Sky Sapience Delivers pre-Production Hovermast to IDF
Hovermast answers the requirement for rapid and timely intelligence gathering at the tactical echelon. The system employs a sophisticated, electrically powered platform using a main lift fan and four stabilizing rotors, maintaining the platform in flight, hovering and maintaining stable line of sight with a target of interest even when subjected to strong winds or wind gusts. The system carries sophisticated multi-sensor payloads operating day and night under all weather conditions. Hovermast 100 carries 13 pounds (6 kg) of payloads.
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Also snatched the YouTube link to their demo video which shows it being deployed, subjected to winds, etc.
https://www.youtube.com/watch?v=e9eyvhhhM7Y#t=44
I did a bit of digging and came up with several images which might answer some of the questions raise by my initial post.
Regarding the FAA question: It is interesting, albeit perhaps coincidental, that this company doesn't use the term "tethered" or "[xxxx]copter" or "aircraft" or "UAV" etc. etc. but rather talks about a "mast" and a "platform" and a "fan" and so on. So maybe what we have here is a "fan assisted pole structure" or something like that. "Nothing to see here, Mr. FAA, just move along..."
Oooh vicor makes nice stuff.
The FAA says that tethered UAVs don't get any special privelages... But maybe they'll change their mind through pressure from industry. I think tethered is safer.
I have a shopping list at Vicor with an AC (110-230V) to HV DC (375V) PFC converter and an isolated HV/LV DC/DC converter at 600W. The latter weighs less than 300gr. This would allow to use light weight 2x 0.5mm2 cable and the power is enough for a hex or light octo.
Still waiting to pull the trigger... the modules aren't cheap.
Thomas:
This is really nice and light power supply. I won't be cheap really. But it makes more sense than using server power supply. But you can get them free if you are in IT.
In the case of the backpack model, which would more than likely be what folks here on DIY would look to create, you use internal power for the motors and camera system. The need for a teather is eliminated, unless you're concerned about someone intercepting yur signal, which would be the case if you were looking to employ it in a combat situation. Also, wonder how the FAA would look at this device, if you did teather it? Would this offer a solution for those looking to photo for profit? Anyone have any ideas on that kind of use for it?
kolin: your quote for power supply weight is WAY high:
http://www.murata-ps.com/en/products/dc-dc-converters/single-output...
The only practical solution is to use higher voltage so the tether can use relatively light wire and not experience too much loss. So at the ground, you boost to maybe 100-2000V (depending on how long your tether is, and the desired wire gauge), and convert that to 12-20V at the vehicle. The vehicle-side voltage regulator/isolator shouldn't weigh more than a normal flight battery.
The advantage here isn't that it can carry more payload, the advantage is long flight duration and immunity to fly-aways, even in high winds. Oh and you can run power-hungry payloads without worrying about impact to your flight time: put a flood light up there, maybe a radar, etc.
I have been thinking about something like this. A tethered quad copter able to "unlimited" hovering. . But there is a big problem with powering cable.
Cable must be light = small diameter.
Small diameter = high resistance.
High resistance cable I needs high voltage.
1) Simple but wrong (and dangerous) is to mount server power supply something like 12V / 60A to copter and power it from mains power grid directly from the ground. With 50m of 0.8mm^2 cable (18AWG), resistance will be around 2ohm.
Server power supply is heavy, like 1,5kg so you need big powerful copter. Let say 12V / 35A to hover. This is 420W. With efficiency of 85% you need 504W of input power. Something like 2,2A from 230V. This means drop of 4V on cable which is negligible.
This is really dangerous, imagine if you cut the cable by prop (a wind gust or what ever) then falling "live" cable on your head may shock you.
2) Safer solution is to have switching power supply on the ground. There will be 2 power wires and 2 feedback wires. Feedback input of power supply will be connected at copter side. Feedback like this would compensate long high resistance wires. Example:
Again with 50m of 0.8mm^2 cable of power wire (feedback can be as thin as you like, no current there), resistance will be around 2ohm.
Copter will be lighter without heavy power supply, will hover at 12V / 20A.
Voltage drop on cable would be then 40V!! and power supply output at ground would be 52V.
This system is desperately inefficient, heat loss in cable would be 800W!! for 240W needed for copter to hover.
3) Any other ideas?
Copter really needs backup battery to land in event of failure.
As I have plenty of server power supplies, I will probably try option 1.
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