• 소음진동
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• 제4권4호
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• pp.497-505
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• 1994

This paper presents a design scheme of the active noise absorber that consists of the feedforward and feedback controller. The feedback controller aims to increase damping for the specific acoustic mode. The feedforward controller synthesizes the input signal coherent with the primary noise source in order to attenuate the noise field in the broad frequency range. The feedforward controller is adapted to the variation of acoustic plants using the proposed algorithm which compensates the effect of feedback link. Experimental results demonstrate that the proposed method is effective for the active control of band-limited noise fields in the enclosure.

• 로봇학회논문지
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• 제17권3호
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• pp.282-287
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• 2022

High shear adhesion on wet and rough surfaces and tactile feedback of gripping forces are highly important for realizing robotic gripper systems. Here, we propose a bioinspired robotic gripper with highly shear adhesion and sensitive pressure sensor for tactile feedback systems. To achieve them, we fabricated multi-walled carbon nanotube sensing layer on a thin polymeric adhesive layer of polydimethylsiloxane. With densely hexagonal-packed microstructures, the pressure sensor achieved 9 times the sensing property of a sensor without microstructures. We then assembled hexagonal microstructures inspired by the toe pads of a tree frog, giving strong shear adhesion under both dry and wet surfaces such as silicon (42 kPa for dry and ~30 kPa for underwater conditions) without chemical-residues after detachment. Our robotic gripper can prevent damage to weak or smooth surfaces that can be damaged at low pressure through pressure signal feedback suggesting a variety of robotic applications.

• 대한전자공학회논문지
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• 제24권2호
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• pp.347-354
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• 1987

Timing simulators are widely used nowadays for analyzing large-scale MOS digital circuits, which, however, have several limitations such as nonconvergence and/or in accuracy for circuits containing tightly coupled feedback elements or loops. This paper describes a new timing simulator which aims at solving these problems. The algorithm employed is based on the wave-form relaxation method, but exploits the signal flow along the feedback loops. Each of feedback loops is treated as one circuit block and then local iterations are performed to enhance the timing simulation. With these techniques, out simulator can analyze the MOS digital circuits with up to 5-20 times of the magnitude speed improvemnets as compared to SPICE2, while maintaining the accuracy.

• 한국통신학회논문지
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• 제36권5A호
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• pp.511-520
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• 2011

본 논문은 다중 사용자 amplify-and-forward relay 시스템에서 전송 모드, 즉, 한 홉 혹은 두 홉 전송, 그리고 적절한 사용자를 두 단계로 선택하는 다중 사용자 스케줄링 기법을 소개한다. 제안하는 다중 사용자 스케줄링을 수행하였을 경우 두 가지 전송 모드별 평균 achievable rate의 닫힘 꼴 표현을 유도하고 단말 수가 무한히 증가할 때 평균 achievable rate에 대한 점근적인 결과도 분석한다. 평균 achievable rate 분석에 기반하여 두 단계 스케줄링 알고리즘을 수행하는데, 먼저 전송 모드 선택을 하고, 그 다음 선택된 전송 모드에 대한 순간 signal-to-noise ratio (SNR)을 기지국으로 피드백 함으로써 이를 이용한 부분적인 피드백 정보를 기반으로 사용자 선택을 수행한다. 또한 다중 사용자 diversity gain이 최대로 취득되는 평균 SNR 조건도 분석하고 추가로 특정 조건에서 피드백 양을 더 줄일 수 있는 방안에 대해 조사한다. 제안된 스케줄링 알고리즘은 모든 전송 모드 (즉, 한홉과 두 홉 전송 모드)에 대한 instantaneous SNR을 피드백하여 최적 다중 다용자 스케줄링을 할 경우와 유사한 achievable rate을 보인다. 반면 제안 기법의 피드백 양은 최적 기법에 비해 대략 절반으로 줄어드는 것을 확인한다.

• 센서학회지
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• 제26권2호
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• pp.85-90
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• 2017

A wide dynamic range (WDR) CMOS image sensor (CIS) was developed with a specialized readout architecture for realizing high-sensitivity (HS) and low-sensitivity (LS) reading modes. The proposed pixel is basically a three-transistor (3T) active pixel sensor (APS) structure with an additional transistor. In the developed WDR CIS, only one mode between the HS mode for relatively weak light intensity and the LS mode for the strong light intensity is activated by an external controlling signal, and then the selected signal is read through each column-parallel readout circuit. The LS mode is implemented with the column capacitors and a feedback structure for adjusting column capacitor size. In particular, the feedback circuit makes it possible to change the column node capacitance automatically by using the incident light intensity. As a result, the proposed CIS achieved a wide dynamic range of 94 dB by synthesizing output signals from both modes. The prototype CIS is implemented with $0.18-{\mu}m$ 1-poly 6-metal (1P6M) standard CMOS technology, and the number of effective pixels is 176 (H) ${\times}$ 144 (V).

• Journal of Power Electronics
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• 제10권3호
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• pp.285-292
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• 2010

This paper presents a current mode integrated control technique (CM-ICT) using a modified voltage space vector modulation (MSVM) for Z-source inverter (ZSI) fed induction motor drives. MSVM provides a better DC voltage boost in the dc-link, a wide range of AC output voltage controllability and a better line harmonic profile. In a voltage mode ICT (VM-ICT), the outer voltage feedback loop alone is designed and it enforces the desired line voltage to the motor drive. An integrated control technique (ICT), with an inner current feedback loop is proposed in this paper for the purpose of line current limiting and soft operation of the drive. The current command generated by the PI controller and limiter in the outer voltage feedback loop, is compared with the actual line current, and the error is processed through the PI controller and a limiter. This limiter ensures that, the voltage control signal to the Z-source inverter is constrained to a safe level. The rise and fall of the control signal voltage are made to be gradual, so as to protect the induction motor drive and the Z-source inverter from transients. The single stage controller arrangement of the proposed CM-ICT offers easier compensation. Analysis, Matlab/Simulink simulations, and experimental results have been presented to validate the proposed technique.

• 제어로봇시스템학회논문지
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• 제20권1호
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• pp.12-17
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• 2014

In this paper, we propose a controller capable of reducing the effect of measurement errors under AC and DC noise. Typically, the control system measures data through a sensor. If sensor noise is included in a controller via the feedback channel, the signal is distorted and the entire system cannot work normally. Therefore, some appropriate action to counter the measurement error effect is essential in the controller design. Our controller is equipped with a gain-scaling factor and a compensator to reduce the effect of measurement error in the feedback signal. Also, we use a switching control strategy to enhance the performance of the controller regarding convergence speed. Our proposed controller can therefore effectively reduce the AC and DC noise of the sensor. We analyze the proposed controller by Laplace transform technique and our control method is verified via MATLAB simulation.

• Journal of Multimedia Information System
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• 제5권1호
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• pp.59-62
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• 2018

The delay between input action and visual interface feedback ("Latency") in a touchscreen inking task reduces the user's performance. When the latency is less than 2.38ms, the user cannot perceive the latency in dragging task. This value is difficult to achieve on recent touchscreens and general purpose computers. So, methods of predicting touch points to reduce perceptible latency has been proposed. In general, touch points prediction is not perfect. When using point prediction, feedback of the predicted points is displayed on the screen, after a while, erased when the actual points are displayed. When this task is implemented by software, it causes additional latency to work to erase predicted points feedback. It therefore propose a platform for rendering point prediction feedback without additional latency by the FPGA. This platform transmits input points and HDMI signals rendering feedback of input points to the FPGA. The FPGA draws the feedback of points predicted based on the input points on the HDMI and displays the screen. Since hardware rendering changes the HDMI signal every frame, it does not require erasing work and rendering can be done within an early time regardless of the amount of rendering, so we will reduce the latency.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.57-60
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• 2004

This paper presents multibit Sigma-Delta ADC using Leslie-Singh Structure to Improve nonlinearity of feedback loop. 4-bit flash ADC for multibit Quantization in Sigma Delta modulator offers the following advantages such as lower quantization noise, more accurate white-noise level and more stability over single quantization. For the feedback paths consisting of DAC, the DAC element should have a high matching requirement in order to maintain the linearity performance which can be obtained by the modulator with a multibit quantizer. Thus a Sigma-Delta ADC usually adds the dynamic element matching digital circuit within feedback loop. It occurs complexity of Sigma-Delta Circuit and increase of power dissipation. In this paper using the Leslie-Singh Structure for improving nonliearity of ADC. This structure operate at low oversampling ratio but is difficult to achieve high resolution. So in this paper propose improving loop filter for single-bit feedback multi-bit quantization Sigma-Delta ADC. It obtained 94.3dB signal to noise ratio over 615kHz bandwidth, and 62mW power dissipation at a sampling frequency of 19.6MHz. This Sigma Delta ADC is fabricated in 0.25um CMOS technology with 2.5V supply voltage.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 제13회 신호처리 합동 학술대회 논문집
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• pp.741-744
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• 2000

본 논문에서는 고밀도 DVD(Digital Versatile Disc) 시스템(4.7GB～l5GB)을 위한 신호 검출기법을 제안하고 FPGA로 구현한다. 본 논문에서 제안하는 FDTrS/DF (Fixed Delay Trellis Search with Decision Feedback)는 트렐리스 구조를 사용하므로 FDTS/DF나 SSD/DF(Signal Space Detection with Decision Feedback)와 같이 이진 가지 구조를 사용하는 신호검출방식에 비해 더 나은 성능을 얻을 수 있다. 또한 FDTrS/DF는 한 단의 트렐리스 구조를 사용해 역추적을 하지 않으므로 하드웨어의 복잡도와 속도면에서 향상된 결과를 얻을 수 있다. 또한 본 논문에서는 하드웨어 구현 시 동작 속도의 향상을 위해 파이프라인 기법과, 계산량 감소를 위해 절대값 분기거리를 사용한다.