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The advantage of holonomic drivetrains
It seemed to me that it was difficult for robots with holonomic drive trains to be succesful this year. Though these robots may have been more maneuvarable, the loss of traction often greatly hindered their robot. For example, I have seen a robot at sac and and svr which had an excellent shooter and ballpickup mechanism, but its omniwheels made it too easy to defend and psuh around. While I think these drivetrains are as cool as the next guy, I felt that these designs were at a disadvantage inthis years game.
My question is this: Has anyone seen a robot effectively use its holonomic drivetrain to an advantage? If so do you have any videos or pictures? What drive system did they use? ie mechanum, omniwheel, swivel, kiwi And to the teams which decided to use such drive train systems, why did you choose to use them, other than the engineering experience and "cool" factor? please note that this post is not intended to be offensive to any teams which have used such drive trains. I am interested in these drive trains myself, and I was wondering what was some of the thinking behind using these drives in this years games. |
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We play this weekend at LSR, so the proof will be there for us and then at Atlanta. I'd like to dialogue with any all teams using a holonomic drive this year as we do our own assesment. Eventually, we'd like to crab :cool: |
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Off topic but somewhat related. How many teams did you see at your two regionals that used a traction wheel set up in the rear with casters in the front? I would say that this set-up has just as much suseptability to a defensive robot yet not gain as much in the area of manuverability. ... |
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Speaking from experience at the Wisonsin regional, a holonomic was definitely at a disadvantage this year. We were pushed and shoved around, and on top of that our drive failed so that we couldn't even drive straight anymore. (We shot at the opponent's goal in autonomous once after executing a neat ground-loop :) )
Looks like the 4 and 6-wheel drives won out this year, even though holonomic's sooo much cooler. :) |
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Though I think using a holonomic drive, if used efficiently, you an have a great advantage to the opponent. But in the case of this years game I think a team would just get pushed around too much. Unless of course one could find omni wheels with some traction on the rollers.
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team 830, my team, made a holonomic robot this year, and I think that the advantages have helped more than the disadvantages. Having it eliminates the need for a turret, since we have code that will auto rotate the base to allign the camera with the shooter, and we can also play an Allen Iverson or Rip Hamilton style offense that allows for quick shots, even if we have to move around a little bit after making 2 or 3. Additionally, if we do get in the right range, we can quickly posisiton and make many shots in a row. We were one of four holonomic robots at waterloo, and I think we were among the best of the overall competition. In the eliminations we found ways to score against the #3 alliance (who ended up as regional finalists ) and we actually scored almost all the points for our alliance, inluding 36 in match.
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Another holonomic team (854) was 8th alliance captain, picking 830 and 1189 (J&J Sportsmanship). My own team (931) also had holonomic drive, won the Saturday Judges Award, and was part of the 5th alliance along with 1680 (the third Niagara triplet) and 1901 (GMID and Rookie Inspiration). So holonomic teams were well recognized and in good company; however, I don't think any advanced to the semifinals. I don't recall which other team had holonomic drive at Waterloo. Any help? |
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859 was the other Holonomic at Waterloo. It was the one with the dragon painted on the Hopper |
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Our team has an omni-drive robot this year. We are usnig our own form of the mechanum wheels. So far(just in our test runs before ship day) it seemed to work really well. The way our wheels are designed, we have a good pushing ability and also it is fairly hard to push us around. We are also able to make it up the ramp(or at least we are pretty sure we can). We leave to go to Las Vegas tomarrow so we will know for sure how well our drive train works.
Josh Team Driver/Designer |
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Just to throw my 2 cent's in... This year has been different than many other years in that you need the fine movements to shoot the balls, and the brute pushing force. In the end I think that because there are so many machines on the field at once, and you will be pushed at some point. It is better to have a quick machine that has a drive system that will facilitate power over finesse. The team I worked with, 388 had the omni system, it worked well, but when it came to side blows, the aim was gone... I know I'm going to start a riot by saying this, but personally I see no use of holonomic systems in the games thus far. Reason: there is too much pushing for a machine to not move so much so that fine movement or aim can not be lost by collisions from other machines. So until the point where we are in a maze and can not touch the sides, I don't see a good use of the system. But crab drive is another story, there you do have more traction when being pushed. My 2 cents, take it or leave it...
mark |
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While I origianally wanted omni drive we decided against it for a strong drive train to play defense with.
Team 40 had an extremely effective shooter using mecanum wheels (jester drive) They were very easy to push around but required constant attention because they could quickly line up and shoot if they were left alone. The biggest advantage to their drive was their multiple Auto modes they often evaded defensive bots and scored 7+ balls this combined with very smart driving and strategy seeded them 3rd and got them all the way to the finals in Boston. 213 also used omni drive very effectively to make one of the best side goal dumpers that I saw in boston and manchester they were very difficult to defend and often dumped 20 balls with no problem. |
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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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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. |
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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: |
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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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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. |
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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. |
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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 |
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Clay |
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We had to use two omni's on the back of our robot to improve our ability to turn. |
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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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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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