摘要
祝融号火星车在火星表面巡视移动3个月周期内,火星车精准定位与摄站周围精细地形重建是一项非常重要的任务,可为后续的路径规划、机构运动和科学探测提供基础信息.利用摄站点间具有重叠区域的立体地形导航全景相机图像,采用图像区域网平差模型实现火星车的连续相对定位,可有效地降低车轮滑移和惯导系统误差累计对定位精度的影响.同时,根据单个摄站的立体地形导航全景相机序列图像,采用闭合区域网平差模型和立体匹配技术实现数字高程模型(digital elevation model,DEM)和数字正射影像图(digital orthophoto map,DOM)的制作.依据祝融号火星车的地面实验,视觉定位精度优于2%,3 m内的地形重建精度优于5 mm,并有效支持祝融号火星车高精度视觉定位、地形重建、快速全局定位、在轨驶离、路径规划、科学目标点位置测量等在轨任务.
During the three month movement of China’s Zhurong Mars rover,it is a very important task to obtain the precise position of the rover and the terrain around the stations,which provides basic information for subsequent path planning,mechanism movement and scientific exploration.At the visual localization step,a bundle adjustment model by using the stereo navigation camera(Navcam)images with overlapping areas between adjacent stations can achieve continuous relative pose for the rover,which can effectively reduce the impact of wheel slip and inertial navigation system errors on positioning accuracy.Firstly,the initial position and attitude information of the Zhurong Mars rover and the rotation angle of the mast can be contained from the telemetry data.Then,through the inverse coordinate transformation,the Navcam pose in the landing north-east-down(NED)system can be obtained,which is regarded as the initial value of the Navcam’s external orientation element.Secondly,the speeded-up robust features(SURF)matching algorithm is used to match stereo images at adjacent stations,and some sparse connection points are obtained.Thirdly,combined with the Navcam’s internal orientation elements and relative pose parameters,a bundle adjustment model is constructed.A least square solution is used in the proposed bundle adjustment model,and the optimized Navcam pose at the current station can be calculated.Then,through the coordinate transformation,the Zhurong Mars rover’s position in the NED system is obtained.At the terrain reconstruction step,a visual closed block network adjustment model and the stereo matching technology are used to obtain a digital elevation model(DEM)and orthophoto map(DOM).Firstly,an epipolar line correction method is performed on the Navcam’s stereo images at the current camera station,and tie points are obtained by SURF.Secondly,the proposed closed block network adjustment model is constructed.When a total least squares solution is used in the proposed model,the optimized relative pose of the sequence images is calculated.Taking one pair of stereo images as a bridge,the sequence camera pose is integrated into the NED System.Thirdly,dense matching and forward intersection are performed in the current sequence images to obtain dense point clouds in the NED system.After point cloud denoising,interpolation and back projection,the DEM and DOM products are obtained,and the terrain reconstruction mission at the current station is completed.According to the ground experiment of the Zhurong Mars rover,the visual localization precision is better than 2%,the terrain reconstruction accuracy is 5 mm@3 m.In the orbit mission,taking the visual localization results of the Zhurong Mars rover at the end of three months as an example,the cumulative error of the visual localization results is 5.1%.Based on the Navcam images sequence on the lander,Mars DOM images and one image from the descent camera with a height of about 200 m,the proposed technology is used to obtain the precise landing position(109.925°E,25.066°N)of the Zhurong Mars rover on May 22,2021.The landing position result corrects the estimated landing position of the rover based on the orbital parameters.The deviation of the two measured positions is about 2.1 km.At the same time,the localization and terrain reconstruction results effectively support on-orbit departure,path planning,and coordinate measurement of scientific target points,etc.
作者
马友青
彭松
张建利
温博
金晟毅
贾阳
徐辛超
张烁
鄢咏折
吴运佳
亓晨
李昊
刘少创
Youqing Ma;Song Peng;Jianli Zhang;Bo Wen;Shengyi Jin;Yang Jia;Xinchao Xu;Shuo Zhang;Yongzhe Yan;Yunjia Wu;Chen Qi;Hao Li;Shaochuang Liu(International Research Center of Big Data for Sustainable Development Goals,Beijing 100094,China;Key Laboratory of Digital Earth Science,Aerospace Information Research Institute,Chinese Academy of Sciences,Beijing 100094,China;Beijing Institute of Spacecraft System Engineering,Beijing 100094,China;School of Geomatics,Liaoning Technical University,Fuxin 123000,China;School of Geodesy and Geomatics,Wuhan University,Wuhan 430072,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2022年第23期2790-2801,共12页
Chinese Science Bulletin
基金
国家自然科学基金(42071447,41601494)资助。
关键词
祝融号火星车
视觉定位
地形重建
区域网平差
数字正射影像图
Zhurong Mars rover
visual localization
terrain reconstruction
block network adjustment
digital orthophoto map
