A-pod, an ant inspired hexapod

Hexapod Robots

Re: A-pod, an ant inspired hexapod

Postby Zenta » Wed Apr 14, 2010 10:28 am

Aggrav8d wrote:Those are exactly the ones. $6 each?! They're $0.20 parts! There's got to be a cheaper source for vacuum molded parts.


Not 5,95$ each, they are sold in pair.

Another better alternative for the 645's are these: http://www.nodna.com/product_info.php?language=en&products_id=1326&XTCsid=sccapacr2ipqlnh39caebu2p37

innerbreed wrote:One thing i did try last year with hitec servos was to remove the back casing from the servo, drill a hole though it, then push a screw though it and attach the ball baring directly to the servo back.

I've also done that for one servo one time, you've to be a bit careful but it worked though. Probably the cheapest solution.

-Zenta
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Re: A-pod, an ant inspired hexapod

Postby Zenta » Tue Apr 20, 2010 7:27 am

Hi,
I've done alot of work lately on the code part for A-Pod. At the moment A-Pod walks very well and the code for movements are improved too. To be honest I'm very satisfied with the result. The combination of the mechanical improvements, some hardware changes to the DIY, Xan's latest v2.0 and Kurt's XBee/SSC binary code did the magic! I've also decreased the total weight of about 85 gram, all servos and electronics are now powered by the same LiPo.

Today I've uploaded a new video:




Let me know what you think.

-Zenta
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Re: A-pod, an ant inspired hexapod

Postby Matt Denton » Tue Apr 20, 2010 7:39 am

Beautiful! :D
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Re: A-pod, an ant inspired hexapod

Postby pem » Tue Apr 20, 2010 7:56 am

Brilliant, and a work of good collaboration.
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Re: A-pod, an ant inspired hexapod

Postby Aggrav8d » Tue Apr 20, 2010 3:46 pm

First I was jealous it moved so smoothly.
Then I was jealous it was strong enough to pick up a box.
Then I was jealous you have THREE.
Lastly I was jealous you never have to stop work to go to the fridge again.

Very nice work, Zenta.

(PS: Where did you get the end caps for his feet?)
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Re: A-pod, an ant inspired hexapod

Postby Zenta » Wed Apr 21, 2010 7:47 am

Thanks for your comments!

No reason to be jealous. I just wish I could afford 18x EX-106+ servos. LOL
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Re: A-pod, an ant inspired hexapod

Postby Matt Denton » Wed Apr 21, 2010 8:02 am

Zenta wrote:No reason to be jealous. I just wish I could afford 18x EX-106+ servos. LOL


Well if you can ever afford them, I would strongly suggest purchasing one and testing it first, based on my experience with the RX-10 and RX-28 servos, the actual achieved resolution may be much lower than that stated by the data sheet, about half or less on the RX-10/28. Also the control algorithm is not a proper PID loop, which also lets them down.

Just as a comparison, on the average analogue servo such as an HS-645MG, you will get about 9 to 10 bit actual resolution. The HS-645MG have particularly good resolution due to their low ratio gearbox, which reduces cogging at the output shaft. The dynamixel range also have good gearbox's but the electronics/control lets them down. IMO! ;)
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Re: A-pod, an ant inspired hexapod

Postby Zenta » Wed Apr 21, 2010 9:05 am

Matt Denton wrote:Well if you can ever afford them, I would strongly suggest purchasing one and testing it first, based on my experience with the RX-10 and RX-28 servos, the actual achieved resolution may be much lower than that stated by the data sheet, about half or less on the RX-10/28. Also the control algorithm is not a proper PID loop, which also lets them down.

Just as a comparison, on the average analogue servo such as an HS-645MG, you will get about 9 to 10 bit actual resolution. The HS-645MG have particularly good resolution due to their low ratio gearbox, which reduces cogging at the output shaft. The dynamixel range also have good gearbox's but the electronics/control lets them down. IMO! ;)


Hi Matt,

Yeah I remember you told me this before. Thats the reason for why I mention the EX-106+ since they say it has 12 bit resolution (280 deg rotation), not 10(9) bit as the other bioloid servos. But testing only one at first would be a good idea anyway.
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Re: A-pod, an ant inspired hexapod

Postby Aggrav8d » Sat Apr 24, 2010 8:01 am

This raises a question: what is the most accurate servo? I'd like to do some CNC milling with my hex, maybe some drawing. I don't have the resources to buy & try every servo brand under the sun. Would you say the HS-645MGs? They seem like the AAA servo to have at the moment.
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Re: A-pod, an ant inspired hexapod

Postby Matt Denton » Sat Apr 24, 2010 8:55 am

645mg's are a good quality and torque for the price, but for accuracy you would probably want a digital servo. My CNC hexapod uses 5995TG servos, which have now been superceeded by something else, or take a look at the futaba BLS range.
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