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MiniHawk VTOL

A fully 3D-Printable VTOL aircraft, designed as a hybrid fixed-wing plank + tricopter planform. For FPV and UAV experimentation.

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The MiniHawk-VTOL is a 3D-Printed VTOL aircraft. The design is intended to provide the robotics community with a common and accessible VTOL testbed for experimentation in flying robotics behaviors and tasking. Specifically, the aircraft is designed to integrate a set of flexible solar cells for migratory (self recharge) behaviors. However, the design also lends itself to reconfigurable robotics research, shown here with a pair of vehicles docking while hovering, and then performing a forward-flight mission.

The airframe is a "plank"-style wing with a center body containing avionics and battery, and conduits for routing connections to the nacelles and servos. Twin vertical stabilizer fins provide mild directional stability. GitHub Project Link: https://github.com/StephenCarlson/MiniHawk-VTOL

The main documentation for the project is contained in the README Markdown file at the GitHub repo, here is a direct link: GitHub README.md .


Metrics

Description Value
Wing Span 800mm
Wing Area 15.6dm^2
Aspect Ratio 4.1
Airfoil (Root and Tip) MH45
Length 520mm
Rotor Spacing 315mm Circle
Lipoly Battery 4s, 1300-1500mAh (~160g)
Motors (front) 22xx or 23xx 2300-2600kV
Motor (rear) 22xx or 23xx ~2000kV
Servos HS-65HB/MG or eqv.
Flight Controller (size) 30.50mm to 16.0mm Grid
Propellers (front) 5050 to ~5249
Propeller (rear) 6030 to ~5249

MiniHawk-VTOL-2.0.0.zip

New for October 2021, the Version 2 of the MiniHawk-VTOL. Files are prefixed with "MH7_"; this zip archive contains a subset of the GitHub repo contents, consisting of only the STLs, README, build pictures and configuration settings. The GitHub repo contains the entire set, including 3MF files for 3D printing with a Creality CR-10.

x-zip-compressed - 17.14 MB - 10/03/2021 at 06:45

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MiniHawk-VTOL-1.0.0.zip

Copy of the v1.0.0 release, minus the CFD Analysis set to save space.

x-zip-compressed - 21.62 MB - 10/16/2020 at 19:33

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  • 1 × Matek Systems F7xx-WING, F405-WING, or mRo PixRacer Pro ArduPlane-compatible Flight Controller with 3 Motor, 4 Servo Outputs
  • 1 × R/C Receiver 8+ Channel, SBUS or PPM Output
  • 3 × Electronic Speed Controller (ESC) At least 4s, 40A with DSHOT. Example: EMAX Formula Series 32Bit 45A ESC
  • 2 × 2207, 2306 or equiv. ~2500KV BLDC Motor Bell diameter under 29mm. Example: T-Motor VELOX V2 2207 2550Kv
  • 1 × 2207, 2306, or equiv. ~2000KV BLDC Motor Any typical multicopter motor around 2000KV. Example: T-Motor VELOX V2 2306 1950Kv

View all 26 components

  • Version 2 is Live!

    Steve Carlson10/03/2021 at 08:01 0 comments

    The MiniHawk-VTOL Version 2 design is up! As described in previous project posts, the new version has "MH7_" prefixing all the STLs and 3MF files. The local zip file here on Hackaday contains the essential files for producing the project, which consist of the README, supporting pictures, the configuration files for ArduPilot, and the STLs for all parts. 

    Special thanks to Danie Conradie for writing the awesome article that was published today (October 2); I had no idea that the project was picked for publication, and nor did I know it had hit the front page until I started getting pings from people on LinkedIn. The article is fair and well written; I suppose the only (minor) correction is that I (Steve Carlson) am the main and sole designer of the MiniHawk-VTOL project, and that its inception as an open-access migratory VTOL predates my start at the RoboWork lab at UNR. But I'm very thankful to my advisor and others here, who have embraced the project and encouraged me to complete it. The "Modular-Aspect-Ratio" implementation using two MiniHawk-VTOLs represents the first true research use case of the platform, and ownership of that work is fully and equally shared between research members. It has been a wild ride developing this project, and I am pleased that it is finally well-formed and progressing. 

    Sentimental narrative aside, lets dive into the changes that have been made, and the known issues and other instructions:

    Changes from Version 1:

    • Carbon-Fiber Spar integrated into the wing.
    • Servo Wire routing is improved and more accessible.
    • Longer Nose for better balance, with NACA vent ducts for better cooling.
    • Larger Vertical Stabilizers, improved directional stability.
    • Larger Motors can be accommodated, up to 29mm outside diameter.
    • LED pockets in the tail, and better spacing for a 6-inch prop.
    • Provisions for GPS and Video Transmitter mounting in the winglets.
    • Jackpoint stations for aircraft display and Weight-and-Balance calculations.
    • Pitot-tube mounting in either wing.
    • Strengthened Motor mounts.

    Known Issues and Mitigations:

    1. Transitions from hover to forward-flight are temperamental. This is a consequence of the tilt mechanism requiring static torque on the tilt servos during hover, and while the servos may be rated for a sufficient torque factor, the existing torsion may still stall one or both servos. A soft fix for this is to reduce the thrust during forward transition by dropping the nose or requesting a descent in the autonomous mission profile.
    2. Hinge pins on the nacelles can "creep" due to vibration, and should be glued or knurled to retain these in place.
    3. Tilt servo endpoints need to be adjusted to prevent prop-strike on the top of the nacelle arms. Related to issue #1 above, weaker-than-expected servos will result in the prop disc brushing the nacelles when under high load.
    4. Servo endpoints in the forward-flight case need to be carefully adjusted to avoid stalling servos against the forward-flight mechanical hardstops.
    5. The 6-inch prop on the tail can brush the vertical stabilizers when aircraft structures flex during harsh treatment. A few millimeters of space usually solves this.
    6. New Lid/Hatch designs are being created, a STEP version of the plain hatch is included for community modding.
    7. Servo arms cannot be removed unless the servos are debonded from the servo bays/pockets.
    8. Vibrations in the system need to be dampened where the flight controller is mounted. If the flight controller picks up harmonic resonance, this can result in the vehicle spontaneously doing a back-flip while hovering, as the vibration is interpreted as an extreme gyro or accelerometer reading.

    Future Improvements and Features:

    • The interface between the nacelle arms and the wing has been redesigned to force correct alignment, and will be introduced in the next update.
    • A Center-of-Gravity Bump will be added to the wings for hand-estimation of Weight and Balance.
    • A Single-Board-Computer mounting tray is being developed for holding the Raspberry...
    Read more »

  • Still Alive and Evolving!

    Steve Carlson09/24/2021 at 19:52 0 comments

    Reports of the abandonment of this project have been greatly exaggerated! Over the past 5 months, I've been as saturated with research work as ever, and the Version 2 formal release is in the works, but not just yet. Please enjoy the videos at the end of this post to see what the MiniHawk-VTOL can do. 

    The GitHub Repo continues to be the bleeding-edge source for any revisions or modifications that are made to the design. The only changes to the design geometry between the soft/secret release in April up to now are minor changes to the empennage and the motor tilt mount. Otherwise, the design is nearly stable/frozen and has converged to a very usable aircraft. However, be ye warned! There are some issues that need to be addressed, and which will likely persist in the Version 2 release and will only be fully solved in Version 3. Specifically, the motor tilt mechanism is absolutely terrible! Even with nice HS-5065MG+ servos on the tilt mechanisms, the VTOL forward transition fails occasionally as the servos get stalled. This is because the linkage design requires static torque contributions by the tilt servos during hover, even through the servos are suppose to have more than twice the required torque. This manifests as uncommanded yaw and spinning when attempting to enter forward-flight. 


  • Stealth/Silent Release of MH7 (v2.0)

    Steve Carlson04/28/2021 at 23:22 0 comments

    -shhhhhh-  ...... I'm saturated with school work in my grad program, so I'm not going to be able to turn much attention to rewriting the instructions and such for a bit, and the formal release with all the pageantry and publicity and awesome video trailer will have to wait. Its been way more than "a few days" since the last update, but the project has finally stabilized enough that I feel confident in pushing the next-generation version of the MiniHawk-VTOL. The new STLs are anything prefixed with "MH7_" at https://github.com/StephenCarlson/MiniHawk-VTOL/tree/master/stl-SourceFiles .

    The vehicle flies in forward-flight; smooth, sustained and continuously, if somewhat tippy. Read through https://github.com/StephenCarlson/MiniHawk-VTOL/issues/12 and https://github.com/StephenCarlson/MiniHawk-VTOL/issues/8 to see how the components have been re-positioned and how to use the balance stand platform to find the exact center of mass. The current vehicle is flying on ArduPilot using a PixRacerPro, using https://github.com/StephenCarlson/MiniHawk-VTOL/blob/master/cfg-Config/ArduPlane_MiniHawk_mRo_PixRacerPro.param

    Updates and full release to follow.

    NB: The ControlHorn STL is missing, just use the MH5 ControlHorn, same thing.

  • MiniHawk-VTOL MH7 (v2.0) Teaser

    Steve Carlson04/06/2021 at 21:39 1 comment

    Teaser for the next version!

    Coming soon, to the GitHub repo and this project page, a new variant approaches!


    Featuring the following improvements:

    • A shaft for a Carbon Fiber spar up to 7mm in diameter!
    • Support for front motors of up to 28mm outside diameter (29mm if you are brave).
    • Wire routing improvements, no more struggling with wires stuck in tunnels!
    • Larger vertical fins with full integration!
    • Separately-installed wingtips with large pockets which should enable various telemetry and GPS modules.
    • Improved building and joining surfaces.
    • A lengthened nose and improved component placement for perfect Center of Gravity.
    • Larger volume for avionics, improved mounting stanchion placement and diameter(s).
    • Pitot-tube mount with correct angle-of-incidence.
    • Other various improvements.

    Arriving in a few days, stay tuned!

  • Initial Release

    Steve Carlson10/16/2020 at 05:06 0 comments

    The GitHub repo is now public. Current Feature-Complete artwork is tagged as v1.0.0. Hello World!

    Check it out! https://github.com/StephenCarlson/MiniHawk-VTOL

  • Pre-Release

    Steve Carlson10/08/2020 at 20:40 0 comments

    The MiniHawk project exits stealth-mode soon, but for now, the GitHub repo is private, and thus the project STL build files are unreleased at this moment. I'll be filling in the build instructions and other details in the mean time.

View all 6 project logs

  • 1
    Airframe - Step 1

    Clean all 3D-Printed parts, remove all brim/support material. For each wing, carefully carve away any stringing or over-extrusion in the hinge reinforcement wells such that the hinge pin will fit.

    Figure 1
    Hinge Pin Clearance

    Carefully cut the elevons free if needed (WARNING! Only cut slots on either end to allow for surface deflection, DO NOT cut the entire elevon out), and gently exercise each surface up and down until the living hinge is established.

    Figure 2
    Elevon Movement Cuts

    Bond the Canopy/Hatch-Lid pieces together using Thin/Medium Cyanoacrylate or Epoxy, and set aside to cure.

    Figure 3
    Hatch/Lid Bonding
  • 2
    Airframe - Step 2

    Bond the Empennage Halves together. Thin or Medium Cyanoacrylate, or Epoxy, are acceptable. Set aside to cure.

    Figure 4
    Empennage Halves Bonding
  • 3
    Airframe - Step 3

    Bond the Control Horn pieces (2) into each Elevon (Left Wing and Right Wing). Thin or Medium Cyanoacrylate, or Epoxy, are acceptable. The Control Horn should be fairly flush on the Elevon Top Surface, approximately 0.5mm extending above the surface. Fit should be tight; carefully carve away any burrs or over-extrusion from the slot in the elevon if needed.

    Figure 5
    Elevon Control Horn Install

View all 33 instructions

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Discussions

dekutree64 wrote 11/05/2020 at 05:11 point

Looks great, very simple and clean design. The front motor arms look pretty delicate though, especially without prop savers on the motors. Do they break off every time you crash?

  Are you sure? yes | no

Steve Carlson wrote 11/05/2020 at 06:06 point

For the accumulated set of crashes that have, all together, broken most parts of the airframe, the motor-tilt servo arms (and servo gears) have been perfectly fine. I've stripped an elevon servo (non-metal gears), but metal gears and nylon arms on the motor-tilt have been either lucky or robust. I'd be happy to find a servo-saver that is sized to this scale, if you have any recommendations.

  Are you sure? yes | no

dekutree64 wrote 11/05/2020 at 13:38 point

Hmm, maybe wrong terminology. By arms, I was referring to the orange 3D printed parts that are glued to the wings and reach forward to hold the tilting motor mounts. Looks like they'd snap off at the glue joint. Enlarging the glue area might sacrifice some airflow efficiency, but I think it would be worth it. The rear propeller sticking up probably limits forward speed quite a bit anyway.

As for servos, I think it would be best to simply use metal gears on the elevons as well. Although I am surprised you managed to break one in the first place. Seems like the wingtips would take all the beating and protect them.

  Are you sure? yes | no

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