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Thread: DYNAMIXELs, PhantomX and ArbotiX Lots of questions

  1. Question DYNAMIXELs, PhantomX and ArbotiX Lots of questions

    First some background, I Have a first run Bioloid, Had fun with it, found the c5 controller painful to use, Support lacking to nonexistent and more or less found the experience less then I would have hoped (I have a feeling I adopted a new tech before its time)
    Moved on to a "normal" servo-ed Hexapod (a lynxmotion Phoenix ) and Had lots of fun with it though it lacks size for addons (I have a hard enough time just packing in what it needs to run), The Bot Board II was fair but really required custom work for everything and anything you did. I added there BotBoarduino and that really extended its use, But still stuck with small size, no payload (worried over over stressing the servos since they are only attached by there horns) and that I need to run more then one power source or add more electronics that may not fit. (also the PS2 controller that came with it does not work well anymore). Support has been fair but really relies on the community (like here) Which is great but can be very spotty.
    My goal is to make a autonomous walker that can avoid basic obstacles locally (ie on board), but can be driven by a human or computer (I own RoboRealm and am perfectly happy to stream sensor data to a computer for "higher" function decision making). I am most of the way there by my platform is just too small.

    So to my questions
    I own an entire set of DYNAMIXEL AX-12+ servos (a Bioloid kit). With the controller and lack of experience, software, etc hampering me. I was not as impressed with the Dynamixels as people here seem to be here and now. . So what has changed?
    I found the Servos, very loud, Strong but with plastic gears, Large, do not follow the standard servo layout for mounting, The communication can be flaky, and slow (inquiry can really eat up bandwidth, and latency can be a problem, at least with the old controller) The telemetry that you could read was only so useful. Etc.
    Now I know my servos are the "old" ones (but with the same stats more or less as the AX-12As) and the c5 controller+ software more or less sucked. But all of that really left a bad taste in my mouth.
    What I did like is the concept, the program ability, the reduction of wires, the higher voltage.
    So, is the new servo versions that much better or is it mainly the controllers, programs and support? or both?

    I am looking (no surprise) at the PhantomX AX. But hesitant due to my old investment of the Bioloid (though in ways it has also added to - as I have additional parts I could use now) and my current investment of the Phoenix (but which may have maxed out and requires a rebuild to continue)

    The PhantomX AX "looks" like it really functions well, has a ridiculously small controller and space for additional components. Has a single and powerful battery, and the best part it is Adriano based With Xbee wireless control. Effectly what I finally got my Phoenix to. Also that there is more then one IK that people are using! as with my current bot I am more or less stuck modding quite complex IK code that fills the Adriano controller just to make some room for some sensors. I an program but the IK code is a bit outside my comfort zone. Since that is it and really not well maintained/supported (by lynxmotion) I am rather stuck.
    Any additional comments? Gotya's, cool things I missed? current limitations that are annoying? current development? Future Road map? etc

    Some direct questions.
    How much space is taken up in the Arbotix with the default sketch?
    How much support is available? (ie any more then here is the default sketch . . go?)
    Is the Arbotix really the main thing holding this line of bots together? and what happens when it is replaced? (burnt on custom devices more the once)
    Has anyone mixed up the Dynamixel AX-12A and Dynamixel AX-18A in the same bot? ie the Femur tends not to move as much/far as the Coxa so may not need the speed (does the software guess the timing or use feedback?)
    What was the reasoning behind in the change of leg configuration between MKI and MKII?
    The Quad looks much smaller/lighter but also has less servos standing it up, has anyone done a comparison of Vs power use, payload weight, payload size, total weight, speed, smoothness of gate etc? Wondering where the sweet spot is for my use.


    Ok I think that is a bit too much . .sorry, Just want to be fully informed and have lots of questions.

  2. #2

    Re: DYNAMIXELs, PhantomX and ArbotiX Lots of questions

    I am sure some others up here can answer some of these questions better than I can, but will give a shot at some of them.

    First back to the Phoenix: First I personally think it is the best looking of any of these hexapods. But as you mentioned it is for sure limited in size. As for running out of room on the BAP28, yep it was pretty tight, Mine still has an ARC32 in it, which replaced both the BAP28 and the SSC-32, so gives you a little more room and also lot more program space and performance... Then the Botboarduino. Yes this is a standard Atmega 328 Arduino, so you are limited on code space and the like. As for no support from Lynxmotion, well I am the one who did the code port to C and then moved it over to the Arduino. This was all done before Lynxmotion was purchased by RobotShop. Since then, they have done very little to maintain or support the systems that are either C or Basic based. There are still some of us who try (I am kurte an that forum).

    However that is not to say the code base has been stagnant since then. There is my more current stuff up on github. In particular the project: https://github.com/KurtE/Arduino_Phoenix_Parts

    The code is setup to allow me and others to build the Phoenix code base to run on several different hexapod (and quadropod) robots including most of the Lynxmotion robots. What I have not done yet was to build one specific for the Phoenix. But that would be simple as you simply need to migrate the configuration file. This code base is also setup to support the PhantomX (both Hex and Quad).
    Note: I also have an easier self contained version specific for the PhantomX in the project: https://github.com/KurtE/Phantom_Phoenix

    As for limitations and the like of this code base. I have built it and had it running on Arduino Megas, Arbotix controller, Arduino Due, and some of the Chipkit (UNO32/Max32). Also a couple of days ago, I received a Teensy 3.1 which I may try out soon with this code base...

    Also myself and others have been playing with Linux based systems and I have my code base migrated over to Linux, more info up on https://github.com/KurtE/Raspberry_Pi . Bad name for project now as I have been playing with several different boards. Currently I have: PhantomX(Raspberry PI), Lynxmotion T-Hex(Raspberry PI), Lynxmotion Round Hex with 4dof T-Hex legs (BeagleBone Black). The code is also working with Odroid U2(will be U3 soon).

    So I hope that this gives you a feeling that you are not limited.

    Now to PhantomX

    Code size: Default? But PhantomX_Phoenix - 23,756 bytes

    Support: The forum. People are great up here. Note: I will answer questions here or Lynxmotion...

    Code computes timing and tells the servos where to go and when.

    Hope that helps
    Kurt

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    Re: DYNAMIXELs, PhantomX and ArbotiX Lots of questions

    A lot of the Arbotix Documentation is now found here: http://learn.trossenrobotics.com/ (along with other kits)

    Nothing is really tied to the Arbotix. It's just a convenient form of Arduino. Arduino doesn't appear to be going anywhere, and all the Arbotix code is open source. So it'll be supported so long as we and the community have a need for it. The Arbotix has been on the market for almost 5 years now and doesn't appear to be going anywhere. There are thousands in the wild.

  4. Re: DYNAMIXELs, PhantomX and ArbotiX Lots of questions

    Thanks for responding!
    I have been spending more of today (Er at work ) reading up on the threads here. I did just find your code (before your response) and will have more questions on that definitely!
    I am sure I can make the config file for the Phoenix, as I had to do that with the old code anyway. But since you did pull it apart into so many libraries (a good thing) In a quick attempt to compile the code . . It fails compiling. (lots of errors)
    I am sure it is just me messing up loading the libraries as some times the IDE can get wacky or missing one? Though I do see them in the IDE (BTW I should be using 1.0.5 right?) I saw you may have done some some work in the 1.5 beta but did not follow that thread yet but got thinking that the changes needed may be confusing 1.0.5 if I picked up the wrong code? I will try again and will ask if I have problems.

    I would love to run on a Raspberry_Pi or other Linux based system so will have to look at that now also .. .
    I do like my Phoenix, but like I said do not like they way the legs are attached and the overall lack of room (I have the power pack Velcroed to the bottom, and made a sensor mast and there is just no more room) I was thinking of expanding it to A-pod like - or at least improve the joints, but would have to sit down and make the parts as it is not a small task (I could not find any digital files to speed things up so I have to draft them - not hard but can be time consuming) Though something I will eventually do to resurrect the Phoenix in any case.

    I am still a bit interested in the performance of the PhantomX and if I did get one that I could use the Bioloid set to easily build onto the bot (again the questions on payload, room, free code space) but I guess that is not AS big a issue now.
    Still now that it is clear that I could mount a Linux based system relatively easy and that there is current development I have allot more elbow room. (Again I am not the best programmer, and often need a kick in the right direction after getting one I can normally figure allot things out. I do allot of 3d printing, fabricating, small electronics, optics, etc - a generalist really.)

    One thing I did see is people talking about cracking of the PhantomX's load bearing lexan parts? is this a real problem? (though I guess this is not a problem for myself as I can make replacements but good to know if true?)

    "does the software guess the timing or use feedback?" I know the normal Phoenix code computes the timing of movement. Though coming to think of it I thought the SSC-32 takes care of the choreographed move all, all complete move, all clear for next step of the cycle of the servos themselves?? But since the Dynamixels can give fed back I was wondering if they report (and it is used in the code) that they are finished moving or anything else since they are capable or are they more or less just used as normal servos at this point?

    Well thanks for the information on the code! it is exciting that so much has been done and is continuing to be done.

  5. Re: DYNAMIXELs, PhantomX and ArbotiX Lots of questions

    Quote Originally Posted by Tyberius View Post
    A lot of the Arbotix Documentation is now found here: http://learn.trossenrobotics.com/ (along with other kits)

    Nothing is really tied to the Arbotix. It's just a convenient form of Arduino. Arduino doesn't appear to be going anywhere, and all the Arbotix code is open source. So it'll be supported so long as we and the community have a need for it. The Arbotix has been on the market for almost 5 years now and doesn't appear to be going anywhere. There are thousands in the wild.
    Got it And good information. I have allot of projects and have really started to shy away from ultra proprietary parts as those tend to dry up when you need them.

    Any more info on the Dynamixel's how they are currently being used (I still have yet to see people use the feed back from the servos), performance, problems etc? it seems inviting again . .
    Last edited by TaErog; 01-08-2014 at 03:07 PM.

  6. Re: DYNAMIXELs, PhantomX and ArbotiX Lots of questions

    Quote Originally Posted by KurtEck View Post
    However that is not to say the code base has been stagnant since then. There is my more current stuff up on github. In particular the project: https://github.com/KurtE/Arduino_Phoenix_Parts
    Yes, got it to work . . I was just too eager and missed a lib. . . on to makeing a config.
    Now something more to play with! thanks for pointing it out and all the work you put into it.

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    Re: DYNAMIXELs, PhantomX and ArbotiX Lots of questions

    The AX-12+ are nearly identical to the AX-12A. The only changes were to the gearset to reduce the likelihood of broken teeth, and changes to the design of the mounting flanges to reduce the chance of breaking off and ease insertion of the nuts. The AX-12 can easily interact with the AX-18, and MX-28, MX-64, and MX-106, and could be used with the new XL-series servos if power is split off (7.4V design voltage, but same comms). Some of the Type-A humanoids in the lab use AX-18A in the knees and/or the entire legs, and have had no issues other than occasional overheating in the knees due to user stupidity (standing on one bent knee for way too long). One unfortunate effect of the change to the gearset is that you cannot use an AX-12A replacement in the AX-12+, and the AX-12+ gearset is no longer manufactured so any damage to the gearset essentially renders the servo non-functional. Although, I do not think I have ever actually tested to see if an AX-12A gearset could not be used in an AX-12+.

    Were you using RoboPlus or the original software? The original software was crap and Robotis has tried to erase its existence and push RoboPlus for a few years now. The CM-5 is pretty bad with the NiMH battery and no C/C++ support, but, as KurtE mentioned, there are now lots of new controllers that can be easily used with dynamixels. There is also the awesomely tiny USB2AX from Xevel for interfacing with a PC instead of the bulky USB2Dynamixel.

    Given the complete physical and electrical compatibility between the AX-12+ and AX-12A, you could buy the "no servos" kit and reuse your AX-12+ in any of the Phantom kits. The cracking plexiglas/polycarbonate blend was due to contact with non-plastic-safe threadlock and/or overtightened screws. The trossen shop now carries proper plastic-safe 'glue' as an alternative, though I have not used it yet since we still use mostly metal and Bioloid plastic frames in the lab and know how little threadlock to use (plus two full sticks of the nice loctite 248 that came with the DARwIn-OP).

    There are many different methods to control motion of the bot, and there are two different default options available with the PC software called PyPose: NUKE and manually created motions. NUKE is an IK engine for only certain quad and hex legged robot designs, while PyPose can create motions for any arrangement of servos. On the arbotix side, BioloidController is its rather nice interpolating motion engine that requires you to call the 'play()' function repeatedly within your sketch and has a default servo position update rate of ~30Hz for rather smooth motion. The version of BioloidController that I modified for the CM-9 series from Robotis has been operating at 125Hz without any issues. Whenever I manage to get off my ass and finish certain existing class projects and papers, I will be creating a 'real-time' motion capture system for the CM-9 and some hardware accessories for the CM-9 to possibly make the few Darwin-Mini we should be getting later this year a bit more capable.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
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  8. #8

    Re: DYNAMIXELs, PhantomX and ArbotiX Lots of questions

    You can buy the Phantom bracket set without the servos, I think. I don't know if the AX-12+ will fit in those brackets, but if you still have them around, that might be a cost-saving option.

    I like the approach of the AX and MX series, over hobby servos, because it's much better to be able to read something back, than reading nothing back :-) Serial comms also doesn't make you run out of pins that you want to use for other things. The servos don't use the hobby RC servos "standard" layout (which isn't really standard, as the depth of the servo is varying) but I don't mind, because I hand-roll whatever my frames are anyway, and having an idler on the back, and mounts that take this into consideration, is much better!

    If you want a new controller, look into the OpenCM9.04, which is an ARM-based controller with plenty of space and CPU power, for not much money. I'm running full IK for a quad, in floating point, in a little over a millisecond per iteration. It's a 3.3V device, rather than 5V, but on the other hand, it has AX/MX-style communications already built in.

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    Re: DYNAMIXELs, PhantomX and ArbotiX Lots of questions

    Quote Originally Posted by jwatte View Post
    If you want a new controller, look into the OpenCM9.04, which is an ARM-based controller with plenty of space and CPU power, for not much money.
    Whenever they add it to the Trossen store...
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
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  10. Re: DYNAMIXELs, PhantomX and ArbotiX Lots of questions

    Great information! Thanks . . many many more options then before (I kinda walked away from Robotics for a bit and focused on 3d printing and other hobbyist electronics.)

    So, OpenCM9.04 How much different is this from programming or converting from Arduino sketches? It still looks C like but sometimes the "details" can make conversion or re-re learning the new variation a pain (option?)
    Would it make sense to set up a CM-9 as a slave to a larger system like they did with the Darwin?
    "The version of BioloidController that I modified for the CM-9 series from Robotis has been operating at 125Hz without any issues."
    Over clocked?

    "default servo position update rate of ~30Hz for rather smooth motion"
    This means updating the positions only? or closed loop (move, read, analyze, repeat)? can you point me to an example posted so I can take a look. I have only used the Phoenix code so far for IK and really feel incapable (so far) in changing the meat of the IK code so it is important that that part is working, extendable, transferable, even modular etc.

    Great info on the dynamixels. Again I liked the concept but when I started it was rather limited.

    I am thinking of a turret frame /wo servos (A friend wanted me to make a airsoft turret) a nice cheap and fast way to get something functional use dynamixels in a project and have a Arbotix to play around with before I go farther. Also the Phoenix is getting a new run with new software build and some new 3d printed parts. Though I am really liking the size, speed and payload capability of those PhantomX bots

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