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Re: [Paparazzi-devel] 4-Dimensional Trajectories (4DT)

From: Reto Büttner
Subject: Re: [Paparazzi-devel] 4-Dimensional Trajectories (4DT)
Date: Tue, 23 Oct 2012 08:13:32 +0200

Hi David

I completely agree to your thoughts. I am a full scale glider and
motor pilot myself (no IFR rating though).

Flying IFR with an UAV is a lot easier that VFR. Unfortunately most
useful tasks for small UAVs must be flown VFR.

The first one certifying a (small and affordable) UAV for VFR flights
in NAS including collision avoidance with non-cooperative
(non-ADS-B-equipped) airspace participants like small aircrafts or
paragliders will get rich. That is the holy grail of small UAVs.
Exactely what is requested by NASA in the Level 2 competition ...

Regards, Reto

2012/10/23 David Conger <address@hidden>:
> All,
> As a new pilot I'm becoming more familiar with FAA rules and pilotage. 
> Commercial planes fly IFR with filed and closely controlled flight plans. The 
> flights are not point to point. That is changing with GPS and WAAS. Airspaces 
> are a consideration when making a flight plan. Also before a plane is 
> released for takeoff there needs to be a place and gate for it to land at. If 
> planes are not leaving San Francisco due to weather planes leaving for that 
> destination are going to be held up. Fuel is another consideration with a 
> flight plan path and altitude.
> Commercial air traffic is pretty complex but highly controlled and monitored.
> Given all those planes are on pre-determined paths and staying on them with 
> little variance (maybe due to turbulence) it's really the VFR pilots that 
> pose the big challenge. When I fly cross country I call ATC And fly "flight 
> following". So they give me a transponder code and follow my flight. They 
> tell me of traffic warnings etc. I am under their control for the flight but 
> I retain the responsibility for flying safely and following the VFR flight 
> rules.
> I'm curious if there are other pilots out there with Paparazzi? This will 
> make more sense to them but it's fairly easy to understand. Given all 
> commercial traffic is IFR let's start there. Make the UAV fly IFR. The reason 
> is a pilot flying IFR maybe in zero visibility for all but take off and 
> landing. So they are no better off than a UAV without eyes. What sets them 
> apart is that they copy the instructions carefully and follow them. Speech 
> recognition is good enough now. If the UAV (even for now the ground station) 
> could file IFR flight plans and follow directions from ATC there is most of 
> the problem solved there. Even better if the UAV can use speech recognition 
> to turn ATC commands into flight commands. Example maybe ATC says change to 
> heading 090, descend to four thousand feet (MSL) and say the barometer at a 
> nearby airport is 29.92 inches of mercury. That is important as a pilot must 
> keep setting their barometer value to that so every pilot in that area is 
> using the same value. IFR flight would be far and above the easiest and I'd 
> imagine the preferred method for UAV flight. No need for Radar, no need for 
> optical recognition and target (visual, IR, radar) detection. I can see now 
> why all UAV pilots are IFR rated. I hope to get my IFR rating next.
> Anyone trying to make a UAV fly VFR in the NAS is really going to have nearly 
> an impossible challenge.
> -David Conger
> On Oct 22, 2012, at 2:06 PM, Bernard Davison wrote:
>> Guys don't forget about the obvious...
>> Usually Commercial aircraft fly to schedules. They take off at a time and 
>> arrive at their destination at a time. (We hope. How annoyed are we when our 
>> flight is late)
>> Cheers,
>> Bernie.
>> Sent from my iPad mini.
>> On 22/10/2012, at 11:16 PM, Reto Büttner <address@hidden> wrote:
>>> Hi Chris
>>> The ATC will work from prior knowledge. The draft rules say on page 7:
>>> "Prior to each mission, competitors must declare several details about
>>> their aircraft and how they intend to operate it. Chief among these is
>>> their preferred cruise speed for their aircraft."
>>> Regards, Reto
>>> 2012/10/22 Chris Gough <address@hidden>:
>>>> Im only just starting to learn about  ADS-B. When my budget SDR kit 
>>>> arrives (hacked tv tuner dongle) I'll start sniffing the ADS-B and TCAS 
>>>> traffic with a copy the protocol specs, to try to get my head around them.
>>>> With regard to commanding 4D trajectories, obviously the ATC should only 
>>>> command trajectories that the aircraft is capable off, and where possible, 
>>>> minimize disruption to it's mission. Do you imagine there would be an 
>>>> naive exchange of messages to discover the vehicle's characteristics 
>>>> (speed limits, remaining range, altitude ceiling etc), environment (wind, 
>>>> temp, humidity etc) and objectives? Or do you think that the ATC should 
>>>> work from prior knowledge about aircraft characteristics and telemetry 
>>>> logs?
>>>> Chris Gough
>>>> On 22/10/2012, at 8:33 PM, Reto Büttner <address@hidden> wrote:
>>>>> Hi Chris
>>>>> The telemetry message you are imagining does exist. It is the ADS-B
>>>>> message. It is part of the collision avoidance (separation, TCAS)
>>>>> functionality.
>>>>> The 4DT part is a simpler and is therefore the starting point of the
>>>>> contest (L1C). That basic functionality can and should be added to
>>>>> paparazzi straight forward. Once that is mastered, the a lot harder
>>>>> collision avoidance functionality can be addressed (L2C).
>>>>> Regards, Reto
>>>>> 2012/10/22 Chris Gough <address@hidden>:
>>>>>> I read the draft rules quickly, and needed to google quite a few terms 
>>>>>> that went familiar to me. 4D trajectory was one of then, and it didn't 
>>>>>> throw up anything that looked like a conventional meaning. I had 
>>>>>> Imagined (probably wrongly) that it was a telemetry message that other 
>>>>>> planes (and ATC) could use as a basis for smart avoiding (or directing) 
>>>>>> behavior. If it's a telecommand as you suggest, in some ways that's a 
>>>>>> lot simpler (it's just an extension or adaption of existing 
>>>>>> flight-planning constructs).
>>>>>> Either way, the harder part of the rules seems to be robustness to 
>>>>>> spoofing (both GPS and "ghost planes"). Has anybody got experience 
>>>>>> integrating paparazzi with light weight affordable radar? :) I've 
>>>>>> started reading up on gnuradio, and passive (SDR) radar solution looks 
>>>>>> to me like Mount Everest. Maybe _just_ possible for ground/terrain 
>>>>>> sensing, but other air traffic?
>>>>>> Has anyone used the paparazzi TCAS code recently? Is it up to date with 
>>>>>> all the code changes from the last year or so?
>>>>>> Chris Gough
>>>>>> On 22/10/2012, at 4:56 PM, Reto Büttner <address@hidden> wrote:
>>>>>>> Here are the draft rules:
>>>>>>> They say:
>>>>>>> Page 3: "Competition missions will be defined by Four-Dimensional
>>>>>>> Trajectories (4DTs), which will be comprised of a series of
>>>>>>> three-dimensional waypoints in space and a specific time of arrival
>>>>>>> for each waypoint."
>>>>>>> Page 7: "The five distinct segments of a mission are: aircraft launch,
>>>>>>> pre-4DT loiter, 4DT flight, post-4DT loiter, and aircraft recovery."
>>>>>>> There will be an air traffic control ("central puppent master"), as
>>>>>>> they want to be able to create specific scenarios for the competitors
>>>>>>> with surrounding air traffic using a combination of real and virtual
>>>>>>> aircraft working synchronously.
>>>>>>> Managing air traffic might be the next step in development of
>>>>>>> paparazzi. I would start out with 4DT. That would be a great new
>>>>>>> feature!
>>>>>>> Regards, Reto
>>>>>>> 2012/10/21 Chris Gough <address@hidden>:
>>>>>>>> I had imagined the 4d trajectories would be chirped about between 
>>>>>>>> vehicles
>>>>>>>> to enhance 'autonomous sense and avoid' with vehicles at potentially 
>>>>>>>> very
>>>>>>>> different speeds. I need to read the rules more carefully, but I 
>>>>>>>> didn't get
>>>>>>>> the impression that a central puppet master was involved. That wouldn't
>>>>>>>> scale well.
>>>>>>>> Chris Gough
>>>>>>>> On 21/10/2012, at 9:50 PM, Gerard Toonstra <address@hidden> wrote:
>>>>>>>> I'd expect this to be interpreted as a starting time when a uav is 
>>>>>>>> *allowed*
>>>>>>>> to be in some location, not so much when
>>>>>>>> it *must* be in some location. My implication is that it's more about
>>>>>>>> devising a strategy where the uav can be kept
>>>>>>>> safely in waiting until it's time to move on. The use case here is 
>>>>>>>> that this
>>>>>>>> allows atc to keep an area void of
>>>>>>>> other traffic until the landing of special craft X has taken place or 
>>>>>>>> other
>>>>>>>> use cases alike, or that a specific mission
>>>>>>>> may only commence at time Z.
>>>>>>>> There may also be an additional requirement where a NoFlyZone has a
>>>>>>>> particular time range. You may cross the zone
>>>>>>>> prior or after, but not during, otherwise you have to go around. These 
>>>>>>>> NFZ's
>>>>>>>> may pop up at any time during a trajectory
>>>>>>>> and may require substantial replanning of the flight itself.
>>>>>>>> Replanning flights isn't necessarily bad, as long as it's clear to the
>>>>>>>> operator why it is necessary and what will happen in the
>>>>>>>> new plan. It should also be clear what will happen if the new plan is 
>>>>>>>> not
>>>>>>>> accepted, because sometimes the old plan becomes
>>>>>>>> totally incompatible with the new situation.
>>>>>>>> Anyway... I'm speculating  :).  The actual rules will define how this 
>>>>>>>> should
>>>>>>>> be interpreted. I do think that here's an excellent opportunity to
>>>>>>>> impress the judges by thinking ahead of the requirements and 
>>>>>>>> demonstrating
>>>>>>>> that beyond a technical implementation, some
>>>>>>>> thinking has been undertaken why 4D is a necessity and how operators
>>>>>>>> 'interact" with uav's to enable this in the best way
>>>>>>>> possible (maintaining overview of the situation, reducing interaction
>>>>>>>> complexity, etc.)
>>>>>>>> G>
>>>>>>>> On Sun, Oct 21, 2012 at 7:12 AM, Reto Büttner <address@hidden>
>>>>>>>> wrote:
>>>>>>>>> I do not think that the calculation of an ETA in flight will be 
>>>>>>>>> enough for
>>>>>>>>> NASA.
>>>>>>>>> I expect rules similar to the following:
>>>>>>>>> - Before flight you file a flight plan including 4D waypoints
>>>>>>>>> (position, altitude and time). This calculation must include the
>>>>>>>>> expected wind.
>>>>>>>>> - In flight the autopilot must control position, altitude and speed to
>>>>>>>>> hit the filed 4D waypoints.
>>>>>>>>> - Perhaps in flight you are allowed to request a change of the filed
>>>>>>>>> flight plan, e.g. if a delay in departure has occured or wind is
>>>>>>>>> completely different than expected. I am sure Air Traffic Control will
>>>>>>>>> allow only a few changes and only for good reasons.
>>>>>>>>> Therefore Paparazzi should accept 4D waypoints (position, altitude and
>>>>>>>>> time) and the flight control should be enhanced to hit the time. Has
>>>>>>>>> anybody done that in Paparazzi?
>>>>>>>>> Regards, Reto
>>>>>>>>> 2012/10/21 Steffen Spies <address@hidden>:
>>>>>>>>>> I think it means, that the flightplan has position and the time. Like
>>>>>>>>>> "be at home at 6pm" while the plane always tells if it will be in 
>>>>>>>>>> time or
>>>>>>>>>> not.
>>>>>>>>>> Am 21.10.2012 um 11:21 schrieb Chris Gough
>>>>>>>>>> <address@hidden>:
>>>>>>>>>>> I noticed that too, and don't really understand what it means. Is 
>>>>>>>>>>> does
>>>>>>>>>>> it mean the telemetry messages that say "I am here now, and expect 
>>>>>>>>>>> to be at
>>>>>>>>>>> that place in two minutes"?
>>>>>>>>>>> Chris Gough
>>>>>>>>>>> On 21/10/2012, at 6:43 PM, Reto Büttner <address@hidden>
>>>>>>>>>>> wrote:
>>>>>>>>>>>> Hi guys
>>>>>>>>>>>> The newest UAS competition of NASA requests 4-Dimensional 
>>>>>>>>>>>> Trajectories
>>>>>>>>>>>> (4DT):
>>>>>>>>>>>> "The Level 1 Competition (L1C) would focus on a competitors 
>>>>>>>>>>>> ability to
>>>>>>>>>>>> fly 4-Dimensional Trajectories (4DT) to provide a reasonable
>>>>>>>>>>>> expectation that they will be where they are supposed to be, when 
>>>>>>>>>>>> they
>>>>>>>>>>>> are scheduled to be there."
>>>>>>>>>>>> See:
>>>>>>>>>>>> Has anyone in Paparazzi realized 4-Dimensional Trajectories, in 
>>>>>>>>>>>> other
>>>>>>>>>>>> words has included the time dimension in flight control?
>>>>>>>>>>>> Regards
>>>>>>>>>>>> Reto
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>>>>>>>> --
>>>>>>>> Gerard Toonstra
>>>>>>>> -----------------------
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