Building a Two Omni Wheel Robot: Questions & Answers

AI Thread Summary
The discussion centers on building a robot with two omni-wheels and addresses questions about its movement capabilities. Participants clarify that a robot with only two omni-wheels cannot effectively control movement in both x- and y-directions due to insufficient directional control. It is noted that at least three omni or mecanum wheels are necessary for full movement and orientation control. The original poster confirms the need for four omni wheels for their project, seeking assurance about the robot's powered movement. The conversation emphasizes the importance of wheel configuration in achieving desired mobility.
harpoon
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Hello! I have a somewhat complicated robot project that I've simplified here to hopefully get a quick answer. I want to build a robot with two omni-wheels that looks like the following (not drawn to scale), where the black is the omni wheels at 45 degree angles and the blue is the robot body:

1622041569917.png


A couple of questions, assuming the robot (let's call it the first robot) can balance and the body doesn't touch the ground:
1. Can the robot still move in the y- and the x-direction?
2. Assuming the floor is rough and the omni wheel rollers are rubber, will the robot slide if I push the robot body in the y-direction?

Now, for this robot (let's call it the second robot, also not drawn to scale), the arrangement of the omni wheels looks like this:
1622041817707.png


I have the same questions:
1. Can the robot still move in the y- and the x-direction?
2. Assuming the floor is rough and the omni wheel rollers are rubber, will the robot slide if I push the robot body in the y-direction?

In my mind, the robot can still move in the x- and y-directions and won't slide when I push it in the y-direction, but I wasn't 100% sure and wanted to confirm my intuition here. Thank you in advance! Please let me know if I need to clarify anything, and I apologize if this post is confusing.
 
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Welcome to PF.

If the robot has only two wheels, like a Segway, then I don't think it can use Omni Wheels since it has one degree too much directional freedom.

With the motors stopped, it could be pushed to move in a circle about a centre of rotation.
 
Ah, good point, didn't think about that. Thanks! What about something like this?

First robot:
1622043539438.png


Second robot:
1622043571629.png

Same questions:
1. Can the robot still move in the y- and the x-direction?
2. Assuming the floor is rough and the omni wheel rollers are rubber, will the robot slide if I push the robot body in the y-direction?
 
harpoon said:
1. Can the robot still move in the y- and the x-direction?
Do you mean when pushed or when powered?

The Omni wheel has rollers at 90° to the axle, while
the Mecanum wheel has rollers at 45° to the axle.
https://en.wikipedia.org/wiki/Omni_wheel
https://en.wikipedia.org/wiki/Mecanum_wheel

It takes a minimum of three Omni/Mecanum wheels to control directional movement and orientation.

If you want to make an Omni Segway hybrid, your new type 1 could do it.
If you want a stable platform then your new type 2 could do that.
But you should first consider the 3 wheel solutions;
https://en.wikipedia.org/wiki/Kiwi_drive
https://en.wikipedia.org/wiki/Killough_platform
 
Baluncore said:
Do you mean when pushed or when powered?
Oops, I guess I should have clarified! I meant when powered. Good to know that it works. The nature of my project requires that I use four omni wheels.

Thank you so much for the help!
 
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