官网教程:http://gazebosim.org/tutorials?cat=guided_i&tut=guided_i6 《一》ros通信的意义 在利用gazebo仿真时。我们可以利用gazebo的通信机制进行创建节点和发布消息。但是这只是在仿真平台实现。如果想要实际使用,就需要利用ros系统的通信机制对模型进行控制。这一节内容就是如果在plugin中加入ros系统的节点,利用ros系统的通信命令进行参数的修改。 《二》实现过程 (1)在velodyne_plugin.cc中添加与ros通信相关的头文件
#include <thread>
#include "ros/ros.h"
#include "ros/callback_queue.h"
#include "ros/subscribe_options.h"
#include "std_msgs/Float32.h"
(2)定义ros通信的成员变量
/// \brief A node use for ROS transport
private: std::unique_ptr<ros::NodeHandle> rosNode;
/// \brief A ROS subscriber
private: ros::Subscriber rosSub;
/// \brief A ROS callbackqueue that helps process messages
private: ros::CallbackQueue rosQueue;
/// \brief A thread the keeps running the rosQueue
private: std::thread rosQueueThread;
(3)ros通信的配置和节点初始化 在Load函数里面添加:
// Initialize ros, if it has not already bee initialized.
if (!ros::isInitialized())
{
int argc = 0;
char **argv = NULL;
ros::init(argc, argv, "gazebo_client",
ros::init_options::NoSigintHandler);
}
// Create our ROS node. This acts in a similar manner to
// the Gazebo node
this->rosNode.reset(new ros::NodeHandle("gazebo_client"));
// Create a named topic, and subscribe to it.
ros::SubscribeOptions so =
ros::SubscribeOptions::create<std_msgs::Float32>(
"/" + this->model->GetName() + "/vel_cmd",
1,
boost::bind(&VelodynePlugin::OnRosMsg, this, _1),
ros::VoidPtr(), &this->rosQueue);
this->rosSub = this->rosNode->subscribe(so);
// Spin up the queue helper thread.
this->rosQueueThread =
std::thread(std::bind(&VelodynePlugin::QueueThread, this));
(4)定义消息接收处理和线程管理的函数:
/// \brief Handle an incoming message from ROS
/// \param[in] _msg A float value that is used to set the velocity
/// of the Velodyne.
public: void OnRosMsg(const std_msgs::Float32ConstPtr &_msg)
{
this->SetVelocity(_msg->data);
}
/// \brief ROS helper function that processes messages
private: void QueueThread()
{
static const double timeout = 0.01;
while (this->rosNode->ok())
{
this->rosQueue.callAvailable(ros::WallDuration(timeout));
}
}
(5)编写CMakeLIstis文件
cmake_minimum_required(VERSION 2.8 FATAL_ERROR)
find_package(roscpp REQUIRED)
find_package(std_msgs REQUIRED)
include_directories(${roscpp_INCLUDE_DIRS})
include_directories(${std_msgs_INCLUDE_DIRS})
# Find Gazebo
find_package(gazebo REQUIRED)
include_directories(${GAZEBO_INCLUDE_DIRS})
link_directories(${GAZEBO_LIBRARY_DIRS})
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${GAZEBO_CXX_FLAGS}")
# Build our plugin
add_library(velodyne_plugin SHARED velodyne_plugin.cc)
target_link_libraries(velodyne_plugin ${GAZEBO_LIBRARIES} ${roscpp_LIBRARIES})
# Build the stand-alone test program
add_executable(vel vel.cc)
if (${gazebo_VERSION_MAJOR} LESS 6)
include(FindBoost)
find_package(Boost ${MIN_BOOST_VERSION} REQUIRED system filesystem regex)
target_link_libraries(vel ${GAZEBO_LIBRARIES} ${Boost_LIBRARIES})
else()
target_link_libraries(vel ${GAZEBO_LIBRARIES})
endif()
(6)启动仿真
roscore
gazebo ../velodyne.world
rostopic pub /my_velodyne/vel_cmd std_msgs/Float32 1.0