说明
- 介绍参数类型
- 介绍如何获取参数，设置参数，删除参数
- 介绍解释参数
- 介绍搜索参数
参数类型
- 可使用整数，浮点数，字符串，布尔值，列表，字典等作为参数
- 字典有额外的意义，可当作命名空间使用。可以这样设置
/gains/P = 1.0
/gains/I = 2.0
/gains/D = 3.0
- 在rospy,可以获取输出/gains
{'P': 1.0, 'I': 2.0, 'D': 3.0}
操作参数
- 获取参数，使用
rospy.get_param(param_name)：
# 获取全局参数
rospy.get_param('/global_param_name')
# 获取目前命名空间的参数
rospy.get_param('param_name')
# 获取私有命名空间参数
rospy.get_param('~private_param_name')
# 获取参数，如果没，使用默认值
rospy.get_param('foo', 'default_value')
- 设置参数，使用
rospy.set_param(param_name, param_value)：
rospy.set_param('some_numbers', [1., 2., 3., 4.])
rospy.set_param('truth', True)
rospy.set_param('~private_bar', 1+2)
- 删除参数，使用
rospy.delete_param('param_name')：
rospy.delete_param('to_delete')
- 判断参数是否存在，使用
rospy.has_param('param_name')：
if rospy.has_param('to_delete'):
rospy.delete_param('to_delete')
解释参数名
- 在ROS,名称可以映射成不同名，你的节点也可以放入到命名空间。
- rospy一般都能自动解释这些名称，但作为调试目的，可能向了解所有名称之间的关联。
- 获取实际的名称， rospy.resolve_name(name)：
value = rospy.get_param('~foo')
rospy.loginfo('Parameter %s has value %s', rospy.resolve_name('~foo'), value)
搜索参数
- 如果你不知道命名空间，你可以搜索参数。
- 搜索由私有命名空间开始，向上到全局命名空间。
- 使用rospy.search_param(param_name)：
full_param_name = rospy.search_param('foo')
param_value = rospy.get_param(full_param_name)
- 获取参数名后，也可以进行参数操作。
制作launch文件
- 访问代码:
https://github.com/ros/ros_tutorials/blob/kinetic-devel/rospy_tutorials/006_parameters
- 通过launch设置参数，进入bringup目录，新建param_talker.launch
$ roscd beginner_tutorials/bringup
$ touch param_talker.launch
$ rosed beginner_tutorials param_talker.launch
- 手工输入代码（可以不输入注释部分）：
-
<launch> <!-- set /global_example parameter --> <param name="global_example" value="global value" /> <group ns="foo"> <!-- set /foo/utterance --> <param name="utterance" value="Hello World" /> <param name="to_delete" value="Delete Me" /> <!-- a group of parameters that we will fetch together --> <group ns="gains"> <param name="P" value="1.0" /> <param name="I" value="2.0" /> <param name="D" value="3.0" /> </group> <node pkg="rospy_tutorials" name="param_talker" type="param_talker.py" output="screen"> <!-- set /foo/utterance/param_talker/topic_name --> <param name="topic_name" value="chatter" /> </node> </group> </launch>
- 代码分析
-
- 看代码注释
制作节点
- 使用参数，进入scripts目录，新建param_talker.py
$ roscd beginner_tutorials/scripts $ touch param_talker.py $ chmod +x param_talker.py $ rosed beginner_tutorials param_talker.py- 手工输入如下代码（可以不输入注释部分）：
#!/usr/bin/env python import rospy from std_msgs.msg import String def param_talker(): rospy.init_node('param_talker') # Fetch values from the Parameter Server. In this example, we fetch # parameters from three different namespaces: # # 1) global (/global_example) # 2) parent (/foo/utterance) # 3) private (/foo/param_talker/topic_name) # fetch a /global parameter global_example = rospy.get_param("/global_example") rospy.loginfo("%s is %s", rospy.resolve_name('/global_example'), global_example) # fetch the utterance parameter from our parent namespace utterance = rospy.get_param('utterance') rospy.loginfo("%s is %s", rospy.resolve_name('utterance'), utterance) # fetch topic_name from the ~private namespace topic_name = rospy.get_param('~topic_name') rospy.loginfo("%s is %s", rospy.resolve_name('~topic_name'), topic_name) # fetch a parameter, using 'default_value' if it doesn't exist default_param = rospy.get_param('default_param', 'default_value') rospy.loginfo('%s is %s', rospy.resolve_name('default_param'), default_param) # fetch a group (dictionary) of parameters gains = rospy.get_param('gains') p, i, d = gains['P'], gains['I'], gains['D'] rospy.loginfo("gains are %s, %s, %s", p, i, d) # set some parameters rospy.loginfo('setting parameters...') rospy.set_param('list_of_floats', [1., 2., 3., 4.]) rospy.set_param('bool_True', True) rospy.set_param('~private_bar', 1+2) rospy.set_param('to_delete', 'baz') rospy.loginfo('...parameters have been set') # delete a parameter if rospy.has_param('to_delete'): rospy.delete_param('to_delete') rospy.loginfo("deleted %s parameter"%rospy.resolve_name('to_delete')) else: rospy.loginfo('parameter %s was already deleted'%rospy.resolve_name('to_delete')) # search for a parameter param_name = rospy.search_param('global_example') rospy.loginfo('found global_example parameter under key: %s'%param_name) # publish the value of utterance repeatedly pub = rospy.Publisher(topic_name, String, queue_size=10) while not rospy.is_shutdown(): pub.publish(utterance) rospy.loginfo(utterance) rospy.sleep(1) if __name__ == '__main__': try: param_talker() except rospy.ROSInterruptException: pass
- 代码分析：
- 看代码注释
整合测试
- 启动launch文件
- 命令：
$ roslaunch beginner_tutorials param_talker.launch- 效果：
SUMMARY ======== PARAMETERS * /foo/gains/D: 3.0 * /foo/gains/I: 2.0 * /foo/gains/P: 1.0 * /foo/param_talker/topic_name: chatter * /foo/to_delete: Delete Me * /foo/utterance: Hello World * /global_example: global name * /rosdistro: indigo * /rosversion: 1.11.16 NODES /foo/ param_talker (beginner_tutorials/param_talker.py) ROS_MASTER_URI=http://192.168.0.88:11311 core service [/rosout] found process[foo/param_talker-1]: started with pid [32684] [INFO] [WallTime: 1478587334.669759] /global_example is global name [INFO] [WallTime: 1478587334.682391] /foo/utterance is Hello World [INFO] [WallTime: 1478587334.693382] /foo/param_talker/topic_name is chatter [INFO] [WallTime: 1478587334.708533] /foo/default_param is default_value [INFO] [WallTime: 1478587334.729605] gains are 1.0, 2.0, 3.0 [INFO] [WallTime: 1478587334.731529] setting parameters... [INFO] [WallTime: 1478587334.831270] ...parameters have been set [INFO] [WallTime: 1478587334.871695] deleted /foo/to_delete parameter [INFO] [WallTime: 1478587334.895860] found global_example parameter under key: /global_example [INFO] [WallTime: 1478587334.922108] Hello World [INFO] [WallTime: 1478587335.925285] Hello World