Horizontal Bar: Vertical Velocity
 

Does anyone know how we are supposed to measure the "vertical velocity" of the rope that was used in the kick-off demonstration for the "robot" to hang from the horizontal bar? What happens if it exceeds 10 ft/sec due to discrepancies in the measurement method used by the team and the judges?

Re: Horizontal Bar: Vertical Velocity
 

I belive what Woody and Dean said is that taking Gravity in to account, The (hook, teather, grabber,rope) can not move more than a foot and a half straight up with out exceding 10 ft/s. Therefore You must design a (hook, teather, grabber,rope) that does not have to travel more that a foot and a half to get over the bar. If this is wrong please correct me, as this is what I got out of the given explanitation.

-Aaron

Re: Horizontal Bar: Vertical Velocity
 

i believe that the distance it travels going up doesn't matter, its how far down it goes...because it's when the device comes down that it would be hitting something.

at least that's what i think...

hmmm...
:D

Re: Horizontal Bar: Vertical Velocity
 

I think they don't want kids getting skewered in the pits, or breaking other people's robots ingame.

Re: Horizontal Bar: Vertical Velocity
 

Use the energy equations

mgh = 1/2 (mv^2)
gh=(v^2)/2
h=v^2/2g
h=100/64.4
h=1.55 ft

if the object goes up over 1.55 feet it is travelingmore than 10 ft/s

(I hope this is right... It's been a long time :) )

Re: Horizontal Bar: Vertical Velocity
 

I can see this being correct... I believe that for safety sake this rule was made... and knowing FIRST they will enforce this very heavily. (Since Dean and the gang put so much emphisis on it in the kickoff)

-Greg The Great

P.S. Scroll Throught the comp docs on usfirst.org they will probabally demonstrate what can and can't be done.... although I am sure you will see many clarifications to this rule in updates... (I would guess in the first 3)

Re: Horizontal Bar: Vertical Velocity
 

1.55 Ft Instead of 1.50 ft, </Mr Burns Voice> Excellent </Mr.Burns Voice> That extra half a foot could be useful.

Re: Horizontal Bar: Vertical Velocity
 

This is interesting, because this maximum velocity is relative to the robot. They did not think this through, because technically, whatever is being sent over the bar is part of the robot. This means that relative to itself, it isn't moving. They need to mention something about this, because I believe that they mean that the mechanisms cannot exceed 10 f/s. Or if it is in reference to the base of the robot, will someone make a jumping robot so the mechanism relative to the robot is not traveling more than 10 f/s, but is traveling faster relative to the field?

And 10.55 f/s is not an extra half a foot more than 10.5 f/s. 0.05 feet is approximately half an inch.

Re: Horizontal Bar: Vertical Velocity
 

I believe it is an extra 1/20th of a foot.... or maybe I am just blinded by my excitement.

-Greg The Great

Re: Horizontal Bar: Vertical Velocity
 

Thats not a half a foot, thats 1/20 of a foot! (~half an inch)

Re: Horizontal Bar: Vertical Velocity
 

Oops, my Bad, I didn't even think when I wrote that, I was just excited.

Re: Horizontal Bar: Vertical Velocity
 

And The Controversy Begins....

I understand how everyone is trying to figure this out.... since the bar appears to be one of the major aspects of the game... remember this is the first day.... let FIRST figure out the exact rules... don't go crazy trying to figure out the ruling of this... I know all to easy how going crazy over a early misunderstood/non-defined rule goes. (Human Player 2K3)

-Greg The Great

Re: Horizontal Bar: Vertical Velocity
 

As far as the velocity being relative to the robot. I would take it to mean the base of the robot (intention of the rule). Or you would probably consider the "robot" the CM or the Robot Controller, one of the two, in either case, they probably won't be flying upwards very fast. Also in the rules, it states that for inspection you need to be able to prove that it doenst' exceed 10ft/s. The way they suggest that you do this is to video it with a known frame rate and a marked background. Ref. 5.4 <R82>

Vmax...
 

My interpretation is that Vmax rule was intended to be a safety measure -- especially from with regard to tethered projectiles shot at the bar by springs (think grapling hooks & crossbows ;-) and with regard to largish longish arms hitting the bar after a long wind up (think executioners axe ;-)

Given this, I really think that it is the veritical component of the "exit velocity" of anything shot at the bar and the vertical component of any windmill arm swinging at the bar.

That is how I'd call it anyway.

Joe J.

Re: Vmax...
 

I agree and would extend this to the "jumping robot" scenario... 1.5 ft maximum jump.

Re: Horizontal Bar: Vertical Velocity
 

sorry i couldn't resist

V^2=Vo^2+2aX

btw all numbers in metric. metric system rules!

where
V= final velocity
Vo=initial velocity
a=acceleration
X=Delta X (change in position)

V^2=0+2aX
Vo=0 m/s because the projectile starts at rest

V^2=2*9.8*X
a=9.8 m/s^2 acceleration of gravity

3.048^2=2*9.8*X
V=3.048 m/s = 10ft/sec metric rules! remember!

solve for X
X= 0.473995102 meters
X= 1.555102 feet

Remember METRIC RULES!
Good luck this year!

-Andy

Re: Horizontal Bar: Vertical Velocity
 

Technically, thou sayest? What dost thou mean with this "technically"? Really, I seemed to get a slight perception that FIRST wanted us to exercise common sense (something in there was vaguely about safety I think), and there was some statement degrading lawyers (alas! my future profession). Really, though, Dean explicitly said not to over-interpret the rules -- he said that he uses words to "mean what they mean" (stradling is stradling, for crying out loud). I for one like the idea of a minimalist rules book. I mean, 3 rules for scoring! 3! I could barely believe it.

I feel your pain. I as well cannot resist (my physics teacher must have done something right ... or would that be wrong :))

Anyway, let's see some accuracy. Why assume that U=mgy is "good enough" afterall! So,

dU = GMm/r - GMm/(r+y) = 1/2 mv^2

(dU means delta U, G is gravitation const., M is mass of earth, r is radius of earth, ..)

Upon solving, y = 5.10! Considerably less than 5.55. I used the values,
G = 6.67 * 10^-11
M = 5.98 * 10^+24
r = 6.38 * 10^6

(something I'm not remembering right from all the physics lectures I slept through?)

Re: Horizontal Bar: Vertical Velocity
 

Of course, you are all assuming that the object, let's call it "projectile," is decellerating at the gravitational constant! If you were to give it the initial velocity of 10 ft/s, as well as give it an acceleration in midair somehow (get to that pneumatics drawing board), you would be able to send it wherever you wanted to! Particularly if you were to give it an acceleration of, oh say 9.81 m/s/s.

Re: Horizontal Bar: Vertical Velocity
 

Yes, I found this suggestion about a camcorder too. Still, it does not explain what the velocity is relative to. In the test with the camera the bot would be standing still, and in the game it might be moving. As well, testing would be needed to see how far you can actually throw something with that velocity :) It may sound like a lot but there is really no way to tell...

Well, anyway, Dean did talk about generalizations in the rules and how we should not read them the way lawyers do :D So Im guessing my team will just figure it out eventually :)

Re: Horizontal Bar: Vertical Velocity
 

Rule <G08> states: Mechanisms which interact with the Pull-Up Bar are limited to a maximum tip velocity (relative to the ROBOT) of 10 feet per second.

Two questions:
1) Does tip mean the tip of a projectile or does tip mean tipping as in falling velocity?
2) If it is the latter, wouldn't that eliminate the possibility for all bar interaction? Your robot has to extend to 9' to get to the top of the bar and if you are tipped, the top part of your robot is certainly coming down at a velocity greater than 10 ft/s.

I'm really trying to simply interpret the rules, but tip is a bad word to use.

Kev

Re: Horizontal Bar: Vertical Velocity
 

They mean the tip as in the farthest part of your climbing device. It cannot extend or retract any faster than 10 ft/sec.

Re: Horizontal Bar: Vertical Velocity
 

And one more question. I think in the video it was said that the "maximum vertical velocity cannot be greater than 10ft/sec". If so, what if the robot launches the projectile at an angle, and not straight up? Is only the vertical component counted? The suggested way of measuring velocity (with the camcorder) would probably do just that.

Re: Horizontal Bar: Vertical Velocity
 

I'm still not real clear on this, you can move upward at 10 feet per second, which roughly translates to 1.5 ft/sec. I have two questions on this.

-First, if you extend an arm, this is not influanced tremendously by gravity (unless i'm mistaken), so that should rise closer to 10ft/sec.
-Second everyone is mentioning it going 1.5 feet, on the same arm theory, you could move this for more than one second correct.

Just trying to get a little clarification.

Re: Horizontal Bar: Vertical Velocity
 

It still can not excede 1.5 ft verticaly. Gravity is accerating all objects downward at a constant 9.8m/s^2. (mixed units work, right?) So anything only given the maximum velocity at the begining of the movement, like a ninja grapling hook, would only be able to travel 1.5 ft verticaly, no matter the angle.

Arms that swing up need to calculate the tip velocity and the end of the arm, and limit it to less the 10ft/s. Arms that move verticaly should take more then 1 second from the carpet to the bar, there abouts when moving from a starting height of 2-4 feet.


Wetzel
~~~~~~~~~~
These equations are easy and you should learn them all in physics.
I've never taken physics. :(
Acutally, I'm going right now to see what physics classes are still open and maybe add it this semestor.

Re: Horizontal Bar: Vertical Velocity
 

The Vertical Velocity Limit is implemented so that teams do not design a robot that may attempt to launch a teathered artillery grappling hook to the bar from a long distance off the field. Although it would be nicely done by triangulating your distance using the IR sensors, and making a program that automatically adjusts angle and power to the artillery cannon on your robot. So if for some reason you missed, it was the programmers fault. Just kidding.

...and it would not be a good idea if the robot went insane during the match, and aimed the cannon to the audience...

But really, it is just for the safety of the drivers/human player, the refs/judges, and more importantly, the audience.

Re: Horizontal Bar: Vertical Velocity
 

i dont think they would allow us to jump ONLY 1.5 feet if the bar is about 10 feet high and there is a restriction on the hight (60 inch) as usual..
what i suppose they mean -with regards to relative velocity is that we should use our robot base as the reference point though this would only affect the horizontal and not the vertical velocity of whatever it i being shot up(unless the robot is jumping up and down... :confused: )
i think we're going to try and go about it with a spring.. use the energy conservation concept to make sure that the release velocity is not going to be over 10 ft/s which is quite reasonable since its about 2.5-3.0 m/s
and we have to account basicaly only gravity and the tension created by the wire or cable(that will be used to pull it up) to analyze the 2 dimenional projectile motion of the hook/grabber

"simple, but not ordinary" Mr Keeting - "Dead Poets Society"

Re: Horizontal Bar: Vertical Velocity
 

The restriction on hieght only applies to the start of the match. So if your robot could double in height during the match, it could grab the bar without having to use a grapling hook.

Keep in mind the vMax only applies to a grapling hook or arm. If your entire robot were to jump then you could jump any height you wanted.

Re: Horizontal Bar: Vertical Velocity
 

I'm thinking we'll need to wait for clarification from FIRST on this one. If it's really just maximum vertical velocity (as they mentioned in the video), I could lift a cannon 10 feet and shoot a projectile at the bar for zero vertical velocity. If it's tip velocity (as in the safety concern they discussed), then the maximum distance you can shoot it up is 1.55 feet times the sin of the angle at release (straight vertical being 90 degrees and the farthest distance).

Re: Horizontal Bar: Vertical Velocity
 

Nick,

I would imagine that this would (and should) be disqualified. The spring may be dangerous (in the view of the inspectors) if it goes off in your face...

I do not think that they want projectiles. Period.

However, they are allowing a "small" projectile that would not cause great concern to spectators, players or referees...

As a member of a team who, in 1994, made a catapult capable of launching a 7 pound ball 30-40 feet, I can testify to the incredible power which could be stored and then released by these robots.

That particular robot was a crowd pleaser but it scared the heck out of me (and the officials). The spring mechanism was made from the 10 feet of latex tubing in the kit and the bands broke under tension (a lot). Not to mention that sometimes the match would end before we fired (but the mechanism was armed) and the field team had to remove the robot and hope that it did not go off in their face.

Any engineer who can't design a "safe" thin arm to deliver a cable (attached to a winch) to the bar needs to go back to school.

Let's all stop being lawyers... When we design these systems ask " would I want my Mom (or daughter) standing next to this thing when it goes off?".

[/end soapbox]

Re: Horizontal Bar: Vertical Velocity
 

FIRST dosn't need be concerned with what an engineer can or can not design safely, but what students can safely design. Teams have alot of different ways of design, from engineers and students working side by side, engineers watching and pointing things out, to no engineer support, to totaly engineer designed.

Nice play on the GP saying.

Wetzel

Re: Horizontal Bar: Vertical Velocity
 

I see this whole thing on, how are they really going to know if somethings going too fast if the object isn't going 20 ft (sarcastically) way up in the air and hitting someone in the head. I think the judges will be very lenient on this role and cut alot of slack within safety reasoning.

Re: Horizontal Bar: Vertical Velocity
 

Just curious, I know that the vmax=10ft/sec, but does that apply to non-projectiles aswell? for intance, if we were to use a tube-in-tube to raise a hook up to grapple the bar, but the hook was (on the first trip) attached to the hard tubing, which was in turn attached to the roboti, would it be considered a projectile? if so, we were be running it with a motor and therefore still running at a constant 10ft/sec, so it would need to take 1 sec to get up there. if not, could we raise it as fast as possible?

Re: Horizontal Bar: Vertical Velocity
 

I don't think that would be considered a projectile by any means but that's just me.

Re: Horizontal Bar: Vertical Velocity
 

The rule states that all mechanisms must not exceed 10 f/s. That would include any telscoping arms, projectiles, or anything else.

Re: Horizontal Bar: Vertical Velocity
 

Er... I am currently taking AP Physics so I am not very experienced with it. But it seems to me that you are saying: Potential Energy = Kinetic Energy... Well, when the robot is hanging it's got PE, but no KE... I think it was lucky that when solving for 'h', you came out with v^2/2g

I used Andy's method of applying the equation "V^2=Vo^2+2aX" and derived the same formula.. Hmmmmm.

Re: Horizontal Bar: Vertical Velocity
 

to :Mike Betts
from: Team #0177 (Bobcat Robotics)

You do have a fair point about it being dangerous and all but than in the simulations they did 'live' from new hamhire or whereever it was; the person that hung on to the bar actualy threw the strap he than secured toh is little bike and hung on the bar by it.... and i think that was woody that said "I think mike there didnt go over 10 ft/s when he threw it" so i'm pretty sure its going to be alowed one way or another, we just have to watch fo more safety rules and stuff like that to observe when we're building it

Re: Horizontal Bar: Vertical Velocity
 

Mike's equation comes from the fact that energy must be conserved. If you take your origin to be the height at which the projectile is launched, then the projectile at the beginning would have no potential energy but would have kinetic energy. At the peak, it wouldn't be moving and so wouldn't have kinetic energy but would have potential energy. Since energy must be conserved, those are equal.

Remember, in physics, there are often many ways to find the same answer. Your way is right also, but harder (to me).

Re: Horizontal Bar: Vertical Velocity
 

He is saying that potiential energy equals kenetic energy!
Conservation of energy vs. kinematics.
This are just two different ways to solve the same problem.
We are both correct except I am more right because I used the metric system.

Just kidding, seriously though, the metric system is so much easier to use then the imperial system. There is nothing easier then multiplying/dividing powers of ten then fractions (shudder).

Useless info:
-Americans are better at fractions then Europeans because Americans have to be fluent with fractions because of their/our measurement system. Interesting
-Our robot will probably be in inches because of the availability of metric vs. imperial fasteners, drive componants, extruded aluminum, 80/20 etc.

Good luck this year!
-Andy

Re: Horizontal Bar: Vertical Velocity
 

I hope so. I was nearly impaled in the pits at Nats by a robot with an arm that extended at atleast 10fl/sec. It can be even more dangerous than a projectile, sin

Re: Horizontal Bar: Vertical Velocity
 

I agree... when everything else is base 10, the american system is just confusing. I came out with 15.5 feet the first time I calculated it due to conversion errors. Lol. Since FIRST promotes culture change, why not change the FIRST standard system of measurement to metric?? It wouldn't hurt the Canadian, British, or Brazilian teams at all :)

Re: Horizontal Bar: Vertical Velocity
 

i think this is wrong...

first convert feet/sec to meters/sec then do the equations then convert back, you get about 15 feet high if i'm right.

you have to do this because v is squared (if i'm right)

but i'm probably wrong.

Re: Horizontal Bar: Vertical Velocity
 

No, the equation is right.

Vmax = 10ft/s
g = 9.8m/s^2 = 32.15ft/s^2

You get 1.55 ft (100/63.3)

Re: Horizontal Bar: Vertical Velocity
 

oh, right, that was dumb, i didn't notice that it'd been corrected originally