Robot feet

[simplesi]

I use 3 wheeled vehicles in my after-school clubs but I was wondering about making a real robot

But a simple short stubby one with just sticking the motors/wheels in the feet and maybe adding a couple of servo's for arms.

Any designs around for that sort of thing?

Simon

[Boeeerb]

Servo controlled arms would be easy, but having feet which can balance and walk would be difficult in my eyes as to walk on 2 legs you need to 'rock the bot' to shift balance on to each leg to move (If you get me). What about starting with 4 legs?

[simplesi]

4 legs good - 2 legs bad - where have I heard that before?

Good idea - Robot dog/cat/ etc

I was more thinking 4 wheels/1 motor/ foot so some sort of motorised cart for each leg

But need a cheap simple design for it

Simon

[Boeeerb]

Like a bot on stilts?

[rurwin]

You can do it with two legs, but you have to ensure that the centre of gravity of the robot is over a foot when either foot is on the ground. So the feet have to overlap. It's doable, for example two interlinked semicircles.

The most stable walking platform is six legs, but I understand that getting it to turn corners is tricky. It's also rather expensive in servos.

[simplesi]

Like a bot on stilts?

precisiely

or more accurately - a bot-on-wheels
@runwin

No - not looking to actually make a walking robot - it was just an idea to say make a "robot" looking creature i.e head,body,arms and legs andjust have it simply glide along like a penguin on rollerskates

its the design on the "boots" that eludes me but I know someone. somewhere will have a cunning plan.

It was just that some people want an actual Robot looking robot - not the 3 wheeled vehicles we call robots

Simon
PS Then we might add a couple of servos to just wave the arms about after wards

[SN]

try something like this

I know its a shocking drawing but you get the idea - I think its a common toy robot approach
Lego Technic is an excellent construction material for this kind of stuff

[simplesi]

More than I wanted but very interesting though

You don't fancy knocking a basic (no frills) effort up in Google Sketchup as I'm having trouble imaging working out what goes where

but it looks cools and maybe not too complicated to do

Simon
PS I'm trying hard to avoid technical Lego arrangement as its just SO expensive (but very very nice BTW)

[Fluo]

Check this: http://findmearobot.com/Pages/Johnny%20 ... 20five.jpg

It is a Johnny Five. Second option -wall-e. It's much easier to done but the same effective like bipod or sth like that

[simplesi]

I suppose I could just make a low slung 3 wheeled chassis and put a Robot looking figure on top of it - starting up Sketchup

Simon

[simplesi]

Ok here is a quick version
http://sketchup.google.com/3dwarehouse/ ... af285a5897

I just borrowed a Robot from the Warehouse to show concept

Simon

[simplesi]

I think these designs have great posibilities if we replaced the single motor by 2 separate ones

I actually had one of the slasher ones but it was too fiddly for me to put together so I gave it to one of my Y6 Roboteers ON Friday and its back today - fully assembled and waddling along

The tricycle flash looks like an easily acheivable design so I think we'll give that a go at next club starting tomorow at one of my schools

Simon

[Ravenous]

What about something like this:

http://forums.trossenrobotics.com/showt ... quad/page4

NOTE NOT the whole thing (it's ridiculously ambitious, I haven't even read the whole thread myself) just maybe three or four spindly legs, perhaps adjustable by hand, with a motorised wheel on the bottom of each. (Maybe just two legs with driven wheels and one or two with sliders, so it can steer like a differential robot?) I have no talent for aesthetics, but I think one of these could probably be designed to look either sci-fi or whimsical, according to taste.

Alternatively maybe a mars rover type thing with six legs (levers really - a rocker-bogie suspension) - only motorise just the middle two legs and put carpet sliders on the outer four, to make it cheaper and simpler to steer. (I built a heavy thing like this with eight points on the floor, not six, so with four driven motors and four sliders at the corners. These can be extremely stable. But mine's a disaster because the wheels slip making odometry very inaccurate; I should have gone with six points instead of eight.) Look at the following, where it does "differential bar", that version might be easier than a differential gear:

http://www.alicesastroinfo.com/2012/07/ ... ferential/

There was something else I meant to mention too, but I forgot. Oh well.

EDIT: I just remembered the last thing I forgot. R2 D2 of course. It's really just a two or three legged version of your idea. The two outer legs could be driven, and the middle could either have a steerable wheel or just a simple caster or slider. As long as the centre of gravity is in the right place it should work...

[SN]

here's your target
http://www.bbc.co.uk/news/technology-19506621
28 mph

[simplesi]

You all know I work in primaries not Cambridge!

Great ideas though

I think the tricycle R2D2 flash type concept is the phone to go for - its basically the same as a flat 3 wheeler but with a very long/high trailing wheel/slider.

I've got one of these https://www.sparkfun.com/products/319 on piece of plywood at the moment as I used it as my first home brew equivalent of the Magician Chassis.

I'll take along a working bot tomorrow so they can start on the programming and let some of them loose on the dual-axle jobby and see what they can construct/design

Simon

[simplesi]

Well, I think I'm going to give it a go to make a 2 motor version of the Slasher http://www.knex.com/collect-and-build/p ... p?pc=12163 using the https://www.sparkfun.com/products/319 in Tuesdays RObot Club (since only person in the club! - must get my advertising skills sorted out!)

I think we'll try at first to just replicate the Slasher movement design using normal sized Knex (the school has a fair bit in the after-school club)

It could be very cool if we can get it to work

Simon

[Ravenous]

since only person in the club!

What is wrong with young people these days? If I was in the area I'd be trying to get myself in, and with all my toys. (Though can you picture a forty something greying pupil asking repeatedly "Please sir explain the Kalman Filter bit again"...)

[simplesi]

I just took eye off ball and asked teachers to send out a note - I left it too late

Next time - its A5 Colour Flyer

Simon