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Topics - adrian

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Rules Discussion / Weight Bonus Ambiguity
« on: July 26, 2015, 04:59:41 pm »
I'm thinking of building a propeller driven robot which would slide across the floor with no wheels, and was wondering what weight bonuses, if any, a non-wheeled, non-shuffling, non-walker robot would get. Under the Tournament Procedures v1.0, the categories are Walkers, Shufflers/novel non-wheeled robots, and everything else. I would either get either no weight bonus, or a 50% bonus, depending on if the event organizer determines I am a "novel non-wheeled robot." However, under the Robot Construction Specifications v1.0 section 4, it is seems to say that I would get a 100% weight bonus for having a non-wheeled robot. Also, walking, shuffling, hopping, flying, and hovering robots would seem count as a non-wheeled robot and get the 100% weight bonus, but also have their own categories. Can somebody clarify this? Can we update the next version of the rules to make this more clear?

Quote from: Robot Construction Specifications Section 4
There is a 100% weight bonus for non-wheeled robots (There may be a 50% weight bonus for shufflers or other forms
of locomotion which do not fall within the definition of non-wheeled robot - see 5.1.2 for
a definition of a non-wheeled robot.)

Quote from: Robot Construction Specifications Section 5.1
Methods of mobility include:
5.1.1. Rolling (wheels, tracks or the whole robot)
5.1.2. Non-wheeled: non-wheeled robots have no rolling elements in contact with
the floor and no continuous rolling or cam operated motion in contact with the
floor, either directly or via a linkage. Motion is “continuous” if continuous
operation of the drive motor(s) produces continuous motion of the robot.
Linear-actuated legs and novel non-wheeled drive systems may qualify for this
bonus. If you are intending to enter a non-wheeled robot in any event contact
the event as soon as possible to determine what if any weight bonus you will
qualify for.
5.1.3. Shuffling (rotational cam operated legs)
5.1.4. Ground effect air cushions (hovercrafts)
5.1.5. Jumping and hopping may be allowed at some events, contact the event
organizer if you’re intending on using this as a method of locomotion.
5.1.6. Flying (airfoil using, helium balloons, ornithopters, etc.)may be allowed at
some events, contact the event organizer if you’re intending on using this as a
method of locomotion.

Quote from: Tournament Procedures
Walkers may weigh up to 100% more than their standard class weight limit.

Walkers are those robots in which multiple linear or limited-travel rotary actuators are
intermittently driven to produce linear travel of the robot. Actuation may be through electric,
pneumatic, or hydraulic means. Walkers must have no parts normally in contact with the
ground undergoing continuous rotation, and must require some change in timing or
sequencing of the driving mechanisms in order to reverse direction. Walkers will typically
have control systems significantly more complex than those found on shufflers or rollers,
involving multiple actuators, servos, or valves running through a specific sequence to
produce motion.

Shufflers and novel non-wheeled robots may weigh up to 50% more than their standard
class weight limit. (Option: Shufflers and novel non-wheeled robots receive no weight
bonus)

If a robot is supported and/or propelled by parts that do not normally undergo continuous
unrestrained rotation around a horizontal axis, but uses a system of mechanical devices
such as cams or crankshafts to generate reciprocating motion of those parts from one or
more continuously rotating drive shafts, it will be considered a shuffler. The defining feature
of a shuffler (versus a walker) will be the ability to generate continual forward motion of the
robot from continual rotation of its drive motors. Shufflers typically have electrical control
systems indistinguishable from those on wheeled robots.

Any other form of locomotion that is not contained within wheeled, walking, or shuffling is
considered a novel non-wheeled form of locomotion. If you are intending on building a robot
that may fall under this classification contact the event(s) that you plan on attending with the
robot to confirm what they will classify the drive system as and what, if any weight bonus
will be allowed.


2
Progress Reports / Last Minute Robotics - Adrian Kelly
« on: July 26, 2015, 02:47:12 am »
I was wanting to share my robot progress, and this seems to be a pretty good place to do it, so here goes! Pictures coming, probably tomorrow.

Sisu at MIT
My first, and still only robot, which debuted at at MIT Mini Maker Faire. It's a very simple antweight wedge that was designed to be fast and indestructible, with armor that's way too thick and motors that have no torque. The name comes from the Finnish word, which is some combination of resilience, guts, and determination, and also sounds really cute. As my team name says, I was working on it the night before when my BEC let out the magic smoke, somehow frying both my speed controllers (wtf??? voltage spike back onto the input rail?). With only one spare, I had had to borrow some speed controllers (thank you so much Jamison and Dylan!), and was even finishing the frame it at the competition. I forfeited my first 2 fights (yay round robin!), and with unmixed controls, lost to Spinzilla by not charging my battery, beat Gabe's duct-taped vertical spinner by sending his blade flying across the box, lost to another wedge by getting stuck in the 3/4" gap at the edge of the arena, and because nobody else was still working, somehow won the rumble and Best Rookie.

Whirl and Hurl
For my next event, Bot Blast in PA a week ago, I wanted to have something more interesting than a wedge. Melty Brain spinners have always fascinated me, and they seemed like an interesting challenge, so I designed Whirl and Hurl, a beetleweight melty with one wheel and an aluminum unibody chassis. The Makerspace I just joined (shoutout to Generator in Burlington VT!) was getting a new CNC router that was supposed to be able to do aluminum, and so I designed my robot for that, to find out a week before the competition that it wasn't going to be running in time. I immediately ordered an aluminum tube and blocks, planning to make the frame by hand, and some stainless steel teeth because I was unable to find someone who could harden S7 locally. They arrived Wednesday night for a Saturday competition. On Tuesday I managed to flash the SimonK firmware onto my ESCs, and so the whole electrical system and software was done and appeared to work (I wrote yet another melty brain firmware...), at least from what I could tell without the bot spinning. Tested the motor at full speed with the wheel on, and apparently Lectra Lites don't enjoy being spun at 25000 rpm, because the slight weight imbalance vibrated out of control and the wheel almost split in half. With three days to build the whole frame and figure out a new wheel system, I realized it wasn't going to get done.

Sisu at Bot Blast
Up until then, I wasn't planning on bringing Sisu, because wedges are boring, but didn't want to go without a robot. I quickly replaced a motor whose gearbox was rather crunchy, and a TinyESC, which was fried in the MIT rumble, and got it running. Dylan had loaned me two Fingertech TinyESCs, and for some reason didn't want them back, and so I had one TinyESC and one Vextroller working. The robot ran, but apparently one of them has a curve programmed in, or my motors are very unmatched, because it refused to drive straight at all. If I push the stick all the way forward, it makes a ~120 degree left turn, then drives straight. With ridiculously fast 11:1 Silver Spark motors, this was not a good combination. In addition, I had no spare ESCs, and forgot my spare motors at home, so this would be another interesting event.

Once I got to Bot Blast, I realized my wedge still had the crude hacksaw cut I had done the morning of MIT Mini Maker Faire, and so I sharpened it a bit with my Dremel grinding stone. It was taking forever (because my wedge is 1/8" 7075. Did I say overkill already?), and I was worried about getting stuck on the plywood floor, so I stopped early. My first fight was against Nate's wedge Slim Pickens, which got under me every single time and carried me around the arena. I lost by judges decision. After that, I spent the next hour grinding down my wedge with the side of the Dremel cutting wheel, which turns out to work much better, because I was up against another wedge. It turned out to be a Viper kit who hadn't sharpened their wedge at all, and now I was the one getting underneath. Unfortunately, Sisu is only 7/8" tall, so whenever I went full speed I would pass right under them. They were also running Silver Sparks on 3S LiPo, but their motors were running very slowly, and had surprisingly little torque, so I was actually able to hold my own in pushing contests and win the judges decision.

For my third match, I finally got to fight a spinner, the drum of Blutsauger. I had been talking to him before, and he got pretty damaged fighting the eventual winner, Gyroscopic, right before our match, but was able to repair it all. About half the time, he would get under my wedge with his wedgelets, pushing my wedge into his drum and bouncing me off the walls and roof. The other half of the time, I would get under him, and didn't have anything on top of my robot to keep him from driving right off, and so lost the judges decision. Right at the end, I landed upside down, and forgot that the controls were now reversed, and so momentarily though I had blown a motor. Sisu had no apparent damage except some large nicks in the wedge, but after opening it up, both motors had unscrewed themselves from their mounts (I couldn't find the Loctite), the motor wires were all twisted up, and the screws holding the wedge on were starting to pull out of the UHMW sidewalls. In the rumble, I pushed some RC cars around, lost the tread on one wheel to the crazy sawblade melty things, and got a few good hits on the Dark Forces overhead spinner.

Sisu into the Future
I was amazed that with no spares of anything, Sisu was still working great after the competition, ready for more. Except now, I can see just how bad the design is. I need something to keep myself from sliding right under opponents, and was thinking of a captive pin near the back that would slide up and down, so that even when I'm upside down, it would stick up. The sharp front edges are terrible against horizontal spinners. I'm only at 13.5 oz, so I could afford the extra wedge material to extend it on both sides, if I could figure out how to bend 1/8" aluminum. I want to add a rear wedge as well, for when I get flipped over. Another issue is that the wide wedge clearly doesn't work against drums with wedgelets. I need to make either a second, modular wedge, or an attachment to the wedge, that is narrow enough to get between the wedgelets and hit the drum.

In terms of drivetrain, the easy solution for more torque would be to switch to 22:1 Silver Sparks, but then my robot would be too slow. Moving to 4 motors would mean I have to make a pivoting wedge, as well as being a bit pricey. I have some 1000 rpm Ebay motors, but the shafts don't seem to be long enough to double support. Also, those motors are taller than my whole robot height right now, so I would need to totally redesign and rebuild the frame, and at that point, I think I'd rather build a robot with a weapon.

Speaking of which, I have pretty much all the components for Whirl and Hurl, which hopefully will be done this summer. We'll see if I make it to Franklin, but I definitely want to go down for Motorama, hopefully with some new recruits in tow.

Mad Props
A few weeks before Bot Blast, when thinking of what kind of beetleweight I was wanting to build, I was debating between a melty brain and a better version of No Fly Zone. No Fly Zone is a totally impractical and uncompetitive design, but so cool I wanted to do it anyway. A few days ago, I thought up a way to make it more competitive and even more ridiculous, by using two propellers to both move and steer the robot. You wouldn't need any wheels, and by making them counter-rotating, you cancel out the gyroscopic precession and make both sides spin upwards. I should get the second major iteration of the CAD model done tomorrow. The whole robot is just twin 4.5", 6.5oz S7 propellors running on 300W of brushless power each, and a self righting mechanism. The problem is that the aluminum SriMech hoops have to be huge to make it self right, and so all the aluminum is rather thin. Also the robot has to be pretty long, so that the force from the props doesn't make it fall on its face. Should I make the hoops aluminum, or UHMW like Totally Offensive? How do people design complex 3D shapes like propellers? And I guess Charles' instructable converted me, I'm thinking of doing a tab and slot aluminum frame, and welding it together at school this fall. I'm going to be a Freshman at RPI, and I'm taking the machine shop course first semester, which includes some welding. And it looks like they have a waterjet cutter, but you have to pay $27/hr to use it. :-\

Hopefully I won't live up to my team name for the next competition, and I'll get these done in time for driving practice. Though both of these robots I wouldn't want to operate outside an arena. Remote camera and go very far away?

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