• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1786-1795
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• 2011

The trajectory control for omni-directional mobile robot is not easy. Especially, the tracking control which system uncertainty problem is included is much more difficult. This paper develops trajectory controller of 3-wheels omni-directional mobile robot using fuzzy multi-layered algorithm. The fuzzy control method is able to solve the problems of classical adaptive controller and conventional fuzzy adaptive controllers. It explains the architecture of a fuzzy adaptive controller using the robust property of a fuzzy controller. The basic idea of new adaptive control scheme is that an adaptive controller can be constructed with parallel combination of robust controllers. This new adaptive controller uses a fuzzy multi-layered architecture which has several independent fuzzy controllers in parallel, each with different robust stability area. Out of several independent fuzzy controllers, the most suited one is selected by a system identifier which observes variations in the controlled system parameter. This paper proposes a design procedure which can be carried out mathematically and systematically from the model of a controlled system; related mathematical theorems and their proofs are also given. Finally, the good performance of the developed mobile robot is confirmed through live tests of path control task.

• Journal of the Korean Institute of Intelligent Systems
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• v.12 no.2
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• pp.144-150
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• 2002

In this paper a design of neuro-fuzzy-based predictive controller for nonlinear systems with time-delay is proposed. The proposed control system contains two neuro-fuzzy systems called ANFIS(Adaptive Neuro-Fuzzy Inference System). One is run as a series-parallel mode and the other is run as a parallel mode. An ANFIS running in series-parallel mode emulates the response of the nonlinear system with time-delay. Another ANFIS running in parallel mode generates the predicted output of the nonlinear system to compensate for the time-delays. Therefore, the proposed control system can be thought of as an extension of Smith-predictor scheme to the nonlinear systems with time-delay. A detailed design Procedure is presented and finally computer simulations are executed for the effectiveness of the proposed control scheme.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.391-398
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• 2009

In this study, we introduce the design methodology of an optimized fuzzy cascade controller with the aid of hierarchical fair competition-based genetic algorithm(HFCGA) for ball & beam system. The ball & beam system consists of servo motor, beam and ball, and remains mutually connected in line in itself. The ball & beam system determines the position of ball through the control of a servo motor. The displacement change the position of ball leads to the change of the angle of the beam which determines the position angle of a servo motor. Consequently the displacement change of the position of the moving ball and its ensuing change of the angle of the beam results in the change of the position angle of a servo motor. We introduce the fuzzy cascade controller scheme which consists of the outer(1st) controller and the inner(2nd) controller as two cascaded fuzzy controllers, and auto-tune the control parameters(scaling factors) of each fuzzy controller using HFCGA. The inner controller controls the position of lever arm which corresponds to the position angle of a servo motor and the outer controller decides the set-point value of the inner controller. HFCGA is a kind of parallel genetic algorithms(PGAs), and helps alleviate the premature convergence being generated in conventional genetic algorithms (GAs). For a detailed comparative analysis from the viewpoint of the performance results and the design methodology, the proposed method for the ball & beam system which is realized by the fuzzy cascade controller based on HFCGA, is presented in comparison with the conventional PD cascade controller based on serial genetic algorithms.

• Journal of Power Electronics
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• v.10 no.5
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• pp.505-517
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• 2010

In this paper, an intelligent sliding-mode speed controller for achieving favorable decoupling control and high precision speed tracking performance of permanent-magnet synchronous motor (PMSM) drives is proposed. The intelligent controller consists of a sliding-mode controller (SMC) in the speed feed-back loop in addition to an on-line trained wavelet-neural-network controller (WNNC) connected in parallel with the SMC to construct a robust wavelet-neural-network controller (RWNNC). The RWNNC combines the merits of a SMC with the robust characteristics and a WNNC, which combines artificial neural networks for their online learning ability and wavelet decomposition for its identification ability. Theoretical analyses of both SMC and WNNC speed controllers are developed. The WNN is utilized to predict the uncertain system dynamics to relax the requirement of uncertainty bound in the design of a SMC. A computer simulation is developed to demonstrate the effectiveness of the proposed intelligent sliding mode speed controller. An experimental system is established to verify the effectiveness of the proposed control system. All of the control algorithms are implemented on a TMS320C31 DSP-based control computer. The simulated and experimental results confirm that the proposed RWNNC grants robust performance and precise response regardless of load disturbances and PMSM parameter uncertainties.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.18-25
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• 2003

A haptic hand controller (HHC) operated by the user’s hand can receive information on position and orientation of the hand and display force and moment generated in the virtual environment to the hand. In this paper, a 3-DOF hand controller is first presented, in which all the actuators are mounted on the fixed base by combining a 5-bar linkage and a gimbal mechanism. The 6-DOF HHC is then designed by connecting these two 3-DOF devices through a handle which consists of a screw and nut. Analysis using performance index is carried out to determine the dimensions of the device. The HHC control system consists of the high-level controller for kinematic and static analysis and the low-level controller for position sensing and motor control. The HHC used as a user interface to control the mobile robot in the virtual environment is given as a simple application.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.201-210
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• 2018

This paper proposes a new start-up method for a load commutated inverter (LCI) in a large synchronous gas-turbine generator. The initial rotor position for start-up torque is detected by the proposed initial angle detector, which consists of an integrator and a phase-locked loop. The initial rotor position is accurately detected within 150ms, and the angle difference between the real position and the detected position is less than 1%. The LCI system operates in two modes (forced commutation mode and natural commutation mode) according to operating speed range. The proposed controllers include a forced commutation controller for the low-speed range, a PI speed controller and a PI current controller, where the forced commutation controller is connected to the current controller in parallel. The current controller is modeled by Matlab/Simulink, where a six-pulse delay of the thyristor and a processing delay are considered by using a zero-order hold. The performance of the proposed start-up method is evaluated in Matlab/Psim at standstill and at low speed. To verify the feasibility of the method, a 5kVA LCI system prototype is implemented, and the proposed initial angle detector and the system performance are confirmed by experimental results from standstill to 900rpm.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.6
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• pp.213-219
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• 2004

This paper describes the developmnet of a web-based boiler controller which can be in parallel operated with an existing boiler controller. The web-based boiler controller mainly consists of RTL8019AS NIC and TS80C32 microcontroller. In order to communicate over the Internet, we need to develop network driver, IP, TCP, UDP, ICMP, and HTTP. For a specific application like web-boiler controller, we have proposed a common global data buffer algorithm to minimize the RAM memory usage. Finally, the correctness and performance of the protocols are tested and verified using CommView and Dummynet. The development is satisfactorily operated only for few hundreds of bytes of RAM usage without sacrificing interoperability between hosts.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.4
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• pp.312-319
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• 2016

Zero-sequence Circulating Current (ZSCC) flows inevitably in parallel converters that share common DC and AC sources. The ZSCC commonly flowing in all converters increases loss and decreases the overall capacity of parallel converters. This paper proposes a simple and effective ZSCC suppression method based on the Space Vector PWM (SVPWM) with the ZSCC controller. The zero-sequence voltage for the proposed SVPWM is calculated on the basis of the grid voltage and not on the phase voltage references. The limit of the linear modulation region of the converters with the proposed method is analyzed and compared with other methods, thereby proving that the limit of the region can be extended with the proposed method. The effectiveness of the proposed method has been verified through the experimental setup comprising four parallel three-level converters. The ZSCC is confirmed to be well suppressed, and the linear modulation region is extended simultaneously with the proposed method. Moreover, the proposed control method does not require any communication between the converters to suppress the ZSCC unlike other conventional methods.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.81-90
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• 2015

This paper investigates the droop control-based real and reactive power load sharing with a virtual inductor when the line impedance between inverter and Point of Common Coupling (PCC) is partly and unequally resistive in high-capacity systems. In this paper, the virtual inductor method is applied to parallel inverter systems with resistive and inductive line impedance. Reactive power sharing error has been improved by applying droop control after considering each line impedance voltage drop. However, in high capacity parallel systems with large output current, the reference output voltage, which is the output of droop controller, becomes lower than the rated value because of the high voltage drop from virtual inductance. Hence, line impedance voltage drop has been added to the droop equation so that parallel inverters operate within the range of rated output voltage. Additionally, the virtual inductor value has been selected via small signal modeling to analyze stability in transient conditions. Finally, the proposed droop method has been verified by MATLAB and PSIM simulation.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.429-432
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• 2000

The new MPEG-4 video coding standard enables content-based functionalities. In order to support the philosophy of the MPEG-4 visual standard, each frame of video sequences should be represented in terms of video object planes (VOP’s). In other words, video objects to be encoded in still pictures or video sequences should be prepared before the encoding process starts. Therefore, it requires a prior decomposition of sequences into VOP’s so that each VOP represents a moving object. A parallel processing system is required an automatic segmentation to be processed in real-time, because an automatic segmentation is time consuming. This paper addresses the parallel processing: system for an automatic segmentation for separating moving object from the background in image sequences. The proposed parallel processing system comprises of processing elements (PE’s) and a multi-access memory system (MAMS). Multi-access memory system is a memory controller to perform parallel memory access with the variety of types: horizontal, vertical, and block access way. In order to realize these ways, a multi-access memory system consists of a memory module selection module, data routing modules, and an address calculation and routing module. The proposed system is simulated and evaluated by the CADENCE Verilog-XL hardware simulation package.