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Intelligent Vehicle for Collision Avoidance Using Artificial Potential Field with Speed Variation
Pengfei Lin(임붕비),Woo Young Choi(최우영),Chung Choo Chung(정정주) 한국자동차공학회 2020 한국자동차공학회 부문종합 학술대회 Vol.2020 No.7
In this paper, we present a novel approach for waypoint tracking scheme with a local path planner based on the artificial potential field (APF) to avoid dynamic obstacles. It is reported that APF is highly efficient in collision-avoidance issues, but there is less work combining the waypoint tracking with APF-based local path planner. To enrich this field, a waypoint tracking using APF with speed variation is proposed to prevent the possibly excessive tire slip angle when the vehicle is driven at a high speed. The simulation results show that the proposed algorithm is effective in collision avoidance with dynamic obstacles, especially for waypoint tracking scenario. The proposed system framework is validated with the vehicle dynamic lateral motion model in MATLAB/Simulink and CarSim.
Pengfei Lin,Woo Young Choi,Seung-Hi Lee,Chung Choo Chung 제어로봇시스템학회 2020 제어로봇시스템학회 국제학술대회 논문집 Vol.2020 No.10
In this paper, we propose a vehicle lane change system using model predictive path planning (MPPP) based on the artificial potential field (APF) for speeding vehicles. It is shown that APF has high performance in real-time obstacle avoidance. However, it remains unpractical for self-driving cars because the point model used for the APF ignores the lateral vehicle dynamics for the lane-keeping system. To resolve the problem, this paper introduces a novel curve-fitting method combined with the APF applied to plan a drivable path for autonomous vehicles in the lane change action. The proposed system was validated through MATLAB/Simulink with the empirical kinematic model. The simulation results indicate that the model predictive path planning algorithm is highly effective in high-speed lane change scenarios to avoid dynamic obstacle vehicles.
Autonomous Lane Change System for Intelligent Vehicle Based on Model Curve Fitting
Pengfei Lin(임붕비),Woo Young Choi(최우영),Chung Choo Chung(정정주) 한국자동차공학회 2020 한국자동차공학회 학술대회 및 전시회 Vol.2020 No.11
In this paper, we present a novel lane change system for intelligent vehicles combined with the model curve fitting method to plan a safe-feasible path in high speed. According to the existing literature, the current virtual potential function (VPF) performs well in real-time collision avoidance. However, this method also exists a flaw that it is based on the point mass model to produce the path in which could be non-safe for intelligent vehicles to track. To improve this method to be more practical, we propose a novel model curve fitting (MCF) method to consider the dynamics of the ground vehicles that can plan a safer path for intelligent vehicles to track. We simulated the overall system framework in MATLAB/Simulink with vehicle dynamic lateral motion model. From the simulation results, we confirm that the MCF method combined with VPF is highly effective compared to the traditional VPF method.
A Hardware-in-the-loop Platform for Modular Multilevel Converter Simulations
Chongru Liu,Pengfei Tian,Yu Wang,Qi Guo,Xuehua Lin,Jiayu Wang 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5
In this paper, a hardware-in-the-loop simulation platform for MMCs is established, which connects a real time digital simulator (RTDS) and a designed MMC controller with optical fiber. In this platform, the converter valves are simulated with a small time step of 2.5 microsecond in the RTDS, and multicore technology is implemented for the controller so that the parallel valve control is distributed between different cores. Therefore, the designed controller can satisfy the requirements of real-time control. The functions of the designed platform and the rationality for the designed controller are verified through experimental tests. The results show that different modulation modes and various control strategies can be implemented in the simulation platform and that each control objective can been tracked accurately and with a fast dynamic response.
Wenchao Yang,Pengfei Qu,Ruirong Zhang,Jiarun Qin,Chen Liu,Jun Zhang,Lin Liu 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.6
Three-dimensional atom-probe tomography was used to characterize the γ/γʹ interface structure in a third-generation Nibasedsingle crystal superalloy with Re addition. It was found that an element-segregation layer with Re, Co and Cr wasformed in the γ phase close to the γ/γ′ interface, resulting in a more negative local interface misfit (− 0.29%) compared tothe measured result (− 0.16%) from high-resolution X-ray diffraction. Furthermore, the total reduction of interfacial freeenergy due to the solute atom segregation based on the Gibbsian interfacial excess was calculated to indicate that Re elementwas the most beneficial element in producing this more negative local misfit with the largest interfacial free energy reduction(13.67 ± 0.21 mJ/m2). Simultaneously, because of the co-segregation of Re, Co and Cr, and the depletion of Ni in the γphase close to the γ/γ′ interface, it was also deduced that some harmful topologically close-packed phases might be easierto nucleate and grow in the γ phase close to the γ/γ′ interface in service.
Jiaxin Wen,Lin He,Tao Zhou,Pengfei Tian,Tian Zhou,Zhiguo Feng 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.6
The presence of burrs in mechanical processing can negatively affect surface integrity and dimensional accuracy and even lead to part scrapping. Grain size also has a significant impact on material properties and subsequently generate different processing effects. However, only few studies have explored the effect of grain size on machined surface integrity and burr formation. To fill this gap, this study develops a model based on dislocation density and incorporates this model into ABAQUS using subroutines to investigate polycrystalline cutting modeling and the burr formation mechanism. In addition, the plastic flow and deformation process of grains are observed using a newly developed 2D polycrystalline model, which is later compared with traditional Johnson-Cook constitutive models. The simulated cutting force value, chip morphology, and experimental results are also compared to preliminarily validate the feasibility of the developed model. The experimental results remain consistent across different simulated cutting speeds and depths. The height and width of the exit burr slightly decrease along with increasing cutting speed. Meanwhile, increasing the cutting depth significantly increases the burr width and height. The lateral burrs observed in the experiment can also be reproduced using a 3D polycrystalline model. The lateral burr size increases along with cutting depth and speed. The effect of grain size on cutting force and burr formation is eventually explored, and results show that increasing the grain size reduces the cutting force but increases the burr size. This study provides a new concept for burr control and surface integrity improvement.
A Hardware-in-the-loop Platform for Modular Multilevel Converter Simulations
Liu, Chongru,Tian, Pengfei,Wang, Yu,Guo, Qi,Lin, Xuehua,Wang, Jiayu The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.5
In this paper, a hardware-in-the-loop simulation platform for MMCs is established, which connects a real time digital simulator (RTDS) and a designed MMC controller with optical fiber. In this platform, the converter valves are simulated with a small time step of 2.5 microsecond in the RTDS, and multicore technology is implemented for the controller so that the parallel valve control is distributed between different cores. Therefore, the designed controller can satisfy the requirements of real-time control. The functions of the designed platform and the rationality for the designed controller are verified through experimental tests. The results show that different modulation modes and various control strategies can be implemented in the simulation platform and that each control objective can been tracked accurately and with a fast dynamic response.
Liang Li,Zhang Fengmei,Feng Naibo,Kuang Biao,Fan Mengtian,Chen Cheng,Pan Yiming,Zhou Pengfei,Geng Nana,Li Xingyue,Xian Menglin,Deng Lin,Li Xiaoli,Kuang Liang,Luo Fengtao,Tan Qiaoyan,Xie Yangli,Guo Fen 생화학분자생물학회 2023 Experimental and molecular medicine Vol.55 No.-
Osteoarthritis (OA) is a full-joint, multifactorial, degenerative and inflammatory disease that seriously affects the quality of life of patients due to its disabling and pain-causing properties. ER stress has been reported to be closely related to the progression of OA. The inositol-requiring enzyme 1α/X-box-binding protein-1 spliced (IRE1α/XBP1s) pathway, which is highly expressed in the chondrocytes of OA patients, promotes the degradation and refolding of abnormal proteins during ER stress and maintains the stability of the ER environment of chondrocytes, but its function and the underlying mechanisms of how it contributes to the progression of OA remain unclear. This study investigates the role of IRE1α/ERN1 in OA. Specific deficiency of ERN1 in chondrocytes spontaneously resulted in OA-like cartilage destruction and accelerated OA progression in a surgically induced arthritis model. Local delivery of AdERN1 relieved degradation of the cartilage matrix and prevented OA development in an ACLT-mediated model. Mechanistically, progranulin (PGRN), an intracellular chaperone, binds to IRE1α, promoting its phosphorylation and splicing of XBP1u to generate XBP1s. XBP1s protects articular cartilage through TNF-α/ERK1/2 signaling and further maintains collagen homeostasis by regulating type II collagen expression. The chondroprotective effect of IRE1α/ERN1 is dependent on PGRN and XBP1s splicing. ERN1 deficiency accelerated cartilage degeneration in OA by reducing PGRN expression and XBP1s splicing, subsequently decreasing collagen II expression and triggering collagen structural abnormalities and an imbalance in collagen homeostasis. This study provides new insights into OA pathogenesis and the UPR and suggests that IRE1α/ERN1 may serve as a potential target for the treatment of joint degenerative diseases, including OA.