Delta robots

Wow!

http://hackaday.com/2009/08/14/home-built-delta-robot/

Wish I could build one of these with an extruder!

very nice...

looks quite similar to the tripod that viktor suggested some time ago.
Easy to make (three hobby servos 5Euros each for 35Ncm @ 0.17s datasheet:[www.produktinfo.conrad.com]) 18 joints (4Euros/5 datasheet(german only):[www.produktinfo.conrad.com]) , two plates and 12 small rods or tubes, some cables...
thats around 50Euros.. since the servos get cheaper if you buy more, even less for "massproduction"

So no big deal on parts.

But to be honest, I don't even want to try writing positioning software based on triangulation
If there is someone who can do this, I'm in though


'sid

I wonder what the repeat accuracy is though, would you need to add vision software etc?

If you search on Youtube for delta robots, there are some amazing creations, including one done in lego NXT! It looks very accurate and fast - really amazing!

Phil

The servos I posted above should move the toolhead almost as fast as in the second video, well depending on the arm length of course;
but I'd say so.

The accuracy depends on the accuracy of the servo, it's controller and the joints of the arms
But I'd say since a zeropoint calibration does take less than half a second (for all three servos), it's maily a question of having the right software.
No vision software would be needed I think.

If mounted upside down (like in the second video)
I thinks it's nothing but software, since gravity will help reducing the error of the joints.

Seems to be a very good (if not the best) way to build a nice pick'n'place tool.
smd here we come...

'sid

PS Viktor..... would you like to help?
I'd love to place an order at conrad for the parts....
But I'd be lost without advice

I was following that approach for some time, unfortunatelly time for projects is very limted.

But what i did so far is, investiagting and write some inverse kinematics stuff.

It is really basic and i am a newbie to arduino,C++ and that stuff, so it took me a bit of time.

However, have a look, it is not commented yet, but apart from the inverse kinematics calculations,everything should be self explanatory. I, am trying to get rid of the atan function by approximation to speed everything up a bit more.


How do i attach files here???
If there is any interest in that IK lib, mail me.


udjat_at_web.de

Cheers,
Torsten

I'd like to see your code.

If you look just above where you type there's a bar of icons. Above that in blue is "attach a file" click there and get a "browse" button. Click it and go find the file!

I attached a picture of the paperduino.

... i'm working on the delta-robot- and tripod-kinematics since two years now and all the single components ready - beside my tripod-demonstrator with 1/8-microstepping i have three 1/256-microstepping drivers (resolution of 51200 steps on a 1.8°/200-fullstep motor) and some different types of old Nema23 and a set of bigger and stronger steppers too for a really 'strong' delta.

For my tripod with linear displacement of the driving joints i developed some working IK-algorhitms, the radial setup with rotating upper arms is waiting in the pipeline.

@sid: i'll help if i can - there are some microcontrollers with RC-PWM and some RC-servos too for testing, but the 1/256-highres-steppers should work much more precise ...

Viktor

As long as I'm getting it to move at all, I'd be impressed...

*note to myself* visit Conrad on tuesday!

'sid

I see, i need to registered to post files...

so here we go...

I organized 4 standard RC servos from my brother ( comes in handy if your brother is into RC Planes sometimes) and will try to hook them up to the sanguino.

Cheers,
Torsten

That looks interesting thanks energetic I bought 3 of the metal geared servos from DX to play with as they were > 1/4 of the UK price. I had not thought of what to do with them till now.. making a wow factor delta robot with them is such a good idea for a fun project.

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Bodge It [reprap.org]
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BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

I rearanged a bit in the lib to get an out of workspace check. the output is in radians.

I am working on an extension to also have the Jacobian and forward kinematics included.
Currently computing angles for one point takes around 2,5ms. For calculating the angular velocities for a given translational velocity, the Jacobian is needed, which requires a lot more use of the trigonometric functions.
I have not found a clever way to overcome this yet.

Cheers,

Torsten

You can get highly accurate controllers from phidgets. The servos resolution is what kills you. The one in the youtube clip gets 131k ppr. Gotta be pretty expensive. His controller boards cost about $1k. That can be done better, but the servos are a whole other matter.

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Hell, there are no rules here - we're trying to accomplish something.

Opportunity is missed by most people because it is dressed in overalls and looks like work.

Thomas A. Edison

I was planning to blog with the picture below and the title "a new kind of bread boarding.. "




I built one of thes delta robots in two evenings the day after my last post here. I used ball joints as I thought it might work better but it needs a simple pin swivel.. I have decided to play again with this later this weekend if i get time. If I get a resonably working version will provide full dimensions drawn in PsP.

My only drawing sofar is some concentic triangles that I used as templates this was based on that drwaing..

here is a pic of the bad mechanical design version..



Ball joints bad idea ~ will replace with crimp terminal eyes.

Top triangle Mechano hinges bad idea. ~ started replacing with model air craft hinges or small brass hinges.

Getting the servo arms on the center line great ..

Bad Idea not making the pivot point / arm mounting point match posyion to the driven arm end. ~ figured out how to fix that but not had time.

So I havent connected any kind of controller yet just playing with the mechanics as it looks like a neat toy....
Any way must get back to the post I came here to make....

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Bodge It [reprap.org]
=======================================

---

BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

Hi Bodge,

your configuration is from the pictures more a falcon config, than a pure delta, which means the inverse kinematics are different too.

You can get more details here:
Libnifalcon Docs page
there is also the reference to the PHD. Thesis by R.E. Stamper i derived my lib from.

Cheers,

Torsten

It will eventualy have the Arms running veticaly paralell not as they are at present with an Off set of 60 degrees this was not the orginal intention.
It was however the only way it would fit together due to the size of lower arms.

---

Bodge It [reprap.org]
=======================================

---

BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

Cheers Everyone,

v1.2 is finished, it fixes a stupid bug with the out of workspace check and adds in jacobian calculation.

please feel free to test it, if you find any errors please post it.

jacobian is not tested yet, unit is 1/length.

length picks up the units you assumed when creating the delta function.

so if you used mm then, it gives you 1/mm.

I have taken a copy thou it might be a while before I can try it out...

I started to rebulid Beartha at the weekend making a little bigger and more of a stand alone CNC now i have a couple of Darwins built.

Very keen to try it out thou thank you....

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Bodge It [reprap.org]
=======================================

---

BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

I have taken a copy thou it might be a while before I can try it out...

I started to rebuliding Bertha at the weekend making it a little bigger and more of a stand alone CNC now i have a couple of Darwins built. Im removing the very noisey couplings and removing the draw slides and replacing rail slides.

Very keen to try it out thou thank you....

---

Bodge It [reprap.org]
=======================================

---

BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

Bodgeit, Im amazed at the amount of time you put into this!

Its taken me a week to take apart Copperlab1 so I can clear some deskspace for my new version!

Phil

There I was thinking I had not been doing much as I have been planning my Solar system and starting the next bathroom in midges house..

The ideas I have on a making a cheap easy to build Darwin were thought of in January. I have had many other more important jobs to do and iv been frustrated as I wanted to try the ideas out.

When it came to applying the ideas the application was incredably quick as most of the work had been done in my mind first. Re building Bertha was needed as I need to start on Big Bertha which needs parts made more acurately than my eye can measure/make. Im kind of stummped again for time now as my Solar pannels arrived on the 25th and are blocking Midges hall way. so I need to finish that design and build the PV array frame work run the wiring and set a comisioning date .. Oh and chouse which power company to swap over to.

I generaly have more ideas than time to do. The cheap Dawin idea is finished I need to take time to write it up and document it. I will build a third Darwin taking pictures as I go maybe next weekend I will try to time every part of the build. I have an untested extruder design as well the Delta robot took only 4-5 hours total.

---

Bodge It [reprap.org]
=======================================

---

BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

Hi. I need dimensions of delta for design.Would you help me?

similar to the stewart platform

Danial the dimensions I used were random lengths the bottom triangle was based on the smalest triangle I could draw that would contain the servos.

The length of the arms are all the same in this caes they were the length of the 3mm threaded bar I had 300mm.

Check my post on this thread.

Re: Delta robots
Posted by: BodgeIt ()
Date: August 21, 2009 11:52PM

And look at some of the Delta designs on you tube videos to see the possible solutions to driving the arms in line keeping them centerd.
My basic construction just used two equlatral trinages and 6 equal lenth arms jointed to hinges with 3 more Arms about one third the length of the long arms.

---

Bodge It [reprap.org]
=======================================

---

BIQ Sanguinololu SD LCD board	BIQ Stepcon	BIQ Opto Endstop
BIQ Heater Block PCB	BIQ Extruder Peek clamp replacement	BIQ Huxley Seedling
BIQ Sanguinololu mounting	BIQ standalone Sanguinololu or Ramps mounting	Print It Stick It Cut it

My rep strap: [repstrapbertha.blogspot.com]

Buy the bits from B&Q pipestrap [diyrepstrap.blogspot.com]
How to Build a Darwin without any Rep Rap Parts [repstrapdarwin.blogspot.com]
Web Site [www.takeaway3dtech.com]

Is anyone else interested in doing a design for a reprapable delta robot structure? I'm currently churning one out, but I could use some help in determining the optimal leg member lengths for the maximum work envelope.

Thanks,
Lawrence

Hi Lawrence,

i'm redesigning my tripod with new available much longer linear bearings.

The tripod is stiffer and more precise than the delta-kinematic, but the delta is better for DIY because of it's simpler structure.

With three high precision Stepper- or Servo-Motors (i have steppers with 7Nm force and 50000 steps per rev) you need only some bearings, rods and the right hinges.

I'l try later to draw a simple design for crossing hinges which are easier to fab (or mill) than the normally used spheric or cardanic joints ...

Viktor

Viktor,

post up some working notes on the wiki and the forum as you go along, if it's convenient and fun.

What I'm going for is not necessarily precision, but to further boost the percent of plastic, and hopfully reprapable parts.

Victor, I would be interested in what your thinking for cross hinges, because what I'm thinking of right now is a plastic tetrahedron. as the basis of the universal joint. Where the axis lay on opposite perpendicular edges of the geometry.

What struck me about the delta robot was that because all I need are some bearings, rods, and hinges I can take advantage of the material properties of the plastics used to decrease the part count even further.

Essentially, I want to make plastic hinges, which are going to be wider and thicker to compensate for the weaker material, and I want to pin them with a long thin stainless steel rod. That takes care of bearings and hinges for the most part, by using universal joints and such.

I'm also hoping to directly couple the motor to the arms with either a gear or by slotting them in half of a spider shaft collar.

Right now I'm being way too fancy trying to learn openSCAD, and trying to build a light and strong geometrically shaped arm members. Frankly, this doesn't bode well considering a lack of talent with ridged body mechanics.

I need a better photo hosting service.

The initial thought on light weight rigid plastic structures is a cylinder or ovoid arm length with plastic ribs going the length of the arm and bounding the arm in between a spiraling cross lattes diamond mesh. The second idea takes inspiration from torsion boxes, and aluminum honeycomb panels. Basically create a thin plastic wall with square or hexagonal mesh on the other side.


Because I don't actually own or have immediate access to a reprap at the moment, I'm considering having the design built by shapeways, and then improve on it by porting it to RepRap. Regardless, the goal of improving the potentially reprapable parts list remains the same.


The first couple of problems I see off the bat is going to be the arm length might be longer than the work envelope of the delta robot. Also, I might not be able to make the long arm members I need with a reprap. This might necessitate an interesting two piece slot and weld construction method. Furthermore, choice of plastics could be critical. I'm confident that ultra high molecular weight polyethylene would work as a good bearing material, but I don't think I would trust its stiffness characteristics. I'm comfortable with ABS, but I don't know how good of a bearing material it would make. This might be the first project that by necessity, needs a dual head dual plastic thermal extruder setup.

I'm serious about building this thing, because I believe it's doable and represents a significant progression in thought patterns and functionality.

I need a better photo hosting service.

Try this:
[objects.reprap.org]


Because I don't actually own or have immediate access to a reprap at the moment, I'm considering having the design built by shapeways, and then improve on it by porting it to RepRap. Regardless, the goal of improving the potentially reprapable parts list remains the same.

Rough. Buy a millStrap (used benchtop mill), along with everything else. Once your post-mendel RepRap works, sell the millStrap for the same you bought it for, less shipping.

SebastienBailard Wrote:
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> Viktor,
>
> post up some working notes on the wiki and the
> forum as you go along, if it's convenient and fun.
>

... could take some time, as i'm actually building a CNC-mini-lathe with a four-jaw chuck atached to one of the 7Nm-microstepping motors (with the CNC-mill as toolpath) ... and then apply the 50Watt/10microns-laserhead to the mill too

Viktor

If it's GPL, you're very welcome to wiki those up too.

If it's not GPL, I think you'd feel a bit conflicted about it. As you'd be trying to line up investors or sell the plans to a company or something.