# Omni vs mecanum wheels for drawing robot

I'm designing a mobile robot which will have to draw some lines (straight and/or curly) on the floor while it moves. The floor will always be flat with almost no obstacles. The robot will have four wheels and its speed won't exceed 0.8 m/s.

I would like to receive some suggestions about the wheels: is it better to use omni or Mecanum wheels in this case? I know that both wheels have advantages and disadvantages (i.e., Mecanum wheels require more torque when you move sideways), but which one is suitable for this project?

Should I use a X-shape with the omni wheels to improve the accuracy while drawing the lines, or would the Mecanum wheels in a tank configuration be more suitable?

• what does this mean? ... almost no obstacles Mar 13 '19 at 20:24
• I mean that it is possible to assume that there are no obstacles on the robot's path since they are very small and tiny and they do not affect the robot's behavior. Mar 13 '19 at 23:12

The Omni wheels are your best option. The math required for it is “symmetric”. The setup for each wheel will be the same.

You can achieve holonomic movement with mecanum wheels but as you said you will have to calculate the difference of power when you move sideways.

If your robot is circular, you won’t have to worry about front and back so much.

So, unless your robot carries a sensor that requires a specific configuration I will go with omniwheels.

• My robot requires a specific configuration, its frame will have a rectangular shape and it will have a front and a rear bumper. Should I use the macanum wheels? Mar 13 '19 at 14:55
• @MarcusBarnet how do you plan to make turns? Moving sideways or like a car? Why do you want to move sideways? If your circuit has shape corners you might want that. And it seems you robot does not have an holonomic shape. Think about how your robot will move and that will help you decide on the wheels for your robot. If you just want to turn you don’t need mecanum wheels, you can achieve that with normal wheels as well, but it is nice to know that you have the ability to move sideways.
– Luis
Mar 13 '19 at 20:59
• The robot will have to draw straight lines for several meters and, in general, he will need to draw rectangular or square figures (5x5 or 10x5 meters) so it will have to draw lots of right angles. For this reason, the robot will need to move sideways and I was thinking to use the mecanum wheels. Do you think it would be a good idea? Mar 13 '19 at 21:06