Robotis based industrial type robot model.

Discussions regarding building a walking robot at home. Most of the robots participating at Robo-One competitions are custom fabricated.
22 postsPage 1 of 21, 2
22 postsPage 1 of 21, 2

Robotis based industrial type robot model.

Post by sap1975 » Sun Sep 20, 2009 10:51 am

Post by sap1975
Sun Sep 20, 2009 10:51 am

Hi guy’s

Well. As a followup to the ”AX-12’s and RS-64’s on the same communications string” thread i figured i’d better share on the progress. (or lack of it)

The “funding” is coming together quite nicely and while i’m sorting that quite important bit i’ve been doing some designing and drawing. So far that’s all that’s been going on.

Anyways here it is. I’m planning on doing the actual build in a combination of resin casting, CNC milling and 3D prototype printing so the scale of the task ahead is a bit on the challenging side but i guess that’s what happens :)

Image
Image
Image
Image
Image

Cheers
/Stig.
Hi guy’s

Well. As a followup to the ”AX-12’s and RS-64’s on the same communications string” thread i figured i’d better share on the progress. (or lack of it)

The “funding” is coming together quite nicely and while i’m sorting that quite important bit i’ve been doing some designing and drawing. So far that’s all that’s been going on.

Anyways here it is. I’m planning on doing the actual build in a combination of resin casting, CNC milling and 3D prototype printing so the scale of the task ahead is a bit on the challenging side but i guess that’s what happens :)

Image
Image
Image
Image
Image

Cheers
/Stig.
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Post by i-Bot » Sun Sep 20, 2009 2:12 pm

Post by i-Bot
Sun Sep 20, 2009 2:12 pm

That looks impressive.

I too am looking at converting my Robot arm for Dynamixel compatibility. My approach is different since I will convert my existing Mitsubishi arm and use custom servo controllers on existing motors and encoders.

When I compare your design with theirs I see some significant differences. The comparison may help you, though I do not know what application you have for your arm.

Here is my arm diagram:

Image

You see the shoulder joint is direct above the waist joint. I guess this simplifies the kinematics and also provides better balance. The waist joint is very substantial and the waist motor is in the base.

The body contains the shoulder motor and some interface. It also has two springs to counter balance the shoulder and the elbow joints.

The chain shown in this diagram is how the elbow is counter balanced:

Image

Your upper arm does not look very rigid, which may affect strength and accuracy.

You see the wrist on my arm has both pitch and roll through a differential gear arrangement. This allows much more flexibility on hand orientation.

You may want to do a diagram like this to understand the arm capability and especially what constraints you have on hand orientation over the range:



Image

I can maybe get some photos of any part of any interest to you, though it is rather difficult to get inside all parts.
That looks impressive.

I too am looking at converting my Robot arm for Dynamixel compatibility. My approach is different since I will convert my existing Mitsubishi arm and use custom servo controllers on existing motors and encoders.

When I compare your design with theirs I see some significant differences. The comparison may help you, though I do not know what application you have for your arm.

Here is my arm diagram:

Image

You see the shoulder joint is direct above the waist joint. I guess this simplifies the kinematics and also provides better balance. The waist joint is very substantial and the waist motor is in the base.

The body contains the shoulder motor and some interface. It also has two springs to counter balance the shoulder and the elbow joints.

The chain shown in this diagram is how the elbow is counter balanced:

Image

Your upper arm does not look very rigid, which may affect strength and accuracy.

You see the wrist on my arm has both pitch and roll through a differential gear arrangement. This allows much more flexibility on hand orientation.

You may want to do a diagram like this to understand the arm capability and especially what constraints you have on hand orientation over the range:



Image

I can maybe get some photos of any part of any interest to you, though it is rather difficult to get inside all parts.
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Post by sap1975 » Sun Sep 20, 2009 5:00 pm

Post by sap1975
Sun Sep 20, 2009 5:00 pm

Thanks’ mate.
I didn’t think id find anyone else in this forum interested in the ”model” version of industrial robots.
That’s a Movemaster right? Have been having a look at those and they look quite interesting but are typically quite expensive.
Just for the info my design is heavily inspired by a Fanuc LR mate 200 series and is a 6 DOF solution. And yes i know that placing the motors etc. there will chew into the handling capabilities of the arm. I guess i forgot to include “photos” of the “wrist”
Payload fully extended is expected to be around ½ kilo. According to my limited math skills that is.

Ehh… how do you plan to go about the conversion?
I’m thinking closed loop servo controllers with RS485 interface. Not the easiest of projects.

Cheers
/Stig.
Thanks’ mate.
I didn’t think id find anyone else in this forum interested in the ”model” version of industrial robots.
That’s a Movemaster right? Have been having a look at those and they look quite interesting but are typically quite expensive.
Just for the info my design is heavily inspired by a Fanuc LR mate 200 series and is a 6 DOF solution. And yes i know that placing the motors etc. there will chew into the handling capabilities of the arm. I guess i forgot to include “photos” of the “wrist”
Payload fully extended is expected to be around ½ kilo. According to my limited math skills that is.

Ehh… how do you plan to go about the conversion?
I’m thinking closed loop servo controllers with RS485 interface. Not the easiest of projects.

Cheers
/Stig.
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Post by sap1975 » Sat Oct 24, 2009 1:51 pm

Post by sap1975
Sat Oct 24, 2009 1:51 pm

I-Bot, i was just wondering. Have you made any progress?

/Stig.
I-Bot, i was just wondering. Have you made any progress?

/Stig.
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Post by sap1975 » Sat Feb 20, 2010 12:35 pm

Post by sap1975
Sat Feb 20, 2010 12:35 pm

Progress report or???

I’ve had the servos for a while now and i’ve finished the first conceptual mockup and learned quite a few things along the way.
This initial POC build is done by hand and is structurally weak hence the wobbling.
It’s currently running off a CM-5 and “programming” was done in Roboplus. I’m going to keep the CM-5 and build my own piece of software to run it in the future but first things first.

The first integration test was a success so i figured it was time to share. There are a few different components in here not initially designed to come together. AX-12’s, RX-64’s a standard servo and a force feedback sensor for the gripper. Basically the gripper when activated will start closing and do so until a preset amount of resistance is met and then stop holding that position.

Anyways. Here’s a video of how things are coming along.



phpBB [media]


Cheers
/Stig.
Progress report or???

I’ve had the servos for a while now and i’ve finished the first conceptual mockup and learned quite a few things along the way.
This initial POC build is done by hand and is structurally weak hence the wobbling.
It’s currently running off a CM-5 and “programming” was done in Roboplus. I’m going to keep the CM-5 and build my own piece of software to run it in the future but first things first.

The first integration test was a success so i figured it was time to share. There are a few different components in here not initially designed to come together. AX-12’s, RX-64’s a standard servo and a force feedback sensor for the gripper. Basically the gripper when activated will start closing and do so until a preset amount of resistance is met and then stop holding that position.

Anyways. Here’s a video of how things are coming along.



phpBB [media]


Cheers
/Stig.
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Post by billyzelsnack » Sat Feb 20, 2010 5:22 pm

Post by billyzelsnack
Sat Feb 20, 2010 5:22 pm

Very nice.

I love that you are using a belt/pulley. Did have any issues such as slippage getting this to work?
Very nice.

I love that you are using a belt/pulley. Did have any issues such as slippage getting this to work?
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Post by sap1975 » Sat Feb 20, 2010 6:15 pm

Post by sap1975
Sat Feb 20, 2010 6:15 pm

Hi billyzelsnack

Thank you very much :)

Well considering the list of potential problems with using a belt drive i was amazed of how well it worked out.
I did a lot of measuring and then just put it on there and it’s been working beautifully.
The joint however is snagging on the bracket in the extreme “up” position and that will cause it to slip. Ohh yea and i ground down the flat on the mounting pin thingie that connects the servo to the pulley so there’s a fair bit of backlash.
This will be sorted in the next version though. Also i don’t have any bearings in this setup so there are issues here and there but as i wrote it’s a mockup and it’s primary function is to figure out what works and what doesn’t.

Cheers
/Stig.
Hi billyzelsnack

Thank you very much :)

Well considering the list of potential problems with using a belt drive i was amazed of how well it worked out.
I did a lot of measuring and then just put it on there and it’s been working beautifully.
The joint however is snagging on the bracket in the extreme “up” position and that will cause it to slip. Ohh yea and i ground down the flat on the mounting pin thingie that connects the servo to the pulley so there’s a fair bit of backlash.
This will be sorted in the next version though. Also i don’t have any bearings in this setup so there are issues here and there but as i wrote it’s a mockup and it’s primary function is to figure out what works and what doesn’t.

Cheers
/Stig.
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Post by sap1975 » Wed Jun 22, 2011 2:32 pm

Post by sap1975
Wed Jun 22, 2011 2:32 pm

Thank you very much.

The project has been dormant for a while but i’m actually just about to pick it up again.

It turned out to be a bit expensive doing the structural components and covers but I just put in an order for a 3d printer and that should allow me to move on.

I’ll update the thread once I get around to it :)

Cheers
/Stig.
Thank you very much.

The project has been dormant for a while but i’m actually just about to pick it up again.

It turned out to be a bit expensive doing the structural components and covers but I just put in an order for a 3d printer and that should allow me to move on.

I’ll update the thread once I get around to it :)

Cheers
/Stig.
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Post by limor » Wed Jun 22, 2011 5:41 pm

Post by limor
Wed Jun 22, 2011 5:41 pm

Hi Stig
It is possible to reduce the shaking and vibrations of that nice arm by gradually slowing down the servos as they reach their target position. We developed an alternative firmware for AX12 that allows much better speed control so that you can create nice motion curve profiles to accelerate and decelerate as as you reach target positions.
check out http://actuated.wordpress.com
Hi Stig
It is possible to reduce the shaking and vibrations of that nice arm by gradually slowing down the servos as they reach their target position. We developed an alternative firmware for AX12 that allows much better speed control so that you can create nice motion curve profiles to accelerate and decelerate as as you reach target positions.
check out http://actuated.wordpress.com
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Post by limor » Wed Jun 22, 2011 5:50 pm

Post by limor
Wed Jun 22, 2011 5:50 pm

If you share your cad files we (RoboSavvy) also have a 3D printer and can maybe work together to improve the structure and get some good shakeless motions
If you share your cad files we (RoboSavvy) also have a 3D printer and can maybe work together to improve the structure and get some good shakeless motions
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Post by sap1975 » Wed Jun 22, 2011 6:03 pm

Post by sap1975
Wed Jun 22, 2011 6:03 pm

Thanks Limor

Once again to the rescue :) That looks really interesting.

Having said that... have you guys made custom firmware for the RX-64's as well?
The only reason i ask is that the two main servo's are RX-64's

And yes i would be happy to share the CAD files.
I have to re-work them first though since i did a bit of re-designing and have ordered and received the bearings that needs to go in there.

Btw. WOW... what an offer.
I hope i get the time to work on it a bit during the weekend.

I was planning on 3D printing the "shells" and CNC milling the "Arm" from aluminium which is one of the two main causes of shaking if that makes any sense. The other one by the way is the base. that should cure itself once it's a closed structure.

I'll get back to you.

And thanks again.

Cheers
/Stig.
Thanks Limor

Once again to the rescue :) That looks really interesting.

Having said that... have you guys made custom firmware for the RX-64's as well?
The only reason i ask is that the two main servo's are RX-64's

And yes i would be happy to share the CAD files.
I have to re-work them first though since i did a bit of re-designing and have ordered and received the bearings that needs to go in there.

Btw. WOW... what an offer.
I hope i get the time to work on it a bit during the weekend.

I was planning on 3D printing the "shells" and CNC milling the "Arm" from aluminium which is one of the two main causes of shaking if that makes any sense. The other one by the way is the base. that should cure itself once it's a closed structure.

I'll get back to you.

And thanks again.

Cheers
/Stig.
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Post by limor » Fri Jun 24, 2011 1:37 pm

Post by limor
Fri Jun 24, 2011 1:37 pm

Hi, the firwmware works on AX12. it was tested on AX18 but there was some noise so the low level PWM frequency needs to be adjusted. no reason why it shouldnt work on rx64 except the RX/TX are independent so the firmware needs adaptation.
Hi, the firwmware works on AX12. it was tested on AX18 but there was some noise so the low level PWM frequency needs to be adjusted. no reason why it shouldnt work on rx64 except the RX/TX are independent so the firmware needs adaptation.
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Post by i-Bot » Fri Jun 24, 2011 2:21 pm

Post by i-Bot
Fri Jun 24, 2011 2:21 pm

The TX and RX are not independant on the RX64 and other RS485 servos. They are 4 wire because the RS485 signalling is differential and needs two wires. It is still bidirectional. The same signal which controls the direction of the TTL tristate buffers also controls the direction of the RS485 driver/receiver.

So the low level code should be very similar, though I never saw schematic of RX64 to check pinouts from processor. They do use an H bridge IC instead of the discrete FET used in AX, so there may be some rearrangement of the PWM outputs.
The TX and RX are not independant on the RX64 and other RS485 servos. They are 4 wire because the RS485 signalling is differential and needs two wires. It is still bidirectional. The same signal which controls the direction of the TTL tristate buffers also controls the direction of the RS485 driver/receiver.

So the low level code should be very similar, though I never saw schematic of RX64 to check pinouts from processor. They do use an H bridge IC instead of the discrete FET used in AX, so there may be some rearrangement of the PWM outputs.
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Post by sap1975 » Sat Jun 25, 2011 9:25 am

Post by sap1975
Sat Jun 25, 2011 9:25 am

Hi again

I have had a look at the model and i can tell that this is going to take some time to finish it since virtually all the mechanical parts needs to be drawn up. I have most of the in my head but it takes time to put them on "paper".

However there should be enough information in the stuff that's ready to see where i'm going and it would leave some playroom for ingenuity.


Limor: I would like to take you up on your offer on a joint venture sort of thing. Any help would be much appreciated and i'd be happy to send the current state to you. Just tell me if you'd prefer STP or STL and where to put it :) These formats do take up some space and i don't think mail is going to cut it. Alternatively i could put them on my web site.

Let me know what you'd prefer.

Cheers
/Stig.
Hi again

I have had a look at the model and i can tell that this is going to take some time to finish it since virtually all the mechanical parts needs to be drawn up. I have most of the in my head but it takes time to put them on "paper".

However there should be enough information in the stuff that's ready to see where i'm going and it would leave some playroom for ingenuity.


Limor: I would like to take you up on your offer on a joint venture sort of thing. Any help would be much appreciated and i'd be happy to send the current state to you. Just tell me if you'd prefer STP or STL and where to put it :) These formats do take up some space and i don't think mail is going to cut it. Alternatively i could put them on my web site.

Let me know what you'd prefer.

Cheers
/Stig.
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Post by sap1975 » Wed Sep 07, 2011 4:07 pm

Post by sap1975
Wed Sep 07, 2011 4:07 pm

So... it's time for a long overdue update.

Getting the 3D printer has sped up things quite a lot. There where some initial teething problems with the printer but i'm just about getting things right now.

I have managed to get most of the structure designed and printed. i think there's about 30% - 35% left on mechanical. After that comes software.

Anyways. here's what it looks like now.
It's funny how all that work turned into something that looks a bit like a mechanical duck :)

Cheers
/Stig.

Image

Image
So... it's time for a long overdue update.

Getting the 3D printer has sped up things quite a lot. There where some initial teething problems with the printer but i'm just about getting things right now.

I have managed to get most of the structure designed and printed. i think there's about 30% - 35% left on mechanical. After that comes software.

Anyways. here's what it looks like now.
It's funny how all that work turned into something that looks a bit like a mechanical duck :)

Cheers
/Stig.

Image

Image
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