Le Module GLdab permet de caler les ailes d'un Ornithopter à la bonne position pour planer
The GLDAB unit is intended for positioning the wings of an RC ornithopter into the gliding position. It works in conjunction with a mechanical ratchet.
Die GLDAB Maßeinheit ist für die Positionierung der Flügel eines RC ornithopter in die gleitene Stellung bestimmt. Es funktioniert in Verbindung mit einer mechanischen Schaltklinke.
Le Module GLdab permet de caler les ailes d'un Ornithopter à la bonne position pour planer
Glide … if you can !
This is not to discourage you, but only to warn you about the problems you will be facing if you intend to have your ornithopter gliding…
At low speed (or hovering ?) a flapping model inherently does not stalls, if the thrust or the lifting forces are sufficient !. When the flapping stops, the model is no longer an ornithopter but behave as a glider.
Almost all ornithopters have membrane wings. For this reason, the drag and the sensitivity to wind are great. The aspect ratio is low. As a consequence the gliding performances are poor. As soon as the flapping stops the flight become tangled if the speed is too low at the gait change.
GLDAB 1.1: our first approach for gliding
The GLDAB 1.1 unit was intended for positioning the wings of an RC ornithopter into the gliding position. When gliding is ordered (throttle low), the wings flap at a pre-selected low rate for 2 seconds. Then, the motor stops when the drive crank is at a pre-determined position, in the lower downstroke, ensuring that the mechanical ratchet mechanism will engage and lock the winks.
Of course, the system works …but, if you do not manage to maintain a minimum speed (plunging fast !) you will put your model in jeopardy (stall !!!) and miss to lock the wings!
GLDAB 1.2: do we pave the way to 100% wings lock?
In order to mitigate the problem, it was necessary to imagine a transition from flapping to gliding with the centre of pressure of the wings staying above the gliding position in order to preserve the stability of the model.
We observed that birds gliding from a roof are used to take off with their wings in the up position:
They gain speed from their drop and then move their wings downward to the glide position !
We decided to apply this principle to GLDAB …
The hardware remains unchanged.
The software have been slightly modified.
The magnetic detector and the magnet are aligned when the mechanical ratchet is engaged.
When gliding is ordered (throttle low), the motor stops…
After 2 seconds, GLDAB checks the status of the magnetic detector:
If the magnet is detected, the model is gliding (we hope so !). The motor stays off, until the throttle control rises …
Else, the wings are assumed to be in up position (pushed upward by the pressure created by the drop of the model). The motor starts moving the wings downward, at a pre-selected low speed and stops when the magnet is detected.
GLDAB 1.2 has been functionally tested. Extensive field tests are to be performed on different kinds of ornithopters in the coming weeks, if the weather conditions are improving !.
It was the decision of Robert Korobelnik (OVIRC) and Alain Bizot (The designer) to offer the GLDAB 1.2 to the Ornithopter community as an open source project.
You will find in the following pages all the technical details (including the source code) for a personal building of the GLDAB 1.2 unit.
You are allowed to copy (and/or improve !) and utilize GLDAB 1.2 for your personal use, under your sole responsibility and at your own risk !
06/06/07 We tested Gldab1.2 on a SH2 with Brushless motor & 1s duration of check status (June 05, 2007 ) On 12 successives glides, result was : 12 successfuly glides on 12.
Francis Girault nous a fait parvenir une video du Gldab installé dans son "Poulet"
Details of GLDAB 1.2
The following figures are self explanatory. It is up to you to draw a clean PCB (2 sides ?) mine is a 1 side “poor draft” with 2 wire connections under the PIC!.
The photos are showing the pins for programming with ICD2… you have to unsolder them when it is done !
The source code (3 files, attached to this document) are fully documented. Have fun with GLDAB 1.2
