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Re: The advantage of holonomic drivetrains
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Re: The advantage of holonomic drivetrains
Oh... Witness the BEAST! This was one amazing robot with a crab system. It took quite abit to push them considering they had a holomonic drive. Sure they were pushable but the advantages of their system was greater than the disadvantages.
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Re: The advantage of holonomic drivetrains
Many people here are getting confused between holonomic and swerve drives. A holonomic drive has 4 omni wheels at the corner of the robot rotated 90 degrees from each other. This allows the robot to effectively move in any direction and spin in place by powering each of the wheels independently a different amount. The reason why people have said that they are weak and easy to push around is because you can never have more than 50% of your power in any one direction. Along similar lines if the wheels are not being driven the robot can be slid across the ground very easily.
A mechanum drive is very similar to a holonomic drive in that it effectively works the same way. It uses complicated mechanum wheels which allow a robot to place its omni-wheels in a front to back configuration like a regular wheeled robot. It however doesn't pose any advantages other than the easier mounting I believe. A swerve drive is a very different animal which is what the picture of the HOT bot from last year and the BEAST from this year use. They usually have 4 wheels which are rotatable. Usually driven by a motor the wheels are able to rotate in place allowing the robot to drive in any direction. The advantage of this is that you don't sacrifice much traction while gaining a lot of maneuverability. The downside comes in the form of extra motors, extra hardware and a lot of complexity. As far as I've seen the competition has been dominated 6 wheel drive set ups and treads. Treads and swerve drives are definitely coming out as the top contenders. Treads for their dominance in terms of strength and immovability and swerve drives for being both maneuverable and strong. However teams with just 6" traction wheels from IFI are going to be doing just great this year. As for the holonomic drives I've seen, they have all broken down under the stress of the competition. They're tough to make really sturdy and powerful and just don't seem up to snuff this year. Its too bad since they're really starting to become common and a bad year like this will slow their adoption I think. |
Re: The advantage of holonomic drivetrains
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Re: The advantage of holonomic drivetrains
649 decided on out holonomic drive train, because we had used it last year, and we thought we could step it up, and we did. Keeping the holonomic drive (we call it omnidrive) allowed our mechanical design team to concentrate on our shooter and ball train. If we had not reused our drivetrain scheme from last year, our shooter and ball delivery system would have been likely to suffer. Keeping the holonomic also allowed our programmer and our electronics guy (me) to do some neat stuff, that just wouldn't have happened on a normal drive train.
Simply put, the drive train did not serve us well in quals where one or both of our alliance partners were disabled, or worse, disabled each other. When we had a proper communication and competant alliance partners, it worked well, because we were able to harvest, and line up our shots in a much quicker manner then with a conventional drive train. Of course none of this panned in the QF because were were essentially out there alone, stuck as back bot :rolleyes: |
Re: The advantage of holonomic drivetrains
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Re: The advantage of holonomic drivetrains
213 decided to pursue a holonomic drive with 4 sets of dual Kornylak omni wheels mounted to the KOP gearbox mounted under our machine. We were at BAE and Boston this year, and we were a corner goal dumper. The disadvantage going into the competition we saw immediately, that being we could be pushed. When we finally got out onto the field, and had our driver perfect his method, we were actually able to become nearly as strong as the other robots. At full power we were capable of stopping (or severely impeding) our competitors. Only when we were not moving could we be pushed around. Because of our incredible maneuverability and ability to stop opponents from scoring we were often utilized as ramp defenders at the end of the match, and against high scoring teams sometimes we played nearly exclusive defense. We got to be pretty good at it (especially in Boston). The only problem came in the form of wheel durability, our wheels could easily shatter and did after matches. I suppose this was not necessarily the year for holonomic drives, but I think my team did pretty well (finals in Boston). To see videos of our matches in Boston, go to this site, and download any videos with 213 in them. You will find that a couple of them showcase the omni drive quite nicely. We are also in the eliminations (qf4m1,2 sf2m1,2,3 finals).
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Re: The advantage of holonomic drivetrains
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I'd much rather have a swerve drive but it's much more complex. We have drawings and the concept for it all done because we planned on doing it for this year. After seeing the game we kind of decided against it. |
Re: The advantage of holonomic drivetrains
Adding to what Ian said this happened with my team this year. We originally were using a tread drive sytem but our tread snapped. By the time we were on our 5th drivetrain and it was Thursday at the NYC regional we swapped for omni wheels in the front, knowing full well we wouldn't be able to get up the ramp.
Consequences of the omni wheels We were able to turn which let us realign ourselves for shooting very quickly We were able to be pushed very quickly while shooting Instead of turning in very small degrees we made huge arcs, although our drivers got that under control Our omni wheels actually broke We were able to wreak havoc during the last 20 seconds of the game on the other side stopping from robots getting up the ramp knowing that we couldn't We usually played backbot In my opinion the good outweighed the bad, (we came in second), so it was a good tradeoff. If we had been primarily defensive and not played backbot, I'm not so sure the omni wheels would have been a good idea. |
Re: The advantage of holonomic drivetrains
Team 231 chose us as alliance partners in the finals. I'm not sure, but I believe they had omni wheels that were all at 45 degree angles.
Yes, they did get pushed around; however, their driver did manage to "roll" around defending robots and pop a couple in the goal. Another advantage they had was, their infeed rollers were mounted on the long side of their robot, and their shooter was too. This provided room for the shooter and a large margin of error for the driver when they needed to pick up balls. Here's the second match in the Lone Star Regional finals, if you really watch it you can see that nifty roll move used a couple of times. http://video.google.com/videoplay?do...gional&pl=true |
Re: The advantage of holonomic drivetrains
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Clay |
Re: The advantage of holonomic drivetrains
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We had to use two omni's on the back of our robot to improve our ability to turn. |
Re: The advantage of holonomic drivetrains
all i can say is that in a game like this if i would make a swerve drive it would be a coaxle with ifi roughtop tread.
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Re: The advantage of holonomic drivetrains
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As for defense, I don't think we sacrificed that much. Because of the extra maneuverability, we are able to out position some robots, stopping them from shooting. We have beaten high-profile teams like 1680 (a triplet) and 68 by doing this. |
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