 Please ask about problems and questions regarding this tutorial on answers.ros.org. Don't forget to include in your question the link to this page, the versions of your OS & ROS, and also add appropriate tags. |
Python tutorial to interact with open_loop_object_manipulation_actionserver
Description: This tutorial will show you how to interact with the drive_to_action_server in PythonTutorial Level: INTERMEDIATE
Contents
Introduction
This tutorial shows you how you can use the rl_2dnav to navigate between the 5 possible robot locations in the remote lab.
Writing The Code
This piece shows the whole code. Then below we'll slowly break things down bit by bit.
1 import roslib; roslib.load_manifest('aaai_lfd_demo_executive')
2 import rospy
3 import actionlib
4 import math
5 import copy
6 import geometry_msgs.msg
7 import rl_2dnav.msg as navigation_action_msg
8
9 class AAAILfDDriver:
10
11 def __init__(self):
12 self.navigation_server = actionlib.SimpleActionClient('drive_to_action_server', navigation_action_msg.DriveToAction)
13 rospy.loginfo('Waiting for navigation server')
14 self.navigation_server.wait_for_server()
15
16 def navigate(self, location):
17 print "navigating location %s", (location)
18 goal = navigation_action_msg.DriveToGoal()
19 goal.pose = location
20
21 rospy.loginfo('Sending goal')
22 self.navigation_server.send_goal(goal)
23 rospy.loginfo('Waiting for results')
24 self.navigation_server.wait_for_result()
25
26
27
28 if __name__ == '__main__':
29 try:
30 # Initializes a rospy node so that the SimpleActionClient can
31 # publish and subscribe over ROS.
32 rospy.init_node('aaai_lfd_demo_driver')
33 driver = AAAILfDDriver()
34 driver.navigate(3)
35
36 except rospy.ROSInterruptException:
37 print "program interrupted before completion"
In this example, we create a class to drive to any of the prerecorded positions. In particular this code will result in the robot driving to the third position.
Initialization
This portion of the code includes the files necessary to write the code
Class Initialization
This declares a class AAAILfDDriver and the init function. Within the init function we can break things down further:
self.navigation_server = actionlib.SimpleActionClient('drive_to_action_server', navigation_action_msg.DriveToAction)
creates self.navigation_server, an action client to the drive_to_action_server.
rospy.loginfo('Waiting for navigation server')
self.navigation_server.wait_for_server()These lines wait for the action server to respond that it is running.
Using the Action Server
1 def navigate(self, location):
2 print "navigating location %s", (location)
3 goal = navigation_action_msg.DriveToGoal()
4 goal.pose = location
5
6 rospy.loginfo('Sending goal')
7 self.navigation_server.send_goal(goal)
8 rospy.loginfo('Waiting for results')
9 self.navigation_server.wait_for_result()
def navigate(self, location):
Defines a function manipulate that takes three arguments: the desired object, the action, and which arm should be used
goal = navigation_action_msg.DriveToGoal() goal.pose = location
These lines create a goal for the drive_to_action_server
self.navigation_server.send_goal(goal)
This line sends the goal to the action server
self.navigation_server.wait_for_result()
This line waits for the result
Move to position 3
This code shows the main function which uses the class we created in the previous sections.
1 if __name__ == '__main__':
2 try:
3 # Initializes a rospy node so that the SimpleActionClient can
4 # publish and subscribe over ROS.
5 rospy.init_node('aaai_lfd_demo_driver')
6 driver = AAAILfDDriver()
7 driver.navigate(3)
8
9 except rospy.ROSInterruptException:
10 print "program interrupted before completion"
rospy.init_node('aaai_lfd_demo_driver')Initializes this rosnode
driver = AAAILfDDriver()
Creates a new instance of the class we created
driver.navigate(3)
Asks the class drive to the third position.
