Easiest way to find your robots center of mass?

What is the easiest way to find our robots center of mass/gravity? Our robot leans to the left when driving and I feel like that might be because our center of mass is far on the left side. I need to know how much weight to put on in order to balance the robot.

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You are more likely suffering from your drive system being slightly faster on one side compared to the other. A common idiosyncrasy of CIMs/brushed motors or even assembly variations.

Have you checked for these common issues already?

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pick it up, from a single point on each end, moving your picking up points until it seems balanced. Then repeat, from a single point on each side. Where the two lines between the 4 pickup points intersect, is your center of mass.

But that has nothing to do with why it doesn’t drive straight ,most likely.

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Is there an easy way to do this with a cadded robot? What you described seams very finicky to me, to get a more accurate location

Can this be solved through programming?

Yes, and it often is. Closed-loop speed control on the drives helps tremendously. Some teams will apply a throttle factor to the ‘fast’ side to try and match the slow side, cruder, but largely effective.

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Yes. SOLIDWORKS can show you the center of mass.(And I expect most other CAD solutions can as well.) It’s a good way to ball park, providing you CAD a majority of your components.

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Google “[cad program you use] center of mass”, it should be pretty straightforward but without knowing what CAD you use I can’t give you the exact way to find it

No matter what you use, it relies on EVERY part in your assembly having an appropriate material or weight assigned. If (for example) the motors you imported don’t have any mass properties, you won’t get an accurate CoM

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Inventor can also do this. Under the “View” tab is a button for center of gravity.

like snichols said though, if your cad isn’t on point with material and mass properties, it won’t help you much. I’d say you would be much better off finding the COG empirically once its out of cad and in the real world.

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Yes, the method I described works with robots that were designed with CAD, or those that were designed with other methods. No difference.

note that it only works with robots that actually exist.

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Thanks all of you I am not a cad expert and it was something I want to be done.

Brand new Cims and great handiwork with the assembly of the drive train

Did you burn the CIMs in?

Can you explain this further maybe some picture or drawing to help explain. I’m kinda confused I’m sure it is hard to explain.

Burn the CIM’s? I’m assuming not.

Brushed motors should be run under no load for 10-20 minutes to allow their brushes to wear in without undue current draw. Without burning in the motors the brushes can get damaged if too much current is applied too quickly.

If you have a relatively up-to-date CAD of your robot, I would recommend using whatever CAD software you use to find the center of mass.

It requires a little discipline on the front end… But as you CAD the robot, assign material proprieties as you design the components. For imported assemblies like motors: Take the published weight and play with the density until it has the correct weight. That will locate the center of gravity for the part close enough most of the time. Use the help of your CAD package to show the CG & weight of the robot model. You will probably need to add a fudge factor for unaccounted parts like wires, but it will get you surprisingly close.

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How has no one asked the most basic question here first?!?!

HOW DID YOU LOSE YOUR ROBOT’S CENTER OF MASS IN THE FIRST PLACE? I DIDN’T EVEN KNOW THAT WAS POSSIBLE!!!

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Grumble inducing joke

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