• Journal of Biomedical Engineering Research
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• v.18 no.1
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• pp.25-36
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• 1997

To regulate cardiac output of the Total Artificial Heart(TAH) physiologically, the hemodynamic information must be toed back to the controller. So far, our group has developed an automatic cardiac output control algorithm using the motor current waveform, It is, however difficult to detect the preload level such as a filling status of ventricular inflow and the variation of atrial pressures within normal physiologic range(0-15 mmHg) by analyzing the motor current which simultaneously reflects the afterload effect. On the other hin4 the interventricular volume pressure(IVP) which is not influenced by arterload but by preload is a good information source for the estimation of preload states. In order to find the relationship between preload and IVP waveform, we set up the artificial heart system on the Donovan type mock circulatory system and measured the IVP waveform, right and left atrial pressures, inflow and outflow waveforms and the signals represented the information of moving actuator's position. We shows the feasibility of estimating the hemodynamic changes of inflow by using IVP waveform. fife found that the negative peak value of IVP waveform is linearly related to atrial pressures. And we also found that we could use the time to reach the negative peak in IVP waveform, the time to open outflow valve, the area enclosed IVP waveform as unfu parameters to estimate blood filling volume of diastole ventricle. The suggested method has advantages of avoiding thrombogenesis, bacterial niche formation and increasing longterm reliability of sensor by avoiding direct contact to blood.

• Journal of the Korean Society of Safety
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• v.15 no.3
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• pp.115-123
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• 2000

Pneumatic actuators are widely used in a variety of hazardous working environments. Any process that involves pneumatic actuation is also recognized as "eco-friendly". In most cases, applications of pneumatic actuators require only point-to-point control. In recent years, research efforts have been directed toward achieving precise position tracking control. In this study, a tracking position control method is proposed and experimentally evaluated for a linear positioning system. The positioning system is composed of a pneumatic actuator and a 3-port proportional valve. The proposed controller has an inner pressure control loop and an outer position control loop. A PID controller with feedback linearization is used in the pressure control loop to nullify the nonlinearity arising from the compressibility of the air. The position controller is also a PID controller augmented with the friction compensation by a neural network. Experimental results indicate that the proposed controller significantly improves the tracking performance.rformance.

• Journal of the Korean Institute of Gas
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• v.15 no.6
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• pp.28-33
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• 2011

The purpose of this paper analyzes and studies to improve the failure cases on the computer that one of electronic control elements for engine in liquified petroleum gas vehicle. The first case, it certified the non-starting phenomenon of engine that it's electronic control unit didn't control the fuel for idle speed actuator because of no given action signal in slow-cut solenoid valve. The second case, it knew the bad condition phenomenon of engine and back-fire by the wire melting of ignition coil and firing of transistor being inside ECU. The third case, it certified the action stoping phenomenon of engine and malfunctioning signal for engine ECU because of leakage of current and an excess current by moisture inflowing inside ECU curcuit plate. Therefore, it is thought that will elevate the durability and reliability of engine computer throughout procure of quality.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.2
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• pp.219-225
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• 2015

Because a hydraulic actuator has high power and force densities, this allows the weight of the robot's limbs to be reduced. This allows for good dynamic characteristics and high energy efficiency. Thus, hydraulic actuators are used in some exoskeleton robots and quadrupedal robots that require high torque. Force control is useful for robot compliance with a user or environment. However, force control of a hydraulic robot is difficult because a hydraulic servo system is highly nonlinear from a control perspective. In this study, a nonlinear model was used to develop a simulation program for a hydraulic servo system consisting of a servo valve, transmission lines, and a cylinder. The problems and considerations with regard to the force control performance for a hydraulic servo system were investigated. A force control method using the nonlinear model was proposed, and its effect was evaluated with the simulation program.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.11
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• pp.1483-1490
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• 2011

Electro-hydrostatic actuators(EHAs), which are usually composed of a direct motor-driven hydraulic pump and a cylinder, have been widely adopted as aircraft actuation systems because of their benefits in terms of improved efficiency, weight savings and the fact that they use a standalone power source. Since the recent trend in construction vehicles has been focus on energy savings in their hydraulic systems, EHAs are expected to be potential substitutes for conventional power transmission, since they are capable of energy recovery as well as highly efficient pump control. In this paper, the start and stop characteristics of EHAs were investigated through cracking pressure analysis of the pilot-operated check valve(PCV), which enables the cylinder to standstill against an external load with no holding effort from the hydraulic pump. A mathematical model that includes the load dynamics and the EHA's internal hydraulic circuit was derived for simulation with the MATLAB Simulink package. This model verified the PCV's opening and closing sequence, which in turn affects the EHA's start and stop characteristics.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.951-956
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• 2011

As the evaluation of loading characteristic on tilting mechanism is the most important one of the function test of tilting mechanism, the changing characteristic of load must be investigated on tilting of carbody for both the static and running condition of train. In this study, we reduced the load of tilting mechanism by adjusting the interface of carbody and bogie such as the weight balance, level of underframe, height of leveling valve, height of axle box and center position of tilting actuator with the characteristic curve of load for optimal condition of the tilting mechanism obtained in the previous study. Furthermore, the factor and effect of the interfacial structures respecting the load of tilting mechanism was evaluated by analyzing the changing characteristic of load obtained in the process of adjustment of interfaces. From these data, we will propose the maintenance standards for interfacial structures and tilting mechanism in order to minimize the load of tilting mechanism by analyzing in detail the characteristic of load for the main factors of the interfacial structure effecting on the load of tilting mechanism.

• International Journal of Aerospace System Engineering
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• v.4 no.1
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• pp.13-21
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• 2017

In this paper, we present some results on performance analysis for flap actuation system of aircraft. For this, by utilizing MATLAB/Simulink solution, which is widely used physical model-based design tool, we particularly construct the architecture of the analysis model consisting of the main three phases: 1)commanding and outer-controlling the flap angle through flight control computer; 2)generating hydraulic/mechanical power through control module and power drive unit; 3)transmitting torque and actuating the flap through torque tube and rotary geared actuators. For mimicking the motion of the actual flap, we apply each mechanical component, which is already being used in actual aircraft, to our performance analysis model so that it guarantees the congruency of the simulation results. That is, we reflect the actual specifications of flap hardware and software as parameters of the model. Finally, simulation results are presented to illustrate the model.

• Journal of Drive and Control
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• v.13 no.4
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• pp.1-6
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• 2016

Typically, the seat of an automotive vehicle generally includes a horizontal seat-cushion portion and a vertical seat-back portion that is operatively connected to the seat-cushion portion. The seat may include a recliner for the reclining of the seat-back portion relative to the seat-cushion portion by the seat occupant. An energy absorber or damper can also be provided for the seat-back portion. Because the recliner is configured to be released at a relatively high speed, and it results in an impact at the end of a folding stroke, the damper needs to dissipate energy as the seat back moves with respect to the seat cushion; therefore, the role of the seat damper in the automotive-seat design is important. In this paper, the mechanism of an hydraulic-type automotive-seat damper is investigated, and the torque characteristic is simulated according to the design-parameter variations such as the orifice area and the working-fluid properties.

• Journal of the Korean Society of Industry Convergence
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• v.19 no.4
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• pp.216-222
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• 2016

Thus, this study aimed to develop a gear-type vane damper in order to replace the link-type vane damper. To achieve this goal, the torque generated in a gear-type vane damper was analyzed, and a structural analysis was conducted. In addition, the fluid flow was analyzed according to the changes in the vane's angle, and experimental tests such as a dry-heat test and cold test were conducted considering the operating conditions of the vessels. Moreover, an appropriate actuator was selected for the developed gear-type vane damper, and studies on the reduction in the backlash due to the facing-pressure adjustment length and flow rate and leakage test due to the vane's angle were conducted.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.159-159
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• 2009

Existence of physical moving parts (ex. check valve) produces several problems (mechanical abrasion, deterioration of reliability, limited temperature performances etc.) in driving pumps. To overcome such problems, we proposed a valveless piezoelectric micro-pump which has new type volume transferring mechanism. The proposed micro-pump has a double faced disk type vibrator that can generate peristaltic motion formed by traveling wave in each surface of a disk. This type of micro-pump is able to apply to a fluid supply system that provides two different kinds of fluid simultaneously. In this paper, we propose a simple and novel design of piezoelectric micro-pump that is peristaltically by piezoelectric actuators and allows the removal of the need for valves of other physically moving parts. The finite elements analysis on the proposed pump model was carried out to verify its operation principle using the commercial analysis software.