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Feedback Linearization Control of a Cardiovascular Circulatory Simulator
Kwan-Woong Gwak,Hae Dong Kim,Chang-Wan Kim Institute of Electrical and Electronics Engineers 2015 IEEE transactions on control systems technology Vol. No.
<P>In this brief, a nonlinear model-based feedback linearization (FBL) control is proposed for a high-performance cardiovascular circulatory simulator (CCS). The challenges are that the piston pump used for a mock ventricle in CCS has high-bandwidth pressure dynamics and hard nonlinearity due to check valves. Limited control performance in the previous researches due to these difficulties even raises the question of the physiological feasibility of the developed CCS. To overcome this problem, FBL theory based on the Lie algebra is applied in this research for the piston pump mock ventricle control. Dynamic model of the piston pump was derived, and parameter values of the model were identified experimentally for the controller design. The experimental results confirmed good performance of the proposed controller for various physiological scenarios. Good match with the reference model behavior was verified as well, and physiological feasibility of the CCS was secured thereby thanks to the proposed high-performance controller.</P>
Experimental Verification of the Feasibility of the Cardiovascular Impedance Simulator
Gwak, Kwan-Woong,Paden, Brad E.,Antaki, James F.,Ahn, Ihn-Seok IEEE 2010 IEEE Transactions on Biomedical Engineering Vol.57 No.5
<P>Mock circulatory systems (MCS) are often used for the development of cardiovascular devices and for the study of the dynamics of blood flow through the cardiovascular system. However, conventional MCS suffer from the repeatability, flexibility, and precision problems because they are typically built up with passive and linear fluidic elements such as compliance chamber, manual valve, and tube. To solve these limitations, we have developed an impedance simulator, comprised of a feedback-controlled positive displacement pump that is capable of generating analogous dynamic characteristics as the conventional fluidic elements would generate, thereby replacing the conventional passive fluidic elements that often cause problems. The impedance simulator is experimentally proven to reproduce the impedance of the various discrete elements, such as resistance and compliance of the cardiovascular system model, as well as the combined impedances of them.</P>
A Review of Steam Generation for In-Situ Oil Sands Projects
Gwak, Kwan-Woong,Bae, Wi-Sup 한국암반공학회 2010 Geosystem engineering Vol.13 No.3
Steam Assisted Gravity Drainage (SAGD), an unconventional enhanced oil recovery process for the oil sands, is getting more attention recently as the international oil price increases rapidly. Basic concept of SAGD is to extract the viscosity-lowered bitumen by high pressure, high temperature 100% quality steam injected into the reservoir containing high-viscosity bitumen. As its name implies, generation of highquality, high-temperature and high-pressure steam is a prerequisite for the SAGD process. Hence in this paper, key aspects of steam generation system for oil sands recovery will be broadly reviewed to provide the engineers concerned with the working principles and the major issues such as configuration, design, control of steam generation system used for oil sands recovery.
Nonlinear Optimal Control of an Input-Constrained and Enclosed Thermal Processing System
Kwan-Woong Gwak,Glenn Y. Masada 대한전기학회 2008 International Journal of Control, Automation, and Vol.6 No.2
Temperature control of an enclosed thermal system which has many applications including Rapid Thermal Processing (RTP) of semiconductor wafers showed an input-constraint violation for nonlinear controllers due to inherent strong coupling between the elements [1]. In this paper, a constrained nonlinear optimal control design is developed, which accommodates input constraints using the linear algebraic equivalence of the nonlinear controllers, for the temperature control of an enclosed thermal process. First, it will be shown that design of nonlinear controllers is equivalent to solving a set of linear algebraic equations-the linear algebraic equivalence of nonlinear controllers (LAENC). Then an input-constrained nonlinear optimal controller is designed based on that LAENC using the constrained linear least squares method. Through numerical simulations, it is demonstrated that the proposed controller achieves the equivalent performances to the classical nonlinear controllers with less total energy consumption. Moreover, it generates the practical control solution, in other words, control solutions do not violate the input-constraints.
기계적 한계를 고려한 심혈관 순환계 임피던스 시뮬레이터 설계 및 평가
곽관웅(Kwan-Woong Gwak) Korean Society for Precision Engineering 2008 한국정밀공학회지 Vol.25 No.1
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.