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Python tutorial to interact with open_loop_object_manipulation_actionserver

Description: This tutorial will show you how to interact with the open_loop_object_manipulation_actionserver in Python

Tutorial Level: INTERMEDIATE

Contents

Introduction
Writing The Code

Introduction

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 
   7 import openloop_object_manipulation.msg as manipulation_action_msg
   8 
   9 from pr2_pick_and_place_demos.pick_and_place_manager import *
  10 from object_manipulator.convert_functions import *
  11 
  12 class AAAILfDObjectGrasper:
  13 
  14  def __init__(self):
  15     
  16     self.manipulation_server = actionlib.SimpleActionClient('open_loop_object_manipulation_actionserver', manipulation_action_msg.OpenLoopObjectManipulationAction)
  17     rospy.loginfo('Waiting for manipulation server')
  18     self.manipulation_server.wait_for_server()
  19 
  20 
  21  def manipulate(self, object, action, arm):
  22     print "manipulating object: %s action: %s arm %s", (object, action, arm)
  23     goal = manipulation_action_msg.OpenLoopObjectManipulationGoal()  
  24     goal.object = object
  25     goal.action = action
  26     goal.arm = arm
  27 
  28     rospy.loginfo('Sending goal')
  29     self.manipulation_server.send_goal(goal)
  30     rospy.loginfo('Waiting for results')
  31     self.manipulation_server.wait_for_result()
  32 
  33 
  34 if __name__ == '__main__':
  35     try:
  36         # Initializes a rospy node so that the SimpleActionClient can
  37         # publish and subscribe over ROS.
  38         rospy.init_node('aaai_lfd_demo_manipulator')
  39         manipulation = AAAILfDObjectGrasper()
  40         manipulation.manipulate("tea-box", "pick", "l")
  41         
  42     except rospy.ROSInterruptException:
  43         print "program interrupted before completion"

In this example, we create a class to manipulate objects of pre-recorded positions. In particular this code will result in the tea-box being picked up using the left arm.

== Initialization ==

   1 import roslib; roslib.load_manifest('aaai_lfd_demo_executive')
   2 import rospy
   3 import actionlib
   4 import math
   5 import copy
   6 
   7 import openloop_object_manipulation.msg as manipulation_action_msg
   8 
   9 from pr2_pick_and_place_demos.pick_and_place_manager import *
  10 from object_manipulator.convert_functions import *

This portion of the code includes the files necessary to write the code

Class Initialization

   1 class AAAILfDObjectGrasper:
   2 
   3  def __init__(self):
   4    
   5     self.manipulation_server = actionlib.SimpleActionClient('open_loop_object_manipulation_actionserver', manipulation_action_msg.OpenLoopObjectManipulationAction)
   6     rospy.loginfo('Waiting for manipulation server')
   7     self.manipulation_server.wait_for_server()

This declares a class AAAILfDObjectGrasper and the init function. Within the init function we can break things down further:

self.manipulation_server = actionlib.SimpleActionClient('open_loop_object_manipulation_actionserver', manipulation_action_msg.OpenLoopObjectManipulationAction)

creates self.manipulation_server an action client to the open_loop_object_manipulation_actionserver.

    rospy.loginfo('Waiting for manipulation server')
    self.manipulation_server.wait_for_server()

These lines wait for the action server to respond that it is running.

Using the Action Server

   1  def manipulate(self, object, action, arm):
   2     print "manipulating object: %s action: %s arm %s", (object, action, arm)
   3     goal = manipulation_action_msg.OpenLoopObjectManipulationGoal()  
   4     goal.object = object
   5     goal.action = action
   6     goal.arm = arm
   7 
   8     rospy.loginfo('Sending goal')
   9     self.manipulation_server.send_goal(goal)
  10     rospy.loginfo('Waiting for results')
  11     self.manipulation_server.wait_for_result()

def manipulate(self, object, action, arm):

Defines a function manipulate that takes three arguments: the desired object, the action, and which arm should be used

goal = manipulation_action_msg.OpenLoopObjectManipulationGoal()  
goal.object = object
goal.action = action
goal.arm = arm

These lines create a goal for the open_loop_object_manipulation_actionserver

self.manipulation_server.send_goal(goal)

This line sends the goal to the action server

self.manipulation_server.wait_for_result()

This line waits for the result

Picking up the Tea-Box

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_manipulator')
   6         manipulation = AAAILfDExecutive()
   7         manipulation.manipulate("tea-box", "pick", "l")
   8         
   9     except rospy.ROSInterruptException:
  10         print "program interrupted before completion"

rospy.init_node('aaai_lfd_demo_manipulator')

Initializes this rosnode

manipulation = AAAILfDExecutive()

Creates a new instance of the class we created

manipulation.manipulate("tea-box", "pick", "l")

Asks the class to pickup the teabox with the left arm.

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