ROBO1 robots?

Who out there has created a ROBO1 biped for competition, or anything else for that matter? I'm curious as to how much it cost for servos and
how many DOF you used. Also, how is the thing controlled? I'm assuming the whole controller isn't on board, but...
Just curious, DLC
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* Dennis Clark snipped-for-privacy@frii.com www.techtoystoday.com *
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Dennis Clark wrote:

and
assuming
How's about 17 servos, with 10 in the legs, for just over $1645.
http://www.sozbots.com/robo-one/buyone.html
And a 600 mAh battery, guaranteed to run it for maybe .... 10 minutes?
http://www.sozbots.com/robo-one/about.html
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dan wrote:

Only $1645? Heck, for that price, where is the buytwo.html page?
-- Gordon
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Gordon McComb wrote:

So, I'm assuming, when one thinks of "budget robotics", this isn't really the first thing that comes to mind :):). Actually, this is the big problem with building any servo-powered walker. Most of the $$ goes into buying the servos, even cheap ones.
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[snip] : So, I'm assuming, when one thinks of "budget robotics", this isn't : really the first thing that comes to mind :):). Actually, this is the : big problem with building any servo-powered walker. Most of the $$ goes : into buying the servos, even cheap ones.
I figured as much. I've recently seen some video of a Japanese competition and thought it was the coolest thing I'd seen in a while. Time to start dropping quarters into the piggy bank to pay for one of these things - Then play with the programming, which sounds even cooler.
fun, DLC
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Dennis Clark wrote:

the
goes
Time

these
Servo used in Robo1 shown on the soz site = KRS-784 ICS Digital Servo KON784 $89.99
http://www.e-clec-tech.com/kricsdise.html
17 servos*$89.99 = $1529.83. So, $1645 for the entire Robo1 bot including 2 servo controllers sounds like a real bargain. [Gordon can now buy 2].
8.7 kg/cm is only 120 oz-in, if I calc'ed right, so these aren't especially large servos, but at Speed: 60 @ 0.17 sec, good speed for the size.
You will also notice the lynxmotion walkers are up in the $500-700 range. Most of the $$ there is also in the servos. My octopod with chintzy analog servos cost $200 for servos, and about $20 for everything else [not inc controller].
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wrote:

[snip]
Dan,
Most of the servos I've seen have been in the $30-$40 range. Is there something special about these $90 servos? If so, do you know what is it?
Thanks, Robert
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Robert Oschler wrote:

Servo
can
there
it?
Looking at a Tower Hobbies ad, all 6 Futaba digital servos shown are in the $59-99 range.
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Robert Oschler wrote:

Servo
can
there
it?
Hitec digital servos, $35-90 range.
http://www.balsapr.com/catalog/servos/hitecHDS.asp
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Dan,
Nice research. :) Yes I was thinking of the low end Hitec servos which is what I have with my Robix USBOR controller.
Thanks.
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Robert Oschler wrote:

Some of it is marketing. The servo companies don't make money on the low-end servos, so they offer units with enhanced features (coreless, ball bearing, etc.) for those users who want performance. Folks are understandably cautious about putting a $15 servo into a $1,000 model helicopter, so they want something of better quality.
The very high end digital servos mught use coreless motors, precision ball bearings, and resin or metal gears, all of which bump up the price. And because there is less competition among these higher-end servos, they don't have to trim every last dollar out of their margins.
Whether the digital servos in the Robo1 are worth the $90 I can't say, but this price isn't unusual. There are some digital servos that cost upwards of $120.
Though you'd be stressing them, I think it's possible to use much less expensive servos, and run them at a higher frame rate, and still get a lot of useful hours of experimenting. Maybe these motors won't last quite as long, but you could replace each one 2-3 times over before you spend the same money.
-- Gordon
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<snip>
Gordon,
Thanks for the info. I never run my motors that long so I'll stick with the low-end ones.
I've seen the Robo-one in action. I like it a lot. I wonder though what they'll have to do to get rid of the movement "jitter". Or do you need to get into the $60k plus range like the Asimo to see that kind of fluidity?
Robert
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what
need to

fluidity?
Jitter and fluidity are slightly different things. To get really fluid flow, you probably need to have a very good closed-loop control algorithm keying off of several accelerometers.
Regards basic servo jitter, from what I gather, it does seem that the digital servos are more prone to this than the analog kind. I know one guy who was using a certain servo controller to control the digital servos in his lynxmotion biped, but there was too much servo jitter. He changed over to one of my servo controllers, which has very stable 1-usec resolution, and also a lot of extra filter caps on the servo power buss, and it worked much better. He's now sending data to the controller at 115.2 in order to get essentially closed-loop real-time stabilization of the biped - although the controller wasn't really meant for this :).
You will notice that very few off-the-shelf servo controller boards have much in the way of filtering on the servo power busses, and you probably need more filtering for digital servos, esp that they suck so much current. Basically, "inductance" in the power and battery leads can lead to noisy signals. Same problem, I think, as the "main capacitor" in regular ESCs .... [you'll also notice that essentially NONE of the model car ESCs we talked about on the other thread have main caps - they're all too tiny, no room] ....
http://www.4qdtec.com/pwm-01.html#cap
Since Gordon mentioned that the power to internal servo motors is interrupted for 18 msec and actually on only during the 1-2 msec control pulse, I am beginning to better understand some of the problems just mentioned. I can also see why it might be a mistake to have pulses going to all servos simultaneously rather than in sequence, like the r/c receivers use.
- dan michaels www.oricomtech.com =======================
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dan wrote:

The Robo1 uses digital servos for the torque, but in my (admittedly limited) testing I found it possible to increase torque on a standard servo by running it at a 200-300 pps frame rate. The servo got hot, but with some intelligent control I think it might be possible to dynamically change the frame rate for those times when torque demands are lower.
Robo1 is storing speed and acceleration settings in the servo, which is something digital servos can do, but you'd have to do this with a dedicated microcontroller (the $5 kind). One MCU could handle several servos.
You still need a ball bearing servo of decent quality...something along the lines of $25 at discount (rather than $50-80 for digital). That's $425 in servos. Figure maybe $100 for the controller, and $50 more for other electronics. If you have access to a metal brake and basic metal-working tools you'd be able to make the metal frame pieces.
In all you're still looking at about $600 to build your own from scratch, not to mention a lot of work.
-- Gordon
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I have a milling machine to cut frame parts.
If someone wants to come up with dimensions for them, I'll cut them and see if we can get a biped put together.
Rich
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snipped-for-privacy@gmail.com wrote:

Well, several of us have CNC routers and mills and such, and guys like Pololu, Lynxmotion, and Bruce Filener provide reasonably-priced laser cutting by the minute. What we need are those dimensions! The design is the trick.
-- Gordon
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Check out
http://www.symbio.jst.go.jp/PINO /
not RoboOne, but similar and is a completely open design with all support documents.
Scott
wrote:

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I have the time to cut them out for free (cost of materials is only price)
#1)dimensions/ drawings #2)cheap servos + servo controller #3)cheap aluminum #4)machinist (already have this) #5)software
Rich
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Gordon McComb wrote:

the
goes
but
I'll tested std servos with update periods of 15 and 10 msec, and they ran fine, and "seemed" to have a lot more torque, but I didn't try it long enuf to notice heating. Alternately, I've used 40-50 msec update periods, and the servos went really wimpy. I'm not 100% certain whether the different effects are due to more/less torque per se, or just to different responsiveness in the internal feedback loops.
With the longer update periods, you can turn the horns a long way before the torgue builds up. I actually thought this might be a software way of creating a "servo saver" - ie, a way to add in some compliance to leg joints, eg, during footfall, etc .... might not work too well for a biped, however ... tilt, tilting, over and down ....

is
along
for
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dan wrote:

Try 4 msec periods. That equates to 250 Hz. Some digital servos run at 300+ Hz.
If you don't mind the hack, you can always cut away some of the plastic housing of the servo and stick a small heat sink onto the side of the motor.

It has to do with the period of time power is applied to the motor. In an RC servo the motor inside is powered only when the servo receives a pulse. Between pulses it receives no power. This is why if you remove pulses from a servo (we're talking analog here, not digital) they simply stop.
Given a maximum 2 msec pulse every 20 msec means the motor is really only receiving current 1/10th of the time. Going with a higher frame rate may affect the PI loop in the servo, but different brands may behave uniquely. I only tried it with some GWS servos, and there was some overshoot (expected) in moving from one location to another. Given a more intelligent controller, you could build acceleration ramps to tackle most of this. This is what goes on inside a digital servo.
When the torque isn't needed by the motor you could revert to a 50 Hz frame. That would conceivably prolong motor life, and for sure extend battery life. Digital servos consume a lot of amps.
-- Gordon
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