressure, thus preventing the hydraulic motor from stopping. This is expected to be helpful for the reduction of defects and increase in productivity.