19、 ROS parameter name setting

1. brief introduction

stay ROS in , Parameter names may have duplicate names , He's not like the topic with the same name , It can be solved by remapping . however , You can add different prefixes , To distinguish between different parameters

• classification ：
  • overall situation ： Level with namespace
  • relative ： Level with node name
  • private ： Children of the node name
• Implementation method :
  • rosrun command
  • launch file
  • coded

2. Implementation method

2.1 rosrun Set parameters : Parameter names use private mode

• Format ：rosrun Package name The node name _ Parameter name := Parameter values
• Code implementation ：

  rosrun turtlesim turtlesim_node _A:=100
  

• Running results ：

  rosparam list
  /turtlesim/A
  

2.2 launch File settings parameters

• type ：
  • stay node Out of label ： Global parameter
  • stay node tag ： Private parameters
• Code implementation ：

  <!--  Set parameters  -->
  <launch>
      <!--  Format 1： overall situation  -->
      <param name="radius" value="10" />
      <!--  Format 2： Local  -->
      <node pkg="turtlesim" type="turtlesim_node" name="t1" ns="xxx">
          <param name="radius" value="20" />
      </node>
  </launch>
  

• Running results ：

  bash1: start-up launch file 
  roslaunch launch_test_01 param_rename.launch
  
  bash2： Check the parameter list 
  rosparam list 
  /radius
  /xxx/t1/radius
  

2.3 Code setting parameters

2.3.1 C++ Realization

• Code implementation ：

  #include"ros/ros.h"
  
  int main(int argc,char *argv[]){
         
      ros::init(argc,argv,"topic_name");
      ros::NodeHandle nh;
      /*  Use ros::param To set parameters  */
      // 1.  overall situation 
      ros::param::set("/radiusA",100);
      // 2.  relative 
      ros::param::set("radiusB",100);
      // 3.  private 
      ros::param::set("~radiusC",100);
      /*  Use NodeHandle Set parameters  */
      // 1.  overall situation 
      nh.setParam("/A",100);
      // 2.  relative 
      nh.setParam("B",100);
      // 3.  private 
      ros::NodeHandle nh1("~");
      nh1.setParam("C",100);
      return 0;
  }
  

• Running results ：

  bash1: Operation node , And add the namespace 
  rosrun rename_01 topic_name __ns:=xxx
  
  bash2： Check the parameter list 
  rosparam list
  /A
  /radiusA
  /xxx/B
  /xxx/radiusB
  /xxx/topic_name/C
  /xxx/topic_name/radiusC
  

2.3.2 Python Realization

• Code implementation ：

  #! /usr/bin/env python
  
  from ast import Str
  import rospy
  from std_msgs.msg import String
  
  if __name__ == "__main__":
      rospy.init_node("topic_name_p")
      # 1.  overall situation 
      rospy.set_param("/p1",100)
      # 2.  relative 
      rospy.set_param("py2",100)
      # 3.  private 
      rospy.set_param("~py3",100)
  

• Running results ：

  bash1: Start node , And add the namespace 
  rosrun rename_01 topic_name_p.py __ns:=xxx
  
  bash2： Check the parameter list 
  rosparam list
  /p1
  /xxx/py2
  /xxx/topic_name_p/py3