• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.3
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• pp.322-327
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• 2003

The water level of a steam generator of pressurized light water nuclear Power generator is known as a subject whose control is difficult because of a shrinking and swelling effect that is been mutually contradictory in a variation of feed water. In this paper, a neural network model selects first coordinative controller by a inappropriate gain of two PI controllers and the selected controller＇s gain is tuned by a fuzzy self-tuner. Model inputs consist of the water level, the feed water, and the stream flow. One controller of both coupling controllers whose gain is handled firstly is decided based upon above data. The proposed method can analyze patterns of signals using the characteristic of neural networks and select one controller that needs to be tuned through the observed result in this paper. If one controller between both the water level controller and the feed water controller is selected by the neural network model then a gain of the PI controller is suitably tuned by the fuzzy self-tuner. Rules of the fuzzy self-tuner drew from the pattern of input and output data. In the summary, the goal of this Paper is to select the suitable controller and tune the control gain of the selected controller suitably through such two processes.

• Journal of the Semiconductor & Display Technology
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• v.16 no.3
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• pp.25-30
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• 2017

Arago's disk system consists of a speed controller of the DC motor (inner loop controller) and a position controller of the magnetic bar angle (main controller), which are implemented by the design of the PI and PID controller, respectively. First, we analyzed the nonlinear characteristics of the Arago disk system and found the operating point range of three locations as a result. In this paper, a gain scheduler method was applied to guarantee a constant control performance in the range of $0{\sim}130^{\circ}C$, and a structure to change the controller according to the control reference value based on the previously obtained operating points was experimentally implemented. The Distributed Control Systems (DCS) configuration using the Controller Area Network (CAN) was used to verify the proposed method by improving the operational efficiency of the entire experimental system. So, simplicity of the circuit and easy diagnosis were achieved through a single CAN bus communication.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1111-1113
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• 2003

This paper proposes an effective self-turning algorithm based on Artificial Neural Network (ANN) for fuzzy speed control of the indirect vector controlled induction motor. Indirect vector control method divides and controls stator current by the flux and the torque producing current so that the dynamic characteristic of induction motor may be superior. However, if motor parameter changes, the flux current and the torque producing one's coupling happens and deteriorates the dynamic characteristic. The fuzzy speed controller of an induction motor has the robustness over the effect of this parameter variation than a conventional PI speed controller in some degree. This paper improves its adaptability by adding the self-tuning mechanism to the fuzzy controller. For tracking the speed command, its membership functions are adjusted using ANN adaptation mechanism. This adaptability could be embodied by moving the center positions of the membership functions. Proposed self-tuning method has wide adaptability than existent fuzzy controller or PI controller and is proved robust about parameter variation through Matlab/Simulink simulation.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.6
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• pp.531-538
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• 1999

This paper proposes a fuzzy logic controller(FLC) for DC-DC converters in order to obtain good l perfonnances that can not be achieved by linear control tc'Chniques in the presence of wide parameter v variations. 'While the standard controller uses error and derivative of e$\pi$or, the proposed controller uses state v variables. Such method is ve$\pi$ efficient in case of DC-DC converters and can guarantee both stable s small-signal responses and improved large signal responses. The presented approach method is general and c can be applied to any dc-dc converter topologies. Through the simulations of booster, we verify the pro[Xlsed C control tc'Chnique can give a satisfactory perfonnance.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.3
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• pp.274-280
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• 2012

In this paper, three current controllers for a grid-connected PCS using an LCL filter are compared and analyzed. Current controllers discussed in this paper are linear controllers such as PI (proportional-integral), PR (proportional-resonant), and DB (deadbeat) controller. Both transient and steady state responses of each controller are compared through both simulation and experiment. Although the DB controller has the fastest transient response and the lowest THD in the steady state, the DB controller has two cycles delay of current response in the steady state and has the stability problem which can be occurred due to variation of the system parameters. On the one hand the responses of PR controller are not much different from that of DB controller but the other hand that are not only strong to noise of grid current but also have smaller THD than PI controller. Considering the response time and stability issue of three controllers, the PR controller has the best performance among three controllers and thus can be strongly recommended as a current controller for a grid-connected PCS.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1317-1321
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• 1987

A new type of motor-driven Total Artificial Heart(TAH) system with rolling cylinder mechanism has been developed. Brushless DC motor was chosen as energy converter and controlled by PI controller according to the given velocity profile under the highly time-varying load. Computer simulation was also performed to calculate the optimal gains of PI controller which minimize the input power, one of the most important parameter in artificial heart system.

• Journal of the Semiconductor & Display Technology
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• v.21 no.4
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• pp.126-131
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• 2022

The number of joint disease patients is increasing every year. Currently, the most CPM(Continuous Passive Motion) equipment uses expensive imported equipment, and one CPM equipment is designed to be used only in one joint, medical personnel or hospitals who are the main users of the medical equipment need to have several types of CPMs for joint rehabilitation. To solve this problem, this paper designed a multifunctional joint medical equipment that enables rehabilitation of knee, shoulder, and elbow joints in one CPM equipment and includes general, intensive, and adaptive exercise functions for effective treatment according to the patient's condition. The patient's condition was diagnosed using a load cell and a current sensor. In this paper, effective rehabilitation methods were presented and high reliability and precision of medical equipment was confirmed through experiments using potentiometer, encoder, and PI controller.

• International Journal of Control, Automation, and Systems
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• v.4 no.4
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• pp.438-447
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• 2006

Fuzzy controller's design depends mainly on the rule base and membership functions over the controller's input and output ranges. This paper presents two different approaches to deal with these design issues. A simple and efficient approach; namely, Fuzzy Subtractive Clustering is used to identify the rule base needed to realize Fuzzy PI and PD type controllers. This technique provides a mechanism to obtain the reduced rule set covering the whole input/output space as well as membership functions for each input variable. But it is found that some membership functions projected from different clusters have high degree of similarity. The number of membership functions of each input variable is then reduced using a similarity measure. In this paper, the fuzzy subtractive clustering approach is shown to reduce 49 rules to 8 rules and number of membership functions to 4 and 6 for input variables (error and change in error) maintaining almost the same level of performance. Simulation on a wide range of linear and nonlinear processes is carried out and results are compared with fuzzy PI and PD type controllers without clustering in terms of several performance measures such as peak overshoot, settling time, rise time, integral absolute error (IAE) and integral-of-time multiplied absolute error (ITAE) and in each case the proposed schemes shows an identical performance.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.1929-1931
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• 2001

An adaptive fuzzy logic controller to regulate molten steel level in the strip casting process is presented, where parameters of fuzzy controllers are adapted stably by using Lyapunov-stability theory and a switching controller is used together to deal with the approximation error of fuzzy logic system. The level error is proven to converge to zero asymptotically. In the simulation, the clogging/unclogging of a stopper nozzle is considered and overcome by the proposed controller. Robustness to uncertainty is shown to be superior to conventional PI controller.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.310-313
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• 2005

In this paper, four quadrant CBPS(Compact Bipolar Power Supply) which development and study using universal PWM controller. The CBPS has 24V DC-link voltage, +/-5A output current, 50kHz switching frequency and 30Hz full load bandwidth using FET device. Proposed system has two independent PWM controllers for each full-bridge switch leg drive and PI control loops for current regulations. It is shown experimental results that good step response of the current output.