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Propeller based robot project with Bioloid Servos — Parallax Forums

Propeller based robot project with Bioloid Servos

lnielsenlnielsen Posts: 72
edited 2007-04-13 08:06 in Propeller 1
I am interested in doing a Propeller robotics project. I know Brian Riley has his PRC board (http://www.wulfden.org/PRC/) for PWM based servos but I am interested in intelligent servos that provide feedback like the Bioloid or Openservo. I am leaning towards the Bioloid (AX-12) because I have not found anyone selling complete openservos only replacement boards.

I thought I would open a thread to see who else is interested or already working on this combination. Ideally we would need...
  • A standard interface for high-speed half duplex TTL based serial
  • A high speed serial object (1Mbps would be the ideal)
  • It would be nice to be able to update the AX-12 firmware without the CM-5 (are there any other CM-5 features we can't live without?)
  • An advance Gyro/Accelerometer sensor for balance
  • I am thinking of an object that calculates the center of balance based on the servo positions and the robot's geometry.

Any thoughts?

Comments

  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2007-01-15 05:17
    What kind of feedback are you interested in from the servo? Have you seen the link below?
    All of your bullets seem as though they all can be accomplished in software.

    http://forums.parallax.com/showthread.php?p=582447

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • lnielsenlnielsen Posts: 72
    edited 2007-01-15 18:56
    Beau,

    Yes, I saw that article earlier but that is a far cry from the feedback these servos provide. The other problem I see is, like the Hitec HMI protocol servos, the robot arm or leg will tend to sag or drop while you are reading the position. The Bioloid and Openservo units operate on a multi-drop serial line with dozens of servos on a single serial link. They also provide feedback on how much torque the servo is under. Check out http://robosavvy.com for documentation on the Bioloid AX-12 or http://openservo.org/ for their servo modification.
  • AlexAlex Posts: 20
    edited 2007-01-15 21:02
    At Crustcrawler we will be releasing·a DIOS Pro board and chip along with a complete library of code to control the AX-12 servos (the code is already complete). We are also developing·Propeller applications this quarter which will be in-line with some new products we will be releasing based on AX-12 actuators.·We will also be expanding the actuator line by including the DX-117, RX-64 and RX28. The AX-12 and others listed here are the way to go as there is no modifications required and at $41.00 for 220 oz./in. of torque with all kinds of feedback, there a great buy as well.

    This is the future of robotics and it's about timetongue.gif



    Alex
  • BergamotBergamot Posts: 185
    edited 2007-01-16 19:19
    Alex: In continuous mode, can the AX-12 rotate to a specified position, or just at a constant speed?
  • AlexAlex Posts: 20
    edited 2007-01-16 23:59
    In continuous mode there is no positional feedback. All other modes have feedback position feedback.

    Alex
  • lnielsenlnielsen Posts: 72
    edited 2007-01-17 00:49
    I do not have an AX-12 to test this but someone on one of the Bioloid forums was testing positional feedback during continuous mode and they reported that it did work to some extent. I believe they were testing to see if it could be used as a rotation counter. The unit has a 60 degree dead band and the unit returned a few erroneous responses near the middle of the dead band but otherwise it worked fine.

    Revision: I reread the initial question, I don't know if you can set a "desired position" in continuous mode and have it rotate to that point. You might be able to use continuous mode to get past the dead band and then try to set a target position but you may need to take it out of continuous mode for this to work.

    Post Edited (lnielsen) : 1/17/2007 2:01:46 PM GMT
  • BergamotBergamot Posts: 185
    edited 2007-01-17 14:09
    That's unfortunate, but understandable. They still kick the pants off a regular RC servo, and don't cost an order of magnitude more.
  • AlexAlex Posts: 20
    edited 2007-01-18 03:38
    Correct, you can read the servo to 300 degrees of rotation in continuous rotation mode and yes there is a dead band of the remaining 60·degrees.·You could not be more correct as with the release·of AX-12 servos and others (DX-117, RX-16 and RX-28), the use of basic servos days are numbered.

    These babies are the future of "smart" robotic applications that is just beginning to emerge as they become more popular. There will be a host of new articles in Servo magazine about them in the next 3 -4 issues with lots of code authored and developed by Michael Simpson. cool.gif

    We will be releasing a lot of new products based on the AX-12 and others mentioned above in the coming months. Propeller development will follow along with these new products. AX-12's and a propeller are a perfect match.

    Stay tuned!



    Alex

    CrustCrawler Inc.

    www.crustcrawler.com
  • simonlsimonl Posts: 866
    edited 2007-04-07 13:23
    Hi Alex,

    Have you released the AX-12 Propeller code yet?

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    Cheers,

    Simon

    BTW: I type as I'm thinking, so please don't take any offense at my writing style smile.gif
    www.norfolkhelicopterclub.co.uk
    You'll always have as many take-offs as landings, the trick is to be sure you can take-off again ;-)
  • peterzpeterz Posts: 59
    edited 2007-04-08 10:32
    Code for managing Bioloid servos from Propeller at 1Mbps was released at the following site: www.robosavvy.com
    Check the threads that contain the word: Propeller

    ·
  • simonlsimonl Posts: 866
    edited 2007-04-10 07:48
    Hmmm, I'm probably being really dense here, but I can't find the code! I've seen several posts that talk about it (inaki posted to say it's there, but doesn't say where).

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    Cheers,

    Simon

    BTW: I type as I'm thinking, so please don't take any offense at my writing style smile.gif
    www.norfolkhelicopterclub.co.uk
    You'll always have as many take-offs as landings, the trick is to be sure you can take-off again ;-)
  • James LongJames Long Posts: 1,181
    edited 2007-04-10 13:35
    Alex,

    Has anyone done code for the other bloid servos besides the AX-12?

    James L
  • John AbshierJohn Abshier Posts: 1,116
    edited 2007-04-10 14:27
    I couldn't find the code either. I registered to see if you needed to be a member. The registration form said that I would get an email to activate my registration, but it hasn't come yet.
  • simonlsimonl Posts: 866
    edited 2007-04-10 14:29
    Hi John,

    Yeah, I tried the same - sadly, it makes no difference :-( I'm hoping that Alex or Inielsen can shed some light...

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    Cheers,

    Simon

    BTW: I type as I'm thinking, so please don't take any offense at my writing style smile.gif
    www.norfolkhelicopterclub.co.uk
    You'll always have as many take-offs as landings, the trick is to be sure you can take-off again ;-)
  • Bill ChennaultBill Chennault Posts: 1,198
    edited 2007-04-10 18:12
    simonl--

    I have tried to register at RoboSavy at LEAST half a dozen times, including just now. To say the least, their software is not human-friendly.

    --Bill

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    You are what you write.
  • lnielsenlnielsen Posts: 72
    edited 2007-04-10 19:23
    I exchanged private emails with inaki and he sent me his code to evaluate. (I was not given permission to distribute it so please PM him yourself) It is a modified version of Parallax's full duplex serial object. This is more complex than it needs since the Bioloid is half duplex. I have the half-duplex code from the HYDRA that I am going to rewrite for the Bioloid. My code will generate Bioloid frames but I have not totally thought out the public functions that I am going to make available.

    James - Most of the Robotis servos/sensors use the same message format. The only difference is the interface chip. The AX can be interfaced with a few resistors where as the DX servos require RS-485 transceivers. I am hoping to use an open collector RS-485 receiver so I can drive both TTL and RS-485 devices on the same 2 propeller pins (data, direction)

    I have not made much progress on this because of other obligations but I hope to spend some time on this real soon.

    Len
  • simonlsimonl Posts: 866
    edited 2007-04-11 08:40
    Hi Bill,

    Yeah, it's a bit sloooow! However, I didn't have any problem registering -- only took me a couple of hours to realise their activation email had gone into my junk mail folder!

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    Cheers,

    Simon

    BTW: I type as I'm thinking, so please don't take any offense at my writing style smile.gif
    www.norfolkhelicopterclub.co.uk
    You'll always have as many take-offs as landings, the trick is to be sure you can take-off again ;-)
  • peterzpeterz Posts: 59
    edited 2007-04-13 08:06
    The code made by inaki is not full duplex, is half duplex. The only odd thing is that it uses two cogs for rx/tx. I was working with my own version for some time and found as well that it was easier to work with two cogs. Apparently the later version by inaki, the one with slave support, uses only one cog for both. However this later version was removed from the site or at least no one has been able to download it. I would suggest to send an email directly to inaki because most people got his code by email. I don't know why the code is not in the website.

    Robosavvy site has changed lately its server so probably they have had some problem with new registrations, and perhaps with file uploads.

    Inielsen, did you had the chance to try the slave mode version ?
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