Quote:
Originally Posted by JVN
James,
Thanks for the link, but that is nothing new to me -- since I wrote it.
It is part of the pre-2012 version of the Autodesk VEX Robotics Curriculum. (New version just went up here, coincidentally).
Where did you find it linked?
Yes, locking the wheels, putting your robot on a ramp of carpet, and tilting the ramp is the test being described in this thread. That was the math I showed in my initial post.
-John |
I found this link using google as I was double checking my wording (after chatting with Ether these past few years I tend to double check my wording before I post). The funny thing is that I totally missed this line in your blog:
"Make sure the wheels are "locked" so the robot cannot roll."
So all of this time I thought it was drive train performance that this was trying to find, and why I've been asking about dynamic/kinetic friction... which by the way for the good of the group, I'd like to share the method you presented to me for this:
"
I believe kinetic and dynamic friction are the same thing.
I think that the method you outlined would work if you want to calculate the kinetic friction at any given wheel speed. I believe these values shouldn't change much based on speed. The simpler test to figure out kinetic friction is similar to the static test. You put the robot on a ramp, tilt it until it starts moving, then tilt it back until it stops moving. Take the tangent of the angle at the time it stops moving to find the kinetic CoF.
"
And funny thing... yep... I thought this too was to solve for drive train performance... as I interpret moving as rolling. Doh!
Part of the reason I missed that this test was about traction the first time around was because I was so focused on being able to simulate how fast a robot will move given time, gearing, motor(s) and, voltage. I think for me personally to avoid confusion I may wish to adopt the term Coefficient of Traction.
On a side note I made an interesting discovery today that I do not have an explanation for yet. It deals with some measuring results that "appear" that it took more voltage to slow down the robot (wheels were up on boards too) than to accelerate. I'm sure there is a simple explanation... I'll just need to study a bit more on kinetic energy.