Hey everyone, now that we’re all back from the World Championship, 1492A and 1492X will be revealing our robots in a bit more detail.
After three days of competition at Worlds here were our results:
1492A:
-9th out of 84 in the Arts Division (8-2-0 qualification record)
-Picked by 1st seed 2921B from New Zealand then picked 2911A also from New Zealand
-Went on to become Arts Division Champions
-Earned the Create Award for innovative chassis design
-Placed 4th in the World after the Round Robin!
1492X:
-1st out of 84 in the Engineering Division (10-0-0 undefeated qualification record)
-Picked 2M from Canada and then 188A also from Canada
-Went on to become Engineering Division Champions
-Placed 3rd in the World after the Round Robin!
All in all, WASABI came home with three giant trophies and two banners for our efforts!
As a team, WASABI has emphasized cooperation in terms of the design process. We don’t really think of ourselves as three separate subteams (A, X and Z) but rather as a single team that’s building three robots. We don’t hide any ideas from each other, but rather throw them out for discussion in humongous email chains hundreds of messages long. Not only that, but after every single tournament, all of WASABI sits down in front of a whiteboard and discusses what went well, what went badly and short-term/long-term plans for all three robots. We strongly urge other teams to adopt similar design philosophies, as we believe this approach has been instrumental to our success.
As such, you’ll see a lot of small similarities between 1492A and 1492X in this reveal, but also huge differences.
Now for the good stuff! Since the design decisions for 1492A and 1492X were often made in tandem or in response to each other, some of the subsystem/mechanism explanations will be combined for both A and X.
1492A and 1492X
1492A Drivetrain
-6 motor X-holonomic drive (2 motors per front wheel, 1 per back wheel)
-1:1 torque direct drive
-Unique “fold-out” 4-bar drive train modules
-Pneumatic brake
This drivetrain was developed over the course of the entire season and has won 1492A multiple regional Create awards as well as the Create award from the Arts division at Worlds (credit to 1492A’s captain, Isaku).
At the most basic level, it’s an X-holonomic drive, but with a twist! The two halves of the drive (left and right) are modularized and attached to mini 4-bar linkages. One side of the linkage is attached to the drive module and the other side to the center of the robot that holds up the rest of the robot (arm and intake). This allows the drive to be folded in at the beginning of the game, raising the robot to the 18" height limit, but as soon as the game starts, the two halves drive outwards and the center of the robot falls down to 15" height and approximately 23" width.
Mini 4-Bar CAD:
1492A Flipout Match Video:
http://www.youtube.com/watch?v=GiVXI-G146Y (Start of match at 1:20)
This was designed with many issues in mind. For one, X-holonomic drives take a lot of horizontal space in the robot, since wheels are at 45 degree angles and motors must be attached directly to each of the four wheels. By allowing the drive to fold out wider, enough space is opened up in the front-middle of the drive to house an ample-sized bucket.
1492A’s drivetrain also included a pneumatic brake. The piston pushed a piece of metal wrapped with anti-slip mat into the ground, making it unpushable to maintain both offensive and defensive positioning.
Pneumatic Brake Images:
http://i.imgur.com/rZIb7Oi.jpg?1
http://i.imgur.com/KAbD1Jo.jpg?1
1492A Lift
-2 motor 6-bar ~13" long
-Unique uneven variable 6-bar
-Can lift up to 25 sacks
-Uniformly tensioned elastics (inspired by 599D Robodox Gateway)
This lift has numerous unique features that increased the efficiency of scoring, descoring, high goal and defending. The most unique aspect of the lift is the uneven variable 6-bar. In Round Up, AURA introduced the VEX community to the 6-bar lift (Fush and Chups). From all years of VEX, there have been tons of examples of uneven 4-bars and 6-bars that allow the lift to lean forward or lean backwards as it raises. However for Sack Attack, roller design robots found that the angle of your manipulator does not have only two positions: scoring and intaking, like say, Gateway. Instead, you have three positions: scoring, intaking and descoring.
Basically, roller design robots wanted the intakes as flat as possible for intaking to allow sacks to slide towards the back of tray more easily. For descoring however, it was beneficial to have your tray lean backwards slightly so that descored sacks fall towards the back of your tray instead of sliding out the front. For the final position, scoring for both trough and high goal, it was beneficial to have the intake lean forwards again to a flat position for faster outtaking (steep ramp).
1492A Uneven 6-bar Demo: https://www.youtube.com/watch?v=3RZwFGpuMSw
1492X Uniform Tensioning Demo: https://www.youtube.com/watch?v=yngtgmTHRRU (Music credit goes to John Ma)
Credits to my teammate John (Jinduckey on the forums) for the mathematical work he put into calculating the lengths of the 6-bar quadrilaterals to get the desired angle change in the amount of space available.
1492X Drivetrain
-6 motor tank drive
-1:1.6 speed direct drive
-Cantilevered unpowered front wheels
-6 omniwheel drive
1492X started the season with a 4 motor 1:1 torque mecanum drive, but quickly found that it had difficulty driving over sacks and that we valued pure speed for quick scoring/descoring trades over the ability to strafe. We ditched the mecanum drive after our December tournament to work on the drivetrain that we have now.
We saw that pushing power and speed would be important for our highly aggressive playstyle so we decided to move two motors from our lift to our drive and to replace the lost arm power with pneumatic assistance (more on that later).
The cantilevered unpowered front wheels are to maintain an 18" wheelbase while also having enough open space in the front-middle of the robot for an ample-sized bucket.
Drive: [http://imgur.com/7pgYdCC](“1492X Development Photos - Album on Imgur”)
We originally had traction wheels as our middle wheels to prevent teams from pushing us sideways, but changed to an all-omni drive to glide along the walls at an angle for the wall sacks and to reduce friction while turning with sacks.
The drive was quite fast and strong enough for mild pushing battles. Although the drive did burn out at times, this was only after severe pushing matches. We were able to win the majority of our pushing matches at Worlds. The speed and the power combined made the important aspect of positioning and transitions between objectives extremely quick and fluid.
This was seen most prominently in 1492X’s QF 1-1: https://www.youtube.com/watch?v=Jg7tdzEny2M
1492X Lift
-2 motor 6-bar ~17.5" long
-3 piston, double stage pneumatic assist
-Unique uneven variable 6-bar
-Can lift up to 20 sacks
-Uniformly tensioned elastics (inspired by 599D Robodox Gateway)
After dedicating two of our four original lift motors to our drivetrain, we needed some extra power on our full-length 6-bar to maintain our lift capacity. We fixed this by adding pneumatic assistance to our arm. Three pistons and four reservoirs provided us with enough air to comfortably lift 15-20 sacks at the beginning of the match and 8-12 sacks by the end.
Pneumatic assist (early iteration): https://www.youtube.com/watch?v=2ewPBltFJSU
Pictures: First iteration Second iteration
Explanations of other specific mechanisms such as the uneven variable 6-bar and the uniformly tensioned elastics are the same as section “1492A Lift”.
Continued below…
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