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Thread: HerkuleX Servo's?

  1. #1
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    Question HerkuleX Servo's?

    Anyone have any experience with these? I found the manual online and they seem interesting, similar to the AX-12/18's. Haven't seen any sign of there cost in $, but someone posted 35 pounds for the UK?

    Thanks,
    Scott

  2. Re: HerkuleX Servo's?

    For a while they were listed at RoboShop, but mysteriously disappeared. There is a place in Australia selling them: http://www.tribotix.com/Products/Don...x/Herkulex.htm.

  3. Re: HerkuleX Servo's?

    Sorry to dig up this old thread, but I recently discovered these servos, and bought one. So far I'm absolutely loving it. Here's my write-up of how I got it up and running:

    http://botscene.net/2012/10/20/getting-started-with-the-herkulex-drs-0101/

    I'm hoping to get some more for my upcoming birthday, at which point I'll start doing real projects with them, and I'll let y'all know how that goes!

    Cheers,
    - Joe
    Check out BotScene.net for the latest news, reviews, & commentary on humanoid robotics!

  4. #4

    Re: HerkuleX Servo's?

    Interesting! Have you put any real stress on it? Does it overheat?

  5. Re: HerkuleX Servo's?

    Hi Joe,

    I'm curious why you selected HerculeX over Dynamixel? Was it the price? Granted, single piece costs less ($36 vs. $45), but 6-pack costs practically the same. Technical reasons?

    Regards,
    Paul

  6. Re: HerkuleX Servo's?

    @jwatte: No, I haven't done any stress-testing yet. I do know they include a temperature sensor, and I'd be mighty surprised if they don't shut themselves off before overheating to the damage point, but I can't say that for certain yet.

    @Paul: I've never been a huge fan of the Bioloid line, partly because I find them aesthetically unpleasing, and partly because maybe I'm just a rebel and don't like being on the same bandwagon as everybody else. My previous favorite servo was the Robobuilder wCK line, until I started trying to mount them to other things for my own project, and discovered that the wCK's shape and mounting methods make this extremely difficult.

    There's another technical reason, though: the wCK servos, and (if I understand correctly) the Bioloid ones too, are not able to interpolate a position over a given amount of time. For example, I want to say (from my mcu) "go from position A to position B over the next 0.7 seconds," and then let each servo do that on its own. But instead, you have to send it a continuous stream of position updates, interpolating between the two — which is just plain dumb. Each servo has a little mcu in it; let it do the interpolation.

    And that's exactly how the Herkulex servos are designed. You tell them where to go, how long to take to get there, and you can tweak various parameters of the ease-in and ease-out curves. And then it just goes. I really like that.

    I also like the form factor; these servos are noticeably smaller than the AX-12 -- about the same size as a wCK -- but with a sensible shape and a really clever mounting system that lets you combine servos in dozens of ways, without needing any ugly flanges sticking out from every servo.

    All that said, I know that Robotis is a great company, and their servos are high quality. I especially like the wide range of servo strengths available; Herkulex has only two at this point. I have no quarrel with people who choose Bioloid/Dynamixel for their bots. But at the moment, I'm pretty excited about the Herkulex underdog.
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  7. #7

    Re: HerkuleX Servo's?

    I think the Dynamixels let you set the target speed and the target position, which is pretty similar to "get to this position in this amount of time."

    I might want to test out a Herculex just to see what it's all about.

  8. Re: HerkuleX Servo's?

    Setting the speed is only the same as setting a duration if the speed control is very fine-grained... if you only get to pick from (say) four different speeds, then there's generally no way you can use that to get all your servos to their target positions in the same amount of time (because they're going to be going different distances). That's the situation with the wCK servos, anyway; not sure how fine-grained the speed control is on Dynamixels.
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  9. #9
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    Re: HerkuleX Servo's?

    Speed control on dynamixels is 0 to 1023, but it does not necessarily reflect reality very well (at least in wheel mode, where the potentiometer cannot sense for 60 degrees of every full rotation - just uses a PWM value and hopes for the best). I haven't really bothered using the speed settings often, but others have had problems in the past with increased overheating when using a single goal position at lower speed settings versus off-board interpolation between multiple positions at maximum speed.

    I'm curious how well the HerculeX servos actually perform in getting the horn to a target position in a target time, since they do look really nice on paper.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
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  10. Re: HerkuleX Servo's?

    Tician, I'm planning to get you an answer on that question (how well do they really do at going to a target position in a target time), but I'm waiting to get my hands on a few more servos — it will be a much clearer demonstration if we can watch them all working at once.

    Meanwhile, though, I do have some news: Dongbu last week announced two new servos in the Herkulex line, with 40 and 60 kg cm of torque. This was announced in the Korean press, but I'm happy to say that my blog is the first English source to break the story (at least, as far as I know). Read all about it here.

    Cheers,
    - Joe
    Check out BotScene.net for the latest news, reviews, & commentary on humanoid robotics!

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