# UAV swarm, anticollision - faa - detect-and-avoid

Since UAV activity is largely constrained by the see-and-avoid issues;

I though it would be appropriate to propose a solution which is compatible for every form of flight from gnat-weight to jumbojets. I've worked this out is a simulator - but here is the jist:

This requires only a single frequency and very short blips.

1. Every plane determines it's location and vector by GPS.
2. Then it transmits this information using one short blip every second or so.
a. The blip timing is based on current GPS location, so that the blips cannot interfere, and their location in Timespace tells us where they are coming from. Since GPS provides a very accurate, shared time base. So let t in microseconds = latitude\1 + longitude\1 * 100 + Alt in Km *1000 .
b. Odd seconds communicate vector (ie destination), Even seconds communicate Location.

3. There is a third variable required - which I call "Density". Each plane calculates the perceived Density of their airspace and sends that as well. Your density is your passenger count divided by the distance between you and other planes multiplied by their perceived density.

4. For manned aircraft nothing further is required - this beacon signal will ward off all unmanned vehicles.

5. For Autopilot or UAV, it is possible to chart a new safe vector by trying random vector changes and calculating their future density based on the vectors and densities of nearby airplanes. The vector which optimizes progress toward destination with lowest density is the vector chosen.

simple calculation requirements (ie Arduino), cheap transmitter/receiver requirements, and low power requirements. cheap unit cost, and no ground control.

Such a system could be demonstrated by coordinating a swarm of Ardu-Planes.

Ben

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### Replies to This Discussion

Ben,

That's very clever. In a sense, it's a simplified form of the transponders that commercial and military aircraft already have. But as you know, the private pilots association has fought hard to stop the FAA from requiring civilian aircraft from carrying transponders. Some of their objections are economic, although it's obvious that transponders could be made quite cheaply, but the less overtly stated reason that matters even more to them is freedom. They like being able to "file and forget" flight plans, or not file at all. The idea that would always be tracked in the air is what they resist.

In short, if this were just a technological problem, solutions like your very smart one could easily provide a solution. But it's cultural too, and there are some very entrenched interest groups who don't want to see this happen.
It's far more than a transponder - it's a complete collision avoidance/peer-to-peer ATC system. If you integrate emergency conditions like fuel remaining into the Density value, it can prioritize distressed flights. It also avoid collisions on the runway and taxiways (eh-em). (All for \$70 per plane).

The Algorithm is based on an Ant-Colony-Optimization.

Agreed that there is political redtape;
which is why I think a effective strategy for UAV-ists would be to establish a working protocol; demonstrate that it works via swarms, hope it becomes adopted as a defacto ground control for some remote island examples; then maybe europe, and soon it's a workable technology.

I think a certifiable demonstration transponder could be made for \$50gps + \$24arduino + ~\$20 for radio. (Although the Xbee is over complicated)

Blip duration should be used to signal density - this would ensure that the signal strength is higher for potentially congested sectors.

Such a system scales nicely as small-slow aircraft can use low power; while large commercial flights can transmit their positions much farther ahead.

Ben
I find a certaing amount of irony in Chris's response because I believe he's right. Too many groups would not want big brother to know where they are, but at the same time I'll bet they'd all have their cell phone ready for those important calls... which can be tracked.
There was one acoustic sense and avoid system at Unmanned 2008 and I spoke to another vendor who claimed to be working on an optical system. Both small enough to be flown on small UAS systems. Although the above approach has merit it would require everybody to get on board for it to work where as an optical or acoustic avoidance systems would function in a mixed environment where aircraft have different capabilities.
Condor -

Are the optical and acoustic systems you describe all passive (i.e. no outgoing beacon) ?

I like Ben's description of a beacon-based system described by Ben. Additionally, lots of radios provide RSSI (received signal strength indicator), and a more sophisticated circuit could compute doppler shift. Presumably, there would be a license to operate in one of the aviation frequency bands to avoid interference from busy 900MHz or 2400MHz ISM channels, though this would no longer be a \$20 radio.
Both the systems were passive. I like the description also. However just imagine the implementation (apologies for being negative just thinking how long the FAA would take to implement something like this),
Ben's description described by Ben. Nicely said ... someday I'll learn to proofread.

One other observation is that vector math required to compute collision trajectories is probably somewhat beyond the range of the Arduino, but within the capabilities of a reasonable DSP.
It's peer to peer, so you don't have to wait for the faa. The signal strength required is on the order of the sputnik. Any rc radio would provide enough signal for small craft avoidance, while larger planes would want to broadcast farther ahead.
I would propose this scheme as the lowest power/lowest cost/smallest size system which can be proven by simulation, and real use to provide zero near-collision events in all conditions regardless of craft size, speed, or congestion - with the added benefit of providing the coordination capabilities of an ATC. In Simulations, planes develop circular patterns around airport as they take turns landing, and they develop prevailing patterns as the least dense vector is likely to be the wake of another plane going the same direction.

Ben
Ben -

Is this just an idea, or something you're already pursuing ? What simulation tools did you have in mind ? At a minimum, it sounds like a great university research project, but perhaps you could take this to another level.
If you are 10,000 feet away from me and you send a blip at GPS t=0, then it takes about 10,000 nS, or 10 uS to arrive at my location. Seems like there would be several solutions to your equation above and it'd be impossible to disambiguate.
I developed the basic ACO algorith some 5 years ago while in Kiev, and tested it in a simple VB6 simulation in 2D. The results were astonishing - meaning that high level concepts like circling (all in the same direction), and combined route/traffic optimizations were appearing automagically as the congestion increased. The ACO is a remarkable technique, and you need only tiny bits of data and math to operate it.

The projections were all linear, and relatively short term.
Benjamin
the problem i as i see it is this , the aircraft need to sense its environment and be able to avoid an solid or liquid object weather it be another plane , a flock of birds , a new cell phone tower , trees ect... as mentioned earlier many manned craft will never carry any form of transponder craft like ultralights , hangliders , parachutes , ect...your algorithm im sure works well but you need to put down the sim at some time and get out there and start flying in real airspace and i can assure you that you will find the problem much more complex then what a simple transponder or even some of the audio / video system can deal with at this moment , the fact of the matter is that even humans (which are way more capable at dealing with the unknown then computers ) still get fooled by certain situations all the time . human pilots are still way more capable then your most advanced AP system

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