• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.10
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• pp.992-997
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• 2010

The Propulsion Control Module(PCM) of Hall-thruster Propulsion System(HPS) for Science and Technology Satellite-3 (STSAT-3) has the flow control accuracy of less than ${\pm}$3% and the pressure control accuracy of less than ${\pm}$5%. The pressure controller adjusts pressure around the set point by using a Proportional Flow Control Valve (PFCV) and a high pressure transducer, while the flow controller regulates the flow rate using PFCV and the anode current telemetry of the Hall Thruster. The controllers are chosen as the Proportional and Integral(PI) type, and the PI gains are tuned based on the Matlab simulations. The result of the PCM test had the flow control accuracy of less than ${\pm}$1.87% and the pressure control accuracy of less than ${\pm}$5%. This paper describes the design, realization, and performance test results of the PCM.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.260-265
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• 2001

This paper describes total flow control of an ice slurry system for pump energy saving. Similar turbo machinery has a characteristic that input power ratio is proportional to the three time of revolution speed ratio. To reduce the energy cost of brine pump in ice slurry storage systems, inverter is adapted instead of 3-way valve to control the speed of brine pump motor. One type of cooling load profile was used as driving load of the system, generated by a boiler and warm water storage tank. As results of the laboratory test, energy consumption and cost of the pump were reduced by 11.4%.

• Journal of Drive and Control
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• v.17 no.2
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• pp.55-62
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• 2020

There are two types of IMV for MCV, the spool type and the poppet type. The spool type is used in the existing excavator MCV and easily meets large-capacity flow conditions, but has a flow force problem which affects the spool control. The poppet type stably blocks the flow and has excellent rapid response. However, the larger the capacity, the larger the diameter of the poppet needed, requiring a strong spring to withstand the oil pressure. In this study, a bi-directional three-stage IMV for MCV that can be used in medium and large hydraulic excavators was proposed. This is a poppet type, enabling bi-directional flow control and resolves the problem of proportional solenoid suction force limitation. To investigate the validity of the proposed valve, the system was mathematically modeled and the static and dynamic characteristics were investigated through the simulation using commercial software. It has been concluded that the reverse flow is possible in a regeneration circuit and that the proposed IMV can be used to perform various excavation modes.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.6
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• pp.67-79
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• 1997

The perpose of this study was to suggest the experimental characteristic of the Cherepnov Water Lifter following the drain mode. The Cherepnov Water Lifter(CWL), which is powered by the potential energy of water, can be set to operate automatically when the water m a tank is drained. In this study, a CWL is constructed in the valve drain controlling mode(VCM) and the siphon drain controlling mode(SCM), and a pressure transducer is installed. It was found that, in the VCM, intake flow volume is proportional to both delivery flow volume and drain flow volume. In the SCM, intake flow volume is proportional to drain flow volume, and the average delivery rate is proportional to both efficiency and the water utilization ratio. Also, in the VCM, the water utilization ratio is 35~49%, efficiency is 62~9O%, average delivery rate is 12.8~81.2$cm^3$/s, and the average drain rate is 14.O~91.5c$cm^3$/s. On the contrary in the SCM, the water utilization ratio is 1.7~38%, efficiency is 3~58%, average delivery rate is 3.1 ~69.2$cm^3$/s, and the average drain rate is shown as 114.5~ 183$cm^3$/s. As a result of the water utilization ratio, efficiency, average delivery rate, and average drain rate are compared, the VCM is found to be superior and the more economical mode. However, the VCM requires manpower and electricity to operate the electronic machinery involved, while the SCM requires no manpower or electricity at all. An economic evaluation of these differences will be necessary in the future. Also, in the SCM, studies to improve water utilization ratio and efficiency, to find the optimum height of the siphon for decreasing the average drain rate, and to determine the radius of curvature of throat have to be conducted in advance, since a large flow rate is drained during the priming action of the siphon.

• International Journal of Control, Automation, and Systems
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• v.5 no.6
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• pp.643-651
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• 2007

The various blood pressure simulators have been proposed to evaluate and improve the performance of the automatic sphygmomanometer. These have some problems such as the deviation of the actual blood pressure waveform, limitation in the blood pressure condition of the simulator, or difficulty in displaying the blood flow. An improved simulator using disturbance observer is proposed to supplement the current problems of the blood pressure simulator. The proposed simulator has an artificial arm model capable of feeding appropriate fluids that can generate the blood pressure waveform to evaluate the automatic sphygmomanometer. A controller was designed and thereafter, simulation was performed to control the output signal with respect to the reference input in the fluid dynamic model using the proposed proportional control valve. To minimize the external fluctuation of pressure applied to the artificial arm, a disturbance observer was designed on the plant. A hybrid controller combined with a proportional controller and feed-forward controller was fabricated after applying a disturbance observer to the control plant. Comparison of the simulations between the conventional proportional controller and the proposed hybrid controller indicated that even though the former showed good control performance without disturbance, it was affected by the disturbance signal induced by the cuff. The latter exhibited an excellent performance under both situations.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.5
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• pp.25-32
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• 1994

A nonlinear control algorithm for the depth control of underwater vehicles is presented. In order to consider the deadzone effect of the flow control valve, a nonlinear fuzzy logic controller (FLC) is synthesized and combined with a linear proportional-derivative-acceleration (PDA) controller, which is called the PDA/FLC controller. And to show the effectiveness of the PDA/FLC control system, it is compared with the linear PDA control system through computer simulation. It is found that the PDA/FLC control system is suitable one to maintain the desirable depth of underwater vehicles with deadzone.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.1 s.94
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• pp.42-48
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• 1999

A control method for a robot hand grasping a object in a partially unknown environment will be proposed, where a proximate sensor detecting the distance between the fingertip and object was used. Particularly, the finger joints were driven servo-pneumatically in this study. Based on the proximate sensor signal the finger motion controller could plan the grasping process divided in three phases ; fast aproach, slow transitional contact and contact force control. That is, the fingertip approached to the object with full speed, until the output signal of the proximate sensor began to change. Within the perating range of the proximate sensor, the finger joint was moved by a state-variable feedback position controller in order to obtain a smooth contact with the object. The contact force of fingertip was then controlled using the blocked-line pressure sensitivity of the flow control servovalve for finger joint control. In this way, the grasping impact could be reduced without reducing the object approaching speed. The performance of the proposed grasping method was experimentally compared with that of a open loop-controlled one.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.2 s.245
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• pp.110-116
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• 2006

A syringe pump or a device using high electric voltage has been used for controlling flows inside a LOC (lab-on-a-chip). Compared to LOC, however, these microfluidic devices are large and heavy that they are burdensome for a portable ${\mu}-TAS$ (micro total analysis system). In this study, a new flow control technique employing pressure regulators and pressure chambers was developed. This technique utilizes compressed air to control the micro-scale flow inside a LOC, instead of a mechanical actuator or an electric power supply. The pressure regulator controls the output air pressure by adjusting the variable resistor attached. We checked the feasibility of this system by measuring the flow rate inside a capillary tube of $100{\mu}m$ diameter in the Re numbers ranged from 0.5 to 50. In addition, the performance of this flow control system was compared with that of a conventional syringe pump. The developed flow control system was found to show superior performance, compared with the syringe pump. It maintains automatically the: air pressure inside a pressure chamber whether the flow inside the capillary tube is on or off. Since the flow rate is nearly proportional to the resistance, we can control flow in multiple microchannels precisely. However, the syringe pump shows large variation of flow rate when the fluid flow is blocked in the microchannel.

• 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 Biosystems Engineering
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• v.14 no.4
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• pp.229-241
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• 1989

The purposes of this study were to develop an electronic-hydraulic draft control system for tractor implements, to investigate the control performance of the system and the possibility of adaptation to the conventional tractor. Experiments were carried out to investigate the responses of the system to the step and sinusoidal inputs in draft control. The effects of control mode, hydraulic flow rate, reference deadband, and proportional constant on control performance of the system were investigated. Moreover, the effects of filtering signals from draft sensor were also investigated. The following conclusions were derived from the study; 1. In draft control, there were hunting problems in controlling the implement without filtering the draft signals. Filtering was performed by a control program of electronic controller and the control performance and stability of the system were improved significantly. 2. For the draft control system operated on on-off control mode, draft was controlled within ${\pm}27-{\pm}55kg_f$ to the reference draft when the hydraulic flow rates were 5-15 l/min. For the draft control system operated on PWM control, draft was controlled within ${\pm}27kg_f$ to the reference draft regardless of hydraulic flow rates. 3. In the frequency responses of the draft control system, control performance on PWM control mode was not better than on on-off control mode because of characteristics of hydraulic valve and drafe sensor. As the hydraulic flow rates increased for the system operated on on-off control mode, the corner frequency of amplitude attenuation increased, but the corner frequency of phase-angle change remained nearly the same. But, the system was unstable beyond the frequency of 3.1 rad/s. 4. The electronic-hydraulic hitch control system developed in this study showed superior control performance, stability and convenience compared to conventional mechanical-hydraulic hitch control system. It is considered to be a superior replacement for the conventional mechanical-hydraulic hitch control system.