RoboSavvy Forum

18F does it deliver staying power?

2011-05-17T10:20:34+01:00

Hi Mohit

Just saw your design and it similar to what I thought.

I'd just like to reinforce my recommendation: make sure both servos move at the same time. I'd try to create the motions using a relatively low speed to ensure the servos are moving at the same time.

Bear in mind that when you send a Set Position command, you first send to one servo and then to the other servo.

This creates a delay between sending the two instructions which means one servo will start moving first than the other (miliseconds difference).

If the speed is set too high, the movement may get out of sync, twist the bracket and ultimately break some servo gear or the bracket itself.

As for the holding torque, it'll likely be higher indeed.

Regards
Pedro

Statistics: Posted by PedroR — Tue May 17, 2011 10:20 am

18F does it deliver staying power?

2011-05-17T04:46:34+01:00

Hi PedroR;

I uploaded one photo in File Manager. Shoot from Nokia 5230.

Please see it. I used the same in Torso part of both Legs. I hope it will give more than 15Kg Torque and make the Bioloid Type A to Stand on one feet for atleast 30 to 40 Seconds.

Thanks.

Statistics: Posted by MOHIT JINDAL — Tue May 17, 2011 4:46 am

18F does it deliver staying power?

2011-05-16T09:54:12+01:00

Hi Mohit

With regards to your suggestion of doubling up the AX-12+ I'm not sure how your design is. I assume you'd be using a large frame with a dynamixel connected to each side/hole on the frame.

It should theoretically increase the stall torque (or double it) but you need to be to ensure both servos have the positions synchronized so that each servo is holding half the torque at all times.

A de-synchronization of a few degrees may result in gears breaking or damaging the bracket.

FYI "double up" is a standard feature included in EX-106+ servos (they can be paired and show as a unique ID) and I know from Robotis they had serious issues synchronizing the two servos when they are double up. I'm not sure how they fixed it in the end but I know it was challenge.

I can't offer a lot more detail as your question is know mostly mechanical and related to the behaviour of a physic system under multiple forces.
I am able to answer in terms oft he individual specs and capabilities of each actuator.

Regards
Pedro

Statistics: Posted by PedroR — Mon May 16, 2011 9:54 am

18F does it deliver staying power?

2011-05-14T03:52:42+01:00

Sorry PedroR
Can you please see and answer about Dual mode Ax12+ ?

Statistics: Posted by MOHIT JINDAL — Sat May 14, 2011 3:52 am

18F does it deliver staying power?

2011-05-13T17:10:25+01:00

Hi Mohit

I notice you've double posted your question here http://robosavvy.com/forum/viewtopic.php?p=31223#31223 and here http://robosavvy.com/forum/viewtopic.php?p=31224#31224

You will nto get more replies from people by repeating your question in different places.
It is usually the opposite: people become frustrated with this practice and many times choose not reply. Also replies become out of sync because the same subject is being dicussed in two different places.

As a general rule, please avoid double posting.

As for your question about posting images on the forum, you need to upload your picture to some place on the Internet and then put the address of the image between the tags.

You can upload to flickr, Picasa, etc. or our forum. To upload to our forum, on the left column, there is a box named "User Menu" in that box, select the "File Manager (new)" option. It will show you an interface to upload your files.
You can find the uploaded files under http://robosavvy.com/Builders/MOHIT%20JINDAL

Regards
Pedro.

Statistics: Posted by PedroR — Fri May 13, 2011 5:10 pm

18F does it deliver staying power?

2011-05-13T11:00:04+01:00

I somehow made Dual Mode(Back to Back) of Ax12+ to get more power to make my Type A to stand on one feet.

Can anyone tell me how much powerful it is now ?I think its now like Ax18A

My photo is in C drive Can you also tell me How to paste photo here. is not working for me.

Statistics: Posted by MOHIT JINDAL — Fri May 13, 2011 11:00 am

18F does it deliver staying power?

2011-05-10T22:17:20+01:00

I need faster arm motions for kung-fu. Just check out the arm speed of Andrews robot in videos from Robogames 2011. He is using all RX-28f for his robot

Statistics: Posted by Gort — Tue May 10, 2011 10:17 pm

18F does it deliver staying power?

2011-05-10T15:54:58+01:00

Hi Gort, Mohit

With regards to Gort's post,
about upgrading the arms on the Bioloid, bear in mind the Bioloid GP uses standard AX-12s in arms. They've only used AX-18s on the legs which are the ones that hold most of the weight and improve the walking speed.

Also from your video, are you using the AX-18s on the legs there? If so, I trust you could probably "squeeze" some more walking speed from your bioloid by adjusting the MTN files.

With regards to Mohit's question, I can't give you 100% guarantee an AX-18 will hold all the weight on one foot.
As I said the servos feel much faster and seem to be dimensioned to handle maneuvering a Bioloid without "sweating" too much (if at all).
However standing on one foot is the same as saying you'll be holding all the weight over one servo which I can't really guarantee it can do.

Regards
Pedro

Statistics: Posted by PedroR — Tue May 10, 2011 3:54 pm

18F does it deliver staying power?

2011-05-10T04:07:25+01:00

I have had good luck with AX-18Fs in the legs! Went to Robogames with this setup! I think I will upgrade the arms with them next!

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Statistics: Posted by Gort — Tue May 10, 2011 4:07 am

18F does it deliver staying power?

2011-05-10T02:49:37+01:00

Hi PedroR,
Do you think the Ax18a have more power so that the Bioloid stand on one leg for 1 minute and will it hold Bioloid COG on one leg

Statistics: Posted by MOHIT JINDAL — Tue May 10, 2011 2:49 am

18F does it deliver staying power?

2011-05-09T09:52:49+01:00

Hi Dewey

We've had a Bioloid GP with us here at RoboSavvy for quite some time now and we've even taken it to some events.

The AX-18s make a very noticeable difference in the robot performance.

My feel is that it's not only the the torque that is higher but the key part is that the torque is high enough to handle any complex movement considering the weight the robot.

What I mean to say is that if you take into consideration the overal weight of a standard Bioloid, the AX-18s have a torque high enough to be making maneuvers and shifting the center of gravity around with extreme fluidity (this is visible in the Bioloid GP)

In case you run a non standard Bioloid assembly, heavier than the standard Bioloid, you may not feel the bennefits this way but our impression is that the AX-18 was dimensioned/engineered to hold and maneuveur the weight of a Bioloid very efficiently.

This is visible in how much faster and sharp the GP is reacting to command requests and doing maneuvers such as the cartwheel.

Regards
Pedro.

Statistics: Posted by PedroR — Mon May 09, 2011 9:52 am

18F does it deliver staying power?

2011-05-07T20:57:34+01:00

I'm looking to upgrade my premium humanoid from AX12+ to AX18F selectively, as funds permit!

While the published torque increase, of the AX18F over the AX12+, is modest, speed gain substantial, can anyone advise on 'efficiency'.

I find the AX12+ overheats if it is asked to provide near maximum torque for more than a few seconds.

I was wondering if the AX18F while not providing a great increase in torque might be able to provide high torque for much longer without overheating, as a result of its superior motor.

Any 'well oiled' roboteer offer any light on this????

Dewey

Statistics: Posted by Dewey — Sat May 07, 2011 8:57 pm