引言: 由于GPS在室外漂移的误差比较大,在长时间静止后启动,程序发布的位置可能已经和预期的位置相差较大,导致无法完成任务,尤其是气压计的数据不准,可能会导致无人机不能起飞或者一飞冲天。本文主要是在进行程序控制的时候,首先拿到最新的漂移误差,在此基础上进行程序控制,可以保证程序的稳定运行。
步骤一:创建订阅者订阅无人机的里程计信息
ros::Subscriber local_pos_sub = nh.subscribe<nav_msgs::Odometry>("/mavros/local_position/odom", 10, local_pos_cb);
步骤二:创建相关变量,获取无人机的实时位置信息
这里定义了较多的变量,最重要的是位置和标志为,其余的可以自行设置
tf::Quaternion quat;
double roll, pitch, yaw;
float init_position_x_take_off =0;
float init_position_y_take_off =0;
float init_position_z_take_off =0;
bool flag_init_position = false;
nav_msgs::Odometry local_pos;
步骤三:定义回调函数,在回调函数中获取漂移值
void local_pos_cb(const nav_msgs::Odometry::ConstPtr& msg)
{local_pos = *msg;if (flag_init_position==false && (local_pos.pose.pose.position.z!=0)){init_position_x_take_off = local_pos.pose.pose.position.x;init_position_y_take_off = local_pos.pose.pose.position.y;init_position_z_take_off = local_pos.pose.pose.position.z;flag_init_position = true; }tf::quaternionMsgToTF(local_pos.pose.pose.orientation, quat); tf::Matrix3x3(quat).getRPY(roll, pitch, yaw);
}
注:启动这个控制节点后,或订阅最新的初始位置,并且通过标志为控制只订阅一次,这个值就是最新的漂移值
步骤四:发布目标点,一定要把获取到的初始漂移值加上,如下:
pose.pose.position.x =init_position_x_take_off + 0;
pose.pose.position.y =init_position_y_take_off + 0;
pose.pose.position.z =init_position_z_take_off + ALTITUDE;
local_pos_pub.publish(pose);
这里ALTITUDE是我宏定义的0.5,表明无人机飞0.5米高度即可。室外使用的话,最好高度设置大于1米
步骤五:整体代码如下:
#include <string>
#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 <move_base_msgs/MoveBaseAction.h>
#include <actionlib/client/simple_action_client.h>
#include <std_msgs/Bool.h>
#include <geometry_msgs/TwistStamped.h>
#include <mavros_msgs/PositionTarget.h>
#include <cmath>
#include <tf/transform_listener.h>
#include <nav_msgs/Odometry.h>
#include <mavros_msgs/CommandLong.h>
#include <string>
#include <geometry_msgs/Twist.h>#define ALTITUDE 0.5
mavros_msgs::State current_state;
void state_cb(const mavros_msgs::State::ConstPtr& msg);
tf::Quaternion quat;
double roll, pitch, yaw;
float init_position_x_take_off =0;
float init_position_y_take_off =0;
float init_position_z_take_off =0;
bool flag_init_position = false;
nav_msgs::Odometry local_pos;
void local_pos_cb(const nav_msgs::Odometry::ConstPtr& msg);
void state_cb(const mavros_msgs::State::ConstPtr& msg)
{current_state = *msg;
}
void local_pos_cb(const nav_msgs::Odometry::ConstPtr& msg)
{local_pos = *msg;if (flag_init_position==false && (local_pos.pose.pose.position.z!=0)){init_position_x_take_off = local_pos.pose.pose.position.x;init_position_y_take_off = local_pos.pose.pose.position.y;init_position_z_take_off = local_pos.pose.pose.position.z;flag_init_position = true; }tf::quaternionMsgToTF(local_pos.pose.pose.orientation, quat); tf::Matrix3x3(quat).getRPY(roll, pitch, yaw);
}
int main(int argc, char **argv)
{setlocale(LC_ALL, "");ros::init(argc, argv, "offboard_single_position");ros::NodeHandle nh;ros::Publisher local_pos_pub = nh.advertise<geometry_msgs::PoseStamped>("mavros/setpoint_position/local", 10);ros::Subscriber state_sub = nh.subscribe<mavros_msgs::State>("mavros/state", 10, state_cb);ros::Subscriber local_pos_sub = nh.subscribe<nav_msgs::Odometry>("/mavros/local_position/odom", 10, local_pos_cb);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");ros::Rate rate(20.0);while(ros::ok() && !current_state.connected){ros::spinOnce();rate.sleep();}geometry_msgs::PoseStamped pose;pose.pose.position.x =init_position_x_take_off + 0;pose.pose.position.y =init_position_y_take_off + 0;pose.pose.position.z =init_position_z_take_off + ALTITUDE;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(fabs(local_pos.pose.pose.position.z- init_position_z_take_off -ALTITUDE)<0.2){ if(ros::Time::now() - last_request > ros::Duration(3.0)){break;}}pose.pose.position.x =init_position_x_take_off + 0;pose.pose.position.y =init_position_y_take_off + 0;pose.pose.position.z =init_position_z_take_off + ALTITUDE;local_pos_pub.publish(pose);ros::spinOnce();rate.sleep();} while(ros::ok()){pose.pose.position.x =init_position_x_take_off + 0;pose.pose.position.y =init_position_y_take_off + 0;pose.pose.position.z =init_position_z_take_off + ALTITUDE; local_pos_pub.publish(pose);ros::spinOnce();rate.sleep();}return 0;
}