• The Transactions of the Korean Institute of Power Electronics
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• v.1 no.1
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• pp.38-46
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• 1996

The commutation operation of the current source converter for switched reluctance motor drives is analyzed in this paper. The commutation operation in the current source converter consists of two modes. At turn-off of phase switch, the phase current decreases sinusoidally, and the sum of two phase currents during commutation period is constant. At this time, the capacitor voltage increases quickly with changing polarity and decreases slowly when another phase switches turn on or off. Frequency of step-down DC chopper in the current source converter is low because of the dump such as BJTs and GTOs are possible as phase switches instead of Power MOSFET and IGBTS. They may result in reductions of conduction losses and manufacturing cost in the current source converter comparing to the voltage source converter of SRM.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.512-513
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• 2012

The electric motor is essential to drive turbo machinery. In order to overcome the speed limitations of general motors, the inverter is used to perform high speed to tens of rpm. The high speed drives are widely used in many applications such as turbo blower, turbo centrifugal compressors, and pump using air bearing technique. Starting of high speed motor can cause step out, stall, oscillation of motor because the phase inductance is much smaller than that of ordinary motor. This paper studied on the starting characteristic of variable speed centrifugal chiller considering high speed motor characteristics. Finally, the superiority of the inverter is verified by experimental results.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1114-1115
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• 2007

In this paper, a new speed sensorless control based on a fuzzy compensator are proposed for the interior permanent magnet synchronous motor (IPMSM) drives. The conventional proportional plus integrate(PI) control are very sensitive to step change of the command speed, parameter variations and load disturbance. To cope with these problems of the PI control, the estimated speeds are compensated by using the fuzzy logic controller (FLC). In the FLC used by the speed compensator of the IPMSM, the system control parameters are adjusted by the fuzzy rule based system, which is a logical model of the human behavior for process control. The effectiveness of algorithm is confirmed by the experiments.

• Journal of the Semiconductor & Display Technology
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• v.21 no.2
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• pp.32-37
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• 2022

As semiconductors become finer, equipment must perform precise and accurate processes to achieve the desired wafer fabrication requirement. Radio frequency power delivery system in plasma system plays a critical role to generate the plasma, and the role of impedance matching unit is critical to terminate the reflected radio frequency power by modifying the impedance of the matching network in the plasma equipment. Impedance matching unit contains one fixed inductor and two variable vacuum capacitors whose positions are controlled two step motors. Controlling the amount of vacuum variable capacitor should be made as soon as possible when the mismatched impedance is detected. In this paper, we present the impedance matching algorithm using the phase sensor.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.11
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• pp.6446-6451
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• 2014

Pneumatic motors are quite attractive for many applications because of their competitive price, light-weight, easy assembly, safety in hazardous areas as well as other features, such as a good force/weight ratio and operation in exceptionally harsh environments. In contrast to these advantages, pneumatic motors have limited use in applications, particularly those requiring a fast and precise response. These undesirable characteristics are due to the high compressibility of air and from the nonlinearities in pneumatic systems. This paper presents the sliding mode controller based on 3-loop(SMCB3L), which increases the load stiffness to control the rotation angle of a pneumatic motor. The characteristics for the step responses and load disturbances of the proposed controller were compared with the conventional PID controller. The experimental results showed that a properly designed SMCB3L is capable of high positioning accuracy within ${\pm}0.05mm$. Furthermore, the load stiffness of the SMCB3L can be improved 3.5 fold compared to that of PID controllers.

• Journal of the Ergonomics Society of Korea
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• v.32 no.3
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• pp.217-227
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• 2013

Objective: The purpose of this study was to analyze 'response time', 'peak response time' and 'overshoot value' for each muscle by applying the EMG signal to the vehicle response in ISO 7401 and to quantify the response of the driver according to vehicle characteristics by comparing vehicle characteristics and muscle responses of the driver. Background: The Open-loop test defined in international standards ISO 7401 is the only method for evaluating the performance of the vehicle. However, this test was focused only on mechanical responses, not driver's ones. Method: One skilled male driver(22 yrs. experience) was participated in this experiment to measure muscle activities of the driver in transient state. Then the seven muscle signals were applied to calculate 'response time', 'peak response time', and 'overshoot value'. Results: In the analyses of the EMG data, the effects of vehicle type and muscle were statistically significant on the 'response time' and 'peak response time'. Also, the effects of vehicle type, muscle, and lateral acceleration level were statistically significant on the 'overshoot value' in this study. According to the analyses of the vehicle motion data, vehicle motion variable(LatAcc, Roll, YawVel) was statistically significant on the 'response time' and vehicle type, vehicle motion variable, and lateral acceleration level were statistically significant on the 'peak response time', respectively. Conclusion: In the analyses of the 'response time' and 'overshoot value', the data of muscle activities(EMGs) was better index that could evaluate the vehicle characteristic and performance than the data of vehicle motion. In case of peak response time, both EMG and vehicle motion data were good index. Application: The EMGs data from a driver might be applicable as index for evaluation of various vehicle performances based on this study.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.9
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• pp.723-734
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• 2018

A structural weight estimation methodology for the multicopter design process is presented. In general, a multicopter is composed of an airframe, motors, propellers, battery and so on. Among these, the weight of motors, propellers and battery can be obtained from the weight trends with respect to design parameters. However, the structural weight is hard to be estimated due to the various configurations and design concepts of multicopters. Moreover, the airframe weights of most commercial multicopter products are not provided. Thus, an accurate airframe weight model is required for the reliable mutlcopter design process. Firstly, the standard configuration of multicopters is defined. Then, we proposed the structural weight estimation method using the number and diameter of propellers determined from the initial step of sizing process. Finally, we validated our suggested method using the commerical products.

• Journal of the Korea Society of Computer and Information
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• v.18 no.7
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• pp.23-35
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• 2013

This paper proposes an effective technique that is used to automatically extract feature vectors from vibration signals for fault classification systems. Conventional mel-frequency cepstral coefficients (MFCCs) are sensitive to noise of vibration signals, degrading classification accuracy. To solve this problem, this paper proposes spectral envelope cepstral coefficients (SECC) analysis, where a 4-step filter bank based on spectral envelopes of vibration signals is used: (1) a linear predictive coding (LPC) algorithm is used to specify spectral envelopes of all faulty vibration signals, (2) all envelopes are averaged to get general spectral shape, (3) a gradient descent method is used to find extremes of the average envelope and its frequencies, (4) a non-overlapped filter is used to have centers calculated from distances between valley frequencies of the envelope. This 4-step filter bank is then used in cepstral coefficients computation to extract feature vectors. Finally, a multi-layer support vector machine (MLSVM) with various sigma values uses these special parameters to identify faulty types of induction motors. Experimental results indicate that the proposed extraction method outperforms other feature extraction algorithms, yielding more than about 99.65% of classification accuracy.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.2
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• pp.179-185
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• 2016

In this paper numerical stability of CSS and ISS schemes in axisymmetric fluid-structure-burning simulation for solid rocket motors are studied. The implemented CSS and ISS algorithms for two-dimensional axisymmetric FSI problems are used to analyze ACM and BCM solid rocket motors. Numerical results from CSS and ISS schemes are compared to investigate the efficacy of ISS scheme over CSS scheme in stabilizing the numerical solution. The ACM and BCM simulation results show that ISS scheme gives stable and converged numerical solutions with appropriately small system time step size, while CSS scheme fails to converge after generating rapidly amplified oscillatory solutions. It is concluded that ISS scheme can be useful in improving the numerical stability of FSI analysis for ACM and BCM solid rocket motor simulations, which is not successfully obtained with CSS scheme.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.1
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• pp.50-56
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• 2010

This paper presents a new design algorithm for piece-removing dynamical system, based on 6-Sigma DMADOV technique using ARIZ and Brainstorming. Our design target is the piece-removing system installed on a mobile platform of bead-grinding equipment. The 6-Sigma DMADOV technique guides us design process according to 6 steps, i.e., Define - Measure - Analyze - Design - Optimize - Verify. A Design strategy to reduce the weight of piece-removing dynamical system will be explored by using ARIZ, i.e.,(the abbreviation of Algorithm for Inventive Problem Solving in Russian). The ARIZ will result in a final solution that the height and angle control parts for a cutting tool should be replaced by a kinematical approach, rather than complicated mechatronic approach(using motors). The Optimize step is composed of two sub-steps: (i) Generating process for obtaining several ideas of piece-removing system by using Brainstorming technique, satisfying the final solution derived from the Design step using ARIZ, and (ii) Optimizing process for selecting the most optimal idea of piece-removing system by using Pugh's matrix from the viewpoints of weight, cost and accuracy. The laststep of Verify has shown that the final design obtained by the 6-Sigma DMADOV technique with ARIZ & Brainstormingcan improve an initial design with design requirements satisfied. In this paper, we have shown that ARIZ and Brainstorming can be cooperatively merged into 6-Sigma DMADOV to give us both a formulatedproblem-solving approach and diverse candidate solutions(or ideas) without trial-and-error efforts.