How to build a big robot?

[robogeek3 offline]

I'm tired of building these tiny robots.

How would I build a robot that is two feet tall, a robot that is 4 feet tall, and a robot that is 5 feet tall? (I'm not going to build all three, just wondering).

The servos for sale are so small and not large enough to support a bigger robot. Robots like robonova, khr, bioloid, are relative small robots for me.

I want to build a robot like qrio, asimo, and romeo.

[serithseraki offline]

I want to build a robot like qrio, asimo, and romeo.

I assume by that comment you wish to build a advanced robot and not just a robot with added height. Regardless, what is your level of expertise in this field? Have you only worked with kit humanoids thus far? If so, you may want to do a lot of personal research before attempting this. For a two foot tall robot you can get away with high torque servos, similar to Andrew's robot Giger, Naoki Maru's King Kizer, and Dr GIY's Yokozuna Great. Here's a link to Dr GIY's blog to give you some build ideas.

http://translate.google.com/translate?sl=auto&tl=en&js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.geocities.jp%2Fdr_giy%2F&act=url

Now if you want larger robots you may want to look at Takeshi Maeda's Omnizero9 for ideas but I recommend the smaller robots and build from that.

[limor]

the cost of geared servos goes up almost exponentially as you get over around 60 cm. there is however a relatively fashionable new area of control for humanoids which is used in robots such as Roboy (google). the idea is that you use 2 linear (or rotational) actuators for each joint with wires and spring/damper. you can then get quite high torque at the joint using two cheap worm gear linear actuators. google antagonist pair robot actuator
This is very biologically inspired and you need to know your control theory.

[robogeek3 offline]

@limor
I saw your building of a humanoid robot like qrio and asimo so kudos to you. Great job!
What do you estimate the cost of geared servos to be? Do you have a link where I can purchase them? I saw roboy, but he looks more thinner and less bulky than robots like the asimo. Do robots like the asimo use geared servos?
--Thands

[limor]

Asimo uses harmonic drive gears
High torque servos such as Robotis Dynamixel can be found here

[robogeek3 offline]

Would these servos be proper enough to support a humanoid robot

http://www.robotshop.com/ProductInfo.aspx?pc=RB-Ins-01

Thanks

[limor]

you should really consider Robotis servos I mentioned before
All RoboCup teams are using these servos to build big humanoids.

[i-Bot offline]

The Torxis servo looks to be very slow and only has basic PWM control. Not a good choice for a humanoid.

Do you have a budget for your humanoid ?

[robogeek3 offline]

No budget as of now. Obviously a reasonable price. I will start out just building the legs with maybe $3000usd. If all goes well then I will increase my budget. Last robot I built was an upgraded robonova for like $2000. Seemed like too expensive for such a small robot. That is why I want to build a bigger bot even if it costs a little more.

The robotis servos dimensions 1.6in x 2.5in x 1.8in

How would that support a big robot? The Torxis servo is 5 inches? Are there any large fast servos?

Also if you have any pictures of robots built from the robotis servos that would be much appreciated.

-Thanks Limor your feedback has been very helpful. And the robot you're building is awsome so keep posting updates!

[robogeek3 offline]

Does anyone know if this servo is proper suitable enough for a humanoid robot?

If we compare this servos to the DX-117's sold from Robotis, this is how it pans out:

They have about 9 times the torque, but if you consider the new lengths of arms & legs etc, they have an effective 2-3 times the torque.

They weigh about 12 times what the DX's weigh.

They take up about 12 times the volume of the DX's.

They are about 5 times slower than the DX's.

So realistically, the torque to weight (and torque to size) ratio is shot, as is the speed. These servos would not work on a humanoid of Asimo's size. Furthermore, they have very limited sensing abilities, so walking (realistically) would be out of the question. Of course someone could make a pair of bipedal walking legs - but that has been done many times before.

Harmonic Drive Gears is what I must research next!



It's a tonegawa servo

[robogeek3 offline]

According to the official site for asimo is has:

Servomotor+Harmonic Speed Reducer+Drive Unit

Anyone hear willing to provide me links to these supplies

[PaulL offline]

Big Bot = Big Money.

[robogeek3 offline]

Aiming for Qrio design. Seems most realistic. Two feet tall.

[MOHIT JINDAL offline]

Well Qrio looks like a toy for kids. ASIMO is a real humanoid robot.
I am also thinking to use Harmonic Drives but real HD's are very costly. You can experiment with 3D plastic print HD's from projectbiped.com His name is jonathan. Jdow on thingiverse.