Quote:
Originally Posted by JVN
I just published a post which highlights my method for calculating the coefficient of friction for robotic drivetrain systems.
See full post here.
So this brings up my next question...
Who actually bothers to do this?
Does anyone? Is it just me?
Does your team have their own method?
Does your team just trust the manufacturer's specs?
Do you even care, or do you just say "this is grippy as heck" and not bother?
Please share.
Originally posted here. |
John, I believe you MUST check as a full robot, and with varying weights on the wheels. The tread we use does not act as an ideal surface - it has sub-surface interaction and interlocks with the carpet pile. In addition, on a six wheel drive the center of gravity is rarely in the center. So how, exactly, are you riding on your wheels?
A number of people have created spreadsheets detailing 'can my robot turn'. I don't believe those tell you what you actually want to know. You've seen robots on the field that can turn. Then you've seen robots like 254 and 1114 that can
FLY. I think everyone knows the difference I'm talking about.
Something that I want to do later this year (during Beta Test) is to get our precision scales from the academy's physics class. Attach carpet to them, and put them on one of our marble measuring tables, then set the robot on them. I'd like to get the normal force each wheel exerts.
Between 1718's 3 nearly fully assembled robots, it should be possible to create a 'model' of drivetrain geometry and weight distribution that produces a robot that turns well rather than one that 'just turns'.
I've got 'turning' stuck in my head because we've fought with it on a couple robots and had to go back and change wheel types and treads to get acceptable performance. Frankly, I have never ONE seen one of our 4 wheel, 6 wheel, or 8 wheel drive robots lose traction, except when getting pushed completed sideways by a robot with treads and a low gear. I think how the friction affects robot turning is the more important application of the data you folks are talkign about. (Completely apart from the fact that I believe if you're in a pushing matches often, you're likely playing the game wrong).