Prototype of a brushless Crazyflie

For a while now we have been selling the BigQuad deck which makes it possible to transform the CF2 to control a bigger sized drone. It does so by becoming the quadrotor control board, controlling external brushless motor controllers, which allows to scale up the size. This can be very convenient when trying out/developing new things as it first can be tested on the small CF2 and later scaled up by attaching it to a bigger quad. However for a more permanent setup it is a bit bulky, so we have been playing around a bit and designed something in the middle. The result is a stand alone control board targeting quads around 0.1 – 0.5kg.

We call it the CF-RZR as it is inspired by the smaller sized racers with some fundamental differences. It is designed with a higher level of autonomous functionality in mind and being easy to repair while still being fully compatible with the CF2 firmware and decks. Listing the biggest features of the current prototype:

  • Fully compatible with the CF2 firmware, expansion decks as well as radio.
  • Connectors to attach motor controllers (still possible to solder though) so it is easy to build and repair.
  • Power distributions built into controller board. (Max ~8A per motor controller though)
  • Motor controllers can be switched of by the system so the system can go into deep sleep and consume around 50uA.
  • Voltage input 1S-4S (3V to 17V)
  • Standard mounting (M3 mounting holes placed 30.5mm square)
  • External antenna for increased range

To summarize, the strength of the CF2 but in a little bit bigger package :-). Last week we got a chance to test fly it for the first time. We used a off the shelf racer frame, ESC and motors. At first it did not fly that well at all but after some PID tuning it became pretty stable and we had a lot of fun :-).

We would love your feedback, good/bad idea, what do you like/dislike etc!

Link to video

20 comments on “Prototype of a brushless Crazyflie

    • Thanks and your motor controller looks very nice! At the moment we have no plans of producing a BLMC but you never know. Could be interesting to do some prototyping with it!

  • Hi Tobias,

    Checkout this 4-in-1 BL ESC: http://fishpepper.de/projects/tinypepper/

    And this 1-2S Brushless Motor: https://m.banggood.com/Racerstar-Racing-Edition-0703-BR0703-10000KV-1-2S-Brushless-Motor-For-6080100mm-FPV-Racer-1_9g-p-1129234.html

    This brushless motor is even lighter than the current brushed motor that the Crazyflie uses.

    I think it’s possible to create a brushless setup that can be retrofitted to the existing Crazyflie FC. For the mechanical aspect it will just need a new motor mount for the BL motor. The only thing that needs to be done is a 4-in-1 BL ESC expansion that connects to the existing brushed motor connection through wire, with a modified firmware to output the correct PWM. It may also be possible to have a low power mode utilizing signal from the NRF IO in the expansion.

    The whole setup will probably be only 2-3 grams heavier than the brushed setup but it will be much more powerful and at the same time retaining some desirable characteristic of the brushed setup for example the size and weight, and the lower potential to cause any harm. Also because it is just an expansion to the existing Crazyflie FC it will be an easy upgrade for institutions which have already purchased a lot of Crazyflies.

    I’ve actually discussed this with Arnaud and Kristoffer when they came over to Singapore for ICRA 2017 recently. I’m interested to design the ESC expansion but I’m caught up with my own project at the moment, will probably start sometime around September but I think it’s a pretty good solution. What do you think about this?

    • I’ve seen some of these small 4-in-1 BL-ESC, I guess most of them are based on fishpeppers design.

      I would love to see the CF2 with those small brushless motors. Shouldn’t be too hard to prototype. Making a 4-in-1 BL-ESC deck might be a bigger challenge though.

      Summery, I give it a big thumbs up! :-)

    • It is still very early stage and we have no timeline yet. If you really need one it might be possible to arrange an early prototype.

  • I’m working on a research project and need more payload capacity, I’m using a 7X20mm motor, with 50mm prop still not able to reach our desired value. It will be great if you could please share your work or a prototype of the CF-RZR. I have written an email to contact(at)bitcraze.io.

  • I would like to see CF2 version being configured off-the-shelf, and adaptable, for BL motors and 4-in-1 BL ESC with larger battery capacity for more industrial strength applications. Not necessarily bigger than CF2, as the small size lends well to certain applications. Particularly longer autonomous flight with the new multi-ranger deck with SLAM mapping and capacity for camera and transmitter.

    • Do you find the RZR a bit too big? To get decent efficiency the propeller needs have as large area as possible while still being in the efficient range of the motor so might be difficult making an efficient small brushless version.

  • Hey Tobias, yes, possibly. I’m interested in being able to map smaller confined spaces using LiDAR and SLAM, possibly together with camera and light, e.g. underground work. So small is the key, but yes, it would need to be able to fly longer with a bigger payload…that would be pushing the envelope a bit ;) Peter

  • That Hoverbot Nano frame has 20mm mounting holes, e.g. for Piko BLX FC. Too small for the FC-RZR…

    • I agree it would be super nice to have an “industrial” grade drone that small however I think efficiency will be a problem. The rotors needs to be bigger (the agility is not really needed) which makes the Hoverbot frame a bit to small. Maybe a frame somewhere around 120mm.

      • Thanks Tobias, yes, I understand about the need for greater lift, so I will look at 120mm when the RZR gets released.

        Keep up the great work!

        Peter

  • What about connecting Flowdeck to the RZR under third party frames? I gather that deck would need another way of connecting to the RZR rather than using the pins as on CF2? As for 120mm frames, I’m thinking the RotorX Atom V3 frame.

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