How to Set Goal Pose for MoveGroupCommander?

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From your code what i thing its happening is that when you execute go() the pose is not estored. I can not remeber well now. But i thing a i faced this issue in the past. So here is something you can test. you can invoke group.go(targe_pose). That worked for me. And in orther to see if youre specifying invalid poses I recoment you to start the target_pose with group.get_current_pose()

And start playing from ther to see if making little modifications to this pose the robot moves.

tpose = group.get_current_pose()
print type(tpose)
print tpose
#modify pose
tpose.pose.position.z = z #<put here z> 
tpose.pose.position.x = x #<put here new x>
tpose.pose.position.y = y #<put here new y>
#plan and execute
group.go(tpose,wait = True)

If after running the go you get the same error it's probable that you are specifying a pose that is not possible due to robots limits (may be orientation or joints limits)