Author Topic: Quadraped walking idea.. (stolen from honda's vtec engines :P)  (Read 3583 times)

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Offline Robotboy86Topic starter

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I was talking to a good buddy of mine about engines and it kinda hit me. 

Right now, quadrapeds, hexapods, all walking robots use servo's.  SOME use that muscle stuff, and some even use dc motors with encoders to determine positions(read: ghetto servo).  They all require a motor that can move back and forth on command, etc etc.  Obviously this has a serious flaw that it is NOT effient.  Everytime the motor starts to get energy and its spinning forward, it has to stop and reverse it self.

What if we could let the motor spin one way, and move the leg forward and backwards only using the motor going one way.  This would allow that motor to spin up faster, 4-5k(thats about 80hz leg movement).  Walking robots are known for a few things:  Unique movement patterns, ability to climb over things that can give wheel problems, and slowness.  Even the fastest of servo's can only move 60 degrees every .15 seconds.    If we use a cam setup attached to a dc motor we could move a leg out and in at a VERY rapid pace.  It could even define a legs movement arc.   For a graphical example I jacked an animation picture:

On the image, replace the two golden brass items beneath the cam with rods that can attach to a robotic leg.   When it has maxium lift(the part of the cam lobe that sticks out the most) it could be lifting the leg.  And then the shallow part of the cam could move the leg back in, thus moving it.    It would have to have a way to move out some when it lifts.  Then suck back under when the legs move back in it could then propell the robot forward.     

This could then allow movement at a faster rate by just increasing the rate of speed. 

Now what of changing terrian where higher leg lifts are needed or it needs to be pushed out farther and such? 

This is where honda's v-tec technology comes into play.  Basically when they need to change the cam characterstics they basiccally apply a higher level of oil pressure to the cam and force a diffirent set of lobes on the cam into play.   Obviously oiling would be far too expensive and complex for a basic walking bot..  so what if we isntead apply a linear accuator(or a solenoid or whatever) to the end of each cam on the top of each leg?  When a different walking pattern is needed, simply push the cam over some into a second set of movements.. 

Instead of typical cam style where it goes from A to B, we could use a gradient cam that gradually increases from 1 design to a second..  this would allow a large variation of movements.  From longer reaches, to shorter pull ins and everything.

I am hoping to get a working 3d model of this going by tonight.. so if all goes well I can have some images to sort of show what I mean by tonight. 

I hope this makes sense, I can see it in my head but its hard to put into words..   also the statement of 80 movements a second is obviously not realistic..  at that point the leg would probaly not move back under quick enough.. it would require a lot of tweaking to find the right mix.

Go being unemployed and having too much free time :P

Offline airman00

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Re: Quadraped walking idea.. (stolen from honda's vtec engines :P)
« Reply #1 on: August 28, 2007, 07:52:54 AM »
I like it!  ;D

I want to see the working model, sounds interesting. But don't the legs have to move sideways also, in order to move forward? ???
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Offline Rebelgium

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Re: Quadraped walking idea.. (stolen from honda's vtec engines :P)
« Reply #2 on: August 28, 2007, 11:57:11 AM »
I hope this makes sense, I can see it in my head but its hard to put into words.. 
No ... really ??  ;D ;)

seriously though, interesting idea, I haven't completely understood everything, but I'm curious for you designs
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Re: Quadraped walking idea.. (stolen from honda's vtec engines :P)
« Reply #3 on: September 29, 2007, 04:08:20 PM »
I dont see it working . . . why? Cause the possible different motions that your robot leg can make are very limited. Ok, so I see it working on flat-ish terrain with slowly changing slopes . . . but not something that can turn in place or climb onto/over stuff . . . and in this situation, wheels would just be better . . .

Another similar idea would be using a 4-bar linkage to control leg motion, as I did here:

But again, its very limited on the motions it can do.

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