• 동력기계공학회지
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• 제18권5호
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• pp.129-136
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• 2014

This paper proposes improvement on sensorless vector control performance of a permanent magnet synchronous motor (PMSM) with sliding mode observer. An adaptive observer gain and second order cascade low-pass filter (LPF) were used to improve the estimation accuracy of the rotor position and speed. The adaptive observer gain was applied to suppress the chattering intensity and obtained by using the Lyapunov's stability criterion. The second order cascade LPF was designed for the system to escalate the filtering performance of the back-emf estimation. Furthermore, genetic algorithm was used to optimize the system PI controller's performance. Simulation results showed the effectiveness of the suggested improvement strategy. Moreover, the strategy was useful for the sensorless vector control of PMSM to operate on the low-speed area.

• 한국통신학회논문지
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• 제22권7호
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• pp.1385-1393
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• 1997

In this paper, a systematic design method of brjoadband tunable bandpass filter is presented by using user defined varactor diode method. The tunable bandpass filter is constructed as the cascade connection of low pass filter and high pass filter. The designed filter shows the characteristeristics of 2.7.+-.0.2dB insertion loss and 37.1.+-.5.0dB insertion loss and 32.1.+-.2.2dB image rejection. The results of the research can be used fodr the broadband tunable filter of DBS tuner and communication instruments.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.197-200
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• 2005

This paper presents the design of a broadband hybrid mixer using dual-gate FET topology with a low-pass filter which improves return loss of output to isolate RF and LO signal. The low-pass filter shows the isolation whose RF and LO signal is better than 40 dBc at 2 GHz and 5 GHz band. The dual-gate mixer which has been designed by using cascade topology operates when the lower FET is biased in linear region and the upper FET is in saturation. The input matching circuit has been designed to have conversion gain from 2 GHz to 6 GHz. The designed mixer with low-pass filter shows the conversion gain of better than 7 dB from 2 GHz to 6 GHz at a low LO power level of 0 dBm with the fixed IF frequency of 21.4 MHz.

• 동력기계공학회지
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• 제19권4호
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• pp.89-96
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• 2015

This paper investigates some strategies to overcome the chattering problem of the conventional sliding mode observer (SMO) and to improve the rotor position estimation performance for full range sensorless control of a PMSM. An adaptive observer gain based on the Lyapunov's stability criterion and a cascade low pass filter with advanced phase delay compensation were proposed to reduce the chattering problem and to strengthen the filtering capability of the SMO. Several cases studies through experiments were carried out to confirm conventional SMO's problems and effectiveness of the proposed strategies. The experimental results show that the proposed method gives precise estimation on speed and rotor position when the motor rotates on 2% of its rated speed.

• 수산해양교육연구
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• 제29권3호
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• pp.778-784
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• 2017

This paper proposes a sensorless speed control of a permanent magnet synchronous motor (PMSM) based on an adaptive sliding mode observer (SMO) for electric propulsion system of small ships. An adaptive observer gain is proposed based on the Lyapunov's stability criterion to reduce the chattering problem at any speed operation instead of the constant gain observer. Furthermore, a cascade low-pass filter with variable cut-off frequency is suggested to strengthen the filtering capability of the observer. The experimental results from a 1.5 kW PMSM drive are provided to verify the effectiveness of the proposed adaptive SMO. The result shows that the proposed method gives good speed control performances even when the PMSM operates at 0.5% from its rated speed value.

• 전기학회논문지P
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• 제60권1호
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• pp.19-26
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• 2011

In this paper, we designed Interpolation FIR(Finite Impulse Response) filter and 1-bit SDM(Sigma- Delta Modulator) for small digital audio speaker, which has low power consumption and high output characteristics. In order to achieve high linearity and low distortion performance of the systems, we adopt Type I Chevychev FIR filter which has equiripple characteristics in the pass band and proposed high efficient FIR filter structure. SDM is the most efficient modulation technique among the noise shaping techniques. In this paper, we implemented SDM using CIFB(Cascade of Intergrators, Feed-Back) which is generally used in DAC of small digital audio speakers. The proposed SDM structure can achieve high SNR, high-efficiency characteristics and low power consumption in mobile devices. Also considering manufacture of SoC(System on Chip), we performed simulation with Matlab and Verilog HDL to obtain optimal number of operational bits and verified a good experimental results.

• Journal of applied mathematics & informatics
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• 제8권3호
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• pp.731-742
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• 2001

A Gaussian smoothing algorithm obtained from a cascade of convolutions with a seven-point kernel is described. We prove that the change of local sums after applying our algorithm to sinusoidal signals is reduced to about two thirds of the change by the binomial coefficients. Hence, our seven point kernel is better than the binomial coefficients when trend curves are needed to be generated. We also prove that if our Gaussian convolution is applied to sinusoidal functions, the amplitude of higher frequencies reduces faster than the lower frequencies and hence that it is a low pass filter.

• 한국항행학회논문지
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• 제9권2호
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• pp.103-109
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• 2005

본 논문에서는 이중게이트 FET 구조를 이용하여 광대역 하이브리드 믹서를 RF신호와 LO신호를 출력단과 격리하는 저역통과필터와 같이 설계하였다. 저역통과필터는 1.5-5.5GHz에서 RF와 LO신호에 대하여 40dBc의 억압특성을 나타낸다. 이중게이트 FET 믹서는 두 개의 FET를 캐스코드 구조로 연결하여 설계하였으며, 첫번째 FET는 선형영역에서 동작되고 두번째 FET는 포화영역에서 동작한다. 입력매칭은 1.5-5.5GHz에서 높은 변환이득을 갖도록 설계하였다. 설계된 믹서는 IF를 21.4MHz로 고정시키고 0dBm의 국부발진기 전력에서 1.5-5.5GHz 대역에서 7dB이상의 변환이득을 가진다.

• Journal of Power Electronics
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• 제6권3호
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• pp.235-244
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• 2006

Recently, speed sensorless vector control for synchronous reluctance motors (SYRMs) has deserved attention because of its advantages. Although rotor angle calculation using flux estimation is a straightforward approach, the DC offset can cause an increasing pure integrator error in this estimator. In addition, this method is affected by parameter fluctuation. In this paper, to control the motor at the low speed region, a modified programmable cascaded low pass filter (MPCPLF) with sensorless online parameter identification based on a block pulse function is proposed. The use of the MPCLPF is suggested because in programmable, cascade low pass filters (PCLPF), which previously have been applied to induction motors, the drift increases vastly wl)en motor speed decreases. Parameter identification is also used because it does not depend on estimation accuracy and can solve parameter fluctuation effects. Thus, sensorless speed control in the low speed region is possible. The experimental system includes a PC-based control with real time Linux and an ALTERA Complex Programmable Logic Device (CPLD), to acquire data from sensors and to send commands to the system. The experimental results show the proposed method performs well, speed and angle estimation are correct. Also, parameter identification and sensorless vector control are achieved at low speed, as well as, as at high speed.

• 한국통신학회논문지
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• 제18권2호
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• pp.184-191
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• 1993

최근 MOS 공정기술로 집적화된 연속시간 필터 연구가 주목을 받고 있다. 본 논문에서는 차단주파수 3,400Hz를 갖는 연속시간 5차 타원 저역통과 MOSFET-C 필터를 실현하기 위하여, 먼저 각 블록을 동조할 수 있는 종속연결법으로 능동 RC 필터를 설계하였다. 그리고 능동 RC 회로의 저항들을 triode 영역에서 작동하는 NMOS depletion mode 트랜지스터 선형저항으로 실현하였다. 이러한 연속시간 MOSFET-C 필터는 스윗치드 커패시터 필터에 비하여 구조가 간단하여 칩의 면적을 줄일 수 있다. 설계된 MOSFET-C 필터 특성을 PSPICE 프로그램으로 시뮬레이션 하였다.