2,649 research outputs found
Attitude control of a bias momentum satellite using moment of inertia
No full textAnalysis on the attitude controller based upon moment of inertia distribution for a bias momentum satellite is discussed. Spacecraft moment of inertia distribution is represented in the form of product of inertia terms in the system inertia matrix. The product of inertia between orthogonal body axes of the satellite is used to build a controller which controls the notational motion caused by the angular momentum of the wheel. The attitude controller in the pitch axis controlling the pitch motion as well as nutational dynamics in the roll/yaw planes is analyzed in detail. Analytic expressions using linearized equations are derived providing further insight into the dynamic coupling effect among orthogonal body axes
Large angle attitude control of spacecraft with actuator saturation
No full textThis paper presents spacecraft large angle attitude control problem with actuator saturation limit. Traditional approach for control design for the spacecraft large angle maneuver is a fixed gain proportional plus integral plus derivative (PID) controller using quaternion attitude variables with stability guarantee. Unwanted external disturbance inputs. may induce excessively large error by the PID control. Anti-windup control and intelligent integrator are effective in reducing the rapid build up of the control signal due to, in particular, integral control action. Application of the anti-windup and intelligent integrator which already have been studied extensively in other areas is made to the large angle feedback controller minimizing reaction wheel type actuator saturation. Conventional PID controller is modified by augmenting additional control actions for the purpose of performance improvement. (C) 2002 Elsevier Ltd. All rights reserved
CAN-HD 을 위한 시스템 디자인 및 성능 평가
No full textDue to the growing demand of the autonomous and connected vehicles, the number of embedded systems and the connectivity increase. Therefore, the data traffic of recent in-vehicle networks is dramatically increasing. In order to improve the data rate and provide reliable and inexpensive quality of service (QoS) of the in-vehicle networks, enormous researches have focused on developing the in-vehicle communication systems recently. However, the data rate of commercial in-vehicle networks such as controller are network (CAN), local interconnect network (LIN), FlexRay and media oriented systems transport (MOST) is insufficient to support the increasing data traffic. In this regard, in order to support the high speed data processing while maintaining backward compatibility with controller area network (CAN) for in-vehicle communication system, the controller area network for high data rate (CAN-HD) was proposed by combining the standard baseband CAN signal with a passband modulated signal. In this paper, we demonstrate both the improvement in performance and the validity of the backward compatibility of CAN-HD system. To be specific, we provide the noise characteristic measured in the real vehicle environment and proper criteria for determining the power constraint of the passband signal to achieve highly compatible system by analyzing the channel capacity of CAN-HD as well as the bit error rate (BER) of standard CAN receiver. ⓒ 2017 DGISTI. Introduction 1--
II. In-vehicle Networks 4--
2.1 Controller Area Network (CAN) 4--
2.2 Local Interconnect Network (LIN) 8--
2.3 FlexRay 9--
2.4 Media Oriented Systems Transport (MOST) 10--
2.5 Controller Area Network with Flexible Data Rate (CAN-FD) 11--
III. Controller Area Network for High Data Rate (CAN-HD) 13--
3.1 Introduction of CAN-HD 13--
3.2 Channel Gain of CAN Bus 18--
3.2.1 Channel Modeling Method 18--
3.3 Noise Measurement of CAN Bus 23--
IV. Performance Analysis for CAN-HD 25--
4.1 Channel Capacity of CAN-HD 25--
4.1.1 Channel Capacity in Frequency Selective CAN Channel 25--
4.1.2 Channel Capacity Analysis 25--
4.2 Backward Compatibility Analysis for CAN-HD 30--
4.2.1 Signal Transmission and Detection 30--
4.2.2 BER Analysis 32--
4.2.3 Simulation Result 34--
V. Conclusion 39--
Reference 40--논문에서는 차량 내부 통신인 controller area network (CAN) 의 호환성을 제공하면서 데이터 전송속도를 향상 시킨 controller area network for high data rate (CAN-HD) 의 채널 용량 분석 및 호환성 제공을 위한 기준을 제시하였다. Vehicle to everything communication (V2X) 및 connected car 가 발전함에 따라 차량에 내장되는 시스템의 수가 급격히 증가하고 있으며, V2X 및 connected car 의 데이터의 전송속도 또한 증가하고 있다. 이에 따라, 차량 내부에서도 높은 데이터 전송속도가 요구되며, 이를 위해 controller area network for high data rate (CAN-HD) 가 제안되었다. CAN-HD 는 기존의 CAN 신호에 통과대역 신호를 추가적으로 사용하여 데이터 전송속도를 향상시키는 동시에 다른 대역을 사용함으로써, 호환성을 제공하는 시스템이다. 본 논문에서는 채널 용량 분석을 통해 CAN-HD 가 이론적으로 1 Gbps 가 넘는 고속 통신을 제공할 수 있음을 보였다. 반면, 제안된 CAN-HD 는 기존의 상용 CAN 의 수신기 내의 저주파 대역 통과 필터의 높은 차단 주파수로 인해 통과 대역 신호를 제대로 걸러내지 못하여, 호환성 제공 여부가 불확실 하였다. 본 논문에서는 채널 용량 분석 외에 CAN-HD 의 호환성을 검증하기 위해 기존 CAN 의 수신기 동작을 파악하고, 이를 기반으로 CAN-HD 신호를 전송하였을 때의 비트 오류율을 시뮬레이션 결과와 분석 결과를 비교하여 검증하였다. 그 결과 통과 대역 신호의 적절한 전력 제한을 통해 1 Gbps 이상의 채널 용량 달성과 동시에 기존의 CAN 시스템과 호환이 가능함을 보였다. ⓒ 2017 DGISTMasterdCollectio
Short-interval observational data to inform clinical trial design in Huntington's disease.
No full textOBJECTIVES: To evaluate candidate outcomes for disease-modifying trials in Huntington's disease (HD) over 6-month, 9-month and 15-month intervals, across multiple domains. To present guidelines on rapid efficacy readouts for disease-modifying trials. METHODS: 40 controls and 61 patients with HD, recruited from four EU sites, underwent 3 T MRI and standard clinical and cognitive assessments at baseline, 6 and 15 months. Neuroimaging analysis included global and regional change in macrostructure (atrophy and cortical thinning), and microstructure (diffusion metrics). The main outcome was longitudinal effect size (ES) for each outcome. Such ESs can be used to calculate sample-size requirements for clinical trials for hypothesised treatment efficacies. RESULTS: Longitudinal changes in macrostructural neuroimaging measures such as caudate atrophy and ventricular expansion were significantly larger in HD than controls, giving rise to consistently large ES over the 6-month, 9-month and 15-month intervals. Analogous ESs for cortical metrics were smaller with wide CIs. Microstructural (diffusion) neuroimaging metrics ESs were also typically smaller over the shorter intervals, although caudate diffusivity metrics performed strongly over 9 and 15 months. Clinical and cognitive outcomes exhibited small longitudinal ESs, particularly over 6-month and 9-month intervals, with wide CIs, indicating a lack of precision. CONCLUSIONS: To exploit the potential power of specific neuroimaging measures such as caudate atrophy in disease-modifying trials, we propose their use as (1) initial short-term readouts in early phase/proof-of-concept studies over 6 or 9 months, and (2) secondary end points in efficacy studies over longer periods such as 15 months
Plasma display panel with Ne+N-2 gas-mixture discharges
No full textThe discharge characteristics of Ne+N-2 gas-mixtures were investigated for possible use in an ac Plasma Display Panel. The firing voltage increased with an increase in the N-2 concentration. When using a near ultra violet excited phosphor, (Ba,Sr)(2) SiO4:Eu, the luminous efficiency of Ne+10%N-2 gas-mixture discharges under 400 torr was about 20% better than when using the conventional phosphor. The UV intensity emitted from the gas discharges was found to increase with an increased N-2 concentration. Furthermore,. the UV efficiency increased with an increase in the N-2 partial pressure at a low N-2 concentration, yet became saturated at a high N-2 concentration
A wideband linear-in-dB VGA using a CMOS in the triode region
No full textThis paper presents a wideband variable gain amplifier (VGA) fabricated using the 0.18-mu m CMOS process. An exponential CMOS triode transconductor scheme is proposed to achieve highly linear-in-dB characteristics of a VGA for ultra-wideband (UWB) systems. The proposed VGA achieves a linear-in-dB controllable gain range of 28.4 dB (7 to -21.4 dB) with a bandwidth of 1200 MHz, while drawing only, 2.7 mA from a 1.8-V power supply. Measurements show a linear gain range with a linearity error of less than +/- 0.5 dB. P-1dB varies from -8.5 to -6 dBm. The chip occupies an area of 0.2 x 0.2 mm(2), excluding bond-pads. (c) 2006 Wiley Periodicals. Inc
Electrostatic Energy Harvaster for Low-Frequency Vibration by Human Physical Motions using Luquid
No full text
Dispersion of Pt-Ru alloys onto various carbons using gamma-irradiation
No full text(PVP)-protected Pt-Ru alloy nanoparticles were prepared using gamma-irradiation at room temperature. Pt-Ru alloy particles were successfully dispersed onto various carbon structures, including Vulcan XC-71, Ketjen-300, Ketjen-600, single-walled carbon nanotubes (SWCNTs), and multi-walled carbon nanotubes (MWCNTs) to form new types of Pt-Ru/carbon-based composites. While Pt-Ru alloy nanoparticles were mainly aggregated on Vulcan XC-71, Ketjen-300 and Ketjen-600, SWCNTs and MWCNTs provided hydrophilic sites for improving the distribution of alloy particles. FT-IR spectroscopy provided evidence for the formation of carboxylate and hydroxyl groups on the surface of the nanotubes after gamma-irradiation. These functional groups serve as the nuclei that resulted in the improved dispersion of alloy nanoparticles onto SWCNTs and MWCNTs. (c) 2005 Elsevier B.V. All rights reserved
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