mech system wanted for smooth walking, with only one motor.

[Rebelgium]

Hi everybody,

I've been designing and experimenting with mechanical systems for legs for a robot, my goals are:
- Walk as smooth as possible. So there must be a flat side if you'd plot the foot of the leg.
- As simple as possible. As few pieces as possible, and preferably no "sliding" points, only normal pivoting points. (whats the word I'm searching for here? :p)
- Use only 1 motor. No servo's ... as simple as possible

I was wondering if you know designs that do this, or come close to it? Any help is welcome!
Or some tips and tricks?


btw, I already know the Theo Janssen desing (i fyou don't know what it is, youtube it! interesting)

[want2learn]

Hi,
 I don't think you'll find all of your criteria can be met in one design to be honest.

When i was building beam robots i tried a load of different designs using one motor to give a smooth motion so my bot didn't suffer from the Frankenstein walk that all other beam designs suffer from.
The only partial success i had was with legs that kind of mimicked the motion of a dogs leg. Problem was when turning the robot had to take tiny steps and walked like Frankenstein when he was drunk. Also i had to use sliders as well as articulated joints (just because it was easier and cut down the amount of linkages)

I personally think you should bite the bullet and use two motors per leg, three would be better still for smoother motion, this honestly is the only way to simplify the mechanics of your design in my opinion.

If your design is for a uController you will probably need encoders on the motors (limit switches at the very least), thats why most people use hobby servos: They are accurate(ish) easy to control in software (says the new guy<<laughs at self) and are easily interchangeable.

Probably not what you wanted to hear, I hope someonelse can be of more help.
Other than what I've said already I'd say look at wow wee's robopet (the dog toy thing) I think thats about as good as you'll get

[Rebelgium]

I know all about servo's, I just want to try and find something better. It's possible, look at theo janssens design...
Robopets walking is pretty bad, hexapods can do much better.

Thanks for your help though

[want2learn]

Sorry.

- As simple as possible. As few pieces as possible, and preferably no "sliding" points, only normal pivoting points.

This is no easy task is what i was trying to point out.
I am aware of janssen's designs but if you look at the mechanism its quite complex, contradicting the quote above

[Admin]

Yeap its possible.

Look up both four-bar linkages and five-bar linkages. You'll need to find a simulator to design them, of which google can help. There are many for four-bars.

You can also use Phun to simulate your four/five-bar biped.

My Jesus Lizard robot used a four-bar.

Keep us updated with what you come up with!

[Rebelgium]

Yeap its possible.

Look up both four-bar linkages and five-bar linkages. You'll need to find a simulator to design them, of which google can help. There are many for four-bars.

You can also use Phun to simulate your four/five-bar biped.

My Jesus Lizard robot used a four-bar.

Keep us updated with what you come up with!

I remembered your jesus lizard robot a few days ago and re-read it, I also have Phun (saw it in your latest tutorial) and a 2D physics simulator.
And I've designed a four bar linkage already, which is almost exactly what I'm looking for, except it's upside down  ...

If I succeed, I'll definetly make a robot with the system and show it to you guys. 

[Admin]

I'd actually been thinking about doing a 4-bar simulator for awhile using Phun . . . so I did one:
http://www.societyofrobots.com/downloads/SoR_Four-Bar_Linkage_designer.phn

I also added the link to my Jesus Lizard robot page.

I tried making a walking biped with it, but couldn't quite get it to work or balance. I'll leave that to someone else . . .

[Spider]

Google "Klann linkage" - it's a little simpler than the Jansen linkage with better linearity and step height.

[Hawaii00000]

This kind of interesting http://robotics.benedettelli.com/UltBiped.htm It uses one motor, can go any direction, and looks quite simple. I'm not sure if you're looking for a biped though. Tell me if it helps.

[Admin]

This kind of interesting http://robotics.benedettelli.com/UltBiped.htm It uses one motor, can go any direction, and looks quite simple. I'm not sure if you're looking for a biped though. Tell me if it helps.

Yea but . . . it requires oscillating the heavy mass at top . . . think if that was you sitting on it! Plus . . . wheels can handle rougher terrain than that thing