Moveit servo how to update the scene

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Hi all,

I have an arm that has to track continuosly some given poses. What I usually did is to use a PID to generate Cartesian velocities from the target poses and then IK to command the robot joints.

I would like to do this with Moveit (ROS1 Noetic) to exploit its features (mainly obstacle avoidance). I managed to set up my robot from the moveit tutorials and I can use move_group to plan and execute a collision free trajectory.

Now I was trying to follow the moveit servo tutorial, in particular I saw the pose tracking example which seems the right one for my needs. But I have problems about something:

1. In the servo tutorial, the move_group node is launched, as well the servo_server. Why are they both necessary? Do not they command the same ros_controllers?

2. I cannot update the arm status within the pose tracking node. In particular, the arm is starting in a homing position, but this node sees all the joints positions to zero, even if the PlanningSceneMonitor is active. The node is subscribed correctly to the joint_states topic which is filled with the correct joint values.
   When I used the move_group node (without servo) the status was correctly syncronized. How the scene is kept updated in the move_group node?
   Nobody in both cases publishes on the planning_scene topic. Should I use this? I saw that move_group internally uses moveit_cpp. Should I use it in the pose_tracking node as well?

Thanks for any help :D