Robot Datum

Ok Chief, lay it on me. What is your preferred CAD datum/origin for the AM14U4 chassis or any chassis really. Go!

Note: I work in solidworks.

Right plane is the left-right mid plane of the robot.
Front plane is the front-back mid plane of the robot.
Top plane is the ground for the top-level robot assembly and the mid plane of the drivetrain frame rails on the drivetrain assembly.


We define:

  • FS0 = midplane in the forward-aft direction
  • BL0 = midplane in the port-starboard direction
  • WL0 = ground

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Exactly how I go about my robot CAD too in Solidworks. A rather intuitive setup of the planes/origin IMO.

Same,except drivetrain floor is actually floor for me.


I use a layout part in SW and a part studio in OS that use the datum: front-to-back centered, left-to-right centered, and floor.

All of the sub assemblies and part studios use the same origin points by placing the reference parts fixed into the sub assembly except for rather simple or insignificant parts. With this setup when you then drop them into the top-level they are already correctly located and you just need to add the one mate. Then if you update the layout model the parts and sub assemblies update as well.

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I simply let the CAD decide for me

It is not uncommon in piston engine work to use the front face of the engine block on the crank centerline as the origin.

But it seems front/back and left/right centered on the “floor” is winning votes for robots.

To define the floor, do you use a shift 3” down from the center wheel of a 6” wheel or the bottom of the wheel “step” file model?

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