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Thread: Is EX 106+ servo still available?

  1. #1
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    Is EX 106+ servo still available?

    Hey,

    I noticed that the status of EX 106+ motor speaks "discontinued", what is the reason? Can I still purchase it?

    According to the dynamixel motor diagram, it supposed to be faster and of higher torque than MX-106, correct?

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    Re: Is EX 106+ servo still available?

    The RX and EX servos have essentially been replaced by the MX servos. RX-28, RX-64, and EX-106 with the MX-28, MX-64, and MX-106, respectively. The MX come in two main versions: -T and -R, which use AX-compatible and RX/EX-compatible communication buss, respectively. Some are also offered with an aluminum front case to improve thermal performance.

    BIG DIFFERENCE: MX servos are rated to only 12V just like the AX servos. Operating at more than 12V is extremely dangerous without drastically reduced maximum torque limits as any stalling or sudden impacts will easily destroy the motor.


    The lower operating voltage is part of why the MX-106 produces a somewhat slower and lower torque output. If higher torque is needed, the newer XL/XM/XH series servos are quite nice but not inter-operable with any older servos (AX, DX, RX, EX) due to newer protocol/packet. IIRC, MX servos received firmware upgrades that permit them to operate using the newer DXL2 protocol just like the XL/XM/XH and Dynamixel-Pro although the specific buss interface may differ between particular models (AX/MX with TTL, RX/EX/MX with RS-485, Pro with CAN, etc.).
    Last edited by tician; 07-06-2017 at 02:53 AM.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
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    Re: Is EX 106+ servo still available?

    Hi,

    Thanks for the information. I look over the X series, but didn't notice that any of them has higher torque output than MX-106s. The EX-106+ has faster speed and higher torque than MX-106, that's why I am interested in it. Our hexapod robot has been running MX-106 by a 4 cell lipo (15-16 V) for about half an year and didn't notice any gear breakdown yet. I think our situation is somewhat similar to EX-106+ except that EX-106+ has lower gear ratio.

  4. #4

    Re: Is EX 106+ servo still available?

    The XH-430 doesn't have more torque than the MX-64 or MX-106.
    For higher torque applications, I think you'd want to go with the Dynamixel Pro series.
    Or is there a higher-numbered XH that I don't know about, that would compete with the MX-106?

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    Re: Is EX 106+ servo still available?

    Also, does mx-64 motors have sync wire port so that we can put dual mx 64? Or if it doesn't have, is there a way to make customized one so that we can sync them?

    Thanks!

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    Re: Is EX 106+ servo still available?

    There is no sync port for automatic hardware mirroring of a second servo, but it can easily be done in software with a sync write packet and a tiny bit of code to produce the correct goal position value for each servo. Generally best to work with floating-point variables in standard units for all position, velocity, acceleration, effort, etc. calculation and storage, then convert as needed to the servo specific value with a simple lookup table or class/struct. It allows you to mix and match any type of servo from any manufacturer while keeping the motion control code exactly the same.


    Kinda surprised to see these types of questions coming from someone in RoMeLa given Dr. Hong's extensive collaboration with Robotis. Guessing quite a bit of knowledge and experience was lost in the move to UCLA and recent graduations.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

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    Re: Is EX 106+ servo still available?

    Sorry, still not quite sure.

    According to my understanding, for dual motors at a single DoF, if you just drive the two motors to the same position, there can be a discrepancy of two angles causing a torque lose. It may come from software or hardware. For software, as you said we can just copy whatever angle motor 1 is driven to and give it to motor 2 then 2 motors should get exactly same goal position signal. However, there can be a hardware issue such as time lag on the wire so that 2 motors don't get same signal at exactly same time (even if use sync write?), and that's why the sync wire comes in. So do you mean that this is not an issue and we can just sync write the dual motors without any torque lose? Has anyone done any test on it?

    Thanks!

  8. #8

    Re: Is EX 106+ servo still available?

    for dual motors at a single DoF, if you just drive the two motors to the same position, there can be a discrepancy of two angles causing a torque lose
    Yes, this is certainly a possibility, depending on how the system is assembled.

    The MX series servos use a 4096 position resolution absolute encoder, with a maximum absolute error of less than three ticks IIRC. (Better check the specifications to make sure, but it's in this order of magnitude.)

    The flex that's inherent in any mechanical assembly (including backlash in the gearbox!) plus the PID controller, will make it so that the servos don't actually fight each other -- the encoders are good enough, and then PID/gearbox/assembly has flex enough, that that won't be a big problem. The motors may run very slightly hotter when idle. When actually needing torque, both motors will be moved outside their center encoder positions, and will work in the same direction, and thus you will have no loss of torque.

    If you need something more than the MX-106 servos can give you (especially when ganged up in pairs,) though, you will likely need a higher-end (and more expensive) motion control solution. Either use Dynamixel Pro servos, or build your own from motors/gearboxes/drivers/encoders.

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