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:
- 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.
- Hinge pins on the nacelles can "creep" due to vibration, and should be glued or knurled to retain these in place.
- 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.
- Servo endpoints in the forward-flight case need to be carefully adjusted to avoid stalling servos against the forward-flight mechanical hardstops.
- 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.
- New Lid/Hatch designs are being created, a STEP version of the plain hatch is included for community modding.
- Servo arms cannot be removed unless the servos are debonded from the servo bays/pockets.
- 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 Pi, Khadas VIM3 and other SBCs of similar form-factor.
- Provisions are being added to the wing for down-facing stereo cameras and LIDAR units such as the TFmini Plus.
- All build instructions and graphics will be redone at some point.
- A logo for the project is nearing final polish and release.