ROS MoveIt 101

My Honours Thesis involves using ROS and MoveIt to simulate and control a robot arm. I am writing a short reference in case I forget.

MoveIt has 3 scripting classes: RobotCommander, MoveGroupCommander, and PlanningSceneInterface.

RobotCommander

The RobotCommander class provides information about the robot.

# Assume RobotCommander is an instantiated object
arr = RobotCommander.get_group_names() # Get an array of string
RobotCommander.get_group(arr[]) # Get MoveGroupCommander() obj. 

Note that you can directly instantiate a RobotCommander() with a str too.

MoveGroupCommander

MoveGroupCommander controls a group.
A group is a collection of predefined joints.

# Assume MoveGroupCommander is an instantiated object
MoveGroupCommander.set_pose_target(pose) # Set the pose of the EE but does not execute.
success = MoveGroupCommander.go(wait= Bool)   # Execute the predefined pose target

# stop residual movement
MoveGroupCommander.stop()

Pose = MoveGroupCommander.get_current_pose() # Get EE Pose
Joints = MoveGroupCommander.get_current_joint_values() # Get an array of float
MoveGroupCommander.go({Pose | Joints}, wait= Bool) # Execute using the Pose (or Joints) as target.

Note that the length of get_current_joint_values() differs for different MoveGroupCommanders. A group may not have an EE. In the case of Kinova Jaco, it has two groups: arm and gripper, and the gripper group has no EE.

PlanningSceneInterface

PlanningSceneInterface controls the environment by adding, removing, or updating collisions.

# Asssume PlanningSceneInterface is an instantiated object
PlanningSceneInterface.add_box(str, pose, size=(x, y, z)) # Add box named str at pose
PlanningSceneInterface.remove_world_object(str) 
PlanningSceneInterface.remove_world_object() # equiv to .clear()
PlanningSceneInterface.clear()


PlanningSceneInterface.attach_box(link, str, touch_links= arr) # attach a box str at link.
PlanningSceneInterface.attach_object(str, link= str) # More flexible

PlanningSceneInterface.remove_attached_object() # Remove all attached objects
PlanningSceneInterface.remove_attached_object(name= str) # Remove the attached object str

For attach_box() and other similar functions, it is possible to create AND attach if the optional param pose is given. Otherwise, attach_object() is a more flexible way to attach an existing object. If touch_links is provided (array of str), collision with the links is ignored (as per the official doc). Otherwise, collision with link is ignored.