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PacktPublishing / ROS-Robotics-Projects-SecondEdition

ROS Robotics Projects, published by Packt
MIT License
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base_footprint missing for mobile manipulator in chapter 3 #2

Closed fjp closed 3 years ago

fjp commented 4 years ago

Hi, thank you for this awesome ROS book. I have a question to chapter 3: according to REP-120 a robot usually has a base_footprint link. Why is this link tag not present in the mobile manipulator covered in chapter 3? At least I couldn't find a base_footprint in the urdf/xacro files in chapter3/robot_description of this repository. Could you also please explain why it is suggested to use the base_footprint mentioned in REP-120?

qboticslabs commented 3 years ago

Hi @fjp

What you mentioned is true. The REP-120 mentioning about base_footprint. In the case of the mobile robots, it is not mandatory though, because of most of the packages like SLAM, AMCL look for base_link instead of base_footprint. For eg. The TF tree of SLAM will be map->odom->base_link etc. So we can put base_footprint in URDF, even if you don't put it, still, it will work. I hope that will fix your doubt.

fjp commented 3 years ago

Thanks for the insight @qboticslabs :+1: I didn't know that most of the packages look for just base_link. Do you know of any scenario where base_footprint is required though? Otherwise I don't know why REP-120 suggests using it. Would you suggest not putting it in the URDF?

qboticslabs commented 3 years ago

Hi @fjp

I used to put base_footprint according to REP-120 in my current projects as well. It will be better to follow the conventions. In the old version of gmapping, I think they have used the base_footprint link if my memory is correct.