目录
一、基础语言
for循环：
c++:
#include<iostream>
using namespace std;
int main()
{
int a=5;
for(a;a<10;a++)
{
count<"a="<<a<<endl;
}
return 0;
}
python:
for a in range(5,10):
if a<10:
print 'a= ',a
a +=1
else:
break
while循环：
python
a = 5
while a < 10:
print 'a = ' , a
a += 1
面向对象：
C++
#include <iostream>
class A
{
public:
int i;
void test()
{
std::cout << i <<std::endl;
}
};
int main()
{
A a;
a.i = 10;
a.test();
return 0;
}
python：
class A:
i = 10
def test(self)
print self.i
a = A()
a.test()
python：
class A:
i = 10
def test(self):
print self.i
a = A()
a.test()
a: c++代码首先要编译：c++_for.cpp
g++ c++_for.cpp -o c++_for
./c++_for
二、开发工具
三、基本概念
查看节点列表:rosnode list
发布话题消息:rostopic pub -r 10 /话题名
发布服务请求:rosservice call /服务文件 “变量:val”
话题记录: rosbag record -a -O fileName
话题复现: rosbag play fileName
四、ROS基础知识
4.1 小海龟例子
1. **启动ROS Master** $ roscore
2. **启动小海龟仿真器** $ rosrun turtlesim turtlesim_node
3. **启动海龟控制节点** $ rosrun turtlesim turtle_teleop_key
命令：
#查看节点
$ rqt_graph
4.2 常用的命令行工具
4.2.1 话题相关命令
#1显示所有节点相关信息的指令
rosnode
# 2 列出系统所有节点
rosnode list
# 3 查看某一节点的具体信息
rosnode info /节点（turtlesim)
图片对应上述命令3,
# 4 rostopic命令工具
rostopic
# 5 打印系统当前的话题列表
rostopic list
# 6 通过指令给话题发布指令让海龟动起来
#rostopic pub 话题名 话题消息类别 消息内容
# /turtle1/cmd_vel 话题名 geometry_msgs/Twist数据内容，消息结构
# "linear:.."消息数据结构的具体数据 linear线速度，angular角速度
rostopic pub /turtle1/cmd_vel geometry_msgs/Twist "linear:
x: 0.0
y: 0.0
z: 0.0
angular:
x: 0.0
y: 0.0
z: 0.0"
# 6 pub只运行一次，所以需要在pub后加上 -r(频率） 10（一秒发布10次）
rostopic pub -r 10 /turtle1/cmd_vel .....
#7 显示数据结构
rosmsg show
4.2.2 服务相关命令
# 1 rosservice +要干的事的类型
rosservice list
# 2 再调用新的海龟 theta角度
rosservice call /spawn "x: 0.0
y: 0.0
theta: 0.0
name: ''"
# 3 运行后rostopic list 将包含turtle2的内容
4.2.3 话题记录
用于数据的保存和复现
# 1 话题记录
rosbag record -a -O cmd_record
# -a 将所有数据保存 -O保存成压缩包 cmd_压缩包名字
# 2 话题复现
rosbag play cmd_record
4.3 创建工作空间与功能包
创建工作空间
建立install空间:catkin_make install 输入catkin_make 出现make -j4 -l4 没有问题
解析：<package_name>:功能包的名字
test_pkg 测试功能包 后面的依赖为用到的库(roscpp rospy std_msgs)c++、py、标准消息
这些包要建立在/home/wyh/catkin_ws/src/文件夹下
# 0 建立相关文件包
catkin_create_pkg test_pkg roscpp rospy std_msgs
# 1 c++程序
catkin_create_pkg roscpp rosp
说明：src 文件夹下放置代码.py c++文件
include放置头文件
cmakelists.txt 编译环境
4.4 发布者Publisher的编程实现
话题模型
小海龟代码练习，建立文件功能包
catkin_create_pkg learning_topic roscpp rospy std_msgs geometry_msgs turtlesim Created file learning_topic/package.xml
c++代码：
/**
* 该例程将发布turtle1/cmd_vel话题，消息类型geometry_msgs::Twist
*/
#include <ros/ros.h>
#include <geometry_msgs/Twist.h>
int main(int argc, char **argv)
{
// ROS节点初始化
ros::init(argc, argv, "velocity_publisher");//定义节点名字，不能重复
// 创建节点句柄，管理节点资源
ros::NodeHandle n;
// 创建一个Publisher，发布名为/turtle1/cmd_vel的topic，消息类型为geometry_msgs::Twist，队列长度10
ros::Publisher turtle_vel_pub = n.advertise<geometry_msgs::Twist>("/turtle1/cmd_vel", 10);
// 设置循环的频率
ros::Rate loop_rate(10);
int count = 0;
while (ros::ok())
{
// 初始化geometry_msgs::Twist类型的消息
geometry_msgs::Twist vel_msg;
vel_msg.linear.x = 0.5;
vel_msg.angular.z = 0.2;
// 发布消息 ROS——INFO相当于输出
turtle_vel_pub.publish(vel_msg);
ROS_INFO("Publsh turtle velocity command[%0.2f m/s, %0.2f rad/s]",
vel_msg.linear.x, vel_msg.angular.z);
// 按照循环频率延时
loop_rate.sleep();
}
return 0;
}
add_executable(velocity_publisher src/velocity_publisher.cpp)
target_link_libraries(velocity_publisher ${catkin_LIBRARIES})
编译内容放置：将.cpp编译成前面命名的可视化文件，target_link_libraries跟所需要的库做链接
编译并运行：
python代码：
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程将发布turtle1/cmd_vel话题，消息类型geometry_msgs::Twist
import rospy
from geometry_msgs.msg import Twist
def velocity_publisher():
# ROS节点初始化
rospy.init_node('velocity_publisher', anonymous=True)
# 创建一个Publisher，发布名为/turtle1/cmd_vel的topic，消息类型为geometry_msgs::Twist，队列长度10
turtle_vel_pub = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10)
#设置循环的频率
rate = rospy.Rate(10)
while not rospy.is_shutdown():
# 初始化geometry_msgs::Twist类型的消息
vel_msg = Twist()
vel_msg.linear.x = 0.5
vel_msg.angular.z = 0.2
# 发布消息
turtle_vel_pub.publish(vel_msg)
rospy.loginfo("Publsh turtle velocity command[%0.2f m/s, %0.2f rad/s]",
vel_msg.linear.x, vel_msg.angular.z)
# 按照循环频率延时
rate.sleep()
if __name__ == '__main__':
try:
velocity_publisher()
except rospy.ROSInterruptException:
pass
4.5 订阅者Subscriber的编程实现
c++代码：
/**
* 该例程将订阅/turtle1/pose话题，消息类型turtlesim::Pose
*/
#include <ros/ros.h>
#include "turtlesim/Pose.h"
// 接收到订阅的消息后，会进入消息回调函数
void poseCallback(const turtlesim::Pose::ConstPtr& msg)
{
// 将接收到的消息打印出来
ROS_INFO("Turtle pose: x:%0.6f, y:%0.6f", msg->x, msg->y);
}
int main(int argc, char **argv)
{
// 初始化ROS节点
ros::init(argc, argv, "pose_subscriber");
// 创建节点句柄
ros::NodeHandle n;
// 创建一个Subscriber，订阅名为/turtle1/pose的topic，注册回调函数poseCallback
ros::Subscriber pose_sub = n.subscribe("/turtle1/pose", 10, poseCallback);
// 循环等待回调函数
ros::spin();
return 0;
}
编译：
add_executable(pose_subscriber src/pose_subscriber.cpp)
target_link_libraries(pose_subscriber ${catkin_LIBRARIES})
python代码：
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程将订阅/turtle1/pose话题，消息类型turtlesim::Pose
import rospy
from turtlesim.msg import Pose
def poseCallback(msg):
rospy.loginfo("Turtle pose: x:%0.6f, y:%0.6f", msg.x, msg.y)
def pose_subscriber():
# ROS节点初始化
rospy.init_node('pose_subscriber', anonymous=True)
# 创建一个Subscriber，订阅名为/turtle1/pose的topic，注册回调函数poseCallback
rospy.Subscriber("/turtle1/pose", Pose, poseCallback)
# 循环等待回调函数
rospy.spin()
if __name__ == '__main__':
pose_subscriber()
4.6 话题消息的定义与使用
过程：1
2 packag.xml文件
3 .cmakelist文件：
message_generation
add_message_files(FILES Person.msg)
generation_messages(DEPENDENCIES std_msgs)
message_runtime
c++实现
person_publisher.cpp
/**
* 该例程将发布/person_info话题，自定义消息类型learning_topic::Person
*/
#include <ros/ros.h>
#include "learning_topic/Person.h"
int main(int argc, char **argv)
{
// ROS节点初始化
ros::init(argc, argv, "person_publisher");
// 创建节点句柄
ros::NodeHandle n;
// 创建一个Publisher，发布名为/person_info的topic，消息类型为learning_topic::Person，队列长度10
ros::Publisher person_info_pub = n.advertise<learning_topic::Person>("/person_info", 10);
// 设置循环的频率
ros::Rate loop_rate(1);
int count = 0;
while (ros::ok())
{
// 初始化learning_topic::Person类型的消息
learning_topic::Person person_msg;
person_msg.name = "Tom";
person_msg.age = 18;
person_msg.sex = learning_topic::Person::male;
// 发布消息
person_info_pub.publish(person_msg);
ROS_INFO("Publish Person Info: name:%s age:%d sex:%d",
person_msg.name.c_str(), person_msg.age, person_msg.sex);
// 按照循环频率延时
loop_rate.sleep();
}
return 0;
}
person_subscriber.cpp
/**
* 该例程将订阅/person_info话题，自定义消息类型learning_topic::Person
*/
#include <ros/ros.h>
#include "learning_topic/Person.h"
// 接收到订阅的消息后，会进入消息回调函数
void personInfoCallback(const learning_topic::Person::ConstPtr& msg)
{
// 将接收到的消息打印出来
ROS_INFO("Subcribe Person Info: name:%s age:%d sex:%d",
msg->name.c_str(), msg->age, msg->sex);
}
int main(int argc, char **argv)
{
// 初始化ROS节点
ros::init(argc, argv, "person_subscriber");
// 创建节点句柄
ros::NodeHandle n;
// 创建一个Subscriber，订阅名为/person_info的topic，注册回调函数personInfoCallback
ros::Subscriber person_info_sub = n.subscribe("/person_info", 10, personInfoCallback);
// 循环等待回调函数
ros::spin();
return 0;
}
配置代码编译规则
添加依赖项：
add_executable(person_publisher src/person_publisher.cpp)
target_link_libraries(person_publisher ${catkin_LIBRARIES})
add_dependencies(person_publisher ${PROJECT_NAME}_generate_messages_cpp)
add_executable(person_subscriber src/person_subscriber.cpp)
target_link_libraries(person_subscriber ${catkin_LIBRARIES})
add_dependencies(person_subscriber ${PROJECT_NAME}_generate_messages_cpp)
python实现：
person_publisher.py
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程将发布/person_info话题，自定义消息类型learning_topic::Person
import rospy
from learning_topic.msg import Person
def velocity_publisher():
# ROS节点初始化
rospy.init_node('person_publisher', anonymous=True)
# 创建一个Publisher，发布名为/person_info的topic，消息类型为learning_topic::Person，队列长度10
person_info_pub = rospy.Publisher('/person_info', Person, queue_size=10)
#设置循环的频率
rate = rospy.Rate(10)
while not rospy.is_shutdown():
# 初始化learning_topic::Person类型的消息
person_msg = Person()
person_msg.name = "Tom";
person_msg.age = 18;
person_msg.sex = Person.male;
# 发布消息
person_info_pub.publish(person_msg)
rospy.loginfo("Publsh person message[%s, %d, %d]",
person_msg.name, person_msg.age, person_msg.sex)
# 按照循环频率延时
rate.sleep()
if __name__ == '__main__':
try:
velocity_publisher()
except rospy.ROSInterruptException:
pass
person_subscriber.py
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程将订阅/person_info话题，自定义消息类型learning_topic::Person
import rospy
from learning_topic.msg import Person
def personInfoCallback(msg):
rospy.loginfo("Subcribe Person Info: name:%s age:%d sex:%d",
msg.name, msg.age, msg.sex)
def person_subscriber():
# ROS节点初始化
rospy.init_node('person_subscriber', anonymous=True)
# 创建一个Subscriber，订阅名为/person_info的topic，注册回调函数personInfoCallback
rospy.Subscriber("/person_info", Person, personInfoCallback)
# 循环等待回调函数
rospy.spin()
if __name__ == '__main__':
person_subscriber()
4.7 客户端client的编程实现
话题模型
创建客户端代码
c++：
/**
* 该例程将请求/spawn服务，服务数据类型turtlesim::Spawn
*/
#include <ros/ros.h>
#include <turtlesim/Spawn.h>
int main(int argc, char** argv)
{
// 初始化ROS节点
ros::init(argc, argv, "turtle_spawn");
// 创建节点句柄
ros::NodeHandle node;
// 发现/spawn服务后，创建一个服务客户端，连接名为/spawn的service
ros::service::waitForService("/spawn");//阻塞型函数
ros::ServiceClient add_turtle = node.serviceClient<turtlesim::Spawn>("/spawn");
// 初始化turtlesim::Spawn的请求数据
turtlesim::Spawn srv;
srv.request.x = 2.0;
srv.request.y = 2.0;
srv.request.name = "turtle2";
// 请求服务调用
ROS_INFO("Call service to spwan turtle[x:%0.6f, y:%0.6f, name:%s]",
srv.request.x, srv.request.y, srv.request.name.c_str());
add_turtle.call(srv); //阻塞型函数
// 显示服务调用结果
ROS_INFO("Spwan turtle successfully [name:%s]", srv.response.name.c_str());
return 0;
};
编译代码：
add_executable(turtle_spawn src/turtle_spawm.cpp)
target_link_libraries(turtle_spawn ${catkin_LIBRARIES})
编译运行客户端
python代码实现：
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程将请求/spawn服务，服务数据类型turtlesim::Spawn
import sys
import rospy
from turtlesim.srv import Spawn
def turtle_spawn():
# ROS节点初始化
rospy.init_node('turtle_spawn')
# 发现/spawn服务后，创建一个服务客户端，连接名为/spawn的service
rospy.wait_for_service('/spawn')
try:
add_turtle = rospy.ServiceProxy('/spawn', Spawn)
# 请求服务调用，输入请求数据
response = add_turtle(2.0, 2.0, 0.0, "turtle2")
return response.name
except rospy.ServiceException, e:
print "Service call failed: %s"%e
if __name__ == "__main__":
#服务调用并显示调用结果
print "Spwan turtle successfully [name:%s]" %(turtle_spawn())
4.8 服务端server的编程
创建服务器代码
c++：turtle_command_server.cpp
/**
* 该例程将执行/turtle_command服务，服务数据类型std_srvs/Trigger
*/
#include <ros/ros.h>
#include <geometry_msgs/Twist.h>
#include <std_srvs/Trigger.h>
ros::Publisher turtle_vel_pub;
bool pubCommand = false;
// service回调函数，输入参数req，输出参数res
bool commandCallback(std_srvs::Trigger::Request &req,
std_srvs::Trigger::Response &res)
{
pubCommand = !pubCommand;
// 显示请求数据
ROS_INFO("Publish turtle velocity command [%s]", pubCommand==true?"Yes":"No");
// 设置反馈数据
res.success = true;
res.message = "Change turtle command state!";
return true;
}
int main(int argc, char **argv)
{
// ROS节点初始化
ros::init(argc, argv, "turtle_command_server");
// 创建节点句柄
ros::NodeHandle n;
// 创建一个名为/turtle_command的server，注册回调函数commandCallback
ros::ServiceServer command_service = n.advertiseService("/turtle_command", commandCallback);
// 创建一个Publisher，发布名为/turtle1/cmd_vel的topic，消息类型为geometry_msgs::Twist，队列长度10
turtle_vel_pub = n.advertise<geometry_msgs::Twist>("/turtle1/cmd_vel", 10);
// 循环等待回调函数
ROS_INFO("Ready to receive turtle command.");
// 设置循环的频率
ros::Rate loop_rate(10);
while(ros::ok())
{
// 查看一次回调函数队列
ros::spinOnce();
// 如果标志为true，则发布速度指令
if(pubCommand)
{
geometry_msgs::Twist vel_msg;
vel_msg.linear.x = 0.5;
vel_msg.angular.z = 0.2;
turtle_vel_pub.publish(vel_msg);
}
//按照循环频率延时
loop_rate.sleep();
}
return 0;
}
编译：cmakelists
add_executable(turtle_command_server src/turtle_command_server.cpp)
target_link_libraries(turtle_command_server ${catkin_LIBRARIES})
编译并运行服务器
python实现：
turtle_command_server.cpp
- ros在Python中没有spinonce方法，可通过多线程来实现
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程将执行/turtle_command服务，服务数据类型std_srvs/Trigger
import rospy
import thread,time
from geometry_msgs.msg import Twist
from std_srvs.srv import Trigger, TriggerResponse
pubCommand = False;
turtle_vel_pub = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10)
def command_thread():
while True:
if pubCommand:
vel_msg = Twist()
vel_msg.linear.x = 0.5
vel_msg.angular.z = 0.2
turtle_vel_pub.publish(vel_msg)
time.sleep(0.1)
def commandCallback(req):
global pubCommand
pubCommand = bool(1-pubCommand)
# 显示请求数据
rospy.loginfo("Publish turtle velocity command![%d]", pubCommand)
# 反馈数据
return TriggerResponse(1, "Change turtle command state!")
def turtle_command_server():
# ROS节点初始化
rospy.init_node('turtle_command_server')
# 创建一个名为/turtle_command的server，注册回调函数commandCallback
s = rospy.Service('/turtle_command', Trigger, commandCallback)
# 循环等待回调函数
print "Ready to receive turtle command."
thread.start_new_thread(command_thread, ())
rospy.spin()
if __name__ == "__main__":
turtle_command_server()
4.9 服务数据的定义与使用
1 定义srv文件：/home/wyh/catkin_ws/src/learning_service/srv/Person.srv
string name
uint8 age
uint8 sex
uint8 unknown = 0
uint8 male = 1
uint8 female = 2
---
string result
2
代码：
<build_depend>message_generation</build_depend>
<exec_depend>message runtime</exec_depend>
3 在CMakeList.txt添加：
add_service_files(FILES Person.srv)
generate_messages(DEPENDENCIES std_msgs)
创建服务器代码：
c++：person_server.cpp
//服务端
/**
/ * 该例程将执行/show_person服务，服务数据类型learning_service::Person
*/
#include <ros/ros.h>
#include "learning_service/Person.h"
// service回调函数，输入参数req，输出参数res
bool personCallback(learning_service::Person::Request &req,
learning_service::Person::Response &res)
{
// 显示请求数据
ROS_INFO("Person: name:%s age:%d sex:%d", req.name.c_str(), req.age, req.sex);
// 设置反馈数据
res.result = "OK";
return true;
}
int main(int argc, char **argv)
{
// ROS节点初始化
ros::init(argc, argv, "person_server");
// 创建节点句柄
ros::NodeHandle n;
// 创建一个名为/show_person的server，注册回调函数personCallback
ros::ServiceServer person_service = n.advertiseService("/show_person", personCallback);
// 循环等待回调函数
ROS_INFO("Ready to show person informtion.");
ros::spin();
return 0;
}
客户端C++代码：person_client.cpp
/**
* 该例程将请求/show_person服务，服务数据类型learning_service::Person
*/
#include <ros/ros.h>
#include "learning_service/Person.h"
int main(int argc, char** argv)
{
// 初始化ROS节点
ros::init(argc, argv, "person_client");
// 创建节点句柄
ros::NodeHandle node;
// 发现/spawn服务后，创建一个服务客户端，连接名为/spawn的service
ros::service::waitForService("/show_person");
ros::ServiceClient person_client = node.serviceClient<learning_service::Person>("/show_person");
// 初始化learning_service::Person的请求数据
learning_service::Person srv; //注意要跟srv的文件名相同
srv.request.name = "Tom";
srv.request.age = 20;
srv.request.sex = learning_service::Person::Request::male;
// 请求服务调用
ROS_INFO("Call service to show person[name:%s, age:%d, sex:%d]",
srv.request.name.c_str(), srv.request.age, srv.request.sex);
person_client.call(srv);
// 显示服务调用结果
ROS_INFO("Show person result : %s", srv.response.result.c_str());
return 0;
};
编译代码：
add_executable(person_server src/person_server.cpp)
target_link_libraries(person_server ${catkin_LIBRARIES})
add_dependencies(person_server ${PROJECT_NAME}_gencpp)
add_executable(person_client src/person_client.cpp)
target_link_libraries(person_client ${catkin_LIBRARIES})
add_dependencies(person_client ${PROJECT_NAME}_gencpp)
python代码：
服务器：
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程将执行/show_person服务，服务数据类型learning_service::Person
import rospy
from learning_service.srv import Person, PersonResponse
def personCallback(req):
# 显示请求数据
rospy.loginfo("Person: name:%s age:%d sex:%d", req.name, req.age, req.sex)
# 反馈数据
return PersonResponse("OK")
def person_server():
# ROS节点初始化
rospy.init_node('person_server')
# 创建一个名为/show_person的server，注册回调函数personCallback
s = rospy.Service('/show_person', Person, personCallback)
# 循环等待回调函数
print "Ready to show person informtion."
rospy.spin()
if __name__ == "__main__":
person_server()
客户端：
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程将请求/show_person服务，服务数据类型learning_service::Person
import sys
import rospy
from learning_service.srv import Person, PersonRequest
def person_client():
# ROS节点初始化
rospy.init_node('person_client')
# 发现/spawn服务后，创建一个服务客户端，连接名为/spawn的service
rospy.wait_for_service('/show_person')
try:
person_client = rospy.ServiceProxy('/show_person', Person)
# 请求服务调用，输入请求数据
response = person_client("Tom", 20, PersonRequest.male)
return response.result
except rospy.ServiceException, e:
print "Service call failed: %s"%e
if __name__ == "__main__":
#服务调用并显示调用结果
print "Show person result : %s" %(person_client())
4.10 参数的使用与编程方法
参数模型
创建功能包
参数命令行使用
修改参数： rosparm set 参数 要改成的参数值
修改后的查询更新 ： rosservice call /clear “{}”
编程方法：
c++实现：parameter_config.cpp
/**
* 该例程设置/读取海龟例程中的参数
*/
#include <string>
#include <ros/ros.h>
#include <std_srvs/Empty.h>
int main(int argc, char **argv)
{
int red, green, blue;
// ROS节点初始化
ros::init(argc, argv, "parameter_config");
// 创建节点句柄
ros::NodeHandle node;
// 读取背景颜色参数
ros::param::get("/background_r", red);
ros::param::get("/background_g", green);
ros::param::get("/background_b", blue);
ROS_INFO("Get Backgroud Color[%d, %d, %d]", red, green, blue);
// 设置背景颜色参数
ros::param::set("/background_r", 255);
ros::param::set("/background_g", 255);
ros::param::set("/background_b", 255);
ROS_INFO("Set Backgroud Color[255, 255, 255]");
// 读取背景颜色参数
ros::param::get("/background_r", red);
ros::param::get("/background_g", green);
ros::param::get("/background_b", blue);
ROS_INFO("Re-get Backgroud Color[%d, %d, %d]", red, green, blue);
// 调用服务，刷新背景颜色
ros::service::waitForService("/clear");
ros::ServiceClient clear_background = node.serviceClient<std_srvs::Empty>("/clear");
std_srvs::Empty srv;
clear_background.call(srv);
sleep(1);
return 0;
}
编译：
add_executable(parameter_config src/parameter_config.cpp)
target_link_libraries(parameter_config ${catkin_LIBRARIES})
编译并运行
python代码：
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程设置/读取海龟例程中的参数
import sys
import rospy
from std_srvs.srv import Empty
def parameter_config():
# ROS节点初始化
rospy.init_node('parameter_config', anonymous=True)
# 读取背景颜色参数
red = rospy.get_param('/background_r')
green = rospy.get_param('/background_g')
blue = rospy.get_param('/background_b')
rospy.loginfo("Get Backgroud Color[%d, %d, %d]", red, green, blue)
# 设置背景颜色参数
rospy.set_param("/background_r", 255);
rospy.set_param("/background_g", 255);
rospy.set_param("/background_b", 255);
rospy.loginfo("Set Backgroud Color[255, 255, 255]");
# 读取背景颜色参数
red = rospy.get_param('/background_r')
green = rospy.get_param('/background_g')
blue = rospy.get_param('/background_b')
rospy.loginfo("Get Backgroud Color[%d, %d, %d]", red, green, blue)
#发现/spawn服务后，创建一个服务客户端，连接名为/spawn的service
rospy.wait_for_service('/clear')
try:
clear_background = rospy.ServiceProxy('/clear', Empty)
# 请求服务调用，输入请求数据
response = clear_background()
return response
except rospy.ServiceException, e:
print "Service call failed: %s"%e
if __name__ == "__main__":
parameter_config()
4.11 ROS中的坐标系管理系统
海龟案例：
a: rosrun tf view_frames
在主文件夹下生成frames.pdf
b:显示
tf tf_echo turtle1 turtle2
c: 利用rviz