Top speed?

[Mike@1023]

Originally Posted by David Brinza

Speed of light is the fundamental limitation. Sonic booms would probably be discouraged. Most likely, safety will be the determining factor - a 20 ft/sec robot may be deemed unsafe by the referees if it behaves as if out-of-control.

Maybe this year a speed limit will be established, which would be an "interesting" development for the program. Radar guns!!!

A low center of gravity would help, although you COULD spin out as a result...maybe 20 ft/sec drive train is a little too fast?

[thefro526]

I think this year there will be robots exceeding 20 fps but these robots will also probably has sophisticated turning systems or eliminate the need to turn entirely (20 fps mecanum/holonomic/swerve). I think teams that used swerves last year may have an advantage the image of team 71 swerving around the rack at high speed sticks in my mind lol.

[MattLi]

Does anyone know if there's any rule about an unsafe speed or is that just a judge related matter?

[geeknerd99]

Seems like a decent way to take the turns...

[BandChick]

Originally Posted by MattLi

Does anyone know if there's any rule about an unsafe speed or is that just a judge related matter?

I scrolled through the manual, but I didn't see a specific rule.
Generally, the refs judge "unsafe speed" based on whether or not you have control over your machine. If you're going flying into walls, if you keep heading toward the outside of the field, if you're ramming into other robots, be prepared to be deemed unsafe.

But as long as you seem to VISIBLY have a handle on your machine and what it's doing, then you should be fine.

[Daniel_LaFleur]

Originally Posted by thefro526

I think this year there will be robots exceeding 20 fps but these robots will also probably has sophisticated turning systems or eliminate the need to turn entirely (20 fps mecanum/holonomic/swerve). I think teams that used swerves last year may have an advantage the image of team 71 swerving around the rack at high speed sticks in my mind lol.

While I agree that you will see many robots going faster than 20fps, I doubt very many teams will do well that go that fast. The reason I say that is because winning races has more to do with control than speed, especially on a short track such as FIRST has provided.

No. I believe that this year the winners will be the robots with the best control over their drive system and the robots that can take the big hits from those that cannot control their drive systems.

[Dave Scheck]

Originally Posted by thefro526

(20 fps mecanum/holonomic/swerve).

This makes me chuckle a little bit. Last year, we had a 7fps crab system. Driving full forward and doing a 90 degree crab maneuver put a ton of stress on the drive modules. We cracked the hubs on quite a few wheels due to the tremendous side load. I can only imagine what would happen if the wheels of a robot moving 20fps were suddenly turned perpendicular to the direction of travel.

[Koko Ed]

As I remeber hearing once. I don't care about the car that goes 0-55 inn 2.5 seconds. I want the car that can go from 80 - 50 in 1.2 seconds. It's not gonna just be how fast you get around the straightaway but can you survive the hairpin turn.

[abeD]

Going around this turn reminds me a lot of autonomous mode of 2003, some teams would steer (mine included) and some teams had tank but would have wheel lowered on an angle that would steer them around the corner then bring it up into the chasis (312 did this and a few others but I can't remember them now)

[Vikesrock]

This is somewhat related to the topspeed discussion so I figure I'll ask it here. When determining the "top speed" of a robot in relation to it's gearing, wheels, motors, ect. what point on the motor curve are you taking the RPM numbers from? My team is a second year team with little or no help from any Mech E's and we are looking to do a bit more in terms of drivetrain design than we did last year.

So when someone says they have a 15fps or 16fps robot what RPM is that on the motor (assuming 2.5" CIM)?

[RobJ]

Originally Posted by Vikesrock

This is somewhat related to the topspeed discussion so I figure I'll ask it here. When determining the "top speed" of a robot in relation to it's gearing, wheels, motors, ect. what point on the motor curve are you taking the RPM numbers from? My team is a second year team with little or no help from any Mech E's and we are looking to do a bit more in terms of drivetrain design than we did last year.

So when someone says they have a 15fps or 16fps robot what RPM is that on the motor (assuming 2.5" CIM)?

It depends on the size of your wheel. If you go 16 fps with 8 inch wheels then your motors will be rotating twice as fast at 16 fps with 4 inch wheels

[Elgin Clock]

I can easily see teams doing laps under 10 seconds with a great line of travel, and no interference.

Whether or not this will happen is to be seen.

But it can, which to me is pretty darn awesome.

[lukevanoort]

Originally Posted by Vikesrock

This is somewhat related to the topspeed discussion so I figure I'll ask it here. When determining the "top speed" of a robot in relation to it's gearing, wheels, motors, ect. what point on the motor curve are you taking the RPM numbers from? My team is a second year team with little or no help from any Mech E's and we are looking to do a bit more in terms of drivetrain design than we did last year.

So when someone says they have a 15fps or 16fps robot what RPM is that on the motor (assuming 2.5" CIM)?

It also depends on the team reporting that speed. Relatively few teams measure actual speed (I think the Martians do, but beyond that I can't think of anybody). So, then you get into theoretical calculations. Some teams approximate inefficiencies (JVN's famous .81% of free speed is an example), some just use the 12V free speed, and some report numbers based off of operation at 40A draw.

I wouldn't use the 40A one, because most of the time you aren't going to draw that much just driving around, and if you are you're probably in trouble. (40A per motor doesn't leave much wiggle room at all on either the motor breakers or the main breaker) Similarly, I highly doubt teams will be driving with their motors running at 12V free speed; however, there is something to be said for the argument that the battery doesn't output 12V, more like 13.5ish, and that can make up for some of the inefficiency losses. The approximation method may end up more accurate than either of the above, but that is obviously dependent on how accurate the inefficiency approximation itself is.

Personally, I just use free speed in calculations because it is easier to work with. In my experience, underestimating speed has worse consequences than overestimating (to many interrupts per sec, dead-reckoning autonomous driving too far, etc). Whatever you choose stick with one; you can then compare speeds year to year much easier than if you had to convert from one method to the other.