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本博客将介绍如何在ROS中,结合MAVROS包,创建一个无人机控制节点,使无人机能够沿着预设轨迹(如圆形)飞行。本教程假设您已经安装了ROS和MAVROS包。
首先,我们需要创建一个新的ROS包。在您的工作空间中的src
目录下执行以下命令:
catkin_create_pkg my_offboard_node roscpp mavros_msgs geometry_msgs
在 my_offboard_node
包中创建两个文件:offb_node.cpp
和 CircularTrajectory.h
。
将以下代码保存为 my_offboard_node/src/offb_node.cpp
:
#include <ros/ros.h> #include <geometry_msgs/PoseStamped.h> #include <mavros_msgs/CommandBool.h> #include <mavros_msgs/SetMode.h> #include <mavros_msgs/State.h> #include "my_offboard_node/CircularTrajectory.h" // 全局状态变量 mavros_msgs::State current_state; void state_cb(const mavros_msgs::State::ConstPtr& msg){ current_state = *msg; } int main(int argc, char **argv) { ros::init(argc, argv, "offb_node"); ros::NodeHandle nh; ros::Subscriber state_sub = nh.subscribe<mavros_msgs::State>("mavros/state", 10, state_cb); ros::Publisher local_pos_pub = nh.advertise<geometry_msgs::PoseStamped>("mavros/setpoint_position/local", 10); ros::ServiceClient arming_client = nh.serviceClient<mavros_msgs::CommandBool>("mavros/cmd/arming"); ros::ServiceClient set_mode_client = nh.serviceClient<mavros_msgs::SetMode>("mavros/set_mode"); // 设置发布速率大于2Hz ros::Rate rate(20.0); // 等待与飞控的连接 while(ros::ok() && !current_state.connected){ ros::spinOnce(); rate.sleep(); } // 创建轨迹对象 CircularTrajectory trajectory(5.0, 0.0, 0.0, 2.5, 0.1); // 发送几个设置点以启动 geometry_msgs::PoseStamped pose; for(int i = 100; ros::ok() && i > 0; --i){ pose = trajectory.calculate_pose(0); // 使用初始位置 local_pos_pub.publish(pose); ros::spinOnce(); rate.sleep(); } mavros_msgs::SetMode offb_set_mode; offb_set_mode.request.custom_mode = "OFFBOARD"; mavros_msgs::CommandBool arm_cmd; arm_cmd.request.value = true; ros::Time last_request = ros::Time::now(); while(ros::ok()){ if( current_state.mode != "OFFBOARD" && (ros::Time::now() - last_request > ros::Duration(5.0))){ if( set_mode_client.call(offb_set_mode) && offb_set_mode.response.mode_sent){ ROS_INFO("Offboard enabled"); } last_request = ros::Time::now(); } else { if( !current_state.armed && (ros::Time::now() - last_request > ros::Duration(5.0))){ if( arming_client.call(arm_cmd) && arm_cmd.response.success){ ROS_INFO("Vehicle armed"); } last_request = ros::Time::now(); } } double elapsed = (ros::Time::now() - last_request).toSec(); pose = trajectory.calculate_pose(elapsed); local_pos_pub.publish(pose); ros::spinOnce(); rate.sleep(); } return 0; }
创建一个头文件来定义轨迹类。将以下内容保存为 my_offboard_node/include/my_offboard_node/CircularTrajectory.h
:
#ifndef CIRCULAR_TRAJECTORY_H #define CIRCULAR_TRAJECTORY_H #include <geometry_msgs/PoseStamped.h> #include <math.h> // 轨迹基类 class Trajectory { public: virtual geometry_msgs::PoseStamped calculate_pose(double time) = 0; }; // 圆形轨迹 class CircularTrajectory : public Trajectory { double radius, center_x, center_y, altitude, angular_velocity; public: CircularTrajectory(double r, double x, double y, double z, double w) : radius(r), center_x(x), center_y(y), altitude(z), angular_velocity(w) {} geometry_msgs::PoseStamped calculate_pose(double time) override { geometry_msgs::PoseStamped pose; double theta = angular_velocity * time; pose.pose.position.x = center_x + radius * cos(theta); pose.pose.position.y = center_y + radius * sin(theta); pose.pose.position.z = altitude; return pose; } }; #endif // CIRCULAR_TRAJECTORY_H
修改 CMakeLists.txt
来编译节点。将以下内容添加到 my_offboard_node/CMakeLists.txt
文件中:
cmake_minimum_required(VERSION 2.8.3) project(my_offboard_node) find_package(catkin REQUIRED COMPONENTS roscpp mav os_msgs geometry_msgs ) catkin_package() include_directories( ${catkin_INCLUDE_DIRS} include ) add_executable(offb_node src/offb_node.cpp) target_link_libraries(offb_node ${catkin_LIBRARIES})
为了方便运行节点,创建一个launch文件。在 my_offboard_node/launch
目录下创建一个名为 offb_node.launch
的文件,并添加以下内容:
<launch>
<node name="offb_node" pkg="my_offboard_node" type="offb_node" output="screen"/>
</launch>
编译ROS包。在工作空间中运行以下命令:
catkin_make
编译完成后,不要忘记运行source devel/setup.bash
来更新环境。
最后,可以通过运行以下命令来启动节点:
roslaunch my_offboard_node offb_node.launch
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