Another physics thing. *sigh*

[kid908]

So I want to know how much work a motor need to do to cause a soccer ball to go a specific distance for robotics. I came up with an equation that I'm not sure is true or false. If you've taken Calculus based Physics, mind checking my equations.



F(rf)= Force of rolling friction
C(rr)= Coefficient of rolling friction (no dimension)
K(r)= Rotational kinetic energy
m= mass
r = radius
w (really is omega, but can't find sign)= angular velocity
d= distance ball travel
v= velocity of ball
I= moment of inertial of sphere
N(f)= natural force equaling to omega on flat surface
W=work
W(f)=work done by motor
W(frf)=work rolling friction

Soccer ball info:
m=.4536kg
r=.11319m

F(rf)=C(rr)*N(f)
N(f)=w
K(r)=1/2*Iw^2
3k/mr^2=w^2
w=sqrt(3K(r)/m)/r
F(rf)=C(rr)*sqrt(3*K(r) /m)/r

W=K(r)
W=1/2*Iw^2
w=r*v/(abs(r))^2
W=((.4536kg(.11319m)^2)/3)((.11319m*v)/(abs(.11319m)^2))^2
W=v^2(.1512kg)

F(rf)=C(rr)*sqrt(3*K(r) /m)/r
F(rf)=C(rr)*sqrt(3*(v^2(.1512kg))/.4536kg)/.11319m
F(rf)=C(rr)*sqrt(1*v^2)/.11319m
F(rf)=C(rr)*v/.11319m

W(f)>W(frf)
W(f)>C(rr)*v/.11319m*d
Work of the motor is equal to or greater than the coefficient of rolling friction times the velocity of the ball divided by .11319m (radius of the ball) times the direction and distance the ball travels (it should be dot d, but times works just fine for this purpose).

Any math and physics wiz can help me out, +rep. we're designing a robot to play a soccer (football for none American) like game for the FIRST Robotic Competition.

[Donut]

i cant really help you with the physics stuff but what FIRST competition are you in? the team im on is doing the hot shot challenge where you have to make the robot throw whiffle balls. your project sounds alot more complicated though
E: now that im looking, the typed out equation is kind of difficult to follow. for me at least... could you write it on a piece of paper and scan it? i have some basic physics knowledge that i might be able to help you with, but at this point i just cant tell what youre trying to do there

[kid908]

i cant really help you with the physics stuff but what FIRST competition are you in? the team im on is doing the hot shot challenge where you have to make the robot throw whiffle balls. your project sounds alot more complicated though

I believe that's the same one we're in. IDK why but my teach want such an equation, but I guess we don't want to over shoot or undershoot the goal.

http://www.usfirst.org/roboticsprograms/frc/content.aspx?id=454

My first year. Maybe you could give a few pointers:-3. We're registered for the Lone Star Regional in Houston, Tx.

[Donut]

Well this is my second year, so im not much better off than you. basically make sure your shit works before you go in for the competition. in rhode island we had 40 teams compete. only 3 of the teams had autonomous code (30 second period where robot runs itself) that did ANYTHING, and only one team (they won 1st) had autonomous code that actually did something productive. one team had a robot that literally fell apart minutes before the match, so their "robot" was a wheel with a flag sticking out of it.

if youre the programmer, make sure your team has their shit together so your not stuck trying to make everything work in the last few days before the competition. i popped 3 all nighters the week before the competition doing research and trying to make the autonomous code work while going to school every day in between. it was awful.

im not sure what competition youre in (im doing the FTC hot shot challenge), but it sounds like the robot is going to operate itself rather than be controlled by user interface with a controller. its good to have a couple of different routines programmed for the robot, like one for defense and one for offense, etc...

E: and this might sound obvious, but practice. any down time your team has, make them run the robot and practice controlling it, if it gets controlled. some of the teams i saw compete appeared to have little to no experience driving their robots

im dont know the details of your competition so this might not apply, but last year our challenge was to deliver hockey pucks from racks on the walls of the field into the center goal. our robot kicked ass at scoring the pucks in the goal and getting them out of the rack, but if they fell out of the rack onto the ground we couldnt do anything. the team that won had a little system to pick up those pucks on the ground and drop them in their main puck holder so they could score them. they cleared and scored all 4 of their racks every round they played. its important for your robot to be able to do a little bit of everything so you can handle anything that comes at you.

spare parts. make sure you have spare motors and servos and whatever else you have on your robot incase something burns out suddenly. my team was in the championship round (not bragging or anything, just using this for drama build up, only like 5 of the 40 teams were even remotely a threat anyway lol) when our main puck scoring arm motor burned out and we didnt have a spare. one of the teams let us borrow one, but if it wasnt for them we would have had to forfeit. theyre a bitch to pay for, but spare parts are a must.

this is it for now, and this is painful to even have to mention this, but if your robot has a power switch on it, MOUNT IT ON THE INSIDE. we lost one of our rounds because one of the enemy robots brought their arm down on our robot, flipping the switch off. it sucked.