In this lecture, we will compose a simple pick and place pipeline with different MoveGroup APIs. Furthermore, the purpose and function of different APIs will be explained.

MoveGroup Interface APIs

• set_named_target (<“robot joint configuration”>)
• plan() – plans a motion to the goal
• get_current_pose() – get pose of the end effector and joint configuration
• compute_cartesian_path (<waypoints>, <resolution>, <jump_threshold>, <collision_checking=True>)

Navigate to the week 4 ROS package
$ source $HOME/hrwros_ws/devel/setup.bash
$ roscd hrwros_week4

Let’s go through the simple_pick_place.py script. The required specific required modules are:

• moveit_commander – tell python we work with MoveIt!
• moveit_msgs.msg
• actionlib –  for the movement with actionlib.SimpleActionClient() 
• geometry_msgs – for planning lineair or carthesian spaced motions

Further in the script:

• The initialisation of moveit_commander and  ROS node simple_pick_place
• Create groups for the robots
• Instantiate the two action clients for execute_trajectory action server
• APIs
  • • set_named_target – set a goal configuration
    • plan() – plans a motion to the goal
    • .send_goal() – send the goal to the action server

As it is nonblocking we can already plan the next motion.