通过MAVROS控制仿真无人机

首先，在目录中建立工作区，并进行初始化操作

mkdir -p ~/catkin_ws/src
cd ~/catkin_ws
catkin init
wstool init src
rosinstall_generator --rosdistro kinetic mavlink | tee /tmp/mavros.rosinstall
rosinstall_generator --upstream mavros | tee -a /tmp/mavros.rosinstall
wstool merge -t src /tmp/mavros.rosinstall
wstool update -t src
rosdep install --from-paths src --ignore-src -y
wget https://raw.githubusercontent.com/mavlink/mavros/master/mavros/scripts/install_geographiclib_datasets.sh
sudo chmod 777 install_geographiclib_datasets.sh
sudo ./install_geographiclib_datasets.sh
catkin build
source ~/catkin_ws/devel/setup.bash

然后，在catkin_ws/src目录中运行如下指令

catkin_create_pkg offboard_pkg roscpp std_msgs geometry_msgs mavros_msgs

在~/catkin_ws/src/offboard_pkg/src/目录中新建一个文件offboard_node.cpp，写入如下代码

#include <ros/ros.h>
#include <geometry_msgs/PoseStamped.h>
#include <mavros_msgs/CommandBool.h>
#include <mavros_msgs/SetMode.h>
#include <mavros_msgs/State.h>

int count;
int flag=1;
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, "offboard");
    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");

    //the setpoint publishing rate MUST be faster than 2Hz
    ros::Rate rate(8.0);

    // wait for FCU connection
    while(ros::ok() && !current_state.connected){
        ros::spinOnce();
        rate.sleep();
    }
    geometry_msgs::PoseStamped pose;
    pose.pose.position.x = 0;
    pose.pose.position.y = 0;
    pose.pose.position.z = 3;
   
    //send a few setpoints before starting
    for(int i = 100; ros::ok() && i > 0; --i){
        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();
            }
        }
		
            if((flag == 1)  && (ros::Time::now() - last_request > ros::Duration(5.0)))
		{ 
			ROS_INFO("position1(0 , 0,  5)");
                	pose.pose.position.x = 0;
    			pose.pose.position.y = 0;
    			pose.pose.position.z = 5;
			last_request = ros::Time::now();
                        flag=2;

                }

		if((flag ==2) && (ros::Time::now() - last_request > ros::Duration(5.0)))
		{
			ROS_INFO("position2(5 , 0,  5)");
                	pose.pose.position.x = 5.0;
    			pose.pose.position.y = 0.0;
    			pose.pose.position.z = 5;
			last_request = ros::Time::now();
			flag=3;
                }
                       
		 if((flag ==3) && (ros::Time::now() - last_request > ros::Duration(5.0)))
                {
                        ROS_INFO("position3(5 , 5,  5)");
                        pose.pose.position.x = 5.0;
                        pose.pose.position.y = 5.0;
                        pose.pose.position.z = 5;
                        last_request = ros::Time::now();
			flag=4;
                }

		 if((flag ==4) && (ros::Time::now() - last_request > ros::Duration(5.0)))
                {
                        ROS_INFO("position4(0 , 5,  5)");
                        pose.pose.position.x = 0;
                        pose.pose.position.y = 5.0;
                        pose.pose.position.z = 5;
                        last_request = ros::Time::now();
			flag=5;
                }


		 if((flag ==5) && (ros::Time::now() - last_request > ros::Duration(5.0)))
                {
                        ROS_INFO("position5(0 ,0,  5)");
                        pose.pose.position.x = 0;
                        pose.pose.position.y = 0;
                        pose.pose.position.z = 5;
                        last_request = ros::Time::now();
			flag=1;
                }
        local_pos_pub.publish(pose);
        ros::spinOnce();
        rate.sleep();
    }

    return 0;
}

该代码的作用为让无人机飞至5米高度，然后循环按照正方形轨迹飞行

然后打开目录~/catkin_ws/src/offboard_pkg/下的CMakeLists.txt添加下面的两行：

add_executable(offboard_node src/offboard_node.cpp)
target_link_libraries(offboard_node ${catkin_LIBRARIES})

然后到目录~/catkin_ws下，运行命令

catkin build

然后，使终端进入PX4的安装目录下，运行命令

make px4_sitl gazebo_iris

即可进入gazebo仿真界面

接着，打开QGC地面站，并运行如下命令连接Mavros和PX4

roslaunch mavros px4.launch fcu_url:="udp://:14540@127.0.0.1:14557"

执行刚才的C++文件

source ~/catkin_ws/devel/setup.bash
rosrun offboard_pkg offboard_node

在gazebo中观察仿真结果即可。