【SLAM随手记】ROS中编译ORB-SLAM2出错及解决方案：[rosrun] Couldn't find executable named Mono_[rosbuild] rospack found package "orb_slam2" at ""

此前的步骤请参考《在ROS中使用usb摄像头跑ORB SLAM2》：

https://blog.csdn.net/Goding_learning/article/details/52950993

【摘要】本文针对运行编译ROS中编译ORB-SLAM2时候遇到的问题，即运行rosrun命令后出现的问题。因编译时候就出现问题，所以后面rosrun运行时肯定也会出现问题，会提示找不到某目录下的可执行文件mono，命令和错误信息分别如下：

rosrun ORB_SLAM2 Mono /home/xx/catkin_ws/src/ORB_SLAM2/Vocabulary/ORBvoc.txt /home/xx/catkin_ws/src/ORB_SLAM2/Examples/ROS/ORB_SLAM2/Asus.yaml 

错误信息：

kinetic@ros-vm:~/mywork/catkin_ws/src/ORB_SLAM2-master-origin/Examples/ROS/ORB_SLAM2$ rosrun ORB_SLAM2 Mono /home/xx/catkin_ws/src/ORB_SLAM2/Vocabulary/ORBvoc.txt /home/xx/catkin_ws/src/ORB_SLAM2/Examples/ROS/ORB_SLAM2/Asus.yaml
[rosrun] Couldn't find executable named Mono below /home/kinetic/mywork/catkin_ws/src/ORB_SLAM2-master-origin/Examples/ROS/ORB_SLAM2
[rosrun] Found the following, but they're either not files,
[rosrun] or not executable:
[rosrun]   /home/kinetic/mywork/catkin_ws/src/ORB_SLAM2-master-origin/Examples/ROS/ORB_SLAM2/Mono

即运行rosrun命令后出现的问题。

具体解决办法见https://github.com/raulmur/ORB_SLAM2/issues/498，即添加catkin_ws/src/ORB_SLAM2/Examples/ROS路径到~/.bashrc文件，使得系统知道已经安装了ROS。否则在ROS的工作目录catkin_ws文件夹中编译适用于ROS系统的ORB-SLAM2时候就会出错，错误信息如下：

kinetic@ros-vm:~/mywork/catkin_ws/src/ORB_SLAM2-master-origin$ ./build_ros.sh 
Building ROS nodes
-- The C compiler identification is GNU 5.4.0
-- The CXX compiler identification is GNU 5.4.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found PythonInterp: /usr/bin/python (found version "2.7.12") 
[rosbuild] Building package ORB_SLAM2
[rosbuild] Error from directory check: /opt/ros/kinetic/share/ros/core/rosbuild/bin/check_same_directories.py  /home/kinetic/mywork/catkin_ws/src/ORB_SLAM2-master-origin/Examples/ROS/ORB_SLAM2
1
Traceback (most recent call last):
  File "/opt/ros/kinetic/share/ros/core/rosbuild/bin/check_same_directories.py", line 46, in <module>
    raise Exception
Exception
CMake Error at /opt/ros/kinetic/share/ros/core/rosbuild/private.cmake:102 (message):
  [rosbuild] rospack found package "ORB_SLAM2" at "", but the current
  directory is
  "/home/kinetic/mywork/catkin_ws/src/ORB_SLAM2-master-origin/Examples/ROS/ORB_SLAM2".
  You should double-check your ROS_PACKAGE_PATH to ensure that packages are
  found in the correct precedence order.
Call Stack (most recent call first):
  /opt/ros/kinetic/share/ros/core/rosbuild/public.cmake:177 (_rosbuild_check_package_location)
  CMakeLists.txt:4 (rosbuild_init)
 
 
-- Configuring incomplete, errors occurred!
See also "/home/kinetic/mywork/catkin_ws/src/ORB_SLAM2-master-origin/Examples/ROS/ORB_SLAM2/build/CMakeFiles/CMakeOutput.log".
make: *** 没有指明目标并且找不到 makefile。 停止。

【解决办法】

1、首先去目录/home/(此处是你创建ROS工作空间的路径)/catkin_ws/src/ORB_SLAM2-master-origin(这个是ROS下ORB-SLAM2的总目录，该目录由ORB-SLAM2.tar.gz解压缩生成)/Examples/ROS/ORB_SLAM2中删除此前错误build过程生成的名为build的文件夹（如果有的话）；

2、添加“/home/(此处是你创建ROS工作空间的路径)/catkin_ws/src/ORB_SLAM2-master-origin(这个是ROS下ORB-SLAM2的总目录，该目录由ORB-SLAM2.tar.gz解压缩生成)/Examples/ROS”到你的ROS_PACKAGE_PATH，即

$ vim ~/.bashrc

在最后一行添加如下代码，再source一下，这样就添加了ORB-SLAM2的ROS文件夹的路径到ROS系统路径中（让两者可以互通互联了）：

export ROS_PACKAGE_PATH=${ROS_PACKAGE_PATH}:/home/...(这里填上你 catkin_ws/ORB_SLAM2的具体路径)/ORB_SLAM2/Examples/ROS

再source一下：

$ source ~/.bashrc

3、去目录/home/(此处是你创建ROS工作空间的路径)/catkin_ws/src/ORB_SLAM2-master-origin 目录中运行

$ chmod +x build_ros.sh
$ ./build_ros.sh

这步之后，就会发现在~/mywork/catkin_ws/src/ORB_SLAM2-master-origin/Examples/ROS/ORB_SLAM2目录下有绿色的mono文件生成，此时就可以成功运行如下代码不会报错（说找不到可执行文件mono啦）：

$ rosrun ORB_SLAM2 Mono /home/kinetic/mywork/catkin_ws/src/ORB_SLAM2-master-
origin/Vocabulary/ORBvoc.txt /home/kinetic/mywork/catkin_ws/src/ORB_SLAM2-master-origin/Examples/ROS/ORB_SLAM2/Asus.yaml

上面命令中“/home/kinetic/mywork/catkin_ws/src/ORB_SLAM2-master-origin”是我的ROS工作空间目录下ORB-SLAM2的安装目录，读者可根据自己的具体情况来修改。

【注】此前的步骤请参考《在ROS中使用usb摄像头跑ORB SLAM2》：

https://blog.csdn.net/Goding_learning/article/details/52950993