ROS with V-rep (2) (ROS学习笔记五）

        昨晚完成了将ROS与V-rep的桥接，虽然没有读出有效消息，但已经从rostopic中看到了相应的ropic出现，今天经过简单的调试，果然可以实现对V-rep中的消息在ROS中的接收与发送。

一、在V-rep中创建ROS话题

接着昨天的工作，仔细研究LUA中的函数参数后修改昨天的LUA代码中的那三行如下：

sensorPub = simExtROS_enablePublisher('/frontUS',1000,simros_strmcmd_read_proximity_sensor,hFrontUS,-1,'std_msgs/Float64')

rightPub = simExtROS_enableSubscriber('/right_cmd',1000,simros_strmcmd_set_joint_target_velocity,hRightMotor,-1,'std_msgs/Float64')

leftPub = simExtROS_enableSubscriber('/left_cmd',1000,simros_strmcmd_set_joint_target_velocity,hRightMotor,-1,'std_msgs/Float64')

以上三个函数其实就是整个工程搭桥的核心部分了，这三个函数不论是从函数名还是参数上都比较难搞，经过一番研究我理解的如下：

sensorPub等号前面的其实只是一个在Vrep中的变量，随便命名不影响在ROS中的调用。

三个函数的第一个参数即为需要发送/接收的话题名称，如果没有这个话题，进程便会在ROS中建立一个话题，并向其中发送/接收消息，

第二个参数为消息队列，在这里如果消息频率没有问题则问题不大。

第三个参数最为重要，意味着V-rep以什么消息类型去接收/发送消息，这里其实需要的是一个number型参数，但V-rep中已经定义好了一些变量，如“simros_strmcmd_set_joint_target_velocity”就是一个stdmsg::Float64 型参数，于是他创建的话题中需要去接收这样一个消息，来控制轮子的转动。

第四个参数决定了将接收到的消息传送给V-rep中的哪个部件，这个参数就是之前从V-rep中get到的Handle，这样就可以将目标handle 与ROS话题链接起来

第五个参数参考上篇中的最后一个参考资料，如果不需要则为-1。

第六个参数目前我还没有搞得很清楚，似乎是一个字符串就可以正常运行，不知道具体用在哪里，但不影响运行。

二、在ROS中读取消息

有了（一）中的工作，我们其实topic中已经有传感器的输出与等待输入的topic了。

我们固然可以直接rostopic pub来控制两轮转速，但对proximity 的读取则无法直接echo出来，因为我们并没有定义这个消息类型，这是需要找到Vrep_common/Pro...Data.msg，将其复制到我们自己工作区中创建的msg文件夹中，然后修改CMakeList与package文件，具体可以参考以下内容：

为了更好的控制，我写了一个myrobot_control.cpp来控制小车转动，代码如下：

#include<ros/ros.h>#include<string>#include "std_msgs/Float64.h"#include "geometry_msgs/Twist.h"using namespace std;int main(int argc, char** argv){ros::init(argc, argv, "controller");ros::NodeHandle n;ros::Publisher leftwheel_pub = n.advertise<std_msgs::Float64>("left_vel",1000);ros::Publisher rightwheel_pub = n.advertise<std_msgs::Float64>("right_vel",1000);ros::Rate loop_rate(1);int count = 0;std_msgs::Float64 left_velocity,right_velocity;left_velocity.data = right_velocity.data = 0;while(ros::ok()){   count++;if(count >= 5) count = 0;left_velocity.data = count;right_velocity.data = -count;leftwheel_pub.publish(left_velocity);rightwheel_pub.publish(right_velocity);ros::spinOnce();loop_rate.sleep();}return 0;}

同时配置CMakeList如下：

cmake_minimum_required(VERSION 2.8.3)project(vrep_common)## Add support for C++11, supported in ROS Kinetic and newer# add_definitions(-std=c++11)## Find catkin macros and libraries## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz)## is used, also find other catkin packagesfind_package(catkin REQUIRED COMPONENTS roscpp rospy std_msgs geometry_msgs message_generation)## System dependencies are found with CMake's conventions# find_package(Boost REQUIRED COMPONENTS system)## Uncomment this if the package has a setup.py. This macro ensures## modules and global scripts declared therein get installed## See http://ros.org/doc/api/catkin/html/user_guide/setup_dot_py.html# catkin_python_setup()################################################## Declare ROS messages, services and actions #################################################### To declare and build messages, services or actions from within this## package, follow these steps:## * Let MSG_DEP_SET be the set of packages whose message types you use in##   your messages/services/actions (e.g. std_msgs, actionlib_msgs, ...).## * In the file package.xml:##   * add a build_depend tag for "message_generation"##   * add a build_depend and a run_depend tag for each package in MSG_DEP_SET##   * If MSG_DEP_SET isn't empty the following dependency has been pulled in##     but can be declared for certainty nonetheless:##     * add a run_depend tag for "message_runtime"## * In this file (CMakeLists.txt):##   * add "message_generation" and every package in MSG_DEP_SET to##     find_package(catkin REQUIRED COMPONENTS ...)##   * add "message_runtime" and every package in MSG_DEP_SET to##     catkin_package(CATKIN_DEPENDS ...)##   * uncomment the add_*_files sections below as needed##     and list every .msg/.srv/.action file to be processed##   * uncomment the generate_messages entry below##   * add every package in MSG_DEP_SET to generate_messages(DEPENDENCIES ...)## Generate messages in the 'msg' folder add_message_files(   FILES   ProximitySensorData.msg#   Message1.msg#   Message2.msg )## Generate services in the 'srv' folder# add_service_files(#   FILES#   Service1.srv#   Service2.srv# )## Generate actions in the 'action' folder# add_action_files(#   FILES#   Action1.action#   Action2.action# )## Generate added messages and services with any dependencies listed here generate_messages(   DEPENDENCIES   std_msgs  # Or other packages containing msgs   geometry_msgs )################################################## Declare ROS dynamic reconfigure parameters #################################################### To declare and build dynamic reconfigure parameters within this## package, follow these steps:## * In the file package.xml:##   * add a build_depend and a run_depend tag for "dynamic_reconfigure"## * In this file (CMakeLists.txt):##   * add "dynamic_reconfigure" to##     find_package(catkin REQUIRED COMPONENTS ...)##   * uncomment the "generate_dynamic_reconfigure_options" section below##     and list every .cfg file to be processed## Generate dynamic reconfigure parameters in the 'cfg' folder# generate_dynamic_reconfigure_options(#   cfg/DynReconf1.cfg#   cfg/DynReconf2.cfg# )##################################### catkin specific configuration ####################################### The catkin_package macro generates cmake config files for your package## Declare things to be passed to dependent projects## INCLUDE_DIRS: uncomment this if you package contains header files## LIBRARIES: libraries you create in this project that dependent projects also need## CATKIN_DEPENDS: catkin_packages dependent projects also need## DEPENDS: system dependencies of this project that dependent projects also need#catkin_package(#  INCLUDE_DIRS include#  LIBRARIES vrep_common#  CATKIN_DEPENDS other_catkin_pkg#  DEPENDS system_lib#)catkin_package(  LIBRARIES vrep_common  CATKIN_DEPENDS message_runtime roscpp rospy std_msgs geometry_msgs   DEPENDS system_lib  )############# Build ############### Specify additional locations of header files## Your package locations should be listed before other locations# include_directories(include)## Declare a C++ library# add_library(${PROJECT_NAME}#   src/${PROJECT_NAME}/vrep_common.cpp# )## Add cmake target dependencies of the library## as an example, code may need to be generated before libraries## either from message generation or dynamic reconfigure# add_dependencies(${PROJECT_NAME} ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})## Declare a C++ executable## With catkin_make all packages are built within a single CMake context## The recommended prefix ensures that target names across packages don't collide# add_executable(${PROJECT_NAME}_node src/vrep_common_node.cpp)## Rename C++ executable without prefix## The above recommended prefix causes long target names, the following renames the## target back to the shorter version for ease of user use## e.g. "rosrun someones_pkg node" instead of "rosrun someones_pkg someones_pkg_node"# set_target_properties(${PROJECT_NAME}_node PROPERTIES OUTPUT_NAME node PREFIX "")## Add cmake target dependencies of the executable## same as for the library above# add_dependencies(${PROJECT_NAME}_node ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})## Specify libraries to link a library or executable target against# target_link_libraries(${PROJECT_NAME}_node#   ${catkin_LIBRARIES}# )############### Install ################ all install targets should use catkin DESTINATION variables# See http://ros.org/doc/api/catkin/html/adv_user_guide/variables.html## Mark executable scripts (Python etc.) for installation## in contrast to setup.py, you can choose the destination# install(PROGRAMS#   scripts/my_python_script#   DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}# )## Mark executables and/or libraries for installation# install(TARGETS ${PROJECT_NAME} ${PROJECT_NAME}_node#   ARCHIVE DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}#   LIBRARY DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}#   RUNTIME DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}# )## Mark cpp header files for installation# install(DIRECTORY include/${PROJECT_NAME}/#   DESTINATION ${CATKIN_PACKAGE_INCLUDE_DESTINATION}#   FILES_MATCHING PATTERN "*.h"#   PATTERN ".svn" EXCLUDE# )## Mark other files for installation (e.g. launch and bag files, etc.)# install(FILES#   # myfile1#   # myfile2#   DESTINATION ${CATKIN_PACKAGE_SHARE_DESTINATION}# )############### Testing ################# Add gtest based cpp test target and link libraries# catkin_add_gtest(${PROJECT_NAME}-test test/test_vrep_common.cpp)# if(TARGET ${PROJECT_NAME}-test)#   target_link_libraries(${PROJECT_NAME}-test ${PROJECT_NAME})# endif()## Add folders to be run by python nosetests# catkin_add_nosetests(test)include_directories (include ${catkin_INCLUDE_DIRS})add_executable(vrep_common myrobot_control.cpp)target_link_libraries(vrep_common ${catkin_LIBRARIES})

package如下：

<?xml version="1.0"?><package>  <name>vrep_common</name>  <version>0.0.0</version>  <description>The vrep_common package</description>  <!-- One maintainer tag required, multiple allowed, one person per tag -->   <!-- Example:  -->  <!-- <maintainer email="[e-mail]">Jane Doe</maintainer> -->  <maintainer email="[e-mail]">jkwang</maintainer>  <!-- One license tag required, multiple allowed, one license per tag -->  <!-- Commonly used license strings: -->  <!--   BSD, MIT, Boost Software License, GPLv2, GPLv3, LGPLv2.1, LGPLv3 -->  <license>TODO</license>  <!-- Url tags are optional, but multiple are allowed, one per tag -->  <!-- Optional attribute type can be: website, bugtracker, or repository -->  <!-- Example: -->  <!-- <url type="website">http://wiki.ros.org/vrep_common</url> -->  <!-- Author tags are optional, multiple are allowed, one per tag -->  <!-- Authors do not have to be maintainers, but could be -->  <!-- Example: -->  <!-- <author email="[e-mail]">Jane Doe</author> -->  <!-- The *_depend tags are used to specify dependencies -->  <!-- Dependencies can be catkin packages or system dependencies -->  <!-- Examples: -->  <!-- Use build_depend for packages you need at compile time: -->  <!--   <build_depend>message_generation</build_depend> -->  <!-- Use buildtool_depend for build tool packages: -->  <!--   <buildtool_depend>catkin</buildtool_depend> -->  <!-- Use run_depend for packages you need at runtime: -->  <!--   <run_depend>message_runtime</run_depend> -->  <!-- Use test_depend for packages you need only for testing: -->  <!--   <test_depend>gtest</test_depend> -->  <buildtool_depend>catkin</buildtool_depend>  <build_depend>message_generation</build_depend>  <build_depend>roscpp</build_depend>  <build_depend>rospy</build_depend>  <build_depend>std_msgs</build_depend>  <build_depend>geometry_msgs</build_depend>  <run_depend>message_runtime</run_depend>  <run_depend>roscpp</run_depend>  <run_depend>rospy</run_depend>  <run_depend>std_msgs</run_depend>  <run_depend>geometry_msgs</run_depend>  <!-- The export tag contains other, unspecified, tags -->  <export>    <!-- Other tools can request additional information be placed here -->  </export></package>

至此应该可以echo出传感器的信息，并且实现控制小车逐渐变快的转动了。

注：为了保证V-rep对消息类型的要求得到满足，建议将rospkg的名字改为vrep_common ,省去了在V-rep中进一步修改其他地方的烦恼。