Ladder Climbing robot (newbie)

[Moda]

Hi guys, came across this site with a search on google and wondered if anyone could help.

I have a small uni project to complete which involves building a basic robot/device which climbs a ladder 6 rungs and then stops, the payload is an egg so weight is no issue...also there must be no modifications to the ladder. the budget is very tight, only £25 (~$50 USD)

If anyone can recommend a type of motor to use, im thinking a low rpm high torque motor that can run off a battery (probs from ebay or old rc car?)

i also need a mechanism to stop the robot automatically at the 6th rung.

Any ideas would be much appreciated.

Thanks!

[ed1380]

Do you know the distance between the rungs? Do you ahve access to the ladder before it's due?

I'm a noob as much as you, but my idea was to construct a mechanism similar to admin's jesus lizard, and have a spool being wound while it is climbig, and when the spool winds out teh specific amount of string it would activate a switch turning off batery power.

[Brandon121233]

Another question, are there any rules that say you have to auctually "climb" each rung? If not you could use some sort of telescoping pole with a cable and hook on the end, and if you know the height of the 6th rung you could just make it that length, then use a winch on the robot to pull itself up.

[JesseWelling]

I'm imagining a tank design that uses big hooks. the only problem might be coming up with a way to release those hooks......
hmmm that needs more thought.....

as for stopping at the top: just add a range finder (binary or analog) looking at the lader and count each step you pass....

So two questions...

1. what is the shape of the steps?
3. what is the angle of the ladder to the ground?

if you have to do an inverted ladder this won't work as well....come to think of it nothing much will if it is inverted....

[JesseWelling]

just had a better idea. use an 'arm' that can pull a 'body' up to it's current position where a 'body hand' graps hold and then the 'arm' can again extend itself to reach another run. There are 2 ways of doing this I think. one is with a jointed arm and griping mechanism, the other is with a poll/extending mechanism.....
how's that?

[ed1380]

I did a quick sketch in paint, to see if those are possible ways of doing it. IIRC Admin is a mechanical engineer, so I'd love some feedback if that is possible or even if the concept is possible. If so then maybe a beam type robot is possible.

The way it's supposed to work is- there would be one of those on each side of the robot and they are timed to oposite of each other.
http://i43.photobucket.com/albums/e398/RussianCommy/robotarms.jpg

Sorry I think it's too big to hotlink to it

[JesseWelling]

Looks really good. add some kind of mechanisim to hold it's place while the rod is extending and you have a winner.
could probably just use a servo that rotate's a hook down on to the current rung.

The only somewhat technicaly hard problem is to know when to swing down the hook. Probably the best solution would be an encoder on one of the axels that runs the shaft. As a side note I think maybe a tank tread would be an easy way to get a somewhat eliptical patern and make it easy to attach the rod.

[Brandon121233]

Most likely you will have to go with the seccond design in that drawing and even then its ganna have to be a long belt, assuming that the rungs of the ladder are a normal 18 inches apart. So no matter what the total length of the robot is doing to be around 15 to 20 inches.