参数服务器 Parammeter Server
参数服务器维护的是一个字典,里面存储的是key、value,每一个key对应一个value。
一、rosparam 命令行操作
- 列出当前的所有参数:
rosparam list
- 显示某个参数的值
rosparam get param_key
- 设置某个参数的值
rosparam set param_key param_value
- 保存参数到文件
rosparam dump file_name
- 从文件读取参数
rosparam load file_name
注意这里的文件必须是YAML格式:
YAML格式举例:
name:‘ZhangSan’
age:20
gender:‘M’
score:{Chinese:80, Math:90}
score_history:[85,82,88,90]
- 删除某个参数
rosparam delete param_key
二、launch 文件载入param
- 通过param 标签设置参数的值
<launch>
<param name="publish_frequency" value="20.0"/>
</launch>
- 通过加载yaml文件来设置param:
下面这句指令也就是执行了 load 命令来实现装载文件的命令。
<launch>
<!-- 把关节控制的配置信息读取到参数服务器 -->
<rosparam file="$(find robot_sim_demo)/param/xbot-u_control.yaml" command="load"/>
</launch>
- 加载URDF 文件
下面这句指令是 xacro.py 执行了 robot.xacro 之后输出的结果作为值赋给 robot_description。
<launch>
<!-- URDF and TF support -->
<param name="robot_description" command="$(find xacro)/xacro.py $(find robot_sim_demo)/urdf/robot.xacro" />
</launch>
launch 文件操作param 示例:
<launch>
<!--param参数配置-->
<param name="param1" value="1" />
<param name="param2" value="2" />
<!--param name="table_description" command="$(find xacro)/xacro.py $(find gazebo_worlds)/objects/table.urdf.xacro" /-->
<!--rosparam参数配置-->
<rosparam>
param3: 3
param4: 4
param5: 5
</rosparam>
<!--以上写法将参数转成YAML文件加载,注意param前面必须为空格,不能用Tab,否则YAML解析错误-->
<!--rosparam file="$(find robot_sim_demo)/config/xbot-u_control.yaml" command="load" /-->
<node pkg="param_demo" type="param_demo" name="param_demo" output="screen" >
</node>
</launch>
三、c++ 中操作 param
#include<ros/ros.h>
int main(int argc, char **argv){
ros::init(argc, argv, "param_demo");
ros::NodeHandle nh;
int parameter1, parameter2, parameter3, parameter4, parameter5;
//Get Param的三种方法
//① ros::param::get()获取参数“param1”的value,写入到parameter1上
bool ifget1 = ros::param::get("param1", parameter1);
//② ros::NodeHandle::getParam()获取参数,与①作用相同
bool ifget2 = nh.getParam("param2",parameter2);
//③ ros::NodeHandle::param()类似于①和②
//但如果get不到指定的param,它可以给param指定一个默认值(如33333)
nh.param("param3", parameter3, 33333);//parameter3 = nh.param("param3", 33333); //这两种方式都可以获取参数
if(ifget1)
ROS_INFO("Get param1 = %d", parameter1);
else
ROS_WARN("Didn't retrieve param1");
if(ifget2)
ROS_INFO("Get param2 = %d", parameter2);
else
ROS_WARN("Didn't retrieve param2");
if(nh.hasParam("param3"))
ROS_INFO("Get param3 = %d", parameter3);
else
ROS_WARN("Didn't retrieve param3");
//Set Param的两种方法
//① ros::param::set()设置参数
parameter4 = 4;
ros::param::set("param4", parameter4);
//② ros::NodeHandle::setParam()设置参数
parameter5 = 5;
nh.setParam("param5",parameter5);
ROS_INFO("Param4 is set to be %d", parameter4);
ROS_INFO("Param5 is set to be %d", parameter5);
//Check Param的两种方法
//① ros::NodeHandle::hasParam()
bool ifparam5 = nh.hasParam("param5");
//② ros::param::has()
bool ifparam6 = ros::param::has("param6");
if(ifparam5)
ROS_INFO("Param5 exists");
else
ROS_INFO("Param5 doesn't exist");
if(ifparam6)
ROS_INFO("Param6 exists");
else
ROS_INFO("Param6 doesn't exist");
//Delete Param的两种方法
//① ros::NodeHandle::deleteParam()
bool ifdeleted5 = nh.deleteParam("param5");
//② ros::param::del()
bool ifdeleted6 = ros::param::del("param6");
if(ifdeleted5)
ROS_INFO("Param5 deleted");
else
ROS_INFO("Param5 not deleted");
if(ifdeleted6)
ROS_INFO("Param6 deleted");
else
ROS_INFO("Param6 not deleted");
ros::Rate rate(0.3);
while(ros::ok()){
int parameter = 0;
ROS_INFO("=============Loop==============");
//roscpp中尚未有ros::param::getallparams()之类的方法
if(ros::param::get("param1", parameter))
ROS_INFO("parameter param1 = %d", parameter);
if(ros::param::get("param2", parameter))
ROS_INFO("parameter param2 = %d", parameter);
if(ros::param::get("param3", parameter))
ROS_INFO("parameter param3 = %d", parameter);
if(ros::param::get("param4", parameter))
ROS_INFO("parameter param4 = %d", parameter);
if(ros::param::get("param5", parameter))
ROS_INFO("parameter param5 = %d", parameter);
if(ros::param::get("param6", parameter))
ROS_INFO("parameter param6 = %d", parameter);
rate.sleep();
}
}
按照这样的配置运行launch文件,输出结果为:
[ INFO] [1599227480.007106576]: Get param1 = 1
[ INFO] [1599227480.007183637]: Get param2 = 2
[ INFO] [1599227480.008421688]: Get param3 = 3
[ INFO] [1599227480.013664463]: Param4 is set to be 4
[ INFO] [1599227480.013728307]: Param5 is set to be 5
[ INFO] [1599227480.016448700]: Param5 exists
[ INFO] [1599227480.016485628]: Param6 doesn't exist
[ INFO] [1599227480.018160277]: Param5 deleted
[ INFO] [1599227480.018213034]: Param6 not deleted
[ INFO] [1599227480.018256838]: =============Loop==============
[ INFO] [1599227480.019019334]: parameter param1 = 1
[ INFO] [1599227480.019704553]: parameter param2 = 2
[ INFO] [1599227480.020431854]: parameter param3 = 3
[ INFO] [1599227480.021171333]: parameter param4 = 4
[ INFO] [1599227483.351733159]: =============Loop==============
[ INFO] [1599227483.354448047]: parameter param1 = 1
[ INFO] [1599227483.355546242]: parameter param2 = 2
[ INFO] [1599227483.356730625]: parameter param3 = 3
[ INFO] [1599227483.357654706]: parameter param4 = 4
.......
四、python 中操作 param
#!/usr/bin/env python
# coding:utf-8
import rospy
def param_demo():
rospy.init_node("param_demo")
rate = rospy.Rate(1)
while(not rospy.is_shutdown()):
#get param
parameter1 = rospy.get_param("/param1")
parameter2 = rospy.get_param("/param2", default=222)
rospy.loginfo('Get param1 = %d', parameter1)
rospy.loginfo('Get param2 = %d', parameter2)
#delete param
rospy.delete_param('/param2')
#set param
rospy.set_param('/param2',2)
#check param
ifparam3 = rospy.has_param('/param3')
if(ifparam3):
rospy.loginfo('/param3 exists')
else:
rospy.loginfo('/param3 does not exist')
#get all param names
params = rospy.get_param_names()
rospy.loginfo('param list: %s', params)
rate.sleep()
if __name__=="__main__":
param_demo()
运行这个python脚本文件输出结果为:
[INFO] [1599227816.193803]: Get param1 = 1
[INFO] [1599227816.194120]: Get param2 = 2
[INFO] [1599227816.198019]: /param3 exists
[INFO] [1599227816.199841]: param list: ['/roslaunch/uris/host_wong_inspiron_3558__37695', '/rosversion', '/run_id', '/param5', '/param4', '/param3', '/param2', '/param1', '/rosdistro']
[INFO] [1599227817.197727]: Get param1 = 1
[INFO] [1599227817.199030]: Get param2 = 2
[INFO] [1599227817.208759]: /param3 exists
[INFO] [1599227817.211776]: param list: ['/roslaunch/uris/host_wong_inspiron_3558__37695', '/rosversion', '/run_id', '/param5', '/param4', '/param3', '/param2', '/param1', '/rosdistro']
........
五、操作 param 时注意命名空间
在 c++ 操作参数的时候,我们经常会看到
ros::NodeHandle nh;
和 ros::NodeHandle nh("~");
两种用法。
主要是全局命名空间和局部命名空间的不同。
ros::NodeHandle nh;
是 全局命名空间,
ros::NodeHandle nh("~");
是 局部命名空间。
<launch>
<!-- 全局的 test_param -->
<param name="param1" value="1" />
<param name="param2" value="2" />
<node pkg="param_demo" type="param_demo" name="param_demo" output="screen" >
<!-- 局部的 test_param -->
<param name="param3" value="3" />
<param name="param4" value="4" />
</node>
</launch>
那么对应到cpp中,对于这两种param的获取方式有所不同:
#include<ros/ros.h>
int main(int argc, char **argv){
ros::init(argc, argv, "param_demo");
ros::NodeHandle nh_global;
ros::NodeHandle nh_local("~");
int parameter1, parameter2, parameter3, parameter4;
parameter1 = nh_global.param("param1", 1111);
parameter3 = nh_global.param("param_demo/param3", 1111); //获取局部参数,需要增加包名
parameter2 = nh_local.param("/param2", 2222); //获取全局参数,需要增加 "/""
parameter4 = nh_local.param("param4", 2222);
ROS_INFO("parameter param1 = %d", parameter1);
ROS_INFO("parameter param2 = %d", parameter2);
ROS_INFO("parameter param3 = %d", parameter3);
ROS_INFO("parameter param4 = %d", parameter4);
ros::spin();
return 0;
}
按照这样的配置运行launch文件,输出结果为:
[ INFO] [1599231214.229291485]: parameter param1 = 1
[ INFO] [1599231214.229367939]: parameter param2 = 2
[ INFO] [1599231214.229398017]: parameter param3 = 3
[ INFO] [1599231214.229421101]: parameter param4 = 4
参考链接:
[1] 中科院软件所-机器人操作系统入门(ROS入门教程)- P15-4.2 Parammeter Server: https://www.bilibili.com/video/BV1mJ411R7Ni?p=15
[2] Changkun -github :https://github.com/sychaichangkun/ROS-Academy-for-Beginners
今天的文章【ROS学习】ROS param 的使用分享到此就结束了,感谢您的阅读。
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