History was indeed made on August 10th, 2011 when the Revelation PoC prototype crashed unceremoniously in my driveway. It did briefly leave contact with the Earth, and one could argue that you have to fly in order to crash, but I do not have the audacity to declare a success out of this debacle. A root cause analysis has determined that multiple Magically Obliterating Smoke and Fire Emitting Transistor (MOSFET) failures are to blame. If you listen real closely, you can hear the power rail line inductance ringing (a bit of electronics levity). I wasn't laughing at the time, but an important lesson is finally learned; MOSFETs fail shorted (full throttle). One failure in the back started the pitch forward, then three in the front failed, catapulting me down the drive perilously close to a parked car, missing a rotor strike by mere inches.
The resolution isn't great due to the use of USB instead of FireWire to copy it off of the camcorder. That said, I'd rather this didn't go "viral", as it is a bit embarrassing. Such is the nature of invention. I proffer it mainly as a veracity enhancer; this effort is real and very close to success.
It is interesting to note that half the array out of ground effect managed to push the whole craft with me in it dragging against the asphalt for almost 20 feet before I managed to shut everything off. The power is certainly there. It's all a matter of control now, and the first thing to do next is make the power MOSFET stage for each thrust unit "bullet-proof".
The damage isn't as bad as it looks. The real work involves a total redesign of the power stage including FUSES for each thrust unit. There are much better MOSFETs around now, considering this iteration is seven years old.
New changes frantically being applied include:
- Higher current and more modern MOSFET devices
- A resistor-capacitor snubber network across every MOSFET to help mitigate ringing overvoltages
- Transient voltage suppressors (zener diode-based technology) across every MOSFET
- A complete rewiring to minimize power rail inductance
- FUSES on each motor as a fail-safe
- Larger decoupling capacitors on the outrigger thrust units
We're a couple weeks away from another run at it.
Yours in Daring Invention Progress,