Ros Nodelet 高速通信单独节点编写

理解Nodelet

ROS引入了Nodelet机制，通过共享指针实现了在多算法、多节点间的零拷贝传输。

ROS通过Nodelet管理器NodeletInterface管理Nodelet，

并通过ROS的pluglib插件机制实现动态加载Nodelet。

Nodelet管理器拥有一个可供所有Nodelet使用的线程池，

线程池的数量通过参数num_worker_threads设置，默认为4。

Nodelet作为线程出现。

使用getNodeHandle()、getPrivateNodeHandle()则回调是串行的，

使用getMTNodeHandle()、getMTPrivateNodeHandle()则回调是基于线程池并行。

加载nodelet

两种加载途径（命令行、Launch），三种加载方式（manager、load、standalone ）

 作为管理器加载节点 manager


$ nodelet manager
"nodelet" type="nodelet" name="example_manager" args="manager" output="screen" >
 
"num_worker_threads" type="int" value="8"/>

 在管理器上加载节点 load


$nodelet load pkg/Type 管理器名
"nodelet" type="nodelet" name="nodeletTalker" args="load example_nodelet/NodeletTalker example_manager" output="screen">
"value" type="double" value="10"/>

 按照单例模式，在管理器上加载节点 standalone


$ nodelet standalone pkg/Type
"nodelet" type="nodelet" name="nodeletTalker" args="standalone example_nodelet/NodeletTalker example_manager" output="screen">
"value" type="double" value="10"/>

共享指针

共享指针typedef boost::shared_ptr< ::std_msgs::String > StringPtr;


ros::Publisher pub = nh.advertise("nodelet_topic", 5);
 
std_msgs::StringPtr str(new std_msgs::String);    //  声明指针把数据给他
 
str->data = "hello world";                        //  将数据写入 
 
pub.publish(str);                                 //  发布数据

Nodelet插件描述脚本

library path标签 :动态库的相对路径；

class 标签描述了由库提供的类。

name标签:类的查找名称(名字空间名/类名)。

供pluginlib工具用作插件的标识符；type标签:类型；

base_class_type：基类的类型；

description 标签：类的描述和它能做什么。


"lib/libexampleNodelet">
 
<class name="example_nodelet/NodeletTalker" type="example_nodelet::NodeletTalker" 
base_class_type="nodelet::Nodelet">
 
nodeletTalker
 
class>
 
<class name="example_nodelet/NodeletListener" type="example_nodelet::NodeletListener" base_class_type="nodelet::Nodelet">
 
NodeletListener
 
class>

查看插件是否可用：rosrun nodelet declared_nodelets

关键编译配置


 package.xml配置
nodelet
"${prefix}/nodelet_description.xml"/>
 
 
 CMakeLists.txt配置
catkin_package(
LIBRARIES exampleNodelet
CATKIN_DEPENDS roscpp rospy nodelet std_msgs
)
include_directories(
include
${catkin_INCLUDE_DIRS}
)
add_library(exampleNodelet src/nodelet_plugins.cpp)

实现Nodelet步骤

步骤1 定义继承nodelet::Nodelet的Nodelet插件 .cpp


#include 
#include 
#include 
#include 
#include 
 
namespace example_nodelet{                                     //  定义空间
 
    void NodeletTalker::onInit(){
        NODELET_INFO("NodeletTalker onInit");
        std_msgs::Float64Ptr input(new std_msgs::Float64());   //  共享指针
        ros::NodeHandle& nh = getMTNodeHandle();               //  获得句柄
        nh.getParam("value",value);                            //  获得句柄参数
        pub = nh.advertise("test", 100);    //  创建接受节点
        ros::Rate loop_rate(1);                                //  发布Hz
        while (ros::ok())                                      //
        {
            /* code */
            input->data = value + 10;
            pub.publish(input);
            NODELET_INFO("the NodeletTalker value is %f", input->data);
            ros::spinOnce();
            loop_rate.sleep();
            value+= 10;
        }
        
    }
 
    void NodeletListener::onInit(){
        NODELET_INFO("NodeletListener onInit");
        ros::NodeHandle& nh = getMTNodeHandle();
        sub = nh.subscribe("test", 100, &NodeletListener::callback, this);
    }
 
    void NodeletListener::callback(const std_msgs::Float64::ConstPtr& input){
        std_msgs::Float64Ptr output(new std_msgs::Float64());
        output->data = input->data + 5;
        NODELET_INFO("the NodeletListener value is %f", output->data);
    }
 
}
 
 
PLUGINLIB_EXPORT_CLASS(example_nodelet::NodeletListener, nodelet::Nodelet);  //声明插件
PLUGINLIB_EXPORT_CLASS(example_nodelet::NodeletTalker, nodelet::Nodelet);    //声明插件

头.h 文件.


#include 
#include 
#include 
 
namespace example_nodelet{
    class NodeletTalker: public nodelet::Nodelet     // 继承节点
    {
    private:
        /* data  发布者 */
        double value = 10;
        ros::Publisher pub;
        virtual void onInit();
    };
 
   class NodeletListener: public nodelet::Nodelet
    {
    private:
        /* data 订阅者 */
        ros::Subscriber sub;
        virtual void onInit();                                   // 初始化函数
        void callback(const std_msgs::Float64::ConstPtr& input); // 回调
    };
}

步骤2 重载插件的onInit()方法

步骤3 声明Nodelet插件

步骤4 创建Nodelet插件描述脚本

步骤5 编写Launch文件


  "nodelet" type="nodelet" name="example_manager" args="manager" output="screen" >
       "num_worker_threads" type="int" value="8"/>
  
 
  "nodelet" type="nodelet" name="nodeletListener"
        args="standalone example_nodelet/NodeletListener example_manager" output="screen">
   
 
  "nodelet" type="nodelet" name="nodeletTalker"
        args="standalone example_nodelet/NodeletTalker example_manager" output="screen">
        "value" type="double" value="10"/>

步骤6 package.xml、CMakeLists.txt配置


cmake_minimum_required(VERSION 3.0.2)
project(example_6)
 
## Compile as C++11, supported in ROS Kinetic and newer
# add_compile_options(-std=c++11)
 
## Find catkin macros and libraries
## if COMPONENTS list like find_package(catkin REQUIRED COMPONENTS xyz)
## is used, also find other catkin packages
find_package(catkin REQUIRED COMPONENTS
  roscpp
  rospy
  nodelet
  std_msgs
)
 
## 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 exec_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 exec_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
#   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
# )
 
################################################
## 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 exec_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 your 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 exampleNodelet
   CATKIN_DEPENDS roscpp rospy nodelet std_msgs
#  DEPENDS system_lib
)
 
###########
## Build ##
###########
 
## Specify additional locations of header files
## Your package locations should be listed before other locations
include_directories(
  include
  ${catkin_INCLUDE_DIRS}
)
 
## Declare a C++ library
# add_library(${PROJECT_NAME}
#   src/${PROJECT_NAME}/example_6.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/example_6_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
if(CMAKE_BUILD_TYPE STREQUAL DEBUG)
add_library(exampleNodelet src/nodelet_plugins.cpp)
 target_link_libraries(exampleNodelet
   ${catkin_LIBRARIES}
 )
 endif()
#############
## 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
# catkin_install_python(PROGRAMS
#   scripts/my_python_script
#   DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
# )
 
## Mark executables for installation
## See http://docs.ros.org/melodic/api/catkin/html/howto/format1/building_executables.html
# install(TARGETS ${PROJECT_NAME}_node
#   RUNTIME DESTINATION ${CATKIN_PACKAGE_BIN_DESTINATION}
# )
 
## Mark libraries for installation
## See http://docs.ros.org/melodic/api/catkin/html/howto/format1/building_libraries.html
# install(TARGETS ${PROJECT_NAME}
#   ARCHIVE DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
#   LIBRARY DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
#   RUNTIME DESTINATION ${CATKIN_GLOBAL_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_example_6.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)

步骤7 编译执行

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原文地址：https://blog.csdn.net/weixin_44025389/article/details/126486616