Simple… Post which type of lift design you think is best, it can be your teams or another’s. Feel free to post the same idea as someone else; I just want to see what other people are thinking! Keep this thread clean of bashing on other teams design please!
My choice…
I personally like my teams lift design the best (biased I know) We did a forklift style lift powered by two r550 bane bots motors through a cim-u-lator and a 12:1 reduction. Our lift is made of three layers of two 80/20 bars spaced an inch apart. The first and second stage go to the top of max starting spec (5ft), and the third stage simply is used to attach out grabber and slides freely on the second stage. Our lift is mounted in the dead center of our robot and our arm pivots 90 degrees and can pick tubes up off the ground. We can reach the top row +. We milled Delrin sliders to fit in the groves of our 80/20 and when all of the stages are engaged it only takes 15lbs of force to raise our lift. We used our lathe to turn our own pulleys and created a system to catch the rope incase it jumps a pulley keeping our friction low. We not only have a power up, but also a power down and a super simple tightening system. This allows our lift to be raised and lowered in well under 2 seconds without jumping pulleys. Being a student built and designed team, we are so proud of what we learned this year. Our mentor’s definitely guided us along the way, but us students are so proud of not only designing a solid robot, but also taking advantage of the new machines (mill and lathe) which our school got this year. We have made one of our best robot’s to date!
Whatever works best! Our team uses a few arms, and an internal gripper, and though it’s not as fast as some of the elevators and roller grippers I’ve seen on CD, but it’s good enough to make it through regionals, which is something amazing for Team 256. We haven’t been the best team for the past few years, but ever since I became a Freshman (this year), I’ve made sure the team does better! Back to the lift design, every robot I’ve seen uses an elevator/forklift like design, so I think our unique design will differ than everyone else’s. In a competition where everybody has similar robots, a unique robot that works in a different way than the others, and cannot be blocked in the same way others can has an advantage. I personally think the BEST lift design is the most unique design.
Our team uses… drumroll… ONE ARM! That’s right, one whole arm! The best part is that it’s only powered up and town; our tube handling mechanisms (really just one long extension of the arm) are all passive. Plus, we can hit any rack. Oh, and it’s made out of PVC pipe.
We’ve got both a passive tube mechanism and a simply driven lift mechanism.
While this does pivot up & down, it does not grasp the game pieces in any way. We have yet to produce a situation in which we lose posession of the game objects.
These pulleys and cables are on the front (non-driven) side of our lift. They’re tensioned in such a way that when we drive up & down the middle sections (sections 2&5), the inner sections (3&4) rise up twice as quickly. This allows us to mount our drive belts to the outer sections (1&6) which are statically mounted to our frame. From 0:06 to 0:11 you get a decent view of the belt drive that lifts the whole assembly.
It’s powered by a FP motor.
The assembly uses 1010 8020 with the roller wheel & bracket assembly.
http://images31.fotki.com/v1085/photos/5/1485315/9523471/DSC_9585-vi.jpg
Our teams elevator is sort of similar to the one above. we used 1010 80/20 pieces to make a 4 stage elevator. It is driven with a rs550 with a 64:1 transmission. We used small pulleys and small woven Kevlar thread (i don’t remember the name of it).
Sadly, no. However, Duluth is a week two event, so hopefully I can post it by then.
The attached drawing should provide a rough explanation. (Not to scale)
The winch consists of two window motors hooked up to a drum. The main bar going up is made of ~1/8" thick ~1" wide aluminum bar, and the PVC pipe varies around 1" in diameter, and the thickness is pretty beefy, although I doubt it weighs more than 10 pounds max, which is maybe twice that of the bar. A potentiometer allows us set a PID loop to set the arm angle to the correct height every time in under two seconds, although it goes from a full drop to maximum height in about half a second. And yes, we can hit all three levels.
My team does something quite similar. Our arm uses the same two-window drum at the back, but the arm telescopes 3 feet and the end hook doesn’t rotate. It hits all three levels and uses a pot to get to the the correct hight for each peg. The arm is made of a professional steel slider with the telescope powered by a banebots and belt drive. The telescoping piece is 1/8" thick x1" wide angle.
Interesting how this has quickly turned into a “my team did this” thread… though I’m not surprised.
After all the work we’ve gone through, I’m thinking that an elevator type manipulator is the simplest approach to this year’s challenge, even with the 60" rule lifted. Not the approach we took, but probably the cleanest.
Even so, it’s not the robot with the ‘best’ lift design that you’ll remember… It’s the robot with the most unique design. 148 stands out in this category by a mile. But as mentioned above, not many bots have been posted yet.
The best I’ve seen so far is 469’s (no surprise there). It weighs next to nothing and goes from the floor to the topmost peg in 0.6 seconds. It will be awesome as soon as they figure a way to control it.
Robustness Some of the arms I have seen have a lot of lateral sway in them as the robot turns. Some elevators have weak attachments to the drive base. Both can be well built. If a robot is doing ground pick-up in traffic it will at some point have a manipulator outside of its frame where it can be hit. I would think the longer arms would sustain greater damage. (They also might be easier to repair and get back on the field though.)
Speed Arms and elevators seem equally fast to me. Arms may handle sudden changes in direction more poorly, especially if the gripper has significant mass at the end of the long swing arc.
Precision If done manually it is eaier for a driver to adjust the height of an elevator to find the peg than an arm. The movement arc is one dimensional instead of two. With driver practice, or software these issues can be mitigated.
Center of Gravity The weight stays more inside of the drive wheel in an elevator than it does for an arm. The s-forbes style arm is a nice way to avoid that problem.
I think **elevators are better **suited for this game, but not by much. Well built arms will beat poorly built elevators every time. The biggest difference will probably be in drive bases. The ability to get through defensive pressure and put the arm/elevator in a position to do its thing will be more important than the lifting system in general.
I think the 2-stage lifts* are working well this year. While slightly on the heavy side, they’ve been seen working with either bearings, custom linear slides (us), or 80/20 slides. They’ve varied in width relative to the robot, and in speed based upon how they’re driven. They also have the most robustness in how they’re driven – pneumatic cyllinders, winches, and threaded rods have all been posted on CD. IMO, lifts are also easier to hold in position than an arm (unless ballast + window motors are used on the arm).
So for “best” from a performance perspective will be hard to tell (and will not be a dominating factor so long as it works well), even after the competition season. Yet “best” from a hollistic perspective is about dead even, given the variety of designs seen on CD.
*(2 stages that move + 1 base stage, it isn’t a box tube within a box tube telescope setup, and the rotary joint for an end effector is on the upper stage)
