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Originally Posted by Taylor
I disagree with this. Many teams encountered difficulties when driving over uneven field. When field components are placed under the carpet, as they often can be, this takes your carefully tuned 'square' base and lifts up a corner or two. I'd recommend taking Nathan's advice and leaving the chassis 'loose' or having some sort of suspension to negate 'imperfections' in the field.
We found quite the opposite during our offseason event - rookie drivers with very little practice driving a robot had no preconceived notions about how a tank-style drive handles, so they bobbed and weaved and spun around traffic with ease using our sensor-less and simply-programmed mecanum drive.
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Brace yourselves, a text wall is coming!
After some distraction, that post really was badly typed.
Red: You will notice my post did mention the recommendation of using of some sort of springy material to absorb deformities. That being said, on both of our robots, in 2011, and in 2012, we had our typical solid-as-a-rock welded aluminum box tubing frames. These were set and welded by one particular employee at our sponsor's shop, with precision as a top priority. For this reason our frames are extremely rigid and (realistically) perfectly 'square'. Like the instance I mentioned in the first post, we were subject to, and
did experience raised/disabled wheels in the competition. But! because (
Blue:) we controlled our drive not with motor power, but with motor RPM (using encoders), we had almost no trouble at all. When a wheel is lost (for whatever reason) and the driver attempts to do anything, the left side with only 1 wheel suddenly finds itself with half the torque of the right side with both wheels
at matching PWM input. The code detects that the only left wheel is not spinning as fast as the right wheels while the robot tries to go, so it amps up the power to the lacking wheel to match RPMs, and thus balances the torques*. This operation was also the case when the robots were strafing. This whole scenario was a very rare occasion though, as most obstacles in 2011-2012 were faced head on anyways (ramps/key in 2012, minibot poles in 2011), so 2 wheels climbed the bank at the same time, making the leveling problem a non-issue. I concede the obstacle of 2013's pyramid, and who knows what 2014 will have in store, so I concur, I am making the recommendation to put springs or some other form of 'loose' configuration on future mecanum 'bots.
*while the 3 wheels are not slipping (or in mecanum's case: equally slipping), the only way they can all turn at the same speed is with the lone wheel compensating for it's disadvantage with double the torque
As for (
Green:) driver experience. Like I said,
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Originally Posted by BBray_T1296
This will make driving feel far more natural to drivers, and will let almost anyone have the basic ability to drive the robot instantly.
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That being said, a driver with hours of practice will be able to more efficiently and more effectively traverse the field, avoiding defense 'bots and evading traps.
Magenta: These guys are trying mecanum for the first time, likely from some variant of tank drive last year. Any drivers-to-be on the team (who will more than likely NOT be rookies) will have probably driven this year's robot, an thus will, likely, have "preconceived notions about how a tank-style drive handles." Sometimes it can be easy to forget the strafing ability, especially in the heat of a match when you are used to driving tank from an event in the past (or simply spending hours driving a tank 'bot while waiting for the mecanum base to be finished).
One last rant:
Green again: In
every single last instance possibly imaginable, tons of practice is superior to a lack thereof. Commercial pilots spend thousands of hours training in flight simulators before they operate a real jet. Imagine handing me a copy of Flight Simulator X and saying "you have one hour". After that one hour, you stick me in the captains seat of a 747 and tell me to fly to Seattle. Not the best idea, I have to say. Same goes for a FRC robot. If practice is so worthless, and anyone can drive the robot as well as a trained 'pro', why not hold a school wide raffle on Thursday before your regional. One lucky student gets to drive the robot in competition, be it a band kid or a cheerleader. Maybe you could sell the tickets-what a great fundraising idea!
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Originally Posted by Flak-Bait
have fun, drive fast, and forget the haters.
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