# Calculating the efficiency of Mecanum wheels

I'm part of a FIRST Robotics team, and we're looking into using Mecanum wheels for our robot.

What are the advantages and disadvantages of using Mecanum wheel versus regular ones? From looking through Google, it looks like Mecanum wheels give more mobility but don't have as much traction. Are there any other advantages or disadvantages?

Compared to regular wheels, are Mecanum wheels less efficient or more efficient in any way? And if so, is there a quantifiable way to determine by how much?

Are there equations I can use to calculate efficiency (or inefficiency) and/or speed of moving forwards, sideways, or at arbitrary angles?

A picture of a robot with mecanum wheels:

• Fantastic first question @Michael0x2a, I've always been fascinated by these wheels and I'd love to know more about how well they work in practice. Oct 24 '12 at 1:24

## 3 Answers

Efficiency isn't the right thing to compare due to various advantages and disadvantages of each type of wheel. Comparing the efficiency of the different types of wheels is like comparing apples and oranges.

However, comparing speed and force can give a good comparison of the different types of wheels. Here is a table that offers a quick and simple comparison (Note that this assumes fictionless bearings and equal traction!):

Trying to take into account slipage gets hairy. From the paper "Kinematic Analysis of Four-Wheel Mecanum Vehicle" which is at the top of this list of papers:

This problem, in general, has no solution, since it represents an overdetermined system of simultaneous linear equations. The physical meaning of this is: if four arbitrary rotational velocities are chosen for the four wheels, there is in general no vehicle motion which does not involve some wheel "scrubbing" (slipping) on the floor. However, a matrix [F] which generates a "best fit" least squares solution can be found

• I had to look up Omni wheels but otherwise a great answer. This image is in the public domain, if you want to use it to illustrate the difference between mecanum and omni wheels. Nov 6 '12 at 21:51

I have some experience with using mecanum wheels, both indoors and outdoors (on grass, sand and dirt no less).

Obvious advantage is holonomic movement. Disadvantages are weight (commercially available wheels are ridiculously heavy) and cost. For a given tread material traction will be along the lines of 65-70% that of a regular wheel due to the smaller contact area and 45% rollers.

Compared to skid steer, mecanum wheels have no additional friction when turning which is an advantage.

Mecanum wheels will be simpler and perhaps more reliable than a swerve/crab drive system.

Everything is always about tradeoffs. If I compared an ideal mecanum system to an ideal swerve drive system (full 360 degree rotation, extremely fast wheel orientation) the swerve wins in performance because it has full traction.

An ideal swerve system will be expensive and difficult to implement compared to mecanum wheels though.

Efficiency is a loaded question. An ideal mecannum wheel will be equivalent to any other system when moving in any direction, and will turn better than a skid steer system. In reality the rollers have reasonable friction so going sideways will be less efficient than going forwards.

Getting exact numbers would require a lot of fairly accurate measurements which isn't practical.

• If you’re looking into a swerve drive, you may want to research a “synchronous drive” Aug 19 '18 at 16:30

You might want to check out FRC 1114 Simbotics' website, especially http://www.simbotics.org/resources/mobility . The FTC team I coach has used that as a starting point for their own work.

• Welcome to Robotics. Thanks for your answer but we are looking for comprehensive answers that provide some explanation and context. Very short answers cannot do this, so please edit your answer to explain why it is right. Additionally, we prefer answers to be self contained where possible. Links tend to rot so answers which rely on a link can be rendered useless if the linked to content disappears. If you add more context from the link, it is more likely that people will find your answer useful. Aug 13 '18 at 21:50