Hello everyone, Am planning to make a humaoid,just a one which walks. with 6-8 servos. Am not sure which microcontroller to use, will a arduino Uno be better than picaxe 40X2 or picaxe 28X2 in picaxe 28 starter board for this project? am new to adruino bt a little familiar with picaxe. The robot has to walk first(for biginning),then i will try to upgrade it. I have ordered some servos:
http://www.hobbyking.com/hobbyking/store/__16269__HK15138_Standard_Analog_Servo_38g_4_3kg_0_17s.html and http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=662
those are analog servos, so will there be a lag while walking ?
And for the body am planning to use fibre glass structure.
UPDATE. The lenght of the robot am planning is approximately 30--40 cm. The weight might be approximately 1-- 2 Kg
The leg part will use 8 servos.. both a mix of 9g and 38g servo. The 9g servos at both foot angle and also at hip for the robot to chang direction. The other servo will be used at hip and knee joint.
Also am not sure what type of power supply to use.
Sounds really cool. If you are trying to get it to walk around at first, how about starting from a bi-ped? I tried building one once, the walk wasn’t perfect though. Most Bi-peds use 4 servos, and then you might upgrade it into a humanoid adjusting other variables along the way. I would go with the Uno because I haven’t used a picaxe yet :P If you are looking for a plug and play kind of thing, the beetle shield from DFRobot is really nice as it’s small and has direct plug in pins for servos. But you can use other Arduino versions too. If you want a big bad humanoid then maybe the spider controller from Dagu might be a great choice. Just a thought. I am no where near a good programmer, but I think the servo lags will primarily depend upon your code. You might want to have a peek at Protowrxs’ TED the BiPed core code to have a feel for the walking routine.
But good luck. Nice project you have there! Fibre glass rocks.
I’m not a PIC guy, but the UNO should be able to do everything you are listing. It supports up to 12 servos with the servo library that comes with the IDE and lag shouldn’t be a problem. You’ll want to give the servos clean power as analog servos a susceptible to jitter if you don’t keep them happy. Someone might have some suggestions regarding the PIC, but as I said, I’ve never used one.
Keep us posted, looking forward to seeing what you come up with.
Hi Paul, I’ve been checking those servos and they are quite different and powerful. I never used Arduino, I prefer other kind of platforms but it doesn’t care here.
I can give you some key points based on my experience. I did a biped last year (see POPSTAR robot and several blogs I started about it).
First you should think about this stuff:
1) Which kind of skeleton structure (material) you will use? (height, weight…)
2) Which number of servos you will use and where the will be placed? (locomotion will be affected by them).
3) Try to search and use ready-to-use algorithms: inverse kinematics, bresenham line algorithm, dynamic stability… (look at my blogs you can find useful information). This will save you a lot of desing/debug time.
4) The most important one: be constant and patient, is a long-term project. Probably you’d reach a point in which you have to redesign your first design. Don’t doubt, do it, you won’t regret it.
I have worked with that stuff a few times. Not sure I would say rocks. Try working with it while you are sweating and there are fiber particles floating about. You can’t shower enough to get that crap out of your pores.
Hi Raul, thanks for the Hi Raul, thanks for the great tutorial you have made.
For servos you said it’s different,by different you mean?
I might try it with a picaxe…
I mean different because the first one is so powerful,while the second is a small 1kg/cm servo (9g). With the first one you can build a heavier/higher robot, while with the second you should look for a lighter structure.
For example in my POPSTAR robot in which I used 9g (1kg/cm) servos, similar to the second one you show, I built it from popsicle sticks and it has a height of around 30cms (total weight around 0.600Kg). Servos were very close to their torque limit. I could keep it stand up and move it, but if I had to rebuild it I’d choose a more powerful servos or I’d study other joints configurations (shorten legs sizes).
See for example (this one) or (this one). Both has small legs (legs are its servo bodies) which implies a CoM point close to the floor and hence a priori more stable than mine.
So in my opinion you should reduce legs size, use a light structure and use a servo according with what you choose, knowing its torque.
Actually i was thinking of using both the servos, the 9g servos at both foot angle and also at hip for the robot to chang direction. The other servo will be used at hip and knee joint. So a total of 8 servos for the legs.
Try working with it while you are sweating and there are fiber particles floating about. You can’t shower enough to get that crap out of your pores. 