Planning a reasonable driving path for trucks in mining areas is a key point to improve mining efficiency.In this paper,a path planning method based on Rapidly-exploring Random Tree Star(RRT∗)is proposed,and several o...Planning a reasonable driving path for trucks in mining areas is a key point to improve mining efficiency.In this paper,a path planning method based on Rapidly-exploring Random Tree Star(RRT∗)is proposed,and several optimizations are carried out in the algorithm.Firstly,the selection process of growth target points is optimized.Secondly,the process of selecting the parent node is optimized and a Dubins curve is used to constraint it.Then,the expansion process from tree node to random point is optimized by the gravitational repulsion field method and dynamic step method.In the obstacle detection process,Dubins curve constraint is used,and the bidirectional RRT∗algorithm is adopted to speed up the iteration of the algorithm.After that,the obtained paths are smoothed by using the greedy algorithm and cubic B-spline interpolation.In addition,to verify the superiority and correctness of the algorithm,an unmanned mining vehicle kinematic model in the form of frontwheel steering is developed based on the Ackermann steering principle and simulated for CoppeliaSim.In the simulation,the Stanley algorithm is used for path tracking and Reeds-Shepp curve to adjust the final parking attitude of the truck.Finally,the experimental comparison shows that the improved bidirectional RRT∗algorithm performs well in the simulation experiment,and outperforms the common RRT∗algorithm in various aspects.展开更多
Due to the unique steering mechanism and driving characteristics of the articulated vehicle,a hybrid path planning method based on the articulated vehicle model is proposed to meet the demand of obstacle avoidance and...Due to the unique steering mechanism and driving characteristics of the articulated vehicle,a hybrid path planning method based on the articulated vehicle model is proposed to meet the demand of obstacle avoidance and searching the path back and forth of the articulated vehicle.First,Support Vector Machine(SVM)theory is used to obtain the two-dimensional optimal zero potential curve and the maximum margin,and then,several key points are selected from the optimal zero potential curves by using Longest Accessible Path(LAP)method.Next,the Cubic Bezier(CB)curve is adopted to connect the curve that satisfies the curvature constraint of the articulated vehicle between every two key points.Finally,Back and Forth Rapidly-exploring Random Tree with Course Correction(BFRRT-CC)is designed to connect paths that do not meet articulated vehicle curvature requirements.Simulation results show that the proposed hybrid path planning method can search a feasible path with a 90-degree turn,which meets the demand for obstacle avoidance and articulated vehicle back-and-forth movement.展开更多
Objective To observe the biological function of human 3-hydroxyisobutyrate dehydrogenase(HIBADH).Methods Human 3-hydroxyisobutyrate dehydrogenase(HIBADH, 3-hydroxy-2-methyl propanoate: NAD+ oxidoreductase) recombinant...Objective To observe the biological function of human 3-hydroxyisobutyrate dehydrogenase(HIBADH).Methods Human 3-hydroxyisobutyrate dehydrogenase(HIBADH, 3-hydroxy-2-methyl propanoate: NAD+ oxidoreductase) recombinant protein was expressed in E. coli BL21, and purified by Ni+ column. The special antisera was obtained from rabbits immunized by this purified antigen. On the distribution of HIBADH, it was found that HIBADH over-expressed in the injured liver cells when serious hepatitis occurred. The phenomenon was confirmed in the animal models of SD rats with acute liver cell injury induced by CCl4, but this phenomenon did not exist in the models induced by endotoxin combined with galactosamine. Further more, HIBADH's overexpression in liver cells will induce cell necrosis through the pathway of oxidative stress.Results When the liver cells injured by drug or other chemical materials, HIBADH will be compensationally over-expressed for the deficiency of energy, so liver cells can make enough ATP through brand-chain amino acid catabolism. However, the overexpression of HIBADH will be harmful for liver cells through the product of much more active oxygens which will induce the cell necrosis. Conclusions HIBADH over-expression is a signal of the liver cell metabolism injury, and it can aggravate the liver cell injury through oxidative stress.展开更多
针对当前电离层现报和预报数据精度不足、多源异构数据融合困难等问题,本文基于全球卫星导航系统(Global Navigation Satellite System,GNSS)和垂测观测数据,设计了一套电离层融合处理和预报系统。采用限带卡尔曼滤波模型,基于银河麒麟...针对当前电离层现报和预报数据精度不足、多源异构数据融合困难等问题,本文基于全球卫星导航系统(Global Navigation Satellite System,GNSS)和垂测观测数据,设计了一套电离层融合处理和预报系统。采用限带卡尔曼滤波模型,基于银河麒麟操作系统和云计算平台,利用容器云、高可用、分布式架构实现全球及中国周边区域电离层总电子含量(Total Electron Content,TEC)、F2层临界频率(Critical Frequency of the F2 Layer,foF2)及电子密度的高精度现报和预报。实验测试表明,该系统现报延迟约5 min、空间时间分辨率达到5°×2.5°×15 min,较传统数据处理方法有较大提升。系统支持三维电子密度可视化,为电离层研究、卫星导航修正、短波通信及地基雷达等应用提供可靠数据支撑,为无线电系统应用提供高精度、高时效的电离层环境信息服务。展开更多
文摘Planning a reasonable driving path for trucks in mining areas is a key point to improve mining efficiency.In this paper,a path planning method based on Rapidly-exploring Random Tree Star(RRT∗)is proposed,and several optimizations are carried out in the algorithm.Firstly,the selection process of growth target points is optimized.Secondly,the process of selecting the parent node is optimized and a Dubins curve is used to constraint it.Then,the expansion process from tree node to random point is optimized by the gravitational repulsion field method and dynamic step method.In the obstacle detection process,Dubins curve constraint is used,and the bidirectional RRT∗algorithm is adopted to speed up the iteration of the algorithm.After that,the obtained paths are smoothed by using the greedy algorithm and cubic B-spline interpolation.In addition,to verify the superiority and correctness of the algorithm,an unmanned mining vehicle kinematic model in the form of frontwheel steering is developed based on the Ackermann steering principle and simulated for CoppeliaSim.In the simulation,the Stanley algorithm is used for path tracking and Reeds-Shepp curve to adjust the final parking attitude of the truck.Finally,the experimental comparison shows that the improved bidirectional RRT∗algorithm performs well in the simulation experiment,and outperforms the common RRT∗algorithm in various aspects.
基金This work was supported by the Jiangsu Natural Science Foundation Project BK20170681National Natural Science Foundation of China 51675281.
文摘Due to the unique steering mechanism and driving characteristics of the articulated vehicle,a hybrid path planning method based on the articulated vehicle model is proposed to meet the demand of obstacle avoidance and searching the path back and forth of the articulated vehicle.First,Support Vector Machine(SVM)theory is used to obtain the two-dimensional optimal zero potential curve and the maximum margin,and then,several key points are selected from the optimal zero potential curves by using Longest Accessible Path(LAP)method.Next,the Cubic Bezier(CB)curve is adopted to connect the curve that satisfies the curvature constraint of the articulated vehicle between every two key points.Finally,Back and Forth Rapidly-exploring Random Tree with Course Correction(BFRRT-CC)is designed to connect paths that do not meet articulated vehicle curvature requirements.Simulation results show that the proposed hybrid path planning method can search a feasible path with a 90-degree turn,which meets the demand for obstacle avoidance and articulated vehicle back-and-forth movement.
文摘Objective To observe the biological function of human 3-hydroxyisobutyrate dehydrogenase(HIBADH).Methods Human 3-hydroxyisobutyrate dehydrogenase(HIBADH, 3-hydroxy-2-methyl propanoate: NAD+ oxidoreductase) recombinant protein was expressed in E. coli BL21, and purified by Ni+ column. The special antisera was obtained from rabbits immunized by this purified antigen. On the distribution of HIBADH, it was found that HIBADH over-expressed in the injured liver cells when serious hepatitis occurred. The phenomenon was confirmed in the animal models of SD rats with acute liver cell injury induced by CCl4, but this phenomenon did not exist in the models induced by endotoxin combined with galactosamine. Further more, HIBADH's overexpression in liver cells will induce cell necrosis through the pathway of oxidative stress.Results When the liver cells injured by drug or other chemical materials, HIBADH will be compensationally over-expressed for the deficiency of energy, so liver cells can make enough ATP through brand-chain amino acid catabolism. However, the overexpression of HIBADH will be harmful for liver cells through the product of much more active oxygens which will induce the cell necrosis. Conclusions HIBADH over-expression is a signal of the liver cell metabolism injury, and it can aggravate the liver cell injury through oxidative stress.
文摘针对当前电离层现报和预报数据精度不足、多源异构数据融合困难等问题,本文基于全球卫星导航系统(Global Navigation Satellite System,GNSS)和垂测观测数据,设计了一套电离层融合处理和预报系统。采用限带卡尔曼滤波模型,基于银河麒麟操作系统和云计算平台,利用容器云、高可用、分布式架构实现全球及中国周边区域电离层总电子含量(Total Electron Content,TEC)、F2层临界频率(Critical Frequency of the F2 Layer,foF2)及电子密度的高精度现报和预报。实验测试表明,该系统现报延迟约5 min、空间时间分辨率达到5°×2.5°×15 min,较传统数据处理方法有较大提升。系统支持三维电子密度可视化,为电离层研究、卫星导航修正、短波通信及地基雷达等应用提供可靠数据支撑,为无线电系统应用提供高精度、高时效的电离层环境信息服务。
