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RISS 인기검색어
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- 저자 : Keping Liu (검색결과 6 건)
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Lian Yufeng,Liu Shuaishi,Zhongbo Sun,Liu Keping,Nie Zhigen,Tian Chongwen 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.4
This paper presents an active collision avoidance system based on a braking force distribution strategy for four-in-wheel-motor-driven electric vehicles (FIWMD-EVs) on roads with different friction coefficients. There are three major contributions in the proposed braking force distribution strategy. Firstly, the braking force distribution strategy based on constrained regenerative braking strength continuity (CRBSC) is further improved, and its general analytic expressions are derived. It provides the theoretical basis of braking force distribution between front and rear wheels. Secondly, the braking forces between front and rear wheels can be redistributed by considering power demand efficiency (PDE) to protect energy storage system from overcharge. Finally, the braking forces between left and right wheels can be distributed with different adhesion coefficients to adapt to complex roads. Simulations using rapid control prototyping (RCP) and hardware-in-the-loop (HIL) simulator are performed to demonstrate the effectiveness of control scheme and adaptability of the active collision avoidance system based on the proposed braking force distribution strategy on complex roads.
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A Fast Clustering Method for Identifying Rock Discontinuity Sets
Feng Gao,Dapeng Chen,Keping Zhou,Wenjing Niu,Hanwen Liu 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.2
Identifying rock discontinuity sets is a major factor for analyses of hydraulic properties and rock mass stability. To perform efficient and precise grouping of discontinuities, a new approach based on clustering by fast searches and finding density peaks is proposed for the identification of rock discontinuity sets. By measuring the similarity of each pair of discontinuities, the local density and controlled distance of each discontinuity can be calculated for a certain cutoff distance. The number of potential clusters and central discontinuities of corresponding clusters can be found by observing the decision graph constructed based on the decision values of all discontinuities in descending order. The discontinuities of each cluster are divided into core discontinuities and outlier discontinuities based on the corresponding boundary density. This strategy can avoid interference from subjective factors and improve the accuracy of the clustering analysis. The new approach is verified using artificial data, and the appropriate cutoff distance thresholds for identifying rock discontinuity sets are given. Finally, the new approach is applied to group discontinuities in an actualunderground mine. The clustering results obtained with the proposed approach are more reliable than those obtained with traditional methods.
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Fast Cooperative Sensing with Low Overhead in Cognitive Radios
( Zeyang Dai ),( Jian Liu ),( Yunji Li ),( Keping Long ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.1
As is well known, cooperative sensing can significantly improve the sensing accuracy as compared to local sensing in cognitive radio networks (CRNs). However, a large number of cooperative secondary users (SUs) reporting their local detection results to the fusion center (FC) would cause much overhead, such as sensing delay and energy consumption. In this paper, we propose a fast cooperative sensing scheme, called double threshold fusion (DTF), to reduce the sensing overhead while satisfying a given sensing accuracy requirement. In DTF, FC respectively compares the number of successfully received local decisions and that of failed receptions with two different thresholds to make a final decision in each reporting sub-slot during a sensing process, where cooperative SUs sequentially report their local decisions in a selective fashion to reduce the reporting overhead. By jointly considering sequential detection and selective reporting techniques in DTF, the overhead of cooperative sensing can be significantly reduced. Besides, we study the performance optimization problems with different objectives for DTF and develop three optimum fusion rules accordingly. Simulation results reveal that DTF shows evident performance gains over an existing scheme.
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Cooperative Relaying with Interference Cancellation for Secondary Spectrum Access
( Zeyang Dai ),( Jian Liu ),( Keping Long ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.10
Although underlay spectrum sharing has been shown as a promising technique to promote the spectrum utilization in cognitive radio networks (CRNs), it may suffer bad secondary performance due to the strict power constraints imposed at secondary systems and the interference from primary systems. In this paper, we propose a two-phase based cooperative transmission protocol with the interference cancellation (IC) and best-relay selection to improve the secondary performance in underlay models under stringent power constraints while ensuring the primary quality-of-service (QoS). In the proposed protocol, IC is employed at both the secondary relays and the secondary destination, where the IC-based best-relay selection and cooperative relaying schemes are well developed to reduce the interference from primary systems. The closed-form expression of secondary outage probability is derived for the proposed protocol over Rayleigh fading channels. Simulation results show that, with a guaranteed primary outage probability, the proposed protocol can achieve not only lower secondary outage probability but also higher secondary diversity order than the traditional underlay case.
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Yufeng Lian,Xiaoyu Wang,Yantao Tian,Keping Liu 한국자동차공학회 2018 International journal of automotive technology Vol.19 No.2
This paper presents a new control scheme for lateral collision avoidance (CA) systems to improve the safety of four-in-wheel-motor-driven electric vehicles (FIWMD-EVs). There are two major contributions in the design of lateral CA systems. The first contribution is a new lane-changing model based on vehicle edge turning trajectory (VETT) to make vehicle adapt to different driving roads and conform to drivers’ characteristic, in addition to ensure vehicle steering safety. The second contribution is vehicle semi-uncertainty dynamic model (SUDM), which is SISO model. The problem of stability performance without the information on sideslip angle is solved by the proposed SUDM. Based on the proposed VETT and SUDM, the lateral CA system can be designed with robust controller to restrain the effect of uncertainties resulting from parameter perturbation and lateral wind disturbance. Single and mixed driving cycles simulation experiments are carried out with CarSim to demonstrate the effectiveness in control scheme, simplicity in structure for lateral CA system based on the proposed VETT and SUDM.
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