基于三目视觉的自主导航拖拉机行驶轨迹预测方法及试验
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摘要
为了实现自主导航拖拉机离开卫星定位系统时能够持续可靠工作,该文提出了基于三目视觉的拖拉机行驶轨迹预测方法。该方法将三目相机分解为长短基线2套双目视觉系统分时独立工作。通过检测相邻时刻农业环境中同一特征点的坐标变化反推拖拉机在水平方向上的运动矢量,并通过灰色模型预测未来时刻的运动矢量变化,最终建立不同速度下的前进方向误差模型。试验结果表明:拖拉机行驶速度为0.2 m/s时,46.5 s后前进方向误差超过0.1 m,对应行驶距离为9.3 m。行驶速度上升到0.5 m/s时,该时间和行驶距离分别降低到17.2 s和8.6 m。当行驶速度上升到0.8 m/s时,该时间和距离分别快速降低至8.5 s和6.8 m。行驶速度越高,前进方向误差增速越高。该方法可用于短时预测拖拉机的行驶轨迹,为自主导航控制提供依据。
In order to make the autonomous navigation tractors work steadily and continuously without the satellite positioning system, a traveling trajectory prediction system and method based on trinocular vision were designed in this paper. The system was composed of a trinocular vision camera, an IEEE 1394 acquisition card and an embedded industrial personal computer(IPC). The right and left sub cameras constituted a binocular vision system with a long base line. The right and middle sub cameras constituted another binocular vision system with a narrow base line. To obtain more precise measurement results, the two binocular vision systems worked independently and in time-sharing. Then the motion vectors of tractor, which were in presentation of horizontal direction data, were calculated by the feature point coordinate changing in the working environment of the tractor. Finally, the error models which were in the direction of heading were established at different velocities, and the motion vectors of tractor were predicted by the models based on grey method. The contrast experiments were completed with a modified tractor of Dongfanghong SG250 at the speed of 0.2, 0.5 and 0.8 m/s. During the experiments, the IPC was used to collect RTK-GPS data and predict movement tracks. The RTK-GPS used in the experiments was a kind of high-precision measuring device, and the measuring precision can reach 1-2 cm. Therefore, the location data of RTK-GPS were supposed as the standard which was used to compare with the data from trinocular vision system. The experimental results showed that the method mentioned above could accurately predict the trajectory of the tractor on the plane with an inevitable error which was mainly caused by the visual measurement error of the forward direction(z direction). When the tractor travelled at the speed of 0.2 m/s, the time and the distance that the error in forward direction exceeded 0.1 m equaled 46.5 s and 9.3 m, respectively. When the speed increased to 0.5 m/s, the time and the distance decreased to 17.2 s and 8.6 m, respectively. When the driving speed increased to 0.8 m/s, the time and distance quickly decreased to 8.5 s and 6.8 m, respectively. It showed that the higher the tractor traveling speed, the faster the error in forward direction increased. After that, the relationship between errors in forward direction and traveling time was acquired and analyzed by the way of nonlinear data fitting. In addition, the experimental results showed that the trend of lateral error(x direction) which was perpendicular to forward direction was not regular. When the speed was 0.2 m/s, the average error was 0.002 5 m with a standard deviation(STD) of 0.003 9. When the speed increased to 0.5 m/s and 0.8 m/s, the average error in lateral direction was 0.008 2 m with an STD of 0.012 4 and 0.003 6 m with an STD of 0.006 4. The result showed that the lateral error was very small and almost invariable. Therefore, the errors of trinocular vision were mainly caused by the errors of the forward direction. The root causes of the error were the natural light and time-delay during the image processing. According to the experimental data and results, the system and method proposed in this paper could be used to measure and predict the traveling trajectory of a tractor in the dry agricultural environment with the sudden loss of the satellite signal in a short period of time. The measured and predicted data could provide temporary help for the operations of autonomous tractors.
In order to make the autonomous navigation tractors work steadily and continuously without the satellite positioning system, a traveling trajectory prediction system and method based on trinocular vision were designed in this paper. The system was composed of a trinocular vision camera, an IEEE 1394 acquisition card and an embedded industrial personal computer(IPC). The right and left sub cameras constituted a binocular vision system with a long base line. The right and middle sub cameras constituted another binocular vision system with a narrow base line. To obtain more precise measurement results, the two binocular vision systems worked independently and in time-sharing. Then the motion vectors of tractor, which were in presentation of horizontal direction data, were calculated by the feature point coordinate changing in the working environment of the tractor. Finally, the error models which were in the direction of heading were established at different velocities, and the motion vectors of tractor were predicted by the models based on grey method. The contrast experiments were completed with a modified tractor of Dongfanghong SG250 at the speed of 0.2, 0.5 and 0.8 m/s. During the experiments, the IPC was used to collect RTK-GPS data and predict movement tracks. The RTK-GPS used in the experiments was a kind of high-precision measuring device, and the measuring precision can reach 1-2 cm. Therefore, the location data of RTK-GPS were supposed as the standard which was used to compare with the data from trinocular vision system. The experimental results showed that the method mentioned above could accurately predict the trajectory of the tractor on the plane with an inevitable error which was mainly caused by the visual measurement error of the forward direction(z direction). When the tractor travelled at the speed of 0.2 m/s, the time and the distance that the error in forward direction exceeded 0.1 m equaled 46.5 s and 9.3 m, respectively. When the speed increased to 0.5 m/s, the time and the distance decreased to 17.2 s and 8.6 m, respectively. When the driving speed increased to 0.8 m/s, the time and distance quickly decreased to 8.5 s and 6.8 m, respectively. It showed that the higher the tractor traveling speed, the faster the error in forward direction increased. After that, the relationship between errors in forward direction and traveling time was acquired and analyzed by the way of nonlinear data fitting. In addition, the experimental results showed that the trend of lateral error(x direction) which was perpendicular to forward direction was not regular. When the speed was 0.2 m/s, the average error was 0.002 5 m with a standard deviation(STD) of 0.003 9. When the speed increased to 0.5 m/s and 0.8 m/s, the average error in lateral direction was 0.008 2 m with an STD of 0.012 4 and 0.003 6 m with an STD of 0.006 4. The result showed that the lateral error was very small and almost invariable. Therefore, the errors of trinocular vision were mainly caused by the errors of the forward direction. The root causes of the error were the natural light and time-delay during the image processing. According to the experimental data and results, the system and method proposed in this paper could be used to measure and predict the traveling trajectory of a tractor in the dry agricultural environment with the sudden loss of the satellite signal in a short period of time. The measured and predicted data could provide temporary help for the operations of autonomous tractors.
引文
[1]Adam J L,Piotr M,Seweryn L,et al.Precision of tractor operations with soil cultivation implements using manual and automatic steering modes[J].Biosystems Engineering,2016,145(5):22-28.
[2]Gan-Mor S,Clark R L,Upchurch B L.Implement lateral position accuracy under RTK-GPS tractor guidance[J].Computers and Electronics in Agriculture,2007,59(1/2):31-38.
[3]Timo O,Juha B.Guidance system for agricultural tractor with four wheel steering[J].IFAC Proceedings Volumes,2013,46(4):124-129.
[4]Karimi D,Henry J,Mann D D.Effect of using GPS auto steer guidance systems on the eye-glance behavior and posture of tractor operators[J].Journal of Agricultural Safety and Health,2012,18(4):309-318.
[5]刘柯楠,吴普特,朱德兰,等.太阳能渠道式喷灌机自主导航研究[J].农业机械学报,2016,47(9):141-146.Liu Kenan,Wu Pute,Zhu Delan,et al.Autonomous navigation of solar energy canal feed sprinkler irrigation machine[J].Transactions of the Chinese Society for Agricultural Machinery,2016,47(9):141-146.(in Chinese with English abstract)
[6]Cordesses L,Cariou C,Berducat M.Combine harvester control using real time kinematic GPS[J].Precision Agriculture,2000,2(2):147-161.
[7]Jongmin C,Xiang Y,Liangliang Y,et al.Development of a laser scanner-based navigation system for a combine harvester[J].Engineering in Agriculture,Environment and Food,2014,7(1):7-13.
[8]张美娜,吕晓兰,陶建平,等.农用车辆自主导航控制系统设计与试验[J].农业机械学报,2016,47(7):42-47.Zhang Meina,LüXiaolan,Tao Jianping,et al.Design and experiment of automatic guidance control system in agricultural vehicle[J].Transactions of the Chinese Society for Agricultural Machinery,2016,47(7):42-47.(in Chinese with English abstract)
[9]姬长英,周俊.农业机械导航技术发展分析[J].农业机械学报,2014,45(9):44-54.Ji Changying,Zhou jun.Current situation of navigation technologies for agricultural machinery[J].Transactions of the Chinese Society for Agricultural Machinery,2014,45(9):44-54.(in Chinese with English abstract)
[10]张漫,项明,魏爽,等.玉米中耕除草复合导航系统设计与试验[J].农业机械学报,2015,46(增刊1):8-14.Zhang Man,Xiang Ming,Wei Shuang,et al.Design and implementation of a corn weeding-cultivating integrated navigation system based on GNSS and MV[J].Transactions of the Chinese Society for Agricultural Machinery,2015,46(Supp.1):8-14.(in Chinese with English abstract)
[11]谢斌,李静静,鲁倩倩,等.联合收割机制动系统虚拟样机仿真及试验[J].农业工程学报,2014,30(4):18-24.Xie Bin,Li Jingjing,Lu Qianqian,et al.Simulation and experiment of virtual prototype braking system of combine harvester[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2014,30(4):18-24.(in Chinese with English abstract)
[12]任述光,谢方平,王修善,等.4LZ-0.8型水稻联合收割机清选装置气固两相分离作业机理[J].农业工程学报,2015,31(12):16-22.Ren Shuguang,Xie Fangping,Wang Xiushan,et al.Gas-solid two-phase separation operation mechanism for4LZ-0.8 rice combine harvester cleaning device[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2015,31(12):16-22.(in Chinese with English abstract)
[13]焦有宙,田超超,贺超,等.不同工质对大型联合收割机余热回收的热力学性能[J].农业工程学报,2018,34(5):32-38.Jiao Youzhou,Tian Chaochao,He Chao,et al.Thermodynamic performance of waste heat collection for large combine harvester with different working fluids[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2018,34(5):32-38.(in Chinese with English abstract)
[14]伟利国,张小超,汪凤珠,等.联合收割机稻麦收获边界激光在线识别系统设计与试验[J].农业工程学报,2017,33(增刊1):30-35.Wei Liguo,Zhang Xiaochao,Wang Fengzhu,et al.Designand experiment of harvest boundary online recognition system for rice and wheat combine harvester based on laser detection[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2017,33(Supp.1):30-35.(in Chinese with English abstract)
[15]Yoshisada N,Katsuhiko T,Kentaro N,et al.A global positioning system guided automated rice transplanter[J].IFAC Proceedings Volumes,2013,46(18):41-46.
[16]Tamaki K,Nagasaka Y,Nishiwaki K,et al.A robot system for paddy field farming in Japan[J].IFAC Proceedings Volumes,2013,46(18):143-147.
[17]胡炼,罗锡文,张智刚,等.基于CAN总线的分布式插秧机导航控制系统设计[J].农业工程学报,2009,25(12):88-92.Hu Lian,Luo Xiwen,Zhang Zhigang,et al.Design of distributed navigation control system for rice transplanters based on controller area network[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2009,25(12):88-92.(in Chinese with English abstract)
[18]胡静涛,高雷,白晓平,等.农业机械自动导航技术研究进展[J].农业工程学报,2015,31(10):1-10.Hu Jingtao,Gao Lei,Bai Xiaoping,et al.Review of research on automatic guidance of agricultural vehicles[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2015,31(10):1-10.(in Chinese with English abstract)
[19]宋宇,刘永博,刘路,等.基于机器视觉的玉米根茎导航基准线提取方法[J].农业机械学报,2017,48(2):38-44.Song Yu,Liu Yongbo,Liu Lu,et al.Extraction method of navigation baseline of corn roots based on machine vision[J].Transactions of the Chinese Society for Agricultural Machinery,2017,48(2):38-44.(in Chinese with English abstract)
[20]Leemans V,Destain M F.Line cluster detection using a vartiant of the Hough transform for culture row localisation[J].Image and Vision Computing,2006,24(5):541-550.
[21]Gee C,Bossu J,Jones G,et al.Crop weed discrimination in perspective agronomic image[J].Computers and Electronics in Agriculture,2007,58(1):1-9.
[22]姜国权,柯杏,杜尚丰,等.基于机器视觉的农田作物行检测[J].光学学报,2009,29(4):1015-1020.Jiang Guoquan,Ke Xing,Du Shangfeng,et al.Crop row detection based on machine vision[J].Acta Optica Sinica,2009,29(4):1015-1020.(in Chinese with English abstract)
[23]Han Y H,Wang Y M,Kang F.Navigation line detection based on support vector machine for automatic agriculture vehicle[C]//International Conference on Automatic Control and Artificial Intelligence(ACAI 2012),Xiamen,2012:1381-1385.
[24]English A,Ross P,Ball D,et al.Vision based guidance for robot navigation in agriculture[C]//2014 IEEE International Conference on Robotics&Automation(ICRA),Hong Kong,2014:1693-2698.
[25]Cariou C,Lenain R,Thuilot B,et al.Motion planner and lateral-longitudinal controllers for autonomous maneuvers of a farm vehicle in headland[C]//2009 IEEE/RSJ International Conference on Intelligent Robots and Systems,USA,2009:5782-5787.
[26]林桂潮,邹湘军,张青,等.基于主动轮廓模型的自动导引车视觉导航[J].农业机械学报,2017,48(2):20-26.Lin Guichao,Zou Xiangjun,Zhang Qing,et al.Visual navigation for automatic guided vehicles based on active contour model[J].Transactions of the Chinese Society for Agricultural Machinery,2017,48(2):20-26.(in Chinese with English abstract)
[27]项明,魏爽,何洁,等.基于DSP和MCU的农机具视觉导航终端设计[J].农业机械学报,2015,46(增刊1):21-26.Xiang Ming,Wei Shuang,He Jie,et al.Development of agricultural implement visual navigation terminal based on DSP and MCU[J].Transactions of the Chinese Society for Agricultural Machinery,2015,46(Supp.1):21-26.(in Chinese with English abstract)
[28]任俊如.改进的预测PID控制器的研究与设计[D].武汉:武汉科技大学,2011.Ren Junru.The Research and Design of Improved Predictive PID Controller[D].Wuhan:Wuhan University of science and Technology,2011.(in Chinese with English abstract)
[29]余天明,郑磊,李颂.电控机械式自动变速器离合器灰色预测PID控制技术[J].农业机械学报,2011,42(8):1-6.Yu Tianming,Zheng Lei,Li Song.Gray prediction PID control technology of automated mechanical transmission clutch[J].Transactions of the Chinese Society for Agricultural Machinery,2011,42(8):1-6.(in Chinese with English abstract)
[30]Point Grey Research,Inc.Triclops software kit Version 3.1user’s guide and command reference[EB/OL].[2018-08-25].https://www.ptgrey.com/support/downloads
[31]陈晗婧.SIFT特征匹配技术研究与应用[D].南京:南京理工大学,2017.Chen Hanjing.Research and Application of SIFT Feature Point Technology[D].Nanjing:Nanjing University of Science and Technology,2017.(in Chinese with English abstract)
[32]Hiremath S,Evert F K V,Braak C T,et al.Image-based particle filtering for navigation in a semi-structured agricultural environment[J].Biosystems Engineering,2014,121(5):85-95.
[33]沈文龙,薛金林,汪东明,等.农业车辆视觉导航控制系统[J].中国农机化学报,2016,37(6):251-254.Shen Wenlong,Xue Jinlin,Wang Dongming,et al.Visual navigation control system of agricultural vehicle[J].Journal of Chinese Agricultural Mechanization,2016,37(6):251-254.(in Chinese with English abstract)
[2]Gan-Mor S,Clark R L,Upchurch B L.Implement lateral position accuracy under RTK-GPS tractor guidance[J].Computers and Electronics in Agriculture,2007,59(1/2):31-38.
[3]Timo O,Juha B.Guidance system for agricultural tractor with four wheel steering[J].IFAC Proceedings Volumes,2013,46(4):124-129.
[4]Karimi D,Henry J,Mann D D.Effect of using GPS auto steer guidance systems on the eye-glance behavior and posture of tractor operators[J].Journal of Agricultural Safety and Health,2012,18(4):309-318.
[5]刘柯楠,吴普特,朱德兰,等.太阳能渠道式喷灌机自主导航研究[J].农业机械学报,2016,47(9):141-146.Liu Kenan,Wu Pute,Zhu Delan,et al.Autonomous navigation of solar energy canal feed sprinkler irrigation machine[J].Transactions of the Chinese Society for Agricultural Machinery,2016,47(9):141-146.(in Chinese with English abstract)
[6]Cordesses L,Cariou C,Berducat M.Combine harvester control using real time kinematic GPS[J].Precision Agriculture,2000,2(2):147-161.
[7]Jongmin C,Xiang Y,Liangliang Y,et al.Development of a laser scanner-based navigation system for a combine harvester[J].Engineering in Agriculture,Environment and Food,2014,7(1):7-13.
[8]张美娜,吕晓兰,陶建平,等.农用车辆自主导航控制系统设计与试验[J].农业机械学报,2016,47(7):42-47.Zhang Meina,LüXiaolan,Tao Jianping,et al.Design and experiment of automatic guidance control system in agricultural vehicle[J].Transactions of the Chinese Society for Agricultural Machinery,2016,47(7):42-47.(in Chinese with English abstract)
[9]姬长英,周俊.农业机械导航技术发展分析[J].农业机械学报,2014,45(9):44-54.Ji Changying,Zhou jun.Current situation of navigation technologies for agricultural machinery[J].Transactions of the Chinese Society for Agricultural Machinery,2014,45(9):44-54.(in Chinese with English abstract)
[10]张漫,项明,魏爽,等.玉米中耕除草复合导航系统设计与试验[J].农业机械学报,2015,46(增刊1):8-14.Zhang Man,Xiang Ming,Wei Shuang,et al.Design and implementation of a corn weeding-cultivating integrated navigation system based on GNSS and MV[J].Transactions of the Chinese Society for Agricultural Machinery,2015,46(Supp.1):8-14.(in Chinese with English abstract)
[11]谢斌,李静静,鲁倩倩,等.联合收割机制动系统虚拟样机仿真及试验[J].农业工程学报,2014,30(4):18-24.Xie Bin,Li Jingjing,Lu Qianqian,et al.Simulation and experiment of virtual prototype braking system of combine harvester[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2014,30(4):18-24.(in Chinese with English abstract)
[12]任述光,谢方平,王修善,等.4LZ-0.8型水稻联合收割机清选装置气固两相分离作业机理[J].农业工程学报,2015,31(12):16-22.Ren Shuguang,Xie Fangping,Wang Xiushan,et al.Gas-solid two-phase separation operation mechanism for4LZ-0.8 rice combine harvester cleaning device[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2015,31(12):16-22.(in Chinese with English abstract)
[13]焦有宙,田超超,贺超,等.不同工质对大型联合收割机余热回收的热力学性能[J].农业工程学报,2018,34(5):32-38.Jiao Youzhou,Tian Chaochao,He Chao,et al.Thermodynamic performance of waste heat collection for large combine harvester with different working fluids[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2018,34(5):32-38.(in Chinese with English abstract)
[14]伟利国,张小超,汪凤珠,等.联合收割机稻麦收获边界激光在线识别系统设计与试验[J].农业工程学报,2017,33(增刊1):30-35.Wei Liguo,Zhang Xiaochao,Wang Fengzhu,et al.Designand experiment of harvest boundary online recognition system for rice and wheat combine harvester based on laser detection[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2017,33(Supp.1):30-35.(in Chinese with English abstract)
[15]Yoshisada N,Katsuhiko T,Kentaro N,et al.A global positioning system guided automated rice transplanter[J].IFAC Proceedings Volumes,2013,46(18):41-46.
[16]Tamaki K,Nagasaka Y,Nishiwaki K,et al.A robot system for paddy field farming in Japan[J].IFAC Proceedings Volumes,2013,46(18):143-147.
[17]胡炼,罗锡文,张智刚,等.基于CAN总线的分布式插秧机导航控制系统设计[J].农业工程学报,2009,25(12):88-92.Hu Lian,Luo Xiwen,Zhang Zhigang,et al.Design of distributed navigation control system for rice transplanters based on controller area network[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2009,25(12):88-92.(in Chinese with English abstract)
[18]胡静涛,高雷,白晓平,等.农业机械自动导航技术研究进展[J].农业工程学报,2015,31(10):1-10.Hu Jingtao,Gao Lei,Bai Xiaoping,et al.Review of research on automatic guidance of agricultural vehicles[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2015,31(10):1-10.(in Chinese with English abstract)
[19]宋宇,刘永博,刘路,等.基于机器视觉的玉米根茎导航基准线提取方法[J].农业机械学报,2017,48(2):38-44.Song Yu,Liu Yongbo,Liu Lu,et al.Extraction method of navigation baseline of corn roots based on machine vision[J].Transactions of the Chinese Society for Agricultural Machinery,2017,48(2):38-44.(in Chinese with English abstract)
[20]Leemans V,Destain M F.Line cluster detection using a vartiant of the Hough transform for culture row localisation[J].Image and Vision Computing,2006,24(5):541-550.
[21]Gee C,Bossu J,Jones G,et al.Crop weed discrimination in perspective agronomic image[J].Computers and Electronics in Agriculture,2007,58(1):1-9.
[22]姜国权,柯杏,杜尚丰,等.基于机器视觉的农田作物行检测[J].光学学报,2009,29(4):1015-1020.Jiang Guoquan,Ke Xing,Du Shangfeng,et al.Crop row detection based on machine vision[J].Acta Optica Sinica,2009,29(4):1015-1020.(in Chinese with English abstract)
[23]Han Y H,Wang Y M,Kang F.Navigation line detection based on support vector machine for automatic agriculture vehicle[C]//International Conference on Automatic Control and Artificial Intelligence(ACAI 2012),Xiamen,2012:1381-1385.
[24]English A,Ross P,Ball D,et al.Vision based guidance for robot navigation in agriculture[C]//2014 IEEE International Conference on Robotics&Automation(ICRA),Hong Kong,2014:1693-2698.
[25]Cariou C,Lenain R,Thuilot B,et al.Motion planner and lateral-longitudinal controllers for autonomous maneuvers of a farm vehicle in headland[C]//2009 IEEE/RSJ International Conference on Intelligent Robots and Systems,USA,2009:5782-5787.
[26]林桂潮,邹湘军,张青,等.基于主动轮廓模型的自动导引车视觉导航[J].农业机械学报,2017,48(2):20-26.Lin Guichao,Zou Xiangjun,Zhang Qing,et al.Visual navigation for automatic guided vehicles based on active contour model[J].Transactions of the Chinese Society for Agricultural Machinery,2017,48(2):20-26.(in Chinese with English abstract)
[27]项明,魏爽,何洁,等.基于DSP和MCU的农机具视觉导航终端设计[J].农业机械学报,2015,46(增刊1):21-26.Xiang Ming,Wei Shuang,He Jie,et al.Development of agricultural implement visual navigation terminal based on DSP and MCU[J].Transactions of the Chinese Society for Agricultural Machinery,2015,46(Supp.1):21-26.(in Chinese with English abstract)
[28]任俊如.改进的预测PID控制器的研究与设计[D].武汉:武汉科技大学,2011.Ren Junru.The Research and Design of Improved Predictive PID Controller[D].Wuhan:Wuhan University of science and Technology,2011.(in Chinese with English abstract)
[29]余天明,郑磊,李颂.电控机械式自动变速器离合器灰色预测PID控制技术[J].农业机械学报,2011,42(8):1-6.Yu Tianming,Zheng Lei,Li Song.Gray prediction PID control technology of automated mechanical transmission clutch[J].Transactions of the Chinese Society for Agricultural Machinery,2011,42(8):1-6.(in Chinese with English abstract)
[30]Point Grey Research,Inc.Triclops software kit Version 3.1user’s guide and command reference[EB/OL].[2018-08-25].https://www.ptgrey.com/support/downloads
[31]陈晗婧.SIFT特征匹配技术研究与应用[D].南京:南京理工大学,2017.Chen Hanjing.Research and Application of SIFT Feature Point Technology[D].Nanjing:Nanjing University of Science and Technology,2017.(in Chinese with English abstract)
[32]Hiremath S,Evert F K V,Braak C T,et al.Image-based particle filtering for navigation in a semi-structured agricultural environment[J].Biosystems Engineering,2014,121(5):85-95.
[33]沈文龙,薛金林,汪东明,等.农业车辆视觉导航控制系统[J].中国农机化学报,2016,37(6):251-254.Shen Wenlong,Xue Jinlin,Wang Dongming,et al.Visual navigation control system of agricultural vehicle[J].Journal of Chinese Agricultural Mechanization,2016,37(6):251-254.(in Chinese with English abstract)