Author Topic: 12 servos for biped robot  (Read 723 times)

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Offline vipulan12Topic starter

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12 servos for biped robot
« on: October 07, 2013, 04:40:25 PM »
hey everyone, i am in the process of building a biped robot but need more servos
the biped robot will have 12 servos in total but i only have 6

will 12 servos be adequate in making a biped robot?

also will these servos be good for the application?
http://www.hobbyking.com/hobbyking/store/__15513__GWS_SO3N2_Standard_Servo_29g_6_4kg_0_111sec.html
if not any recommendations would be nice(hopefully under 5 dollars)

thanks

Offline jwatte

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Re: 12 servos for biped robot
« Reply #1 on: October 07, 2013, 09:59:38 PM »
You want a servo that is precise, robust, fast, and strong.

You will not find a servo that achieves all of this for under $5. The closest you can find is Dynamixel AX-12 or Herkulex DRS-0101, each for about $45 each.

Typically, with the cheap Chinese servos, you trade off at least precision and robustness, and there is a particular choice between speed and torque -- with the same motor, twice the speed can be had at half the torque with a change in gears only, making multiple servos within the same range easy to produce.

You *can* build a biped with 12 cheap Chinese hobby servos. It will likely also be able to shuffle/walk. However, it will not be as nice, smooth, and rigid as you would hope.

Offline vipulan12Topic starter

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Re: 12 servos for biped robot
« Reply #2 on: October 08, 2013, 02:31:27 PM »
why does it need to be precise? yes it has to get to certain angles accurately but why does it need to be very precise?
it shouldn't really matter

Offline jwatte

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Re: 12 servos for biped robot
« Reply #3 on: October 09, 2013, 10:23:30 AM »
Quote
it shouldn't really matter

The best way to learn why it matters (and where) is to try things, and then analyze the failures you're getting and figure out how you would improve in the next iteration. I highly suggest you try building your biped with the 12 servos, and then measure things like precision in location, speed of movement, ability to adjust to obstacles (like a wire laying on the table,) stability of gait, etc.

Offline vipulan12Topic starter

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Re: 12 servos for biped robot
« Reply #4 on: October 09, 2013, 08:14:00 PM »
ok but where should the weight be placed the batteries and etc?

Offline jwatte

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Re: 12 servos for biped robot
« Reply #5 on: October 10, 2013, 09:59:32 AM »
The weight should be placed wherever you can fit the necessary components, and still stay within the design limitations for center of gravity while moving.

Lower, such as thighs or feet, is better from a COG point of view, but generally makes it harder to actually build legs with sufficient movement.

Most successful bipeds put the battery/electronics in the hip/chest area.

Offline vipulan12Topic starter

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Re: 12 servos for biped robot
« Reply #6 on: October 12, 2013, 06:25:16 PM »
okay but about the servo's I recommended would these be sufficient for my biped robot?other than the precision spec
Do you know of any cheaper and stronger servos(not out of stock)  with good quality?
also if i wanted precision would buying light weight stepper motors be the right choice?( do they even exist?)

Offline jwatte

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Re: 12 servos for biped robot
« Reply #7 on: October 12, 2013, 09:13:17 PM »
You already selected about as cheap as you can go.
No, stepper motors would not be better for your application.

Offline vipulan12Topic starter

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Re: 12 servos for biped robot
« Reply #8 on: October 13, 2013, 10:15:26 AM »
alright thanks for the reply

 


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