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Type: Posts; User: macdowswe

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    Re: Open source low cost servomotor controller

    Hey guys, long time no post. Thought I'd show off the new demo video:

    https://www.youtube.com/watch?v=FUh36RUHzdU
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    Re: Open source low cost servomotor controller

    Hi,
    Just wanted to let you guys know that there is an ODrive community getting started over at https://discourse.odriverobotics.com, with some discussion that you might find interesting.

    Cheers!
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    Re: Open source low cost servomotor controller

    Hey Ian, Thanks!
    The plan is to make v4 3-axis. But it will be at least half a year until v4 is ready. But you can just use two v3's connected over CAN to get a 4 axis setup.

    Cheers,
    Oskar
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    Re: Open source low cost servomotor controller

    I am excited to let you know that the time has finally come for the alpha stage of the ODrive project!

    Alpha release
    This consists of two components, the alpha software release and the...
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    Re: Open source low cost servomotor controller

    Dear websrvr. Please stop whining about Eagle. Get a free trial of Altium and convert it yourself.
    Or just use CircuitMaker instead, it's free. The design for CircuitMaker is here:...
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    Re: Open source low cost servomotor controller

    Hey guys, the v3.1 boards have come back from the factory, check it out!
    https://cdn.hackaday.io/images/77131484932488490.jpg

    I have some more pictures here: link
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    Hey guys, to help picking out the right brushless...

    Hey guys, to help picking out the right brushless motor for your application, I made this spreadsheet, feel free to make a copy and play with it: Link.

    Its intended to be a basic guide, so it has...
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    Re: Open source low cost servomotor controller

    By the way guys, check this out! ODrive v3.1 being manufactured ;D


    https://www.youtube.com/watch?v=EVpCxpZ14NE
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    Re: Open source low cost servomotor controller

    So about the cooling and thermal management of the motor, the above is the plan. Actually, just to enumerate some of the possible ways to prevent overheating:

    1. Use reduction gearing to reduce...
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    Re: Open source low cost servomotor controller

    Yeah I thought about it. I haven't really seen any low cost encoders that have differential signalling (without adding a differential tx yourself ofc). If more people request it, I can put it on, ...
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    Re: Open source low cost servomotor controller

    Yeah it will have thermal control as part of the motor control algorithm. I think the best way would be to have a thermal model of the motor, but if that's not available, a simple time-based backoff...
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    Re: Open source low cost servomotor controller

    Wow I wasn't aware that GT2 5mm can handle so much! Thx for the reference! ;D
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    Re: Open source low cost servomotor controller

    So in the project page I link to this (link) battery, which is a 6S Lipo. However, you can run with any battery you want: 6S LiPo, 3S LiPo, 12V car battery, 24V two-car-batteries-in-series. Basically...
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    Re: Open source low cost servomotor controller

    If you want more power, you can simply get a bigger motor ;D
    I know we have beed using the ~1Nm motor as an example, but you can get something like this motor (link), which should happily do 4Nm.
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    Re: Open source low cost servomotor controller

    I agree that the motors will run more efficiently if you do something like 4:1 reduction gearing. But I am interested in discussing what defines the torque requirements. My hypothesis is that you...
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    Re: Open source low cost servomotor controller

    Thanks for the heads up.
    I have tried to make sure that there is as much copper as possible in the current path that is expected to carry the motor current. The copper track impedance going around...
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    Re: Open source low cost servomotor controller

    I checked ebay very briefly, and I found that there are kits available without any motors or controllers for $800, Link, and that kits with motors, driver, spindle and spindle driver are about...
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    Re: Open source low cost servomotor controller

    Yeah when it comes to deceleration, the motors are not very high friction, so you will need to actively brake the motors. The resulting energy absorbed can be either dumped into a brake resistor, or...
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    Re: Open source low cost servomotor controller

    So I had a look at the stepper you are using, and it has the following speed/torque profile:
    343774

    I calculated the mechanical power capability at the selected point, and it turns out to be 17W....
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    Re: Open source low cost servomotor controller

    Cool!
    How difficult would it be for you to install a motor that was 1Nm, but could spin 4 times faster?
    Would this be a dealbreaker?
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    Re: Open source low cost servomotor controller

    So the schematic pdf is already available on GitHub: Link.
    Yeah other people have already asked for gerbers. The reason I haven't provided them yet is because there are still some bugs in the...
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    Re: Open source low cost servomotor controller

    So on the topic of websrvr's offer and the resulting discussion:
    I am intending to make the price point lower than $96, as I already stated previously in the thread, the target price is around $50....
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    Re: Open source low cost servomotor controller

    Hey, thanks!
    So yeah many people have requested a 3 axis version, and the plan is to do that for v4. I have already identified a microcontroller that has the peripherals required for that.
    ...
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    Re: Open source low cost servomotor controller

    The design is available on GitHub, CircuitMaker, and CircuitHub. Please let me know where you looked and failed to find the links, and I will put the links there.

    The price is quite high, I agree....
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    Re: Open source low cost servomotor controller

    https://cdn.hackaday.io/images/2665861480778750936.jpg

    The time has finally come for the manufacturing run of ODrive v3.1. They are now on the way, and should arrive early to mid January.

    At...
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    Re: Open source low cost servomotor controller

    I will be facilitating a couple of production runs at different stages of maturity of the project. I expect that the early prototypes will be around $100, and with a larger run later on will be...
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    Re: Open source low cost servomotor controller

    Yes, I agree with you. The method I outlined will only work if your fault force is much higher than any unmodeled disturbance force that occurs during normal operation. For some machines and...
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    Re: Open source low cost servomotor controller

    Ah fair enough. No, I haven't done anything like that. I don't think it will be a big issue though, as long as the gearing is well dimensioned.
    Get a board, and try it ;D
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    Re: Open source low cost servomotor controller

    Thanks!
    On the third video on the project page, you can see a demo with a 3kg mass moving 80cm.
    Yeah, step/direction input will be, by popular request, the the first available interface to control...
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    Re: Open source low cost servomotor controller

    Yes, this should be quite straightforward with ODrive. I already plan to do automatic machine mass/friction identification, and to use model based feed-forward for most of the control action. So it...
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