OK, here is the story:
I am planning to build a small hexapod based on an electronics package that can be reused for a bigger one later.
Requirement Specifications are
6 Legs, 3DOF
uses cheap servos because
fitâs the budget
mechanical parts made by myself (rather get some ROI on my mill than spend the money on a kit)
try foot sensors for terrain adaption
understand the software that is available (and possibly do some personal modifications ) rather than starting from scratch
create hunger for more
The last item on the list will be the easiest one to achive. The budget part⊠well.
Due to that, I am planning to make my own body parts.
So far, have done some constructing on the CAD, bought servos (SG90, 3,50ĂąâÂŹ a piece), and I wil start cutting some parts later this week.
I am still scratching my head over the hip joint (coxa?), since I am planning to do it with sheet material (same as the rest of the parts, for simplicity in manufacturing).
On the next todo list is ordering the electronics.
BTW: Is there a reseller in Germany for the lynxmotion products? All I can find (so far) on google is in the UK.
i like your enthusiasm for robotics.
its great that you are designing and custom making the body parts. its always nice to see home built robots.
i completely understand the budget leaning against projects like this but i will make one recommendation as others will tooâŠ
Servos:
i would recommend you think hard about this. its all very well buying cheap servos for a project if they will work but im not sure you will succeed with 17.5oz/in (1.2 kg/cm) of torque! also you are very limited with only 60ĂÂș of total movement!
especially with a 3dof leg!
you can buy some cheap servos with plenty more torque so id still shop about a bit more. if you can do a projected calculation of the total robots weight then you can hit the nail on the head on what servos will work.
What is the confusion you are having over the coxa joint, need more info there!?
About the servos - for this âprototypeâ I am not aiming for performance at all. If I can see the movements that I intended, I am happy.
There will be a bigger robot later, but with the budget-issue, I have to stretch investmentsâŠ
I just got my car back from the shop - ĂąâÂŹ550, just for a multiswitch, state inspection and 2 new tires. And that was not planned, either.
Hobby is Zen - the path is the destination.
I hope that I can keep the size and weight low enough for the servos to work.
Thanks also for the link to nodna, they have what I need.
However, I come out around ĂąâÂŹ210 (BB2, SCC32 and Atom-Pro), in the original US-Shop I end up at US-$125 for the same list of groceries.
So in DE it must be the platinum-plated versions, right?
Here is what I did so far: imagebanana.com/img/29s8kush/thumb/Schulterbaugruppe.jpg
This is the hip box containing the 2 servos. I have to realign the counter bearing below the horizontal servo a bit, and also check for collisions of the femur with the box. But I can cut those parts with my mill easily.
Update:
I found out that my kidâs school has a project going, using some kind of legged robot educational kit.
I will skip the office early tomorow and go there to investigate.
I had a copy of solid works but lacked the patience to learn how to use it. It was like trying to figure out all the controls of a 747 when you only need the controls of an ultra light. I use ViaCad3D which is a lot simpler for me.
Mike,
I came from Microstation (Bentley/Intergraph), and SW is a complete different way of approaching things. Since all the guys here in my various RC-model groups are using SW for some reason, I started to look at it.
I work in IT, and I have seen a lot of incomprehensible systems.
Starting with SW, I first had to learn a list of new curses, cuz my vocabulary just didnât meet the level of frustration. Itâs from a french company, so maybe thatâs why. I am not saying it is bad, but it just needs the user to understand how things a meant to be done - reverse-engineer the brain of the programmer, like.
I almost gave up - but a friend pointed me to a small paperback tutorial and some youtube-video-tutorials. That did the job!
There is a point when your brain goes from âWTF???â to âa-HA!!!â in a big klick (rather than gradually, as with other software).
And then it is realy all downhill.
Now I donât want to miss it, for all the realy neat features it comes with.
But you are right - stick with what you get alog with. For me, Microstation is still the best for 2D drawing. But it stops right there. And with this designig stuff, I realy donât want to miss out on those motion analysis features, collision-detection, and whatnot.
I have to admit, I wish I could render stuff like you do with your designs. I would also like to be able to assemble components and move them around to see if there are any conflicts of movement, that would be useful also. I didnât think about looking up some Youtube videos for examples, thatâs a good idea.
A German one: amazon.de/SolidWorks-kurz-b% ⊠3834803146
If you are looking for a book, make sure it contains some step-by-step examples, plus a little explanation what the idea behind this described approach is. That way, youâll ned to follow maybe one chapter trough, and the rest is just cross-reading from then on.
I got the school-kit started. It is quite small and uses microservos. The SSC can handle 22 servos (18 in use for the legs).
Communication to a very basic PC software is via XBee modules.
The SSC uses a 24byte language, 1 start byte, one checksum byte, and 22 bytes for the servos (1 is lower stop, 126 is middle position, 254 is upper stop).
The body parts are injection molded and probably originated on some rapid-prototyping 3D-Printer.
I will post some pictures later.
As for my project:
Still working on the hip joint. I am still deciding if I will use sheet FG, or maybe 5mm Makrolon (PC) for the servo brackets.
Electronics package is underway!
Software. I have looked at the projects page on lynxmotion.com, and there are a lot of quite interesting things to find.
However - I canât seem to make the connection:
Could somebody please point me to how I would connect a PS2-Controller to the BB (OK, I guess I will find the jack), and which software to use to interpret the commands, and how to translate this to movement?
Was it an educational version? I wish I could afford the cost and support of SolidWorks. I canât even afford to get back on support for Alibre Design right now. Too many things happening, including my main PC failing hard (replaced with an Athlon X2 QL60 dual core laptop now from Rent-A-Center). Iâve been really disconnected for the past week.
If you are in education or training (either as trainer/teacher, or student/trainee), most software companies offer a âschool-licenseâ. Usually, this is a full-option version, but for a lower price.
However, you need to check what the license contract allows you to do with this version. Usually, it is OK unless you use the software for anything commercial.
Most CAD systems will work quite well on a standard (not necessarily a low-end) PC or laptop. All that happens is that if you try to do CPU and/or memory intensive tasks (such as rendering), the software may either take very long, or crash (in case it wantâs to allocate more memory than is available).
Personally, due to experiences in the past and present, I try to stay away from both AMD and ATI. But this is only a personal opinion.
Update on my project:
Waiting for the BB-II, SSC-32 and BasicAtomPro to arrive
Hi Bogomir67. I starting my hexapod and have issue on buget also. if you looking for low buget servo. may be try âTower Proâ this brand from china. I can find lowest price for micro servo about 6.5 $ for Tower Pro SG91R or SG92. This two model have Stall torque at 1.8kg for 5v. only (not accept 6v.). This price for local thailand shop (I live in thailand). But for my project I choose Tower Pro SG5010 Stall torque 5.5kg/cm(4.8V) (6.5kg for 6V.). This is better than Futaba S3001 and price only 10.8 $ (i order 18 item so i get discount at 10%)
But if you want more quality then try GWS servo form taiwan. This brand is ok. I have used micro servo from GWS for 3 year ago for my RC helicopter and it never have any proble on stunt fly
Too many things happening, including my main PC failing hard (replaced with an Athlon X2 QL60 dual core laptop now from Rent-A-Center). Iâve been really disconnected for the past week. 
