RoboSavvy Forum

Re: programming in c#

2009-09-04T07:40:34+01:00

NUB wrote:
But each and every one, I feel, since it is part of something we're creating from scratch is a little bit of a link in the chain, and when having to replace them that kind of stings...or is it merely the fact that I haven't used that many of 'em yet, does the feeling fade out when gaining more expertise? Anyways...

It depends. I don´t own a humanoid privately, but work in a relatively large team of 10+ people. Our robots are the platform that run our software, which took a lot of work to make. So when we´re at a competition and a servo breaks, there´s not much room for sentimentality, the robot has to work and that´s what matters.
But of course I can fully appreciate that this is different when creating a humanoid from scratch yourself.

Robo1, bren, I have yet to google inverse kinematics, but I didn't quite get the intention...

In a nutshell, in my own words:
Forward kinematics answers the question "Which is the pose of the endeffector (or foot, or whatever) of my kinematic chain for the given joint values?"
Conversly, Inverse kinematics answers the inverse question: "Which are the joint values by which the endeffector can reach a given pose?"

Forward Kinematics are normally relatively easy to compute (just multiplication of multiple transformation matrices), while inverse kinematics can be very hard to compute, with often no closed form solution (mainly with many DoF).

Statistics: Posted by SK — Fri Sep 04, 2009 7:40 am

Question in relation to starting out building a bi-ped

2009-09-04T07:18:05+01:00

Robo1 wrote:
Or for me, you send them to a position they can't reach and not notice for 6 minutes and burn out the motor.

Now that you mention it, we did that a few times too. I distinctly remember a head servo change at the RoboCup 2008 German Open where that happened twice.

Statistics: Posted by SK — Fri Sep 04, 2009 7:18 am

Question in relation to starting out building a bi-ped

2009-09-03T23:38:24+01:00

rubber bands and plastic strips... That sounds very interesting!
I too am too lazy to use nuts and bolts so I'm using servo tape (hard to pull off when applied but better than more expensive and complicated nuts and bolts.)

I think we all would like to see some pictures of your progress so far!

Thanks

Ooh, ooh! Belgium is well-known for its world-famous cuisines right?

Statistics: Posted by xx2747 — Thu Sep 03, 2009 11:38 pm

programming in c#

2009-09-03T18:45:22+01:00

Thanx everyone for the support,
SK it's indeed not so uncommon for servo's to go awry, especially with these kind of "weird" things we're trying to get them to do, I guess.
But each and every one, I feel, since it is part of something we're creating from scratch is a little bit of a link in the chain, and when having to replace them that kind of stings...or is it merely the fact that I haven't used that many of 'em yet, does the feeling fade out when gaining more expertise? Anyways...
Robo1, bren, I have yet to google inverse kinematics, but I didn't quite get the intention...
As for the sample codes I would be genuinely greatful if you would be able to share some, yet I warn you I am a NUB, starting my programming course in c# this saturday so I probably won't be able to share anything in return but some more questions and silly remarks about stuff I really haven't gotten the hang of just yet...
xx2747, yes nuts and bolts would be my first best guess, or is that a 'no go' in robotics? I do have to mention I have come up with a rather lazy but very easy way to assemble a very basic testing structure using nothing but some rubber bands and plastic strips, if I find the time I'll post the ridiculously looking creature maybe this weekend...and yes, you figured correctly I ain't no US resident, instead try a little European country called Belgium. Famous for its...well if you know let me know
greetz Kris

Statistics: Posted by NUB — Thu Sep 03, 2009 6:45 pm

Question in relation to starting out building a bi-ped

2009-09-03T18:44:15+01:00

Or for me, you send them to a position they can't reach and not notice for 6 minutes and burn out the motor.

To all the people starting out I would say buy this Kit.

http://www.parallax.com/Store/Education ... fault.aspx

It's the basic stamp starter kit. It will teach you embedded programming and electronics at the same time. You will end up using the stamp for lots of things. This is how I started out 4 years ago, and now I'm at cmu working as a researcher working on full sized bipeds for a living. It gives you every thing you need. Once you finished with it you can sell it and make most of your money back.

Bren

Statistics: Posted by Robo1 — Thu Sep 03, 2009 6:44 pm

Question in relation to starting out building a bi-ped

2009-09-03T11:53:55+01:00

Even though the Robotis servos are very tough and certainly among the best out there, they are not unbreakable. You just have to abuse them enough (like with RoboCup bipeds doing very stressfull goalie movements) and some will break eventually.

Statistics: Posted by SK — Thu Sep 03, 2009 11:53 am

Question in relation to starting out building a bi-ped

2009-09-03T00:52:21+01:00

Robo1:

I thought DX-117s were like unbreakable... Don't they cost like $200 a piece?

Statistics: Posted by xx2747 — Thu Sep 03, 2009 12:52 am

Question in relation to starting out building a bi-ped

2009-09-03T00:49:44+01:00

Hi Kris,

I'm sorry to hear about the servo.
So far I haven't thought of the programming for my robot. I do not know any programming languages (not even BASIC) so I'll use the SEQ software by Lynxmotion.

To keep the costs down, I made my brackets by hand. I used aluminum.
Also, how do you plan to attach the frames to the servos? nuts and bolts?

As I understand it you don't live in the US?

Thanks

Statistics: Posted by xx2747 — Thu Sep 03, 2009 12:49 am

Question in relation to starting out building a bi-ped

2009-09-02T17:33:06+01:00

Hi NUB

Blowing up servos. Happens to the best of us. I blow up a DX117 and was not happy, cost me lots to get a new one.

If I was you and want to practice programming and the servo control. Put 2/3 servos together and try and control them using inverse kinematics. It's not to hard and will be a good thing to learn. Try and get them to move around in a circle keeping the same hight.

If your interested I could always send you some example code.

Bren

Statistics: Posted by Robo1 — Wed Sep 02, 2009 5:33 pm

Question in relation to starting out building a bi-ped

2009-09-02T14:22:59+01:00

Hi xx2747, thanx for the reply! Sounds indeed very similar to what I had in mind...your plans.
the brackets and stuff are supposed to be hand made, I was thinking about some sort easily crafted plastic, alluminium or maybe even just plain old silicon boards...
Right now I'm actually really pissed since I blew up one of my servo's because I used a lipo with a higher voltage!!! That little mistake will probably set my project back a week or three, till the new servo's arrive in the mail
but that will give me the chance to look into the programming part of the project, I am exactly what the name says... a newby so have to start looking into c# and all of it's options...
Nice to know someone else is out there with the same hopes and troubles!

hope you make it with your project!
Keep me informed, ok?

Greetz
Kris

Statistics: Posted by NUB — Wed Sep 02, 2009 2:22 pm

Question in relation to starting out building a bi-ped

2009-09-02T04:57:34+01:00

Hello from the US,

I am working on (almost) the same project as yours. I am building a custom made biped with cheap chinese servos and a SSC-32. The servos are not MG995s but something similar to that. As of the controller board, I will be using the SSC-32 but right now I'm going to use the one from my RoboNova for now because I want to see if my design works before I spend $60 on the board.(I have a very tight budget so...

But that's awesome to know that someone else is doing the (sorta) same project.

Also, how are you making the frames? Are they going to be hand-made or ordered?

Good Luck

Statistics: Posted by xx2747 — Wed Sep 02, 2009 4:57 am

thanx sk

2009-08-15T06:32:49+01:00

i'll definitely steer clear from it when trying to have as much fun as i could possibly have figuring out how to build and program a servo-driven bi-ped.
but if i do ever get there i'll let you know. And yes, specifically Nitinol seemed like it could do the trick! Was just wondering since the prices seemed far less expensive than i'd have guessed. then again i wouldn't have a clue what kind of hardware would be needed, hopefully as my experience slowly grows I'll learn a thing or two and maybe one day be able to get something cookin' as for now, still waiting for the regular servo goodies

greetz
kris

Statistics: Posted by NUB — Sat Aug 15, 2009 6:32 am

Question in relation to starting out building a bi-ped

2009-08-15T00:09:11+01:00

There were some experiments with an SMA-based (specifically Nitinol) robot at my university some years ago. With observations from this robot and the generally very sparse use of SMA by the robotics community my conclusion is that this stuff just isn´t ready for primetime yet. Sounds great in theory, but there are all sorts of problems regarding latency, low robustness, hysteresis etc.
I certainly wouldn´t recommend building such a robot to a beginner. It would probably only be usable for very basic research, which doesn´t necessarily translate to fun (On the other hand, if you´d get that robot working really well and solve those problems, you could earn big bucks from that )

Statistics: Posted by SK — Sat Aug 15, 2009 12:09 am

muscle wires

2009-08-14T22:07:45+01:00

I've been reading about the muscle wires, some electrical wiring that has a contracting ability when charged or heated and re-assumes it's primary shape when unconstrained when the external power/heatsuply stops... would seem like an ideal way to create muscled joints for arms and torso... has anyone got any experience with these sma? What is the reason they haven't found their way into hobby robotics yet? Are they hard to control of is it because they are really heavy consumers?
just wondering...
project underway still waiting for the goodies...

Statistics: Posted by NUB — Fri Aug 14, 2009 10:07 pm

ssc32

2009-08-06T20:00:27+01:00

Hi there, back again, stuborn me, huh...

Well I did it, I just ordered the lynxmotion SSC-32 serial servo controller...anyone have any experience with that?
Specs looked good, price even better... only paid the european equivalent of about 40 bucks for it.
Now on to the servo's, I'm about to get myself two packs of 4 MG996R servo's.

Thanx for having patience with me, will try to check in very regularly since I have more and more questions...

kind regards
Kris

Statistics: Posted by NUB — Thu Aug 06, 2009 8:00 pm