• 대한의용생체공학회:의공학회지
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• 제36권6호
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• pp.264-270
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• 2015

A mock circulatory loop system has been developed to construct a simulator for trainees in cardiopulmonary bypass systems or to simulate a test environment for cardiac-assist devices. This paper proposes a computerized mock circulatory loop system whose node is modularized by using a servo control flow regulator to simulate dynamic change of the hemodynamic status. To observe the effect of time-varying resistance, one with hemodynamic properties, the proposed system replicates the planned cross-sectional areas of the outlet of a ventricular assist device in terms of voltage input of a servo valve. The experiment is performed (1) for steady-input commands of selected area sizes and (2) for dynamic commands such as monotonous increase and decrease, and oscillatory functions of the voltage input, and a computer program based on LabVIEW (National Instruments, Austin, USA) processes every measured data and control command to the servo valve. The results show that the pressure and flow at the target points with respect to time-varying resistance match intuitive estimation: the pressure at the outlet and the pressure drop between both sides of the valve increased and the flow at the outlet decreased for increased resistance.

• 한국정밀공학회지
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• 제25권1호
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• pp.151-159
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• 2008

The parameter-based cardiovascular impedance simulator that is able to overcome the limits of conventional mock circulatory systems is critical for the development and test of biomedical devices including artificial heart. The concept of impedance simulator was validated mathematically in a previous study using high-gain feedback linearization control which, however, may cause serious difficulties and limits for practical implementation. In this study, therefore, practical applicability of the impedance simulator is investigated considering the physical limits such as motor speed and torque. Simple PID controller which do not require complex model of the simulator is used considering the practical implementation. Design guidelines of the impedance simulator are also provided based on the results.

• 대한의용생체공학회:의공학회지
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• 제17권3호
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• pp.387-394
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• 1996

This paper presents a Neural Network Identification(NNI) method for modeling of highly complicated nonlinear and time varing human system with a pneumatically driven mock circulatory system of Left Ventricular Assist Device(LVAD). This system consists of electronic circuits and pneumatic driving circuits. The initiation of systole and the pumping duration can be determined by the computer program. The line pressure from a pressure transducer inserted in the pneumatic line was recorded System modeling is completed using the adaptively trained backpropagation learning algorithms with input variables, heart rate(HR), systole-diastole rate(SDR), which can vary state of system. Output parameters are preload, afterload which indicate the systemic dynamic characteristics. Consequently, the neural network shows good approximation of nonlinearity, and characteristics of left Ventricular Assist Device. Our results show that the neural network leads to a significant improvement in the modeling of highly nonlinear Left Ventricular Assist Device.

• 대한의용생체공학회:의공학회지
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• 제19권1호
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• pp.47-52
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• 1998

인공판막의 부작용을 크게 줄일 수 있을 것으로 기대되는 보조판막을 개발하기 위해서 생체외에서 판엽운동과 혈역학을 분석하였다. 보조 판막은 추출한 돼지 판막에서 판엽의 일부를 절개한 후 심낭을 이식하여 재건하였다. 심낭은 글루타르알데히드 완충용액으로 처리한 후 금속목드를 이용하여 판엽모양을 재생시켰다. 제작한 보조판막은 모의순환장치에서 성능을 평가하였다. 35mm 카메라를 이용하여 순간운동 모양을 촬영하였고 압력강하와 심박출량을 측정하여 분석하였다.

• 제어로봇시스템학회논문지
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• 제4권3호
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• pp.315-320
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• 1998

In this paper, we present the PID control method for the controlling flow rate of highly complicated nonlinear Left Ventricular Assist Device(LVAD) with pneumatically driven mock circulatory system. Beat Rate (BR), Systole-Diastole Rate (SDR) and flow rate are used as the main variables of the LVAD system. System modeling is completed using the neural network with input variables (BR, SDR, their derivatives, actual flow) and an output valiable(actual flow). Then, as the basis of this model, we perform the simulation of PID control to predict the performance and tendency of the system and control the flow rate of LVAD system using the PID controller. The ability and effectiveness of identifying and controlling a LVAD system using the proposed algorithm will be demonstrated through computer simulation and experiments.

• 한국정밀공학회지
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• 제15권4호
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• pp.83-90
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• 1998

In this paper, we present neural network for control of Left Ventricular Assist Device(LVAD) system with a pneumatically driven mock circulation system. Beat rate(BR), Systole-Diastole Rate(SDR) and flow rate are collected as the main variables of the LVAD system. System modeling is completed using the neural network with input variables(BR, SBR, their derivatives, actual flow) and output variable(actual flow). It is necessary to apply high perfomance control techniques, since the LVAD system represent nonlinear and time-varing characteristics. Fortunately. the neural network can be applied to control of a nonlinear dynamic system by learning capability In this study, we identify the LVAD system with neural network and control the LVAD system by PID controller and neural network feedforward controller. The ability and effectiveness of controlling the LVAD system using the proposed algorithm will be demonstrated by experiment.

• 제어로봇시스템학회논문지
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• 제1권2호
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• pp.127-134
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• 1995

For use in patients with severe forms of heart disease for which no surgical repair is possible, development of artificial hearts has many importance in point of economics, medical and industrial applications. To provide a sufficient cardiac output to the physiological demands of circulatory systems is the objective of control systems for an electromechanical artificial heart, which is based on the stable controller design for the motor in the artificial heart. In this paper, an implantable microcontroller-based brushless DC motor control system with the implantability, reliability, and stability is introduced. The developed control system for the artificial heart has the following advantages: (1) It is possible to be implanted in a body by realizing the fundamental functions such as a motor speed detection, proportional-intergral control, timer, and PWM generation through a software programming. (2) Thus, the power consumed in the controller is reduced. (3) The reliability and stability are improved through the reduction of electronic parts and line connetions at the controller. The performance of the artificial hearts and control system developed was evaluated through a series of mock circulatory experiments and a reliability test for one and half years. A sheep with the artificial heart and control system was survived for three days.

• 대한기계학회논문집B
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• 제30권1호
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• pp.87-94
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• 2006

This paper presents the hydrodynamic design and performance analysis method for a miniaturized centrifugal blood pump using three-dimensional computational fluid dynamics (CFD) code. In order to obtain the hydraulically high efficient configuration of a miniaturized centrifugal blood pump for cardiopulmonary circulation, a well-established commercial CFD code was incorporated considering detailed flow dynamic phenomena in the blood pump system. A prototype of centrifugal blood pump developed by the present design and analysis method has been tested in the mock circulatory system. Predicted results by the CFD code agree very well with in vitro hydraulic performance data for a centrifugal blood pump over the entire operating conditions. Preliminary in vivo animal testing has also been conducted to demonstrate the hemodynamic feasibility for use of centrifugal blood pump as a mechanical circulatory support. A miniaturized centrifugal blood pump developed by the hydraulic design optimization and performance prediction method presented herein shows the possibility of a good candidate for intra and extracorporeal cardiopulmonary circulation pump in the near future.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.329-332
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• 1997

To develop the supplementary heart valve which could reduce the complications of prosthetic heart valve, in vitro experiments were performed to analyze the movement of the supplementary valves. The autologous pericardium was attached to deficient portion of the porcine valve which was dissected completely and partially. The instantaneous motion of the leaflet was pictured by the 35mm camera and the pressure drop through the valve and cardiac output were measured in mock circulatory system. The durability of the valves were tested in severe hemodynamic conditions.

• 대한의용생체공학회:의공학회지
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• 제22권5호
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• pp.439-448
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• 2001

이식형 양심실 보조 장치 (Biventricular Assist Device, BVAD)에서 판막이 닫힐 때 나는 소리의 특성과 판막의 물리적인 상태의 상관성을 고찰하였다. 본 연구에서 Bj rk Shiley Convexo Concave tilting disk 판막을 사용했으며, 모의 순환계와 양의 체내에서 동작하는 BVAD 에서 판막음을 측정하였다. 모의 순환계에서는 정상 판막. 기계적으로 손상된 판막. 모의 혈전이 형성된 판막의 3가지를 고려하였다. 양에 이식된 BVAD의 경우, 이식 후 1일부터 5일 동안 규칙적인 간격으로 판막음을 측정하였다. 측정된 신호의 스펙트럼 특성은 Multiple Signal Classification (MUSIC)을 이용하여 추정하였다. MUSIC의 최적 차수는 Bayesian Information Criterion (BIC)을 이용하여 계산하였다. 실험 결과, 판막의 기계적인 손상은 판막 폐쇄음의 주파수 스펙트럼 구조를 변화시키고 있으며, 혈전의 형성은 판막음 스펙트럼의 기본 구조는 유지하지만 피크 주파수와 에너지의 크기를 변화시키는 것으로 관찰되었다. 최대 에너지를 가지는 MSP (maximum spectral peak)는 정상 판막에서는 2 kHz에 위치하고 있으나 모의 혈전을 부탁한 판막에서는 3 kHz로 이동하였다. 손상된 판막은 7 kHz 부근에서 강한 피크 보이고 있다 실험 동물 내에서 판막에 혈전이 형성되어감에 따라 판막음은 저주파 성분 (〈 2kHz)이 상대적으로 크게 감소하였고, Ist 2nd. 3rd MSP 주파수는 약간씩 상승하였다. 또한 혈전이 형성되어 감에 따라 반복해서 측정된 판막음의 1st, 2nd. 3rd MSP 주파수의 변화 정도 및 BIC 차수는 감소하는 것으로 나타났다