View Full Version : Calculating of traction/friction
01-17-2010, 09:45 PM
is there a formula that can calculate the amount of traction/friction your robot has with a set number of wheels
01-17-2010, 09:48 PM
The number of wheels (the amount of surface area you have on the field) does not effect the amount of friction that you will have. It's a physics thing.
Different types of wheels will have different coefficients of friction on the playing field, though.
01-17-2010, 11:06 PM
well the wheels have 1.3 coefficient of friction
01-17-2010, 11:20 PM
Force of Friction = Coefficient of Friction * Normal Force
Normal force = Mass * Acceleration due to gravity
If all of your wheels touching the ground have the same coefficient of friction the calculation can be performed once using the entire mass of your robot to find the normal force.
If some of your wheels have a different coefficient of friction the calculation becomes more difficult as the location of your center of gravity will determine how much normal force is applied by each wheel.
01-17-2010, 11:29 PM
each has 1.3
01-17-2010, 11:33 PM
I just posted it.
Find the normal force by taking the mass of your robot and multiplying by the acceleration due to gravity (F=mA). Then multiply this number by the coefficient of friction to find the force of friction.
You should be able to find the conversion between lbs (weight) and (kg) for Earth and the acceleration due to gravity on Earth in m/s fairly easily. Those are the only things you need to perform the calculation.
01-17-2010, 11:37 PM
The formula for force of friction is sum(mu*F_n), where mu is the coefficient of friction for each wheel (i hear 1.3 for the FIRST sticky wheels) and F_n is the normal force (weight) on each wheel. Surface area (i.e. number of wheels) does not come into play. If all your wheels are identical, mu=1.3, and your robot weighs 150 lbs, the force of friction is 195 lbs. This means you can accelerate at up to 195 pounds force / 150 pounds mass = 41 ft/sec^2 before your wheels start to slip.
01-20-2010, 05:59 PM
The coeficient of friction for the KOP wheels are located in section 10 of the game manual. 10.2.4.
10.2.4 The Drive Train
Wheels - The wheels supplied in the 2010 KOP are a combination of slick and sticky treads. The slick
tread material is Celcon M90, and has the following coefficients of friction on white, rippled fiberglass
Inline, static: 0.06
Inline, dynamic: 0.05
Transverse, static: 0.14
Transverse, dynamic: 0.10
01-20-2010, 07:35 PM
The numbers in the manual are bogus since we are playing on carpet instead of white, rippled fiberglass plastic sheet
Additionally, we have two different wheels in the kit and that is only a spec for one... which coincidentally is the exact data from last year.
From the AndyMark site I find that the sticky wheels (http://www.andymark.biz/am-0420.html) are listed at 1.0 and the slick wheels (http://www.andymark.biz/am-0494.html) at 0.2.
I'd go with those numbers. Expect this to be covered in a future update.
01-21-2010, 08:33 PM
thanks, i didn't see that.
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