Woo-Hyen Kwon

Parallel Sensorless Speed Control using Flux-axis Current for Dual SPMSMs Fed by a Single Inverter

This paper proposes a sensorless speed control algorithm for parallel-connected dual Surface-mounted Permanent Magnet Synchronous Motors (SPMSMs) fed by a single inverter. For stable parallel operation of synchronous motors with a single inverter, each motor has to be constantly kept in the synchronization state regardless of load torque. If the master motor with the larger load is controlled, the synchronous state will be maintained. Therefore, detection of the master motor is essential. Conventionally, the master motor is determined by comparing the rotor position error from the relation between the back-EMF for torque angle and the flux position; consequently, the position sensor is deemed essential for finding the rotor position. The parallel sensorless speed control method proposed in this paper uses no position sensor, instead it compares the flux-axis current from the connection between the back-EMF for torque angle and current in unbalanced load conditions. The results of simulation and experiment conducted verify the efficacy of the proposed method.

Modified distributed constrained power control using reference model in CDMA cellular systems

The current paper proposes a modified distributed power control (M-DCPC) algorithm that can improve the performance of a CDMA power control system. The control performance of the proposed method is verified using two performance measures: the SIR response of each mobile and the outage probability in a cell. The transient and steady state responses are also compared with those for DCPC, CSOPC, and LQPC. As regards the SIR response, in simulations, the M-DCPC algorithm produced a faster convergence and lower overshoot in transient time than the other power control algorithms when the desired SIR value was varying. For the outage probability, M-DCPC converged to a fixed outage rate faster than CSOPC while also maintaining the system capacity to make as high a connection as CSOPC. In particular, when the desired SIR was varying, CSOPC showed an abrupt outage probability increase during the desired SIR increase, yet M-DCPC was unaffected. Accordingly, M-DCPC was confirmed to be more effective than any of the other power control algorithms.

The Resonance Characteristic Analysis for Speed Control of Parallel Connected Dual SPMSMs fed by a Single Inverter

This pap4er analyzes resonance characteristics of a slave motor that is not controlled by load and parameter differences between Dual motors during parallel operation in middle-low speed. Dual SPMSMs(Surface mounted Permanent Magnet Synchronous Motor) connected in parallel to a single inverter controlled by the master and slave control in this paper. Based on the stability analysis of the SPMSM for a variation of torque angle, the 6th nonlinear state equation of the torque angle variation in the SIMM(Single Inverter Multi Motor) structure is derived according to a mathematical model for the dual motors. In general, an analysis of the 6th order nonlinear state equation is complex. Therefore, a resonance frequency generated from the slave motor is found from the characteristic equation of the 2nd order system obtained by linearization and model reduction near steady state operation point. Through simulations and experiments, it is confirmed that the stability analysis of the SPMSMs and state equation models are useful for the variation of the torque angle analyzed in this paper.

The Design of Code Detector for Sell Call Radio Buoy

Sell call radio buoy is mostly used for searching for the location of fishing nets. Sell call radio buoy for the detection of the code uses the band pass filter(BPF). All BPF is used by imported from Japanese companies. But, Japanese companies stopped selling buoys for searching for the location of fishing nets, and domestic manufacturing companies could not sell buoys any more. Therefore, In this paper, a new method to replace the conventional buoy code detector is proposed. The proposed methods are constructed with an analog filter division composed of BPFs and notch filters as well as a microprocessor with analog digital converters. The advantage of proposed methods is able to combine various codes, can enhance receiver sensitivity. The experimental results confirm the usefulness of the proposed method.

Design of Robust Stability Maximizing PI Controller in Motor Parameter Variation

This paper propose a PI controller that maximizes the degree of stability using a stability in a simplified motor model the applies decoupling control. The PI controller gains are directly from the motor parameters, thereby reducing the element of trial and error, and, the Kharitonov equation was used to evaluate the robustness of the gains to changes in the motor parameters. In addition, the system poles are located in the same position, the proposed method can provide a fast response. The effectiveness of the proposed controller is verified by simulation results.

Development of Automatic Gamma Optimization System for Mobile TFT-LCD

This paper presents an automatic LCD gamma control system using gamma curve optimization. It controls automatically gamma adjustment registers in mobile LCD driver IC to reduce gamma correction error and adjusting time. The proposed gamma system contains Module-Under-Test (MUT, LCD module), PC installed with program, multimedia display tester for measuring luminance, and control board for interface between PC and LCD module. Proposed algorithm and program are applicable for most of the LCD modules. It is realized to calibrate gamma values of 1.8, 2.0, 2.2 and 3.0. The control board is designed with DSP and FPGA, and it supports various interfaces such as RGB and CPU. Developed automatic gamma control system showed significantly reduced gamma adjusting time of 240 sec. and much less average gamma error of 11% than 42h and 27% with conventional manual method. We believe that the proposed system is very useful to provide high-quality LCD and to improve production process.

Resonance suppression method using lead controller for speed control of parallel connected dual SPMSMs fed by a single inverter

This paper analyzes the resonance phenomenon that occurs in the uncontrolled slave motor of two surface mounted permanent magnet synchronous motor (SPMSM) drives, connected in parallel to a single inverter. This phenomenon is observed when the inverter is controlled by the master-slave method, due to the differences in parameters between the two motors and load, during medium and low speed operation. To resolve this problem, we propose a resonance suppression method. First, we find the resonance frequency that occurs in a slave motor by the torque angle variation in a single inverter multi motor (SIMM) structure, based on the stability analysis of the mathematical model for both motors. Then, based on the results of our analysis of the resonance characteristics of the SIMM system, a lead controller is designed to improve the damping of the entire system, thus solving the problems of instability and noise amplification at higher frequencies. The proposed system is verified through simulation.

The Design of Filter for Hearth Liquid Level Estimation in Blast Furnace

Optimizing the tapping time of a blast furnace is important to a stable operation and life extension. To optimize the tapping time of the blast furnace, the location of Hearth Liquid Level should be recognized. There are several ways to measure the hearth liquid level in the blast furnace, such as Electromotive Force(EMF) measurement, pressure measurement by putting in nitrogen probe and manometry with strain gauge. In this paper, it will be discussed using strain gauge among the three methods. Conventional strain gauge must be revised periodically. Since, internal pressure, temperature of internal refractory material and wind pressure have effect on the strain gauge. However, static pressure value is required to compensate. To solve these problems, this paper suggests finding relationship between Hearth Liquid Level and strain gauge output, adding digital filter in strain gauge. Using the proposed method, it was possible to estimate the hearth liquid level and determine the appropriate tapping time. Usefulness of the proposed method through simulations and experimental results are confirmed.

Design of Linear Model Following Controller using the Plant Output

The linear model following controller(LMFC) scheme controls a plant based on the output of a reference model, thereby replacing a PI controller that has better time response characteristics, which are irrelevant to the structural perturbation of a plant. However, the main weakness of the LMFC scheme is a slow response time to load changes. Thus, to solve this problem, a robust linear model following controller(RMFC) was developed that is robust in load changes. However, when compared with the LMFC scheme, the RMFC scheme has a weaker performance in the case of system parameter changes. Therefore, this paper presents a new LMFC scheme, where the controller is designed based on the output of a plant rather than the output of a model, as in the case of the conventional LMFC scheme. As a result, in the case of load changes, the response characteristics of the proposed scheme are slower than those of the RMFC scheme, yet laster than those of the conventional LMFC scheme, however, for parameter changes, the proposed scheme has a superior performance over the RMFC scheme. The usefulness of the proposed LMFC scheme is verified through a comparison using MATLAB/SIMULINK.

Distributed Constrained Power Control with Variable Feedback Gain

The current paper presents a power control method with variable state feedback gain (VFPC) to improve outage convergence rate of distributed constrained power control. The variable state feedback gain includes the information of the desired SIR changes and must be a decreasing sequence for the convergence and the proof for the convergence is given. The proposed algorithm in this paper can be improved the outage convergence rate and SIR (signal to interference ratio) response at the both start time and the steady state when SIR changes are occurred. The simulation results are given