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Thread: DYNAMIXELs, PhantomX and ArbotiX Lots of questions

  1. #11
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    Re: DYNAMIXELs, PhantomX and ArbotiX Lots of questions

    Quote Originally Posted by TaErog View Post
    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?)
    The CM-9 GUI is based on Arduino-1.0 with a few changes to handle arm-gcc and uploading to the various CM-9 boards. I also managed to get the CM-900 working on Arduino-1.5 as a custom hardware core here. Most of the code within the 'core' used by the CM-9 is based on the existing code from the Maple project (a previous derivative of the Arduino project for STM32 microcontrollers). All of the code is C/C++ with additional macros and functions to make USB and DXL communications, interfacing with sensors and actuators, and controlling pins very easy.

    Quote Originally Posted by TaErog View Post
    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?
    The CM-9 uses a 32-bit processor running at 72MHz, so it is really easy for it to handle all the interpolation calculations much faster than the 16MHz ATmega644p in the arbotix. The CM-9 is sort of a really stripped down version of the CM-730 used in the DARwIn-OP, but uses the on-board USB instead of an FT232. It can easily be used as an intermediate controller like the CM-730, arbotix, or USB2AX, but it depends on your desired usage.

    Quote Originally Posted by TaErog View Post
    "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.
    The BioloidController object does not usually update the internal servo values with the actual servo positions except at initialization. So after initialization, it is mostly open-loop and relies on the closed-loop control of the dynamixel servos. The BioloidController has an internal variable where the millis() value of the last interpolation calculation and uses the default wait period of 33 ms to determine when it should again perform the interpolation calculations and push new goal positions to the servos. When you call play() or interpolateStep(), it checks to see if the current millis() is greater than the counter variable + 33, and only updates the servos if true. If you wait a lot longer than 33ms to call either of those functions, then you might get a bit of uneven motion (depends on how much longer you wait).

    The DARwIn-OP framework motion player and walking engine operate in a similarly open-loop manner but with an automatically controlled 8ms update rate, which caused a bit of annoyance when building a gripper controller class since I had to dig into the framework to re-enable the position and 'load' feedback.

    Quote Originally Posted by TaErog View Post
    Great info on the dynamixels. Again I liked the concept but when I started it was rather limited.
    There have been lots of firmware and hardware upgrades over the last couple years. Dynamixels have been completely dominating RoboCup humanoids since the DARwIn-OP was introduced, whether in DARwIn-OP or custom robots.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh
    more bleh

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

    Thank you for all the help. I was able to get my Phoenix up and running again (the old controller was rather messed up and since I was using that to test functionality it really made me think more was wrong then there was) The little bugger is moving again this time under PC control and new software (thanks KurtEck)

    For kicks I got a Turret Kit to familiarize myself with the newer DYNAMIXELs and Arbotix . . working out nicely. I have a tracking vision controlled Turret that has many modes
    Tracks a laser (on the turret) from a stationary camera and moves that laser to the current target (target = motion or color blobs)
    Tracks a target (motion or color blobs) from a stationary camera and moves the turret appropriately (needs setup calibration)
    Tracks a target (motion or color blobs) with a camera on the turret and keeps the blob in the middle.
    Fun stuff . . . started using http://processing.org/ Language and openCV on a PC which processes the video and sends commands to the Arbotix.

    All nicely transferable to other projects.

    Now I just need to painfully wait for another trossenrobotics SALE!!!! as I missed the last one

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

    So, Tell me more about AX-18As in a PhantomX . . . any interesting practical information?

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

    The 18A's give you a lot more speed than the 12s. Some of our early tests show something like .44 meters per second for the AX-12A hexapod and .86 meters per second for the AX-18A. The 18's are also a little bit stronger than the AX-12As. Also, the 18s use a mix of metal and plastic gears while the 18s are all plastic.

    The negative site of the AX-18's is two fold. First there's power - the AX-18s are capable of pulling more than twice the current of the AX12s (I don't have any data at the moment on how much they actually draw while in the crawler during various gaits). More power usage means less battery life. The second part, which is related to the power use, is heat. The 18s get hotter much faster than the 12s. Overheating can cause the servos to shut down, or over time damage the motors if you're running them for too long.

    Of course you can run the cralwer slower, which will reduce power usage and heat, but at that point you might want to just stick with the AX-12A. But if you want the speed, the AX-18A version is scary fast.

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    Re: DYNAMIXELs, PhantomX and ArbotiX Lots of questions

    Quote Originally Posted by kgranat View Post
    Of course you can run the cralwer slower, which will reduce power usage and heat, but at that point you might want to just stick with the AX-12A. But if you want the speed, the AX-18A version is scary fast.
    Moving slower probably won't help all that much with heating. Both the AX-18A and RX-24F use coreless motors, which is probably the primary reason they heat up faster. When I had 24Fs, I couldn't find any way to keep them cool.

    -Fergs

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

    Is over heating a real problem/concern or just something to watch for and be aware of?
    Also does anyone have any data on battery life?

    (also does the new AX-12A Gear sets work in the old AX12+ servos? I have a few that may need a refit)
    Last edited by TaErog; 01-31-2014 at 06:53 AM.

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