ROS学习（八）——参数的使用与编程方法

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1 参数模型

2 创建功能包

cd ~/catkin_ws/src
catkin_create_pkg learning_parameter roscpp rospy std_srvs

3 参数的命令行使用

YAML参数文件

rosdistro: ‘melodic’
roslaunch: uris: {host_localhost__37751: ‘http://localhost:37751/’}
rosversion: ‘1.14.12’
run_id: dfc9b678-5124-11ec-b998-744ca1825d2b
turtlesim: {background_b: 0, background_g: 0, background_r: 0}

• 列出当前所有的参数
  $ rosparam list
  
• 显示某个参数值
  $ rosparam get param_key

• 设置某个参数值
  $ rosparam set param_key param_value
  

刷新参数：$ rosservice call /clear {}

• 保存参数到文件
  $ rosparam dump file_name
  
• 加载参数文件
  $ rosparam load file_name

$ rosparam load param1.yaml
$ rosparam get /turtlesim/background_b
$ rosparam get /turtlesim/background_g
$ rosparam get /turtlesim/background_r

• 删除某个参数

$ rosparam delete param_key

4 C++文件操作

文件编写如下：

/**
 * 该例程设置/读取海龟例程中的参数
 */
#include 
#include 
#include 

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("/turtlesim/background_r", red);
	ros::param::get("/turtlesim/background_g", green);
	ros::param::get("/turtlesim/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("/turtlesim/background_r", 255);
	ros::param::set("/turtlesim/background_g", 255);
	ros::param::set("/turtlesim/background_b", 255);

	ROS_INFO("Set Backgroud Color[255, 255, 255]");

    // 读取背景颜色参数
	ros::param::get("/turtlesim/background_r", red);
	ros::param::get("/turtlesim/background_g", green);
	ros::param::get("/turtlesim/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;
}

5 Python文件操作

文件编写如下：

#!/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('/turtlesim/background_r')
    green = rospy.get_param('/turtlesim/background_g')
    blue  = rospy.get_param('/turtlesim/background_b')

    rospy.loginfo("Get Backgroud Color[%d, %d, %d]", red, green, blue)

	# 设置背景颜色参数
    rospy.set_param("/turtlesim/background_r", 255);
    rospy.set_param("/turtlesim/background_g", 255);
    rospy.set_param("/turtlesim/background_b", 255);

    rospy.loginfo("Set Backgroud Color[255, 255, 255]");

	# 读取背景颜色参数
    red   = rospy.get_param('/turtlesim/background_r')
    green = rospy.get_param('/turtlesim/background_g')
    blue  = rospy.get_param('/turtlesim/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()

6 程序运行结果

"怕什么真理无穷，进一寸有一寸的欢喜！"本讲完，继续加油！