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Thread: PC or Arduino, or Android board for humanoid control?

  1. PC or Arduino, or Android board for humanoid control?

    Looking back at the darwin project, the main board is a small PC. But this project is a few years old now. In doing a similar project does anyone have any other preferences, or ideas for boards to save weight? I imagine a mini pc could be bought now that is smaller than the one used in original darwin. Suggestions welcome. Or even a wifi/bluetooth solution that could talk to a larger pc or laptop nearby. My project is similar in scope to Darwin, but looking into other options for saving weight and space.

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    Re: PC or Arduino, or Android board for humanoid control?

    In Hikari I am running a Fit-PC coupled with an arbotix2. The arbotix2 handles all of her movements, and the PC (which doesn't not need to be used 100% of the time) handles vision processing sounds, and playing video through a micro projector mounted on her shoulder.

    There was talk a few months ago about using a raspberry pi to directly control the servos and do the vision stuff, but that was through Robosavvy and I've fallen behind on where that project stands.

    You could also check out what is going into the Jimmy Robot...The PC looks a little big, but seems to be packing quite a bit of power.

    Word is that there is a lighter smaller version in the works that will be using some sort of intel chip...

    The Intel Galileo is also a viable option...Haven't seen much done with it, but I haven't exactly been looking.

    Hope this helps.

    DB

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    Re: PC or Arduino, or Android board for humanoid control?

    There are two boards in the DARwIn-OP, one is the CM-730 and the other is a rather crap fit-pc2i-sbc. You can get much more powerful in the same or similar form factor as the fit-c2i-sbc, but the CM-730 is a bit more difficult to replace as Robotis sells it only as part of the full DARwIn-OP electronics kit (can possibly special order if you get on the good side of their support team). The Trossen shop is supposed to start selling an Arbotix-Pro sometime in the next year as a replacement for the CM-730 currently used in their Jimmy platform, so hopefully that will solve that portion of the problem by the time you finish your bracket design and/or build. The CM-730 is basically a 6DOF IMU, several buttons and LEDs, and a dynamixel bus interface capable of cutting power to the dynamixel bus in emergencies, so if some functionality are not important then it could be replaced by other, currently available boards if you modify the framework accordingly. The Xevel's USB2AX (or the much larger USB2Dynamixel) could enable any PC (fit-pc, Intel NUC, etc.) to easily control the MX-28T, but it would not have any extras like the IMU, buttons, LEDs, etc.

    While the Edison looks rather nice, the Galileo is just chock full of 'meh' (its I/O is slow because it's controlled by an I2C I/O expander. 400MHz 32-bit Pentium-class with 256MB RAM, while my laptop from 2001 was 700MHz Pentium 3 with 128MB RAM; yeah, the architecture has improved over time, but that much?). The Intel NUC is rather common on the forum, and a few of us still have Zotac Zboxes. The RaspberryPi and BeagleBoneBlack are capable of directly controlling the dynamixel bus, but they still require external ICs to do the 5V-3.3V level shifting and full-duplex to half-duplex conversion. They were the initial controllers of several bots here, but were replaced with NUCs and other PCs after they proved inadequate for the high data rates and heavy processing required for effective vision with webcams and primesense devices.

    Plastic frames versus metal frames... When a skeleton is used, it must be rigid or it must be equipped with distortion/displacement sensors. Unpredictable and/or immeasurable flexing in the skeletal structure is bad news for FK/IK and even simple pre-recorded motions. Loose screws (frame to horn, or frame to frame) or cracked/flexing frames anywhere in the assembly of an AX-12 humanoid can cause it to fail to walk well or even walk at all. The wobbling from flexing/backlash may be a little less severe in an MX-28 bot because of the better position sensing and really low geartrain backlash, but the higher torque makes it easier to damage frames (even aluminum frames; have the mangled foot of a dropped DARwIn-OP to attest to this).
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
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  4. Re: PC or Arduino, or Android board for humanoid control?

    sounds like I have a lot to think about. Buying the kit from Robotis doesnt sound attractive to me though, because its a few years old now and I feel technology has advanced and is smaller and faster. If I wanted to make a mx-28 biped without the darwin hardware/software starting with just the walking functionality what would you suggest? I am a software engineer, so programming and experimentation is no problem.

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    Re: PC or Arduino, or Android board for humanoid control?

    Almost started with "just making it walk"... (making it walk is exceptionally hard to start with for a biped...) In my main humanoid Hikari I use an Arbotix2 coupled with a Fit-PC. I currently use both dynamixel CM based controllers and arbotix controllers in my other robots...A part of me really likes the CM0730 (though I don't have a good place for it) and a part of me has had a great experience using the arbotix (I am running both the original and the arbotix2.) Basically any way you swing it you will be able to control the servos and access all of their added functionality.

    The CM-730 has a built in IMU which is really nice...for later on once you get things moving around, and really all of the above have relatively big user bases.

    The CM-9 is tiny. absolutely itty bitty...which would give you room to include other things, but I think I might also find it limiting...

    I currently like the xbee capability that is built in to the arbotix. (the cm730 would use the boomerang controller which is also nice, though I think has fewer buttons?)

    All in all whichever way you go you can get where you want to be.

    One thing I must say in favor of "just buying a kit from Robotis..." You build it and it just works...You can use the default Darwin software and the default Darwin everything and just be up and running...I think you would prefer to go it on your own though...

    Sorry if this all sounds vague and unhelpful, and I hope this post helps more than it hurts.

    DB

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    Re: PC or Arduino, or Android board for humanoid control?

    If you want cheap and quick, a USB2AX or USB2Dynamixel would be adequate for a while and will always useful for troubleshooting. There are several libraries available for using the USB2Dynamixel with ros and other platforms, and the USB2AX is mostly compatible with them (lower maximum baud rate of 1Mbps imposed by the AVR in it). Other than the much smaller size, the microcontroller in the USB2AX also implements a 'bulkread' that can pull register values from multiple servos in a single USB packet instead of the one USB exchange per servo that would be required with the 'dumb' FT232RL in the USB2Dynamixel. You could potentially use the USB2AX as a direct replacement of the CM-730 if you were to modify the firmware appropriately, but it would have no LEDs, buttons, or IMU to interact with the framework (the buttons on the back are used by most examples to control mode and the IMU is used a bit in the default walking engine). Also, no way to cut power to the servos in an emergency, but that can mostly be achieved with a broadcast packet to turn torque off, and maybe an external device (an E-Stop button at the main battery connection to the servo power pin).

    The CM-730 is somewhat weird in that it acts as an intermediate device linking the PC's USB to the dynamixel bus using the same FT232RL as the USB2Dynamixel. The FT232RL connects to one UART of the CM-730's STM32, and if the dynamixel packet sent from the PC is not intended for the CM-730 then it passes it through to another UART that actually connects to the dynamixel bus and servos. Whenever it gets released, the Arbotix-Pro is supposed to be a (near) drop-in replacement for the CM-730, which will make using the DARwIn-OP framework much easier with custom robots without the massive waste of buying the electronics kit.

    Pose based walking is easy enough to implement with just about anything that can interface to the dynamixel bus (arbotix's BioloidController and PyPose are a decent starting point). Extracting the walking engine from the framework is possible, but it will require a bit of work since the framework is not as modular as ROS or a ZMQ messaging system.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    [git][mech][hack]
    gives free advice only on public threads

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