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Unread 11-10-2004, 23:19
Unsung FIRST Hero
Karthik Karthik is offline
VEX Robotics GDC Chairman
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Re: How slow is too slow?

Designing a FIRST robot is all about trade-offs. Picture this pre-build season conversation, with a "Robot Dealer"...

RD: Hey you, strategy guy.
ME: Who me?
RD: Yeah you. Do you want a robot that can go 10+ ft/sec?
ME: Well yeah. Who doesn't? The extra speed can always come in handy. But wait a second, this is a FIRST robot. There must be a catch...
RD: Okay, maybe there's a catch. The one robot I had in mind has a one speed transmission.
ME: Hmm, no deal. I'd have to give up a lot of pushing power to be geared to go at that speed. Most FIRST games, require more torque than that gearbox would probably provide.
RD: HM, so you're one of those smart strategy guys. Okay, I'll give you a two speed gearbox. 10 ft/sec in high, 2 ft/sec in low...
ME: Wow, that'll let me be really fast and give me the ability to be a strong pusher I like that. But hold on. That sounds like a mighty big reduction. How much does that thing way?
RD: Fine. It weighs a lot. But I've got another one that weighs less and plays in the 4-10 ft/sec range.
ME: That sounds a lot better, but my drivers are pretty green. I don't know if they can handle that much speed.
...
This conversation could go on for a while...

The point is, speed is always an asset in FIRST game. You just can't give up too much to achieve it. I've seen many teams slave away in an effort to try and build the fastest robot. A lot of the time it's not worth it.

Remember, on a 48 ft field, there's not many times when you'll need to go much faster than 8 ft/sec. On the other hand, the ability move at 12 ft/sec, can be a huge asset. The decision you have to make, is whether or not it's worth the effort and weight to build in a function that may not be used very readily. This depends on your team's capabilities.

When it comes to the issue of control, I have seen some very fast robots which moved across the field with lots of precision. Team 25 in 2003 really sticks out in my mind. I've also seen some really fast robots slam into a lot of obstacles, and look like they've been driven by a drunk. More often than not, anything more than 8 ft/sec is uncontrollable. But with a nice PID algorithm and skilled, well practiced drivers, it is possible to control.

Would I build a robot that could only go 5 ft/sec? Probably not. I think it's very doable to build a simple two-speed tranny that puts you in the 4-10 range. This is a great range for most games. Remember, if your driver isn't comfortable with top speed, s/he can always pull back on the throttle. All that being said, there are many possible game designs that would cause me to go significantly faster or slower.
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:: Karthik Kanagasabapathy ::
"Enthusiasm is one of the most powerful engines of success. When you do a thing, do it with all your might. Put your whole soul into it. Stamp it with your own personality. Be active, be energetic, be enthusiastic and faithful and you will accomplish your object. Nothing great was ever achieved without enthusiasm" -- R.W. Emerson
My TEDx Talk - The Subtle Secrets of Success
Full disclosure: I work for IFI and VEX Robotics, and am the Chairman of the VEX Robotics and VEX IQ Game Design Committees
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