Hypothetical Situation - Stairs
 

some people interpret the game hint Little Eva - locomotion - Robotic Locomotion http://en.wikipedia.org/wiki/Robot_locomotion

The point of this is not to discus the game hint, there are 500 other posts about that. This is a fun mental exercise that can challenge us for the next week.

I assume that for the sake of rookies the kit drive-train would have to be able to play the game so perhaps a bonus obstacle close to the driver station such as the ramp in 06.

So here is my Hypothetical Situation:

4 steps each 6 inches high, spaced 6 inches apart. At the top of the stairs there is a platform 2 feet tall, 3 feet wide, 8 feet long. At the end of the match each robot on the platform scores 50 points.

don't actually build a robot just describe you strategy and how you would attempt to mechanically solve this challenge.

Re: Hypothetical Situation - Stairs
 

Look at robots from 2004. They climbed steps very well.

A couple of highlights:
our robot (33):
The entire top piece (the big refrigerator-box) moved by window motors, and had wheels on the front. It would tip back, and get the wheels onto the platform, then move down (lifting the robot, but the back two wheels remained on the ground). Then it would drive up. Almost all of the weight of the robot was in the chassis (it was full weight, 130lbs with battery, and the entire top piece weighed around 10lbs), so it wouldn't tip over easily.

Simbotics (1114): They had four wheel pods (two crab pods and two casters) each with a pneumatic piston. They would lift all of the pistons, then run into the platform. Sensors on each pod would lift it as it hit the platform.

Re: Hypothetical Situation - Stairs
 

that was a different challenge. The steps I was thinking of are much larger than 04, but similar concepts should work

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I know this doesn't address the OP's original question, but to add on to what was said hereWe had a similar solution, except it was just front and back instead of 4 independent modules like they did. We had 8 light sensors that we used to detect where the robot was relative to the platform and raised/lowered the modules accordingly. It worked great, but in practice the time that it took to raise the modules wasn't as fast as we had hoped (the goal was to be able to drive on without slowing down)

Check out our Encore promo video from that year to see more details.

Again, that was a different challenge with only a single step to deal with.

Re: Hypothetical Situation - Stairs
 

As a mentor of one of those rookie teams who will most likely be using the kit frame unless CADed otherwise, I would recommend designs such as 190's 2004 robot. Or I would really like to try 1276's off-season prototype.

190: http://www.youtube.com/watch?v=Q5nnGGRi-94

1276: http://www.chiefdelphi.com/media/photos/35982

Re: Hypothetical Situation - Stairs
 

Just in case there are stairs this year, would it be best to have tracks or what ever they are call ed, like on tanks. ??? unlesss we have to use legs i mean. and Where can i find some or purhase them??? :)

Re: Hypothetical Situation - Stairs
 

If I remember the game correctly, WPI (Team 190) had a great platform climber, went around a goal obstruction, and hung on a bar, all autonomously. Can't wait to see the new game. Speculation is generally fruitless, but can be fun for some.:)

Re: Hypothetical Situation - Stairs
 

They went up the 2" stairs, and intentionally built narrow to go around the goal. I remember that part of their robot was a piece of laminated paper to reach over a line and "straddle" it so they'd be in position for the stairs.

I might try 330's approach: oversized rear pneumatic tires (12") with an angled front and 6" wheels to lead up the step.

Tank tracks: Outback Manufacturing has a kit for those, but most teams make their own with varying degrees of success (the Triplets in 2006) and unsuccess (any robot that throws more than one or two in a season). They'll work for stairs, but I wouldn't recommend them for flat floors necessarily.

Re: Hypothetical Situation - Stairs
 

I'd probably approach the 6" stairs with a tank tread design as well. Perhaps only to climb - wheels could provide the regular movement.

Re: Hypothetical Situation - Stairs
 

A very fast and exciting way would be for a robot that had the ability to shift is CG very high (approximatley 3feet or higher), and then take a run at the platform and let the physics of momentum do the work.
Of course this strategy could literally turn into a trainwreck...

Re: Hypothetical Situation - Stairs
 

id try to create a design that could some how also get the other robots up, maybe a modified ramp bot like 08. Or after it climbs flips down a ramp so the other bots can get up easier

Re: Hypothetical Situation - Stairs
 

I just had to complete a stair climbing challenge for RPI's Intro to Engineering Design class. Here's what my team learned with a tracked Vex robot.

The key to going up - and down - stairs with a tracked system is CG. Your left-right CG should be centered so that you track as straight as possible. You will want to move your CG around going up and down steps, however. If your tracks span more than one step, you'll want your CG more forward than aft. On the way down, you'll want it more aft than forward to prevent rolling right down the stairs. Of course, with all CG problems lower is always better, and a low CG means you have to displace your CG less.

The other tricky part of stairs can be climbing the vertical face of the step (the "first step problem"). With enough traction, you can "roll" up the side of the stairs, and if you lack the traction you'll need to find other means to "pop up"...

Re: Hypothetical Situation - Stairs
 

I did some researching on my own of stair-climbing a few months ago and I found some very interesting things.

This one is personally my favorite, and if the modules were made larger, they could potentially climb much larger stairs:

http://www.youtube.com/watch?v=XzKo6KE2H5A

Even something like this is possible in the FRC:

http://www.youtube.com/watch?v=kVEsOxhubFg

The most interesting thing I found was something like this:

http://www.youtube.com/watch?v=uPvj-2KC9G4

But that would be pretty out of the question for FIRST.

But something like this would be extremely interesting to see:

http://www.youtube.com/watch?v=qyVj4...eature=related

I even did some small mental experiments with the mechanics that go into climbing stairs and came up with some pretty interesting ideas.

Re: Hypothetical Situation - Stairs
 

This tank tread system worked very well for us in climbing the platform in 2004 - our arm tilted in the direction of the climb to give us CG advantage when climbing. When climbing down, we kept the arm in the same position and drove in the opposite direction. Very stable.

Game rules (bumper design requirements, ability of appendages to leave base footprint, etc.) may prevent the use of such a method in future "step" games. There are also nagging little weight, cost, and reliability of tread factors associated with this and similar treaded designs.

Re: Hypothetical Situation - Stairs
 

You shouldn't be buying*, building, or designing anything to be used on your final robot before Kickoff.

*with the probable exception of tools, supplies, raw materials, etc.

Re: Hypothetical Situation - Stairs
 

Why not? I would love to be prototyping a tank drive in the off-season even though it is almost over. Off-season is THE time for prototyping new ideas or mechanisms you are unfamiliar with so come build season you have knowledge that you can build off of.

Re: Hypothetical Situation - Stairs
 

The 190 robot also had across it, 4 sets of wheels, instead of just two. As it climbed up, parts of the robot were over hanging off the platform, and the robot could be supported by wheels in the center of the robot.

Also, this design worked well when it was able to get up on the platform in auto. I saw a few matches they were in where they did not make it up onto the platform. This posed a problem, as the robot could not turn well.

Just remember, many great designs have also had a major drawback.

A perfect example of this is finals match 2 from the championship of 2002. SPAM 180 beat 71 to the center goal, and knocked them out of the way. Without the goals secured to itself, not all that much they could do. http://www.thebluealliance.net/tbatv/match/2002cmp_f1m2

Not to move this off topic, but just remember there are always tradeoffs to be made. How you deal with the game elements and field is up to you.

Re: Hypothetical Situation - Stairs
 

Edited my post to clarify.

Re: Hypothetical Situation - Stairs
 

what about something like:
http://www.youtube.com/watch?v=a0NFrA-Nx4Y
prototyping that kind of drive train would even be useful for that fabled water game :p

also, for those wanting a real challenge, try this method:
http://www.youtube.com/watch?v=kpfjnqaFwtU&NR=1
:yikes:

Re: Hypothetical Situation - Stairs
 

Although we were relatively successful with both the complex wheel pods of Simbot Simon in 2004 and the tank treads of Simbot Beckham in 2006, neither solution was chosen for pure climbing ability.

In 2004, the reason we went with with the independent lifting wheel pods was because we felt it was the best way to climb a 6" step, while using a swerve drive. If we weren't already committed to swerve drive, there's no way we would have gone down this road. This was just way too complex of a solution for a problem that could be handled in a much more conventional way.

In 2006, our use of tank treads had very little to do with climbing the ramps that were on the field. We went with the treads because we felt we could get more traction by taking advantage of the longer contact patch between the tread and the carpet. Granted, this does seem a bit odd considering the equation for traction has no surface area component. When you're dealing with two surfaces that interlock in the way carpet and roughtop tread do, the traditional model for evaluating traction doesn't exactly apply. Regardless, we chose treads because we wanted that robot to be immovable, the benefit of climbing the ramp was an added bonus. Again, the complexity, maintenance and cost could not have been justified just for climbing when a much simpler solution could have sufficed.

So, I don't have any groundbreaking suggestions for innovative stair climbing devices. However, I can say this: If you are going to go with a complex design like the ones discussed above, you better make sure the extreme design costs are justified by the game benefits. Typically the best way to justify these costs for a function is to make sure you get multiple points of utility out of them.

(And if you didn't bother reading all of that, here's the synopsis: Keep it simple!)

Re: Hypothetical Situation - Stairs
 

http://www.societyofrobots.com/robot_asme.shtml
Now, depending on the rules, this kind of robot might be possible. As long as the 3 inch rule is not in this year's rules, it should work great.
http://www.societyofrobots.com/robot...t_monkey.shtml
Now I am not sure if this is possible with the bumpers in the way, but his has honorary mentions.

Try this:
http://www.youtube.com/watch?v=67CUudkjEG4

Re: Hypothetical Situation - Stairs
 

if i was on a rookie team the way that i would do this is an 8wd with the 10 inch kit wheels. the middle two being drop center and rubber traction, the back one being a slick wheel, and the front being a 10 inch IFI wheel, i think the IFI wheel would hold up better with impacts and has a higher traction coefficient. 10 kit wheels will not fit in the 38 inches that we are given but if they are layed out like this:

XXXXXXXX.......................XXXXXXXXXX
..........XXXXXXXX.XXXXXXXXXXX


with the chain in between the two rows of wheels, then it would work.

Re: Hypothetical Situation - Stairs
 

1. The wheels you speak of are probably the 8" AndyMark wheels, either the FIRST, FIRST slick, Plaction, etc. and the 8" IFI wheels

2. The IFI wheels use the same tread as the AndyMark Plaction wheels (Actually, they can use either, the difference is minor between wedgetop and roughtop, and you can get both from AndyMark or IFI, but the Roughtop tends to have more usable life).

3. Why not just use 8 Plaction wheels (or other wheels with roughtop tread) in a dropped center 8wd?

Re: Hypothetical Situation - Stairs
 

Also, keep in mind, that you could modify some snowmobile treads. Team 1091 did that, last season, and we had some excellent success with traction and manueverability. We could easily navigate over the bumps, and by gearing down, we lost some speed, but we weren't pushed around.

Re: Hypothetical Situation - Stairs
 

Did you have any issues with the tank treads coming off while in use or have suggestions that you guys used? I noticed that is was a common issue for team 195 and during a few drive train lessons have heard that treads have problem staying on track. Your 1114, 1503, and 1680's robots are some of the top tread robots in my honest opinion.

Re: Hypothetical Situation - Stairs
 

I have a question: what kind of legal servos are able to support a 100+ lb robot? Would pneumatics or other parts be necessary to support such a robot?

Re: Hypothetical Situation - Stairs
 

Go go gadget Packbot?

Re: Hypothetical Situation - Stairs
 

I don't understand your question. What kind of application are you using to use them in? Which robot are you referring to?

Re: Hypothetical Situation - Stairs
 

The Answer:

ANY

If you gear it enough


But id be faster if you used a more powerful motor such as a CIM or Fisher-Price.

Re: Hypothetical Situation - Stairs
 

Perhaps a gearbox, geared for torque, with an encoder on the output. You could use a P loop to control the position.

You could use a ratchet device to support the robot most of the time, only releasing it when you want to change postion.

Re: Hypothetical Situation - Stairs
 

Or a worm gear. That would probably provide all of the reduction you would need.

I would probably mix a pair of encoders, a gyro (maybe) and an inclinometer. The encoders would determine wheel speed and distance, the gyro would (as usual) determine rotational velocity (Although you might have to do some stuff to keep it sensing correctly, or just use it when in a known orientation), and the inclinometer would detect the ground. An accelerometer *might* work but would be affected by the robot's forward velocity. A weight on a pot would work as well, but would have weight to it (and weight is always a bad thing).


David - about servos - They are weak motors with built-in logic to steer to a certain position, and work the same as a motor, Victor, and pot. Except they are weak. With a CIM or Fisher-Price as the motor, you have significantly more power, which with gearing means you can drive whatever load you must drive faster. Any motor can move the load, but a more powerful (not necessarily a higher/lower free speed or stall torque, but output power, measured in Watts) motor can perform the task faster.

Re: Hypothetical Situation - Stairs
 

This is in my top 5 FRC Promo videos, I show this to students everytime they even think about making a promo video !

Re: Hypothetical Situation - Stairs
 

We had issues beyond belief. We were throwing treads all over the place. Most of the time we were snapping them rather than just having them fall off. This post discusses the issues a bit:

http://www.chiefdelphi.com/forums/sh...94&postcount=5

My the end of the season we had the belt trapped so it couldn't find a way to slide off. Unfortunately this really cut down our efficiency so our robot was slower than we hoped. Definitely not an ideal situation.

Re: Hypothetical Situation - Stairs
 

In 2004 we happened upon a simple, robust, and fast method for climbing the stair. We put drop down ramps made of UHMW plastic on the front of the robot and had 4 large knobby pneumatic tires. The ramps would start the match folded up and would drop down and latch into place, giving the front face of the robot a sloped leading edge that would be just above the top of the step, sort of like an amphibious car.

To climb the stair the driver would simple turn the robot to face the stair and apply throttle. The ramps would lift the nose and when the front tire hit the stair’s edge it would climb onto it. Because the robot would high center between the wheels, we put UHMW plastic strips on the frame so we could glide across until the rear wheels would engage. To get down from the platform we would just drive off and bounce a bit. It was not a finesse move and required the robot to tip about 30-45 degrees, so you needed a relatively low CG. I don’t think we ever tried, but I think we could have climbed multiple stairs if there was a good edge to bite into like in 2004.

This method served us very well and was very KISS, perhaps the KISSiest;)

Jay

Re: Hypothetical Situation - Stairs
 

Why would this be out of the question for FIRST?

Re: Hypothetical Situation - Stairs
 

Surprised nobody has mentioned Whegs yet :) They are crazy cool, extremely simple, and can climb obstacles as high as the diameter of the wheel.

http://www.youtube.com/watch?v=F4GF2UFhv8Y
http://www.youtube.com/watch?v=P7UkXh8-cBw

And if you don't want to bump around on flat ground...
http://www.youtube.com/watch?v=lrE8CcquOuQ

Re: Hypothetical Situation - Stairs
 

By out of the question, I did not mean that FIRST teams could not do this. I am sure that FRC teams could do this actually!

What I meant was the usefulness of this. The only thing this (What I guess you would call a drive train) is made for is climbing stairs. This could potentially be used on a bot, but the usefulness of it is what I would question.

Now after saying this, I know the 2011 game is going to consist predominately of stairs, and some team will come up with this design and make it to Einstein. :p

That would be just my luck, and I would love every second of it!

Re: Hypothetical Situation - Stairs
 

Actually, if properly configured, this design allows for omnidirectional movement (similar to mecanum drive) as well (http://www.youtube.com/watch?v=1uynm...ature=related).

Re: Hypothetical Situation - Stairs
 

Yes, it very well could. Like I said in my post:

I would personally love to see this design and have it work! I would shake whoever's hand who decided to create it for a FRC bot. :D

Re: Hypothetical Situation - Stairs
 

i explored the idea of using a screw drive with first, the main problem is a lack of power, unless the screws were made of rollers, like a mechanum wheel, they require a tremendous amount of torque to move. i looked at ice fishing augers as a supplier for the screws, they are long and fairly perfect.

Re: Hypothetical Situation - Stairs
 

I guess if you needed ALOT of power you could make a single gearbox that runs all 5 CIMs (think 118 crab syle) and use pneumatics to shift the direction the auger is spinning. (as opposed to a high and low gear)

You could also significantly decrease the amount of torque needed to move by making the auger a slightly smaller diameter on either end so it's only contacting the floor in the middle.(think 8 wheel drive; the outer wheels are raised for the same purpose.)

Re: Hypothetical Situation - Stairs
 

With an auger drive, how would you turn? You can't run one side forward/one side backwards, that would make it drive straight. You can't run both one way, that would make it strafe.

I don't think it would take as much torque as you think, since you are transferring the power to the floor approximately the same as you would in a mecanum drive. That said, you could always go with 2 CIM 1 FP per side (and have more power than 5 CIMs total) and leave a single CIM for whatever mechanism you want to build.

Re: Hypothetical Situation - Stairs
 

I think the only way to do it would be to run it as if you were going forward but with one auger going more slowly. It certainly would be an arc-like turn though.

All in all, in my opinion even if there was stairs in this years game augers would not be an eligant solution. They are simply over complicating the problem.

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This may have been posted before, but here it is again...

http://www.youtube.com/watch?v=nVzj3_MUBjE

Re: Hypothetical Situation - Stairs
 

i cannot remember, but wasent there a team that made a 12 wheeled robot for aim high, i believe they used roller blade wheels or something, nobody thought their robot would be able to climb anything but it was one of the best.

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Thanks guys this may become very helpful in a few weeks. The wheels that fold out into leg wheels looks very cool, I don't know how that would work with our motor limitations though

Re: Hypothetical Situation - Stairs
 

Along the WEGS idea, yet without linkages, something that uses this wheel pod design would probably be more suited to the capabilities of FRC teams while still providing the robustness seen on an FRC field:
.

Advanced teams could do a coaxial dog gear design for each pod that drove the pod's legs versus the pod's wheels. Novice teams could drive the wheels with 2 total CIMS and the legs with 2 separate CIMS (not ideal or perfect, agreed, yet still feasible to climb stairs).

"Caution: the moving walkway is ending"

Re: Hypothetical Situation - Stairs
 

I don't know if you read the rest of the thread, but watch this video:

http://www.youtube.com/watch?v=XzKo6KE2H5A
:D

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Is it known whether anyone has tried combining a swerve drive and tracks, like in one of the hummers converted for use on extreme snow conditions?

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A team used them in 2004, 1218.

The external wheels and the entire hub are actually driven together, I believe the ratio is calculated such that when the wheels are stalled, the entire assembly rotates.

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I want to know what extends and retracts these wheels. Anyone have some insight on how this works? It almost looks like there's a rope/string of some sort inside.

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I too spent a lot of time looking at the video to try and figure it out. I was hoping I could find a conference or journal paper with more details (since these are university researchers), but I haven't found one yet.

So I can only guess at what approach they took. I could imagine a coaxial shaft inside the drive shaft that moves inward and outward linearly to extend and retract the "whegs" - this would seem to me to be the most FRC-friendly design. There are also possibilities that may involve electrical or pneumatic rotary connectors (slip rings).

A lot of approaches used to achieve variable valve timing in internal combustion engines would seem to be appropriate here.

Re: Hypothetical Situation - Stairs
 

Sounds like the time to learn how to do a patent search. I guarantee it will take your mind off hint #2, hypothetical stairs, and many other things. You might even get good at it, but just in case, set a wakeup call for the 8th. :D

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An Estonian patent can be found here: patent link

If you Google the term "ratasjalg" you will find more videos of this wheel-leg device. Ratasjalg appears to be the Estonian term for wheel-leg (Google translates it to "Bike leg").

Merle
Granby GRUNTS #3146 - Mentor
Granby Red Blox - FLL Coach
Granby JrFLL Team Coach

Re: Hypothetical Situation - Stairs
 

Great find. I used this website to translate the text to English (I found a plaintext version of the patent that supports copy & paste here):

The untranslated words are probably technical terms that don't appear in a general purpose Estonian dictionary.

Re: Hypothetical Situation - Stairs
 

When I was a kid I had a battery-powered toy truck that had claws that would automatically pop out of the wheels any time an obstacle was encountered. It was pretty cool, and really helped it move along through rough terrain.

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http://www.cyberblue234.com/images/p...04/robot/3.jpg

This is a link to our 2004 robot. It had heavy duty tank treads. The treads gripped the edge of the platform and pulled the robot up.

These were functionally good, but very heavy and required a special drive "cog" on the inner tread.

However, they were practically indestructable - they had a kevlar layer in them and we actually designed for bomb finding robots.

Several other robots used similar designs of treads to make the step up.

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In 2004, 340 used the Tri-Wheel design that is being discussed in this thread on our robot. "Roxanne" made it all the way to Einstein that year.

Check out photos of the robot here.

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Learn from the masters:
Mars Rover:




ATHLETE:

Re: Hypothetical Situation - Stairs
 

None of those robots are climbing stairs, and one of them is a six-wheel independent double jointed articulated swerve drive. Somehow I doubt that is the simplest solution.

Re: Hypothetical Situation - Stairs
 

Whegs bubbled up again at this spot. This time it's more clear about how the wheel changes shape. You don't get a scale idea until midway when a knee and hand appear. I won't expect andymark to have any before next year. :cool: l