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- 저자 : Li Keqiang (검색결과 6 건)
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Mechanism of vehicular periodic operation for optimal fuel economy in free-driving scenarios
Li, Shengbo Eben,Xiaosong Hu,Keqiang Li,Changsun Ahn IET 2015 IET intelligent transport systems Vol.9 No.3
<P>In addition to the fuel-efficient design of vehicles, eco-driving technologies can further reduce the fuel consumption and carbon emissions of road transportation. One of the major issues in eco-driving technologies is how to determine the fuel savings or fuel-optimised operating strategies of the power train. We examine the periodic operation of autonomous vehicles in free-driving scenarios with the purpose of maximising fuel economy. The design of such strategies can be considered to be an optimal control problem, which is proved by <I>π</I>-test to have singular arcs because of the S-shaped engine fueling rate. The optimal operations are solved numerically by using the Legendre pseudospectral method, and many are found to demonstrate periodic behaviours, that is, pulse and gliding. In periodic operation, the engine switches between the minimum break specific fuel consumption point and the idling point, while the vehicle speed oscillates between its upper and lower bounds. The formation of periodic operation, as well as some key properties, is analysed and presented.</P>
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Yuxin Li,Keqiang Su,Peikang Bai,Liyun Wu,Bin Liu,Hongwen Su,Wenbo Du 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.5
The Ti/TiBCN composite coatings were fabricated on the substrate of Ti6Al4V alloy by laser cladding. The effects of TiBCNcontent on the microstructre, microhardness, corrosion resistance and tribological properties of the composite coatings werestudied. The results showed that, when the TiBCN content was 60 wt%, the composite coatings were mainly composed ofthe dendritic and rod-shaped TiBCN phases, small white lump TiC phases, fine lamellar TiN phases, small and scatteredwhite block TiB2phases, In addition, there was a small quantity of short whisker Al3Tiphases and uniform layer blockTiAl phases. Furhtermore, the maximum microhardness was 1596 HV, which was about 4.6 folds greater than that of thesubstrate; the corrosion potential (Ecorr) reached − 1.258 V and the corrosion current density (Icorr) was 4.035 × 10−5 A/cm2,which was one order lower than that of the substrate (1.172 × 10−4 A/cm2); the worn surface was relatively smooth and themass loss (1.22 g) was only 9/50 of that of the substrate (6.71 g).
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Guo Jinghua,Li WenChang,Luo Yugong,Li Keqiang 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.4
This paper presents a novel model predictive adaptive cruise control strategy of intelligent electric vehicles based on deep reinforcement learning algorithm for driver characteristics. Firstly, the influence mechanism of factors such as inter-vehicle distance, relative speed and time headway (THW) on the driver’s behavior in the process of car following is analyzed by the correlation coefficient method. Then, the driver behavior in the process of car following is learned from the natural driving data, the car following model is established by the deep deterministic policy gradient (DDPG) algorithm, and the output acceleration of the DDPG model is used as the reference trajectory of the ego vehicle’s acceleration. Next, in order to reflect the driver behavior and achieve multi performance objective optimization of adaptive cruise control of intelligent electric vehicles, the model predictive controller (MPC) is designed and used for tracking the desired acceleration produced by the car following DDPG model. Finally, the performance of the proposed adaptive cruise control strategy is evaluated by the experimental tests, and the results demonstrate the effectiveness of proposed control strategy.
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ROBUST H∞ FAULT-TOLERANT LATERAL CONTROL OF FOUR-WHEEL-STEERING AUTONOMOUS VEHICLES
Jinghua Guo,Yugong Luo,Keqiang Li 한국자동차공학회 2020 International journal of automotive technology Vol.21 No.4
This paper presents a robust H∞ fault-tolerant lateral controller of four wheel steering autonomous vehicles to enhance the autonomous driving performance and to track the desired road when a steering wheel fault happens. First, the lateral dynamic model of four wheel steering autonomous vehicles is constructed, which contains the features of parameter uncertainties and actuator faults of vehicles. Then, since the faulty steering wheel may fail to offer the desired torque and harm the lateral motion control system of autonomous vehicles, a novel robust H∞ fault tolerant state feedback lateral control law of four steering autonomous vehicles is designed to deal with actuator faults and parameter uncertainties. Finally, simulation tests are implemented in the Adams-Simulink joint platform with a high-fidelity and full-car model, and results verify the validity of this proposed control scheme.
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Jinghua Guo,Yugong Luo,Chuan Hu,Chen Tao,Keqiang Li 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.2
In order to enhance the tracking performance and improve the stability of intelligent electric vehicles, combined Lane keeping and direct yaw moment control is a good choice. In this paper, an uncertain model of intelligent electric vehicles for combing the lane keeping and direct yaw moment control is deduced, in which time delay and data dropouts are involved. Since the intelligent electric vehicles have the features of time delay and strong uncertainties, a novel robust guaranteed cost combined lane keeping and direct yaw moment control system is constructed to manage the lateral motion of intelligent electric vehicles. The asymptotic stability of combined lane keeping and direct moment control system is verified based on the Lyapunov stability theory. Simulation tests are carried out to demonstrate the feasibility of the proposed control approach, and the results indicate that the presented robust combined control approach can accurately achieve the lane tracking capability, stability and maneuverability of intelligent electric vehicles.
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Effects of a chitosan nanoparticles encapsulation on the properties of litchi polyphenols
Xingan Cheng,Qiwen Zou,Hanhui Zhang,Jianwei Zhu,Murtaza Hasan,Fangyun Dong,Xin Liu,Junjie Li,Yuehua Wu,Xiaojing Lv,Keqiang Wang,Xiangling Deng,Zhanmei Liu,Xuhong Jiang 한국식품과학회 2023 Food Science and Biotechnology Vol.32 No.13
Litchi polyphenols have very specific biological activities. Nevertheless, the low and inconsistent oral bioavailability and instability hinder the further application of litchi polyphenols in food systems. This work prepared litchi polyphenols loaded chitosan nanoparticles (LP-CSNPs) by ionic gelation method to enhance the encapsulation on the properties of litchi polyphenols. The optimum conditions of formation via single factors and the Box–Behnken design were chitosan (CS) concentration 1.065 mg/mL, sodium tripolyphosphate (TPP) concentration 0.975 mg/mL, and the mass ratios of polyphenols and CS 1:1 with encapsulation efficiency (EE%) of 45.53%. LP-CSNPs presented the nanosized range of particle size (mean 170 nm), excellent polydispersity index (PDI) (0.156 ± 0.025), and zeta potential values (+ 35.44 ± 0.59). The in vitro release in simulated gastric fluid (pH 1.2) and intestinal fluid (pH 6.8) during 100 h was 58.34% and 81.68%, respectively. LP-CSNPs could effectively improve the storage stability and had great antibacterial activity compared with unencapsulated litchi polyphenols.
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