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Zenta
05-28-2008, 05:11 PM
Hi!
As some of you know I have been working with a new robot project. This time I'm trying to make a quad walk. I must say when I saw the Big Dog on youtube I was VERY impressed and thinking that must be almost impossible to copy :lol: Anyway I'm not trying to say that my goal is to make a "mini Dog" or a quad that has the abilities like this big dog (its probably way way over my little head :rolleyes: )but some of the design are inspired of the Big Dog.
One big challenge with all quads is the walking part. Its almost like having a four legged table, cut of one leg and its very unstable. And the table has not even tried to move :p . So I have been thinking of a leg design where you easily can shift the COG, by adding one DOF. Another challenge with some quads (2 DOF) is the turning part.
Here is a picture of the body (this is an earlier version, a bit shorter)
http://forums.trossenrobotics.com/gallery/files/1/5/3/5/felix_body_v1_001.jpg

As you can see I'm using a 5645 servo and this is the 4. DOF. The body are made of 3mm aluminium, all parts are handmade with a bandsaw.
For powering I'm using 2x LiPo's and I'm trying to use 2 Turnigy 8Amps (maks 15 amp burst) DC-DC converter. This is a picture showing them modified with a spacer I used for mounting:

http://forums.trossenrobotics.com/gallery/files/1/5/3/5/felix_013.jpg

Another picture of the brackets/spacers for holding the servowires and the powerswitch:

http://forums.trossenrobotics.com/gallery/files/1/5/3/5/felix_016.jpg

And here they are mounted to the body. I'm gonna place the SSC32 on top of the black plastic plate.

http://forums.trossenrobotics.com/gallery/files/1/5/3/5/felix_014.jpg

Another view (underside):

http://forums.trossenrobotics.com/gallery/files/1/5/3/5/felix_015.jpg

This is a picture (also bottom view) showing the Turnigy mounted between the servos:

http://forums.trossenrobotics.com/gallery/files/1/5/3/5/felix_001.jpg

And finaly a complete mounted body with the SSC32 onboard. I still have some work left. Calibrating, mounting batteries and BlueSMIRF.

http://forums.trossenrobotics.com/gallery/files/1/5/3/5/felix_008.jpg

Another view:

http://forums.trossenrobotics.com/gallery/files/1/5/3/5/felix_010.jpg

Legs curled up:

http://forums.trossenrobotics.com/gallery/files/1/5/3/5/felix_006.jpg

For the time I'm also working with the kinematics on a Excel sheet. The reason for why I'm using Excel is that its very easy to experiment with different fomulas and kinematics methods. But my goal is also here (like for the Phoenix) to have a onboard brain doing all the math.
Felix is not walking yet...
BTW: The foot are made of parts from my very first hexapod I made late 2006:

http://forums.trossenrobotics.com/gallery/files/1/5/3/5/my-first-hexapod.jpg

I'll post more information when I have a video ready :wink:

-Zenta

Adrenalynn
05-28-2008, 05:49 PM
Beautiful fabrication work! I'm excited to see it walk!

Wingzero01w
05-28-2008, 05:50 PM
Wow zenta that looks real real good!

LinuxGuy
05-28-2008, 06:59 PM
Wow, Zenta, that's one cool design and actually does resemble what I have seen of Big Dog. You are one awesome robot builder, worth more rep!:veryhappy:

8-Dale

4mem8
05-28-2008, 07:16 PM
Zenta.Magic work, I always enjoy your projects,Such neatness in your work. Nice clear pics.

JonHylands
05-28-2008, 11:14 PM
Zenta,

It actually looks something like LittleDog (http://www.bostondynamics.com/content/sec.php?section=LittleDog), which is the small quad by the same company (Boston Dynamics) that makes BigDog...

Very cool...

- Jon

Zenta
05-29-2008, 02:03 PM
Thanks to you all for your kind words, it means a lot for me!


Zenta,

It actually looks something like LittleDog (http://www.bostondynamics.com/content/sec.php?section=LittleDog), which is the small quad by the same company (Boston Dynamics) that makes BigDog...

Yes, I remember their LittleDog, VERY cool! I'm really impressed for what Boston Dynamics has made with their quads!

-Zenta

Matt
05-30-2008, 01:34 PM
Wow, I'm also impressed by the fab work. Very nicely done, my bots always looked like the spaghetti monster!

openmindedjjj
06-19-2008, 05:32 PM
ya the big dog is very impressive but yours looks pretty nice aswell.
i dont know if you saw the part of the big dog where he slips on the ice but when i saw that i was amazed that he regained his ballance.

darkback2
06-19-2008, 11:52 PM
Zenta...you give me hope. I like the way you wrapped the wires, and also, the way you thought horizontally when creating this robot. If you look at most robots, the frame is parallell to the floor. By turning your robot on its side you end up with a much cleaner / more streamlined product. I'll have to keep that in mind for the future.

I am curious. Are you going to add touch or pressure sensors to the bottom of the feet? Also, could you publish some of your kinematics spreadsheets? I'm at the very beginnings of thinking about this stuff, and it would be neet to see how you solve the problems.

Db

Zenta
06-20-2008, 12:18 AM
Zenta...you give me hope. I like the way you wrapped the wires, and also, the way you thought horizontally when creating this robot. If you look at most robots, the frame is parallell to the floor. By turning your robot on its side you end up with a much cleaner / more streamlined product. I'll have to keep that in mind for the future.

Thanks!
The main reason for "turning my robot" was because of the 4. DOF



I am curious. Are you going to add touch or pressure sensors to the bottom of the feet? Also, could you publish some of your kinematics spreadsheets? I'm at the very beginnings of thinking about this stuff, and it would be neet to see how you solve the problems.

I'm not thinking of adding any sensors at first. I've got to solve the kinematics first and then play with some sequences. Then (in the future) add an onboard brain to do the math together with various sensors.

The kinematics spreadsheet (for phoenix) are available in the TRC download section.

-Zenta

sthmck
06-20-2008, 08:33 PM
Hey how is this project been going lately?

Zenta
06-22-2008, 01:04 AM
Hey how is this project been going lately?
Hi, good question!
ehm... I've been busy with building my Lynxmotion Phoenix (I love the building part :D) So it has been put on a little hold. I'm on a vacation now too..

I'll probably get more done after summer season. (Have to paint my house too :mad:)

-Zenta

sam
07-10-2008, 09:34 AM
It's been two weeks now, I hope you finished making it walk! :wink: Just joking ;) But seriously, how is it advancing?

I love the 4 DOF idea and the design is incredibly beatiful, sleek.

Nice job!

Zenta
07-10-2008, 02:55 PM
It's been two weeks now, I hope you finished making it walk! :wink: Just joking ;) But seriously, how is it advancing?

I love the 4 DOF idea and the design is incredibly beatiful, sleek.

Nice job!

Hi,

I've been working with the 4 DOF kinematics. First I'm going to use precalculated sequences (like I did for Phoenix). I'm not finished with all of the kinematics. But most of it are solved. This is a screen dump from my PEP version for a 4*4 Quad. The picture are showing the quad doing a 4*4 DOF kinematic body rotation:
http://forums.trossenrobotics.com/gallery/files/1/5/3/5/pep-felix_original.jpg

I've to finish the pitch and roll rotation too. And I've not started with the gait part yet. I also have to make a battery holder and calibrate all legs.

But as I mentioned in my previous post I'm working with my LM Phoenix (besides taking care of my wife, kids, house, work etc.....) LOL

-Zenta

ScuD
07-10-2008, 03:09 PM
Zetna, there's no icon's here that can express what I would want to say...

Your work is amazing, ever inspiring. I love how you create that slick "industrial" look to perfection, it always looks like a bot straight from some million dollar funded company, but mostly it's in the details that you never cease to amaze.

I'm really looking forward to seeing this baby walk!

Zenta
07-10-2008, 03:17 PM
Zetna, there's no icon's here that can express what I would want to say...

Your work is amazing, ever inspiring. I love how you create that slick "industrial" look to perfection, it always looks like a bot straight from some million dollar funded company, but mostly it's in the details that you never cease to amaze.

I'm really looking forward to seeing this baby walk!
Hi,
thanks for your kind words!
I'm begining to feel the preasure of getting Felix walking, but you all have to give me time (plenty of time).

One of my bad ability is that I tend to shift between different projects....:p
For the time I'm also waiting for a bioloid comprehensive kit too! (Yeah!) But thats another story (read project, LOL). Can't wait to get my fingers on the AX-12's (have some project ideas for them too.)

-Zenta

Zenta
07-19-2008, 05:15 AM
Hi!

I've just finished calibrating the servo's for Felix. Also made a simple battery holder for one 7,4v 4000 mAh LiPo's. The LiPo supply both servos and electronics for power.

This is a video of Felix doing complete 4 DOF per leg body rotation:


http://www.youtube.com/watch?v=GceQQENO-mo

You might see that every servo works together to make the rotation. This was also a test of the towerpro MG996R I'm using at the tibia parts. And to be honest I'm not satisfied with them, I'm gonna replace them with MG645's later.

Have not tried the walking part yet, so far it's a real challenge! Have to study that part first. ;)
_________________
Kåre Halvorsen, Zenta

4mem8
07-19-2008, 05:50 AM
Very nice Zenta as always a delight to see.

Zenta
07-21-2008, 03:57 AM
Very nice Zenta as always a delight to see.

Thanks!
The kinematics has been a really challenge here. Also because some times one position has several solutions, so I've to priority the kinematics. My math skills are limited too, so I'm only using plain trigonometry;)

-Zenta

ScuD
07-21-2008, 04:34 AM
I know the feeling.

I've picked up the book "Introduction to robotics, mechanics and control" in the hope of getting a better view on inverse kinematics, but my limited math knowledge combined with english had me giving up hope quite fast...

As always a great 'natural' feeling to the movements, zenta, great work !

A-Bot
07-21-2008, 07:22 AM
My math skills are limited too

Geniuses are not usually that modest. ;)

sam
07-21-2008, 07:37 AM
lol

Good job zenta! It's a very nice start. Can't wait to see it walking

Zenta
10-18-2008, 03:31 AM
Hi,
I've not got much time for robotics lately but I've been working with Felix a bit and have replaced the tibia servos with 645MG (I gave the Towerpro's to my dad :wink: ). And i was amazed how much smoother and accurate the result was. So no more crappy Towerpro's for me.

I've also worked with the PEP Felix version for live control.

I added some new sequences to the Felix project. Here is a little demo of Felix together with Phoenix:


http://www.youtube.com/watch?v=vIK1vmuRxG4

I've not tried to make Felix walk yet, but I promise that my next video of Felix will include walking!

(sorry about the messy background..)

4mem8
10-18-2008, 05:03 AM
So cool man, so cool. Just gotta love your work.

darkback2
10-18-2008, 09:01 AM
I've been waiting to see this guy move. Thanks.

Your wicked good at making things move smoothly and realistically.

Keep up the amazing work.

DB

Zenta
10-18-2008, 02:15 PM
Thanks DB and 4mem8!

Well, I must say the walking part are NOT easy. Very hard to get it smooth and stable. And I'm not sure if my choise of feet are the best either. Hexapods was SO much easier.

srobot
10-26-2008, 03:30 AM
Very nice project!

I'm so inspired I may even make a mech for Mech Wars that is like this 'bot!

Are you finding that the servos have enough torque? Do you think I could change the parts over to plastic and use servos like these with the SSC32 and still get enough control? What are the pluses using digital servos with the SSC32?

http://servocity.com/html/hs-475hb_super_pro_bb.html

Thanks,
--srobot

Edit - I will also have a full panel of sensors and camera on my mech so this will add some weight.

Adrenalynn
10-26-2008, 05:19 AM
Pulse Widths are identical between digital servos and non-digital servos. Some number of microseconds = some angle.

The only time that changes is if you get into non-PWM servos, like the Dynamixels - in which case - you don't need the SSC-32.

Zenta
10-27-2008, 11:41 AM
Very nice project!

I'm so inspired I may even make a mech for Mech Wars that is like this 'bot!

Are you finding that the servos have enough torque? Do you think I could change the parts over to plastic and use servos like these with the SSC32 and still get enough control? What are the pluses using digital servos with the SSC32?

http://servocity.com/html/hs-475hb_super_pro_bb.html


Hi,

Thanks! Good luck with your project.
I'm using 5645 and 645 servos, and I find the torque OK. Actually, I find the 5645 a bit better because of the digital holding torque. So I'm thinking of replacing the tibia servos (645 -> 5645) because the analog servos are not able to hold the position as good as the digital does. One part I don't like about the digital are the sound / noise.

You are refering to the 475, I won't recommend them for a Felix copy. Unless your robot are very lite.

4mem8
10-27-2008, 12:09 PM
yeah, I know what you mean with those digital servos Argh, noise. But digital are good all the same.

Zenta
07-06-2009, 01:58 PM
Hi,
I've had some free time lately and have worked with the BAP code (Xan's code). I modified the IKLeg sub so that the 3 DOF kinematics are calculated for the Hip, Femur and Tibia servos. The coxa servo was set to 90 deg constantly. At this moment I've full RC control of all body and leg movements. But there is an inaccuracy in the kinematics when the legs are extended and doing Z translations when the tars are around +/- 10 Z values.

To be honest I'm not very satisfied with Felix at the moment. He is a bit heavy (2,3 kg complete with 4000 mAh LiPo) too. So I'm considering of removing the coxa joint and doing some other improvements. Removing the 4 coxas will also save me for about 300 gram and also make the legs a bit more stable.

For a long time I've been thinking that the 4 DOF was a bit overkill. If removing the coxas dosen't give the result I want I'll probably end this project too.

Today I got Felix walking, not perfect though.. I made a quick and dirty approach. So I think I've to study others work about making a quad walk. Just for testing I made a table that told the body to shift COG along the X-axis.
I used a 14 step wave gait method and added a little break (all 4 legs at the ground) when shifting from RR->LF leg and LR->RF leg. A better method would probably be to continous calculate where the COG are and then compensate the body.
Well there is alot of work left. Here is a little video of Felix taking his first steps. Not very smooth or impressive at all.:(


http://www.youtube.com/watch?v=YuuPWwpd6VI

I'll post more information when I've done some work with it.

-Zenta

ScuD
07-06-2009, 02:58 PM
Any home made bot that walks without shuffling it's feet is more than impressive in my book, Zenta..

The sway in it's motion does have a little "twitching" to it, but you could tell people it's AI, and got scared of the camera, no? :d

darkback2
07-06-2009, 03:56 PM
I'm really glad to see you get back to this one. This bot was the inspiration for squidword.

As for quad gates, I've found that they are really tippy...I do more of a shuffle gate with charlie, and squidword gets away with a lot because his steps are so short and fast...

The gate your using is crazy cool...I would keep lookng at the body sway as a way to balance the bot possibly using a gyro. You have a lot more capacity in your legs for moving around you COG...

Keep up the good work!

DB

robologist
07-06-2009, 04:03 PM
Pretty cool-to-watch walker, AKA "Slightly Bigger Little Dog". Like this type of walking mechanism, more mammalian than lizard like.

Zenta
08-01-2009, 12:45 PM
Hi,

Thanks for your comments!
I've not done much latley since its summer season and vacation.
One thing is for sure, making Felix walk smooth isn't easy. I think a quad with the legs spread out (like an insect) would be easier (more stable). I did also try a faster walking gait (lifting two and two legs at the time), but that didn't work very well. I've been thinking of making some small 2DOF feet (and remove the coxa joint), that would make him much more stable. The IK shouldn't be a big challenge to add I hope, as long as you know at what angle the tibia has in relative to the ground.

But then again maybe a bit odd/strange looking? More like the AT-AT walker (from Star Wars) LOL. What do you think?

-Zenta