opendoors/Tutorials/Writing a simple client for opendoors action

Note: This tutorial show how to write client for GraspHandleAction action.

How to write a simple client for opendoors action server

Description: This tutorial shows how to write a simple client for the GraspHandleAction

Keywords: move_arm, opendoors, opencupboard

Tutorial Level: INTERMEDIATE

Contents

Code

Code

   1 import roslib; roslib.load_manifest('opendoors')
   2 import rospy
   3 import actionlib
   4 import opendoors.msg
   5 from geometry_msgs.msg import Pose , PoseStamped
   6 
   7 def main():
   8         gripper_client = actionlib.SimpleActionClient('grasp_handle_action',opendoors.msg.GraspHandleAction)
   9         print "waiting for server"
  10         gripper_client.wait_for_server()
  11 
  12         goal_pose = opendoors.msg.GraspHandleGoal()
  13 
  14         pose_stamped = PoseStamped()
  15         pose_stamped.header.frame_id = "torso_lift_link"
  16         pose_stamped.header.stamp = rospy.Time.now()
  17         pose_stamped.pose.position.x = 0
  18         pose_stamped.pose.position.y = 0.7
  19         pose_stamped.pose.position.z = 0
  20         pose_stamped.pose.orientation.x = 0
  21         pose_stamped.pose.orientation.y = 0
  22         pose_stamped.pose.orientation.z = 0
  23         pose_stamped.pose.orientation.w = 1
  24         goal_pose.pose_stamped =  pose_stamped
  25         goal_pose.arm = "right arm"
  26         print "waiting for result"
  27         gripper_client.send_goal_and_wait(goal_pose)
  28 
  29 if __name__ == '__main__':
  30         rospy.init_node('test_handle_grasp_node')
  31         main()

Now let's break down the code.

   1 import roslib; roslib.load_manifest('opendoors')
   2 import rospy
   3 import actionlib
   4 import opendoors.msg
   5 from geometry_msgs.msg import Pose , PoseStamped

These lines are importing things that are necessary for this client.

```
   1  #!python block=stiffness_control
   2  gripper_client = actionlib.SimpleActionClient('grasp_handle_action',         
   3                   opendoors.msg.GraspHandleAction)
   4  print "waiting for server"
   5  gripper_client.wait_for_server()
```
Here we are creating a node that serves a simple action client for GraspHandleAction and waiting for it to complete initialization.
```
   1 goal_pose = opendoors.msg.GraspHandleGoal()
```
This is where we create goal which we will subscribe to the action server client we just created. The goal is an GraspHandleGoal and see the specifics at opendoors/GraspHandleGoal.

   1 pose_stamped = PoseStamped()
   2 pose_stamped.header.frame_id = "torso_lift_link"
   3 pose_stamped.header.stamp = rospy.Time.now()
   4 pose_stamped.pose.position.x = 0
   5 pose_stamped.pose.position.y = 0.7
   6 pose_stamped.pose.position.z = 0
   7 pose_stamped.pose.orientation.x = 0
   8 pose_stamped.pose.orientation.y = 0
   9 pose_stamped.pose.orientation.z = 0
  10 pose_stamped.pose.orientation.w = 1
  11 goal_pose.pose_stamped =  pose_stamped

Here we are initializing a PoseStamped for the goal. The position and orientation of the pose was arbitrary but it should be reachable within the frame of reference which was set to "torso_lift_link" in this case. Then we assigns the pose to be a field of the goal we are creating.

   1 goal_pose.arm = "right arm"

Here we are setting the goal to take right arm as a field.

   1 gripper_client.send_goal_and_wait(goal_pose)

Finally, we are sending the node to the action server client and wait for it for execute the action.

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