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Thread: How to increase torque by paralleling multiple servos

  1. #1
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    How to increase torque by paralleling multiple servos

    Found this link
    http://www.redplanearf.com/uploads/tbs_flyier_new.pdf
    It claims that it has solved servo fighting problem. But I don't see it. Any other ideas ?
    CAD Tools: Solidworks 2011. Altium Designer 10
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    Re: How to increase torque by paralleling multiple servos

    You probably can set it up pretty well, but they're going to eventually fight as servo conditions change. I think you actually want a tiny bit of fighting as that'll help with backlash.

    How big of robot are you planning on building?

    Also keep in mind that doubling up servos does not change the torque to weight ratio. There's a definite trend where as the torque of a servo goes up, its torque to weight ratio goes down. For example.. It would take "2.76" HV-300's for the same torque as an EX-106, but just the "2.76" HV-300 servos would weigh 217g. An EX-106 weighs 155g.

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    Re: How to increase torque by paralleling multiple servos

    You are right about the ratio part. I was thinking that I may need more torque from one or two joints. My plan is to build a 50cm(2 feet) robot.
    BTW my 10 HV300's are on their way to Ontario :-D
    CAD Tools: Solidworks 2011. Altium Designer 10
    Micro Controller: ARM7/9, AVR 8bit/16bit, PIC, Nordic nRF, HOLTEK, 51s, NEC
    RF: 2.4G, 433M
    IDE: KEIL MDK3.5, AVR Studio 4, MP LAB, HOLTEK HT-IDE3000, Elipse
    High End: VC, VB, Unix/Linux C/C++, J2ME (For cell phone game), SQL
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    Re: How to increase torque by paralleling multiple servos

    50cm should be attainable without doubling up. My AX-12 robocup bot was 40cm.

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    Re: How to increase torque by paralleling multiple servos

    Good to hear that. All of these types of things are about experiences. Reading threads from you guys is part of the fun too!
    CAD Tools: Solidworks 2011. Altium Designer 10
    Micro Controller: ARM7/9, AVR 8bit/16bit, PIC, Nordic nRF, HOLTEK, 51s, NEC
    RF: 2.4G, 433M
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    Re: How to increase torque by paralleling multiple servos

    I'm not at my home computer, but if I can remember, I'll post torque to weight ratio of various bots that I've been keeping tabs on...

    In a whole system like robotics (pedal robots to be specific), the torque to weight ratio of a particular location in an apendage really matters...

    For instance, the Kondo bots have always had servos (except for the KHR-3s) that were roughly 133 oz/in which equates to servos such as the HS-645MG from Hitec, however, their bots always displayed fluidity because it is one of the lighter pedal robots out there...

    The Bioloid's AX-12s have just shy of 200oz/in of torque if I remembered correctly, but the bot is quite heavy...

    In servos though, you can gain more torque from simply fidgeting with the internal gear ratio (which manufacturers do), however, this will effect transit time. If transit time wants to be decreased, this may effect accuracy (overshoot and correction)....

    We need a super servo, one which can put out 1000 oz/in of torque, run at 6V, and weight as much as a few feathers!
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    Re: How to increase torque by paralleling multiple servos

    Quote Originally Posted by billyzelsnack View Post
    You probably can set it up pretty well, but they're going to eventually fight as servo conditions change. I think you actually want a tiny bit of fighting as that'll help with backlash.
    I am not going to chase that then. I am building lower part body anyway. But if I do need to parallel servos, I will combine servo drivers into one servo, other servos will be dumb. This will stop the "fighting", at least "controlled fighting". Also the ONLY brain can balance the current into the motors.
    CAD Tools: Solidworks 2011. Altium Designer 10
    Micro Controller: ARM7/9, AVR 8bit/16bit, PIC, Nordic nRF, HOLTEK, 51s, NEC
    RF: 2.4G, 433M
    IDE: KEIL MDK3.5, AVR Studio 4, MP LAB, HOLTEK HT-IDE3000, Elipse
    High End: VC, VB, Unix/Linux C/C++, J2ME (For cell phone game), SQL
    Education: EE Master.
    Hobby: RC Helicopter.

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