本文由 简悦 SimpRead 转码， 原文地址 blog.csdn.net

目录

• 一. 创建功能包
• 二. 编译运行
• 三. 修改官方代码
• 参考

前言： 本次教程是官方提供的 MAVROS Offboard (板外) 控制示例，使用之前请搭建好 PX4 仿真环境
注：搭建仿真环境可以看下面教程👇

ubuntu 搭建 PX4 无人机仿真环境 (1) —— 概念介绍

ubuntu 搭建 PX4 无人机仿真环境 (2) —— MAVROS 安装

ubuntu 搭建 PX4 无人机仿真环境 (3) —— ubuntu 安装 QGC 地面站

ubuntu 搭建 PX4 无人机仿真环境 (4) —— 仿真环境搭建

ubuntu 安装 ROS melodic(最新、超详细图文教程)

一. 创建功能包

没有创建工作空间，可以执行下列代码，如果创建了可以跳过（如果是跟着我之前的教程，那就不用执行这一步）

注： catkin_make 与 catkin build 是编译功能包的两种方式，catkin_make 用的多一点，有兴趣的话可以看看它们的区别 👉 Migrating from catkin_make — catkin_tools

mkdir -p ~/catkin_ws/src
cd catkin_ws/src && catkin_init_workspace
# 使用catkin build话，则为cd catkin_ws && catkin init


<NolebasePageProperties />




cd .. && catkin_make# 使用catkin build话，则为 catkin build
# 再将 source ~/catkin_ws/devel/setup.bash 提案加到 .bashrc 文件中

在工作空间下新建一个 off_node 功能包

cd ~/catkin_ws/src
catkin_create_pkg off_node roscpp std_msgs geometry_msgs mavros_msgs

创建好后目录大致是下图所示：

在 off_node 功能包下的 src 目录下新建一个 offb_node.cpp 文件，将下列官方提供的代码复制进去（代码详解可以看官方的代码解释 MAVROS Offboard 控制示例 (C++) | PX4 自动驾驶用户指南 ）

/**
 * @file offb_node.cpp
 * @brief Offboard control example node, written with MAVROS version 0.19.x, PX4 Pro Flight
 * Stack and tested in Gazebo Classic SITL
 */

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

mavros_msgs::State current_state;
void state_cb(const mavros_msgs::State::ConstPtr& msg){
    current_state = *msg;   // 无人机当前状态
}

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");

    //the setpoint publishing rate MUST be faster than 2Hz
    ros::Rate rate(20.0);

    // 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 = 2;

    //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))){
            // 切换 Offboard 模式
            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))){
                //无人机解锁
                if( arming_client.call(arm_cmd) &&
                    arm_cmd.response.success){
                    ROS_INFO("Vehicle armed");
                }
                last_request = ros::Time::now();
            }
        }

        local_pos_pub.publish(pose); // 发送目标点位置

        ros::spinOnce();
        rate.sleep();
    }

    return 0;
}

将下面内容添加到 off_node 功能包下的 CMakeLists.txt 文件里

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

二. 编译运行

cd ~/catkin_ws
catkin_make # 使用catkin build话，则为 catkin build

编译成功后，为了使用方便可以写一个 offb.sh 脚本来启动仿真

touch offb.sh

将下面代码复制上去

#!/bin/bash
source ~/.bashrc
gnome-terminal --window -e 'bash -c "roscore; exec bash"' \
--tab -e 'bash -c "sleep 5; roslaunch px4 mavros_posix_sitl.launch; exec bash"' \
--tab -e 'bash -c "sleep 10; rosrun off_node offb_node; exec bash"' \

运行

chmod +x offb.sh
./offb.sh

（无人机会切换到 Offboard 模式起飞两米，然后一直悬停）
注：如果遇到仿真正常启动，但是运行程序无人机不动，可以参考这篇 博客 ，修改参数即可。

三. 修改官方代码

官方的示例代码会一直悬停不会降落，我们可以修改 offb_node.cpp 文件，加个降落的功能，代码如下：

/**
 * @file offb_node.cpp
 * @brief Offboard control example node, written with MAVROS version 0.19.x, PX4 Pro Flight
 * Stack and tested in Gazebo Classic SITL
 */

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

using namespace std;

mavros_msgs::State current_state;
geometry_msgs::PoseStamped curr_pos;   // 无人机当前位置

// 获取无人机当前状态
void state_cb(const mavros_msgs::State::ConstPtr& msg){
    current_state = *msg;
}
// 获取无人机当前位置
void arrive_pos(const geometry_msgs::PoseStamped::ConstPtr& msg){
    curr_pos = *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");
    // 订阅无人机的位置话题
    ros::Subscriber local_pos_sub = nh.subscribe<geometry_msgs::PoseStamped>
        ("mavros/local_position/pose",10,arrive_pos);

    //the setpoint publishing rate MUST be faster than 2Hz
    ros::Rate rate(20.0);

    // wait for FCU connection
    while(ros::ok() && !current_state.connected){
        ros::spinOnce();
        rate.sleep();
    }

    geometry_msgs::PoseStamped pose;  // 目标位置
    pose.pose.position.x = 0;
    pose.pose.position.y = 0;
    pose.pose.position.z = 2;

    //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();

    int count = 0;  // 计时
    bool flag = true;
    while(ros::ok()){
    	if( flag ) { 
	        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");
	                }   // arm
	                last_request = ros::Time::now();
	            }
	        } // else
		} // flag

		// 当检测到与目标高度相差 ± 0.3 就开始悬停 30s
        if(fabs(curr_pos.pose.position.z - pose.pose.position.z) <= 0.3){
            count++;
            if(count >= 600)  // 30s
            {
                mavros_msgs::SetMode land_set_mode;
                land_set_mode.request.custom_mode = "AUTO.LAND";  // 发送降落命令
                if(set_mode_client.call(land_set_mode) && land_set_mode.response.mode_sent){
                    flag = false;
                }
            }  
        }
	  //任务结束,无人机降落完成并关闭该节点
     if ( !flag && current_state.mode == "AUTO.LAND" && current_state.armed == false ) {
          ROS_INFO("Drone has landed");
          ros::shutdown();
      }
        local_pos_pub.publish(pose);

        ros::spinOnce();
        rate.sleep();
    }

    return 0;
}

修改完后，直接编译运行，下面👇视频是运行效果

PX4 无人机仿真示例

参考

MAVROS Offboard 控制示例 (C++) | PX4 自动驾驶用户指南

PX4 与 MAVROS 实现 offboard_rtt too high for timesync_manbushuizhong 的博客 - CSDN 博客

如有其他问题，或者发现文章有错误，请在评论区留言
Keep learning！

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RainbowRain9

Cai Hongyu

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