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Victim of Fate 15-11-2003 21:26

Top Speed
 
I need to know the highest speed attained with a FIRST robot, perferably during competition or practice, not highest predictied speed, but highest speed perferably in meters per second...

this will really help me out in my transmission design, which, i will probably post later when my friend CADs it.

thx

xplod1236 15-11-2003 21:41

The top speed of 818's robot was about 10 mph, which is about 4.5 m/s.

Joe Johnson 15-11-2003 21:52

10-12 fps is pretty fast...
 
While it is definitely possible to make faster robots, I think that 10-12 feet per second is a pretty good top speed for a FIRST robot.

Remember that acceleration matters too when you are not in a 1/4 mile race but negotiating a field with other robots, balls, etc. around.

Also, being fast can be important, but if you are only fast, you are likely to have some trouble pushing, climbing ramps, etc.

Shifters can help with some of this but only to a point.

Good luck.

Joe J.

Cory 15-11-2003 21:59

in 2002 Kingman's bot went around 18 fps, and I believe that the second robot the Cheesy Poofs made this year went around 20 fps. Keep in mind that at these speeds your robot is likely not going to have enough torque to overcome friction and turn, unless you drop the center wheels 1/4" or so. Unless you are a very good driver, its also going to be very hard to control.

Cory

KenWittlief 15-11-2003 22:17

early on we created a 'speed trap' using the optical sensors and an oscilloscope (measured how long the bot frame interrupted the beam as it went past)

with the drill motors locked in the high speed position, our bot was going fast. I just checked my notebook and I cant find the exact speed, but Im sure it was over 20mph - maybe as high as 25mph

mind you, the load was so high the bot would not go from a standstill by its self. We had to give it a push to get it going.

This was really all an accident - it was the first time we had driven the bot, and just happened to have the drillmotors locked in high gear instead of low.

Obviously we didnt use it that way in competition - but to get back to your question

the only thing that would limit the top speed of the bot is wind resistance, friction on the wheels and drive train, and the fact that the field is only 60 feet long. If you have a multispeed transmission, and a long enough 'runway' - then you could get one of these things going pretty quick

just like a radio control car: :c)

now im not saying you could get a FIRST bot going fast enough to jump over your house - well, maybe you could. watch the linked video and you decide !

http://showcase.netins.net/web/isuguy/housejump.wmv

Solace 16-11-2003 11:09

571's 2003 copetition bot had a top speed of about 12-13 ft/sec.
that would be a little over 5 meters/sec. Using 2 drills and 2 chips, we had adequate acceleration, but turning could get difficult when the battery got low.

Ian W. 16-11-2003 15:40

Quote:

Originally posted by xplod1236
The top speed of 818's robot was about 10 mph, which is about 4.5 m/s.
That was our first robot, from 2002. I don't know if it was quite that fast, cause we had major friction problems. If we had overcome those completely, it would've been much faster.

I do know that at NYC, I "grabbed" a goal. The bot was across the field, and I had to get back, about ten seconds left. I also happened to be lined up with a goal, for the other team, that was empty. So, I go into full reverse, and slam into the goal and drive the goal into the player station.

After that match, we're inspecting our robot. I made a huge dent in the extruded aluminum, like, completely bent it out of shape. Several other teams saw it, and rumor spread that we grabbed goals by deforming our robot. Can't say it happened again.

That was also the regional that we snapped a piece of lexan off our robot, again, hitting a goal. To all the teams that say lexan can't shatter/crack/break, believe me, it can ;) (I remember Team 19 didn't believe us).

Wayne C. 16-11-2003 18:48

I can tell you that team 25's Evil Machine from this year hit 13.6 ft/sec. Only 102's (Gearhead's) machine was comparable at NJ.

Frankly, robots moving that fast are hard to handle (as many who have seen EM in action can attest). I have a puncture in my right leg just below my knee from Aignam's practice driving to prove it too!

edomus 16-11-2003 20:07

25 was definately the fastest bot I saw this year

Victim of Fate 16-11-2003 21:16

thx all, I think I have enough data to design my drive train now, if you guys still want to post say, to brag or continue posting information then by all means go ahead

KenWittlief 16-11-2003 21:43

NIck - you need to fix your sig. Your historical facts are a little skewed.

I believe Galileo was not inprisoned, I think he was placed under house arrest (confinded to his home).

and Im pretty sure Copernicus wasnt executed - he was reluctant to publish his ideas - and they were not taken very seriously until after his death.

another scientist, Giordano Bruno, was burned at the stake, for asserting space was infinite, and that other suns and solar systems, and earth like planets existed.

See: http://www.blupete.com/Literature/Bi...Copernicus.htm

Victim of Fate 16-11-2003 22:15

gee thx, I was pretty sure that Nicholas got put to death, but I dont want to start an argument about it, it was late at night when I made that one so please forgive any "historical errors" Thank god somebody found and corrected me before this little skew got out of hand.

That was all sarcasm, not my best, but it will have to do.

Next time, if you see a mistake as inconsequencial as that, just PM me so you dont get off topic in the forums, and besides, it makes me look bad to be the subject of public humiliation.
alright? Please show a little more tact when you "correct" someone offtopic.
thx.

PS. I still think he was executed

KenWittlief 16-11-2003 22:27

It wasnt inconsequencial to Copernicus :^)

didnt mean to put you on the spot publically - the internet is a vast storehouse of misinformation

now if someone read in your sig that Nicky got executed, and put it in a term paper or something, THAT would be humilating.

I make mistakes from time to time. I think Im up to 5 now :c)

BTW - one of the great things about forums like this is the stuff you learn and pickup - mostly OT stuff - kinda like a conversation where one topic or idea leads to another.

If we get 20 people off searching the web now to see what happened to those people, thats pretty cool.

PS: sorry for making you upset - wasnt intentional

Victim of Fate 17-11-2003 23:25

yea, I have to apologize on that last post as well, it was also late at night after a cruddy weekend when I did that one
(hmm... Im begining to see a trend)
so dont sweat it.

Now Ive got to find something interesting for a new sig...

Victim of Fate 17-11-2003 23:28

Yea...getting back on topic, this information is helping me correct for an extremly high ratio on the transmission that was giving me numbers like 93mph, Im going to gear it down again to bring its max speed closer to 25mph

thx all

Madison 17-11-2003 23:38

Quote:

Originally posted by Victim of Fate
Yea...getting back on topic, this information is helping me correct for an extremly high ratio on the transmission that was giving me numbers like 93mph, Im going to gear it down again to bring its max speed closer to 25mph

thx all

Are you sure that transmission will put out enough torque to make your robot...oh, I don't know...move? :)

RogerR 17-11-2003 23:43

Quote:

Originally posted by Victim of Fate
Yea...getting back on topic, this information is helping me correct for an extremly high ratio on the transmission that was giving me numbers like 93mph, Im going to gear it down again to bring its max speed closer to 25mph

thx all


don't you think that might be a little steep? 25's machine was almost 14 ft/s, and it was one of the fastest bots out there. 25 mph is about 36 ft/s by my calculations, so unless you're anticipating some really beefy motors, you're going to have trouble accelerating up to top speed.

Cory 18-11-2003 00:15

you wont have trouble accellerating, youll have trouble moving even if you could move, theres no way in heck youre going to be able to control a robot at those speeds.

Cory

Victim of Fate 18-11-2003 08:13

All of you bring up good points, and i do sound like a total idiot now that I look back, but I my of left out several important details...

Its a new kind of continuously variable transmission...

Well, thats top speed, and I dont want to sound all secretive, but its lowest speed is about as extremely low as its top speed is extremly fast.

team222badbrad 18-11-2003 12:06

Rc car
 
FYI

I have a gas powered RC car that goes 40 MPH and I doubt that it will reach a speed of over 25 MPH before it would hit the wall, starting at the other side of the field. It weighs 10 pounds and has a 1.6 horsepower engine


Bad Brad

KenWittlief 18-11-2003 12:26

A continiously variable transmission is a great idea.

The motors they give us can put out around a half a HP, if you keep them in the center of their RPM range. Look that the speed and torque VS current curves for the drill motors and the Chalupas.

problem is we start off at zero - the motors put out very little power at 0 RPMs.

I like this idea you have - I think it could be even better if you could find a way to keep the motors spinning at their optimal power output (midrange of their speed curve) and then vary the transmission ratio as commanded by the driver for speed. in other words, you would have a closed loop sensing the motor speed, and holding it constant through the Victors output, and the driver would vary the transmission ratio, not the motor speed. the performace (acceleration, pushing power, and top speed) of a setup like this would be phenomenal!

Im looking forward to seeing your published ideas on this.

Joe Johnson 18-11-2003 14:56

CVT's -- nice idea, but unproven benefits...
 
While I love the idea of continuously variable transmissions, in practice, I have never seen one that is robust enough, cheap enough and small enough to make sense on a FIRST robot.

I can get behind a shifting. I MAY even get behind shifting on the fly (though I am clearly on the fence about that cost/benefit ratio given the fact that you can make a fairly simple 2 speed shifter from the drill transmissions as long as you are willing to write a bit of shifting code and can live without shift on the fly). I could perhaps be convinced (though I doubt it) that a 3 speed transmission could be a net benefit.

BUT... I really question whether a CVT is going to buy you more than it costs (in terms of power savings, complexity of design, engineering effort, etc.)

But... ...it is a free competition... ...knock yourself out.

Joe J.

KenWittlief 18-11-2003 15:40

Quote:

While I love the idea of continuously variable transmissions, in practice, I have never seen one that is robust enough, cheap enough and small enough to make sense on a FIRST robot.
Translation: Nick - if you have an idea for designing a continiously variable transmission, and its something you invented yourself

then you should reconsider posting it on a website

You may have invented something extreemly valuable (that could be patented) in which case, if you post it on here, or disclose it anywhere before its patented, you just gave your idea away for FREE!

If you are using principles for a CVT that you got from someone else (another team, a website...) then go ahead and post your ideas.

Victim of Fate 18-11-2003 16:24

Sorry about the edit up there...

The transmission I am talking about is my own design, but it is a second generation concept based on a design myself and several other people sketched...

Both are unique but the both use the same concepts..

sorry again

Gope 18-11-2003 18:21

While the fastest I remember are 2002 Kingman - around 18fps and 2003 team 25 - around 14 fps.

However, one thing to remember is your driver isn't as good as he thinks. Team 25's driver last year was in my opinion about as good a driver as first has ever seen, and he was barely able to control their robot last year. So, unless your driver is a god then having a robot over 10-12 fps is almost useless. And for most drivers 8-10 fps is pushing it.

KenWittlief 18-11-2003 19:09

I agree - if your bot is really fast, then you dont want it driven open loop - you need a 'flight control algorythm' - feedback on the steering, limited braking...

WOOP WOOP WOOP! Altitude Altitude Altitude! :^)

Hey Nick - if you really think you have come up with a new invention or an idea for a system that can be patented, then this is what you should do.

1. Get a notebook that is bound like a book, like a composition notebook, and write you idea in there as best you can explain it - use drawings or whatever else to document your concept.

2. date and sign the pages, and have someone who would be able to understand the concept (a teacher, an engineering mentor, maybe a physics teacher) also sign and date the last page.

3. Start doing a patent search ( I think you can do this on your own on the internet for free) to see if someone else already has your idea patented.

4. if you dont find anything out there like your idea, then its time to talk to a patent attorney, and begin the patent application process - this will get expensive quickly and its not something you can do quickly.

remember - you dont have to actually build a working prototype to get a patent - as long as the idea is sound (you cant get a patent for gibberish).

PS - about your new signature... <= (just kidding :c)

Victim of Fate 18-11-2003 22:37

Thanks for the tips. Ive already drawn everything out and Im having a (trustworthy)friend CAD it out for me.

I happen to know afew patent attornys so they might be able to help me out.

The Lucas 02-12-2003 22:46

Re: Top Speed
 
I'll tell you what I tell everyone who attempts to build a really fast drive. Watch your current draw! When motors stall it will wreak havoc on the electrical system. The battery will max around 300-400 Amps and the voltage will drop horribly. I experienced this firsthand with 2002's MOEhawk which had direct driven bosch motors in high gear (probaly ran about 20 feet per sec but accelleratin was slow). So monitor the current in the protoype phase to save yourself a lot of hassle later (we had to regear during competition). You have a CVT so make sure you keep it geared down while accellerating or pushing. Most of the impedance that limits current is not the internal resistance of the motor but the emf generated by the spinning coils in the magnetic feild. You might want to use an encoder to determine wheel speed and then let the program decide gearing. Good luck.

Raul 03-12-2003 13:29

Re: Top Speed
 
The Wildstang robot has been designed to go about 7 ft/s top speed for the past 5 years. We have used 2 drill and 2 Fisher Price motors for the drive for the past 3 years. We have convinced ourselves that with the power of these motors, this is about the optimum gearing for speed versus torque if you do not have a shifter (we never have done a shifter – why would be the subject for another thread). Anyway, at this gear ratio, we can accelerate a 130lb robot pretty quickly. And when you have “crab” steering, this is about as fast as you want to go for control reasons. We use another technique to reduce the sensitivity of the controls for “fine motor skill” maneuvers – we cut the PWM output to the motors in half when the trigger on the joystick is not depressed, and set it to full PWM output when it is depressed.


I will say that if we decided to use more powerful motors (the Chips instead of the FP’s) then we could bump up our top speed accordingly. This is why 25’s Evil Machine, which used 6 motors for their drive, was effective at a higher top end speed. But yeah, at those speeds, the drive control sensitivity is very high and thus difficult to control the robot.

Raul

Victim of Fate 03-12-2003 21:27

Re: Top Speed
 
I should of made this clear earlier.

My mentors got sort of edgy about me talking about my transmission. Maybe at the end of the season ill be able to show everybody.

PM me if you want to talk more about it...away from prying eyes.

Madison 03-12-2003 22:03

Re: Top Speed
 
Hey, Brandon, can we give his mentors bad reputation via this post? ;)

Victim of Fate 03-12-2003 22:47

Re: Top Speed
 
Quote:

Originally Posted by M. Krass
Hey, Brandon, can we give his mentors bad reputation via this post? ;)

DONT DO THAT!!!

They have a good reason, something about those acurrsed copyright/patent laws...

Paul Copioli 05-12-2003 18:35

CVT ... I Disagree
 
This is the only subject to date that I somewhat disagree with Dr. Joe. Team 217 used the CCT in 2002 (see whitepapers) and, once it was working (I know we blew 2 regionals), was a definite advantage. I do agree, in part, with Joe on the cost aspects of the design and the initial risk, but the benefit is there along with the cool factor (I.E. Inspiration). I had never seen our students more excited than when the CCT went out on the field and worked. With the things we learned from the first year, I wouldn't be suprised if we used the CCT (refined, of coarse) again in 2004.

Having a CVT is not a "must have", but a "cool to have"

-Paul

Arefin Bari 11-12-2003 20:13

Re: Top Speed
 
how does... 11 ft. per sec... with 416 lbs of torque per inch ... (on high).... and 4 ft. per sec.. with 960 lbs of torque per inch (on low) sounds... would you like to call that a fast bot with good torque?

Victim of Fate 11-12-2003 21:53

Re: Top Speed
 
One of the best ways that i use to evaluate speed is just to go out to a big, open space with a tape measurer, and measure out how far it goes in 10 seconds...it just sort of puts it in perspective

Jay Lundy 11-12-2003 23:25

Re: Top Speed
 
We've been experimenting with a fast robot with an offset center wheel. We did it for the smaller turning radius (less resistance to turning), and we did it rather than the omniwheels because we were worried about being too easy to push sideways.

Anyway, it sure is fast, and with our transmission it can be fast and weak or slow and strong, but we have run in to one big problem: it is nearly impossible to control.

When we turn the robot, it only turns on the center wheels, and it flies at about 1 rev / s. That may sound good but it makes it impossible to control. Luckily they improved the controller this year, so we're working on a positioning system, most likely with the 300 deg / s gyro from Analog Devices (with increased range) and optical encoders on the wheels (at least, that's what I'd like to do).

If we can get it working, I'm hoping to create a control system where the driver pushes the joystick in a certain direction and the robot turns to that same orientation and drives forward with a speed proportional to the joystick's distance from center. We may also experiment with other ways of driving.

Basically, my point is: speed is good, but make sure you design something that can be controlled by a human.

Victim of Fate 12-12-2003 10:10

Re: Top Speed
 
Quote:

Originally Posted by Jay Lundy

When we turn the robot, it only turns on the center wheels, and it flies at about 1 rev / s. That may sound good but it makes it impossible to control. Luckily they improved the controller this year, so we're working on a positioning system, most likely with the 300 deg / s gyro from Analog Devices (with increased range) and optical encoders on the wheels (at least, that's what I'd like to do).

Hmm...does it only turn on the center wheel?
If it was able to steer using the other four, i would recommend that the center wheel be used for quick turns ie. push a button and you get an immidiate 90* turn left or right. But if you could get it so that it steers the way you describe, it should be pretty neat. I think that i know a trig equation that could help you out, but i dont know if it would work with the "C" language(im a pbasic kind of guy).

KenWittlief 12-12-2003 17:07

Re: Top Speed
 
I would try closing the steering loop with the yaw rate sensor that FIRST supplies - It may seem slow, but you very seldom need to spin your bot around quickly

and the fact that your bot can turn that quickly, means you have a lot of gain available, which will allow you to close the loop with the yaw rate sensor and have the response be very tight

this is one of those concepts that are hard to explain - to be very accurate and precise, you system needs to be powerful - more powerfull than necessary for the task you are trying to perform

then you can use a large amount of negative feedback, and the response will be quick to your commands - not that it will turn quickly, but that it will quickly do exactly what you are commanding it to do.

so if you move the stick slightly, and want the bot to turn very slowly, it will immediately begin to turn very slowly, and it will continue to move very slowly at the same precise speed, no matter what gets in its way (other bots, obsticals)

to put it another way, you must have great strength in order to be gentle.

Mike Schroeder 13-12-2003 23:17

Re: Top Speed
 
Quote:

Originally Posted by Raul
I will say that if we decided to use more powerful motors (the Chips instead of the FP’s) then we could bump up our top speed accordingly. This is why 25’s Evil Machine, which used 6 motors for their drive, was effective at a higher top end speed. But yeah, at those speeds, the drive control sensitivity is very high and thus difficult to control the robot.

Raul

Acctually Raul, team 25 only used 4 motors for our drive, like alot of other teams, we used the Drills in conjunction with CIMs, it was our gearbox that gave us the higher speeds..... who knows what could happen next year


Sachiel7 14-12-2003 00:07

Re: Top Speed
 
Hmm. We just stick with what we know. We didn't have very good tools at our disposal...
Anyway, Last year we used the 2 Cims at an 18:1 ratio on a chain system with tank style drive and it worked great. We had a final top speed of about 8.5 - 9fps and I can't remember the torque exactly, but we had no problems pushing bots around. In fact during one of our final matches, we spent the whole time taking 435 (RoboDogs) virtually out of the match by pushing them around. It was cool.
I think the CIMs 18:1 at 40A is a good balance between speed and torque for a stable system. Throw in the strength of chain drive and a good chassis, and you've got a pretty good drive.
We've redesigned the drive a bit and plan to use the modified design this season. (So scouts, you already know what to expect for our upcoming drive :yikes: !)

Matt Adams 14-12-2003 02:30

Re: Top Speed
 
Quote:

Originally Posted by Sachiel7
I think the CIMs 18:1 at 40A is a good balance between speed and torque for a stable system. Throw in the strength of chain drive and a good chassis, and you've got a pretty good drive.

Just a heads up for future posting for everyone (not picking on ya Sachiel):

ALWAYS POST WHEEL DIAMETER! 18:1 with a 4" diameter wheel is totally different than with 8" diameter. (Even a one inch difference can be up to a 25% different gear ratio!)

And with all due respect to Sachiel, I'll disagree and refer to my previous thoughts that you can't be both competitively* quick and strong with only one pair of motors and a single speed transmission. Though it might be a good balance, max pushing force or max speed must have compromised in that design.

Matt


* I definite competitive as a max speed greater than 10 feet per second, and having a maximum applied force of 150 lbs.

KenWittlief 14-12-2003 13:02

Re: Top Speed
 
well actually you can be effective if you are quick, and dont have a low gear ratio

if you work out the physics, when you get your bot moving fast and ram another bot, you apply far more force and energy than you could by trying to push them, no matter how much you gear down or how much traction you have

need a simple example? take a common nail and try to push it into a 2x4 with a hammer - push on it as hard as you want

the lift the hammer a few inches and tap the hammer on the head of the nail -it doenst take much energy at all cause you are storing up kinetic enegy as the hammer speeds up, and releasing it ALL on the impact.

Sachiel7 14-12-2003 14:01

Re: Top Speed
 
Sorry about that. We used 8" wheels.
We didn't really use impact force for our pushing. We pushed bots from a low impact speed. I'm sure it helped, but it wasn't our "source of force".

In my defense,
My big thing is you have bots out there with 2 speed transmissions that shift from 5 fps to 35fps. In what sense do you need all that speed? Even if it was 10fps, you're planning on clearing the field in less than 6 seconds? I do understand the need for speed, but I think there is a line somewhere in there.
If you can find a good balance between torque and speed then I usually stick with it. We didn't sacrifice much torue in that design, I'm trying to dig up our spec sheet to put some numbers up. But we had just enough speed and torque we needed to get the job done. Isn't that the key?
I can understand teams who think having a torque and speed shifting transmission would be good. It can be, but why slam the drive with more torque needed than the task requires? Why give it so much speed when it doesn't need it?
I like youre definition of a competitive drive train. I pretty much agree with it. Although, depending upon which region you're coming from, things might be different. In our region (VA) most bots top speed was 7fps or less. They were also running off of drills or lesser equivalent. So, we topped them with our speed without shifting, and their torque, apparently.
Our key is just to maintain the KISS principle; if we have a drive that has the speed and torque we require for our tasks, why take it over the edge?
Also, remember, we wouldn't be able to construct a shifting transmission if we wanted to anyway, as our resources have been very low.

IrisLab 16-12-2003 22:10

Re: Top Speed
 
Quote:

Originally Posted by KenWittlief
another scientist, Giordano Bruno, was burned at the stake, for asserting space was infinite, and that other suns and solar systems, and earth like planets existed.

Some folks say that "space" is finite but unbounded (like the surface of a sphere is finite yet unbounded as a 2D analog). I was just thinking that poor Bruno may have toasted for nothing. :ahh:

Probably off topice but that hit me as funny.


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