Slighly reword the planning group section

Also add different screenshots that more clearly display the hand
of the robot, which is kind of hidden in the startup pose.

Author: rhaschke

doc/setup_assistant/setup_assistant_panda_100.png

@@ -49,14 +49,19 @@ Step 1: Start
 
 .. image:: setup_assistant_start.png
 
-* Click on the browse button and navigate to the *panda_arm.urdf.xacro* file
-  installed when you installed the Franka package above. (This file gets installed in
-  ``/opt/ros/noetic/share/franka_description/robots/panda_arm.urdf.xacro`` on Ubuntu
-  with ROS Noetic) Choose that file.
+* Click on the browse button and navigate to the ``.urdf`` file of your robot.
+  MoveIt Setup Assistant supports both, plain ``.urdf`` files as well as ``.urdf.xacro`` files
+  that require the `xacro <http://wiki.ros.org/xacro>`_ pre-processor to generate the final URDF.
 
-* Now add **hand:=true** as the *optional xacro arguments and then click *Load Files*.
-  The Setup Assistant will load the files (this might take a few seconds) and present
-  you with this screen:
+  For the Panda robot, the file is called ``panda_arm.urdf.xacro`` provided by the ``franka_description``
+  package, located in ``/opt/ros/noetic/share/franka_description/robots/panda_arm.urdf.xacro`` when installed
+  from the ROS Noetic package repository as done above.
+
+* Optionally, enter xacro commandline parameters to steer the URDF generation process.
+  For the Panda, you should add **hand:=true** to enable creation of both arm *and* hand.
+
+* Finally, click *Load Files*. The Setup Assistant will load the files (this might take a few seconds) and present
+  you with this screen, showing the robot in a default pose with all joints at the center of their range:
 
 .. image:: setup_assistant_panda_100.png
    :width: 700px
@@ -117,6 +122,10 @@ Step 4: Add Planning Groups
 
 Planning groups are used for semantically describing different parts
 of your robot, such as defining what an arm is, or an end effector.
+A planning group essentially defines which joints will actively participate in
+motion generation, what are reference frames for inverse kinematics, etc.
+
+In the following, we will define two planning groups for the arm and one group for the hand.
 
 * Click on the *Planning Groups* pane selector.
 
@@ -125,9 +134,8 @@ of your robot, such as defining what an arm is, or an end effector.
 .. image:: setup_assistant_panda_planning_groups.png
    :width: 700px
 
-Add the arm
 
-* We will first add Panda arm as a planning group
+* We will first add ``panda_arm`` as a planning group
 
   * Enter *Group Name* as **panda_arm**
 
@@ -141,14 +149,15 @@ Add the arm
 .. image:: setup_assistant_panda_arm.png
    :width: 700px
 
-* Now, click on the *Add Kin. Chain* button. Click the *Expand All* button. You will see a
-  list of links on the left-hand side. The links are arranged in the order that they are stored in
-  an internal tree structure.
+* Groups can be define in various ways. Here, we prefer defining the group via a kinematic chain,
+  i.e. defining its first and last link along the chain.
+  Thus, click on the *Add Kin. Chain* button and, on the next pane, click the *Expand All* button to see the full
+  kinematic tree of your robot.
 
   * Click on the **panda_link0** link and press the *Choose Selected* button next to the
-    Base link text field.
-  * Click on the **panda_tool** link and press the *Choose Selected* button next to the
-    Tip link text field.
+    **Base link** text field.
+  * Click on the **panda_link8** link and press the *Choose Selected* button next to the
+    **Tip link** text field.
 
 .. image:: setup_assistant_panda_arm_links.png
    :width: 700px
@@ -158,11 +167,15 @@ Add the arm
 .. image:: setup_assistant_panda_arm_links_saved.png
    :width: 700px
 
-Add the gripper
+Repeat this procedure for another arm group, called ``manipulator``, ranging from base link ``panda_link0``
+to tip link ``panda_hand_tcp``. While ``panda_link8`` defines the tool mount frame of the Panda, the virtual frame
+``panda_hand_tcp`` defines the tool center point between the two gripper flanges. Both frames have a different orientation
+as well, ``panda_hand_tcp`` being aligned with the hand.
+
+Add the ``hand`` group
 
-* We will also add a group for the end
-  effector. NOTE that you will do this using a different procedure
-  than adding the arm.
+* We will also add a group for the end effector.
+  NOTE that you will do this using a slightly different procedure than adding the arm.
 
   * Click on the *Add Group* button.
 
@@ -175,7 +188,7 @@ Add the gripper
 
   * Click on the *Add Links* button.
 
-  * Choose **panda_hand**, **panda_leftfinger**, **panda_rightfinger** and **panda_hand_coarse* and add them
+  * Choose **panda_hand**, **panda_leftfinger**, and **panda_rightfinger** and add them
     to the list of *Selected Links* on the right hand side.
 
   * Click *Save*
@@ -206,12 +219,12 @@ certain position of the robot as a **Home** position.
 .. image:: setup_assistant_panda_saved_poses.png
    :width: 700px
 
-Step 6: Label End Effectors
+Step 6: Add End Effectors
 ---------------------------
 
-We have already added the gripper of the Panda. Now, we
-will designate this group as a special group:
-**end effectors**. Designating this group as end effectors allows
+We have already added the gripper of the Panda as a planning group. Now, we
+will designate this group as a special group, an **end effector**.
+Designating the group as an end effector allows
 some special operations to happen on them internally.
 
 * Click on the *End Effectors* pane.
@@ -222,9 +235,16 @@ some special operations to happen on them internally.
 
 * Select **hand** as the *End Effector Group*.
 
-* Select **panda_tool** as the *Parent Link* for this end-effector.
+* Select **panda_link8** as the *Parent Link* and **panda_arm** as the *Parent Group* for this end-effector.
+
+Add another end effector group, called **hand_tcp**, using **manipulator** as its parent group
+and **panda_hand_tcp** as its parent link. Thus, the two arm planning groups essentially differ in
+their associated end effector as well as the corresponding end-effector link = parent link.
+Thus they will provide different interactive markers to steer the robot in Cartesian space.
 
-* Leave *Parent Group* blank.
+Note, that it is possible to associate several end effector groups to a single parent group.
+If you select such a planning group for planning, *all* associated interactive markers will be provided
+to steer the arm - potentially using different end-effector reference frames.
 
 .. image:: setup_assistant_panda_end_effector_add.png
    :width: 700px
@@ -240,7 +260,7 @@ directly controlled. The Panda does not have any passive
 joints so we will skip this step.
 
 
-Step 8: ROS Control
+Step 8: Controllers
 ---------------------
 
 ROS Control is a set of packages that include controller interfaces, controller managers, transmissions and hardware_interfaces, for more details please look at `ros_control` documentation_