Alt-BEAM Archive

Message #09128



To: beam@sgiblab.sgi.com
From: Bruce Robinson Bruce_Robinson@telus.net
Date: Wed, 12 Jan 2000 23:34:37 -0800
Subject: [alt-beam] Re: Nihon Lens Motors


Bob wrote:
>
> Since this is going to be my first walker, I may
> just go with a basic two motor design.

You could follow Andrew Miller's tutorial for a microcore, or use Ian
Bernstein's Almost Complete Walker circuit for a master-slave bicore
with reverser.

http://vsim.freeservers.com/amiller/microcore.html

http://www.beam-online.com/Robots/Circuits/circuits.html
WAY down near the bottom.

> Gotta include sleep in there somewhere.

Why?

Regards,
Bruce



9129 Wed, 12 Jan 2000 23:45:59 -0800 [alt-beam] Re: microcore experimentation kit beam@sgiblab.sgi.com Bruce Robinson > David Perry wrote:
>
> What if (as someone suggested) i reate a small circuit board complete
> with a single schmitt inverter and either a plug to put in your own
> resistor or an adjustable pot built in.

So, what exactly are you gaining, David? Just MORE stuff to plug in.

Why not include the pot (make sure it isn't one of those 50-turn-life
things) AND the capacitor. Provide 4 connection points:
- capacitor input (Nv input).
- pot input (Nu input).
- inverter input (so you can inject or kill pulses.
- inverter output (obviously).
And power & ground, of course. That's a six-pin board.

You may want two or three versions with different size capacitors.

But if you're going to do that, why not use a hex surface mount and
supply six circuits similar to the above? That gives you 26 pins.
Perhaps you could size the board to plug into a 28 pin socket.

Hmm ... Is this really getting any easier? :)

Bruce



9130 Thu, 13 Jan 2000 09:21:42 +0100 [alt-beam] Re: SV: BIPEDS Was: Pressure Sensors beam@sgiblab.sgi.com Evaristo Westplate Hi,

Lets see if I follow you

>if the ultimate purpose of the sensors is to 'level out' the forces on a
>foot by activating motors to shift the center of gravity so the heel, toe,
>left and right sides of the foot all have equal weight distributed on them,

Yes.

>take for example just the heel/toe axis. as the heel strikes the ground the
>toe needs to be forced down to make contact until both the heel and toe have
>equal weight or force exerted on them.

>so if the force on the heel is converted directly into mechanical force,
>instead of electrical that is in turn converted back into mechanical via
>motors/servos, like what happens when you connect two air/hydraulic
>cylinder's ports together. i'll try to explain what i mean.
>
>if you have two identical air pistons, and connect air line between the
>inlet port of one to the inlet port of the other, when you push one of the
>pistons in air is forced out the inlet into the second piston, causing it to
>extend. disregarding friction for a moment...and substituting a
>noncompressing fluid for the air, the two cylinders will try to equalize the
>forces between them.
>
>so depending on how they are coupled to the foot, as the heel strikes the
>toe end is raised or lowered until the front back pressure is equalized.

{I'm just thinking this over}

So the cylinders are connected to the legs and the pistons to the foot.
Pushing the heel will force the cylinder to the toe to extend. The foot
will rotate and the angle of the leg remains fixed. So you need something
to regulate the pressure so that the leg will change its angle. This could
be a valve but what will control this valve?

Lets see. Suppose the foot is flat on the ground and the leg (plus robot)
is upright. Pressure in both cylinders are equal. Now the robot starts to
fall slightly forwards. Pressure in the heel forces the toe down so
pressure in the toe forces the heel down. If this is true then the robot
will push itself forward to the ground. Hmm. Could you make a system that
will push the toes when pressure is applied to the toes? Hmm.

I don't know. Did I overlook something? Sounds to me you need something to
control the pressure in the cylinders.

See'ya




Evaristo

Gizmo homepage: http://www.crosswinds.net/~evaristo
Biped photos : http://www.crosswinds.net/~evaristo/biped.html

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