How to determine the origin point of footprint while applying the teb_local_planner on a car-like robot?

[FishInWave]

Thanks for your outstanding work. I have read teb_local_plannerTutorialsObstacle Avoidance and Robot Footprint Model to figure out how to determine the origin point of footprint while applying the teb_local_planner on a car-like robot. But I still cannot understand what this sentence means:

The robots axis of rotation is assumed to be located at [0,0] (Unit: meters).

Assume there is a car-like robot with an Ackerman chassis, whose outer contour is 1 m* 0.8m, and I'd like to use teb as its local planner.

1. Should his parameters in teb_local_planner_params.yaml be like as follow?

 footprint_model: # types: "point", "circular", "two_circles", "line", "polygon" 
  type: "polygon"
  vertices: [[-0.5, -0.4], [-0.5, 0.4],[0.5,0.4],[0.5, -0.4]]

2. should the footprint in costmap_common_params.yaml be the same as above?

Additionally, I noted the footprint of https://github.com/rst-tu-dortmund/teb_local_planner_tutorials/blob/melodic-devel/cfg/carlike/costmap_common_params.yaml is: footprint: [ [-0.1,-0.125], [0.5,-0.125], [0.5,0.125], [-0.1,0.125] ]. Why the origin of footprint is to the left?

[laszloturanyi]

Hi, teb_local_plannerTutorialsObstacle Avoidance and Robot Footprint Model

It suggests: Important: For car-like robots, the pose [0,0] is located at the rear-axle (axis of rotation)!

Hence, your origin should be more to the rear, for sure.

[FishInWave]

rear

Hi, I want to reconfirm : "located at the axle" means that the pose [0,0] is located at the center of the rear-axle? i.e.
car contour coordinates are like

 footprint_model: # types: "point", "circular", "two_circles", "line", "polygon" 
  type: "polygon"
  vertices: [[-0.5, -0.4], [-0.5, 0.4],[0.5,0.4],[0.5, -0.4]]