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The Imprecision of Using Drones for Precision Pesticide Applications
University of Nebraska – Lincoln
Dr. Greg Kruger Research update on the use of drones for application of pesticides, looking at coverage uniformity.
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Hello, today I'm gonna talk a little bit
about the imprecision of using drones
for precision pesticide applications tool.
What I'm gonna do is talk a little bit
about using drones for pesticide applications
and a little bit of the research that we've done.
As you can see,
I've got a couple of coauthors down there.
Dr. Brad Fritz, USDA, ARS scientist,
and one of my graduate students Trenton Houston,
these two both have been integral in terms
of helping develop the material for this section.
Without them, this really wouldn't have been possible.
Using the drones for pesticide applications,
it's not necessarily a new concept,
but it's a concept that's really slowly starting
to take off in the US.
Here you can see a couple pictures of drones
that we have in our lab.
These are both set up to make pesticide applications.
As you can see there, there's some more,
but yet there are some differences
between the both of those.
For example, the one in the top left hand corner,
the one on the bottom right hand corner has got four.
The two drones have a different tank, carrying a tank sizes
and different lift capacities and things like that.
So as you, as we go through this, you'll see that,
there's really a key thing there that every one
of these drones seems to be a little bit different
in terms of their function, in terms of what they do
and how they work.
So when we think about the benefits of drones
for pesticide applications, the true benefit
is that we can reach areas that may not be accessible
by traditional application methods,
areas where airplanes and helicopters
might have a hard time getting in,
but yet for one reason or another,
we can't get a ground application right there,
you know areas.
So along riparian areas,
sometimes fruit and vegetable production,
high value crops that may not be growing
on the perfectly well flat line areas, things like that.
Or maybe make an applications in enclosed airspace's
moreso inside the orange building sort of things like that.
Really makes us a benefit if it's fully autonomous.
So we have the technology today that a drone
could land on our refueling tank.
And really the only thing they operator
would be doing in terms of the actual operation
would be changing the batteries out.
The rest of it would be autonomous flight
off of pre-scripted flight plans.
I put them the next bullet point on here,
and then they can't be compared to aerial
or ground applications.
We'll going into some detail about that,
but they really are truly different
than our traditional area or ground applications
in a number of different ways.
One of the things that you must recognize is,
in the US that we have to have a drone operator license
through the FAA but it also requires a special permit.
So there's a number of exemptions and things like that,
that you have to file with the FAA in order
to actually release pesticides from the drone application.
And that process is continually evolving
and quite cumbersome.
Now, however, even though there's not a lot of folks
in the US that are flying drones
for pesticide applications,
globally there's a lot of of work that's already been done.
And a lot of applicators
that are out there making applications.
And it's estimated that there's approximately 55,000 drones
in China that are making applications.
And that number maybe as much as a 200,000 or more today,
the 55,000 as a reliable number that we've got.
But we suspect that there may be quite a few more than that.
And globally, there may be as many as 10 to 15,000
other drones making applications,
where in the US we're certainly a less than 50 today.
So when we think about manned versus unmanned applications,
there's really three areas that I think deserve a little bit
of attention when we talk about, be a different,
the speed, capacity and scale.
So if we think about the speed of the application,
a typical air tractor, five or two today,
is gonna have a working speed of 120 to 160 mile an hour.
And that may be a big conservative
that maybe even a little bit faster than that.
So absolutely high-speed, environment,
we've got a high shear environment on that liquid coming
out of that also as a quite different environment.
When we think about the drone, typical working speeds,
I have 90 miles an hour here.
The 18th is probably pushing what the drone can do.
And the nine, maybe a little bit high,
even though some of the research
that we're seeing may suggest
that even in that six to eight mile an hour,
it might be a better working speed.
So, we're talking about speeds
that are much just more similar to ground applications
than actual aerial applications.
When we talk about capacity,
particularly for us here in Western Nebraska,
as you guys all know large fields,
this is not the type of application that we're looking
to replace an airplane with.
An air tractor five or two has got a 500 gallon capacity.
Our air tractors range anywhere from a 400 or three
or 400 gallons on up to as much as 800 gallons,
the high end capacity of an unmanned aircraft
that we'd be using to make a drone application today
would be five gallons.
Most of them are smaller than obvious.
And then the last one scale,
and this is what really limits us in terms
of scaling this thing up into something
that could be used for a row crop.
The limitation really becomes the size of the aircraft.
So, if we go back to that air tractor five or two,
we're looking at a 4,500 pound aircraft,
a 52 foot wingspan and a working range of 620 miles,
so round trip.
So, we look at that compared to that drone.
Now we're gonna be a 40 pounds
without the batteries on there.
FAA is gonna restrict us to a 55 pound gross weight takeoff,
and we could have a wingspan eight rotor wingspan
that maybe a few foot across,
on a range of anywhere from eight to 15 minutes loaded.
So we're really not going to go much further
than line of sight even if we were allowed to.
However FAA restrictions that instructs us to define it,
the line of sight,
so this thing's not going to go 600 miles.
It's gonna only operate in the area
where we're making that application.
Now, the big issue when we start talking about drones
or unmanned aircraft, is there's a big data gap in terms
of both information available for applicators
as well as information available for the FAA
and particularly the EPA to make policy
and regulatory decisions.
The gaps, and you'll see in some of our data user,
these are real first one, at least height.
So if we think about a ground application,
we're ideal, boom height is gonna be anywhere
from 15 to 30 inches,
forwarding an air tractor five or two or another airplane.
We're looking at the ideal boom height of 10 to 12 feet.
The drones are probably gonna be somewhere
in between those two, but exactly where that false,
we don't know.
A flight speed effects.
So we talked a little bit about that range of flight speed,
but we don't know exactly what flight speed effects
are gonna have on the distribution deposition
of that pesticide application
and the efficacy of that application.
So there's a big gap there.
The next one on my list
was nozzle boom placement impacts of,
we think about it,
the droplet size coming out of a drone is gonna
be very similar to a ground rig if we're using
the same nozzles, because we don't have that sheer.
But if we use the same application parameters
that we have, that boom height higher
than what we have for ground application,
we have the airflow effects coming off of that aircraft.
As you see in our next bullet point,
the multi-rotor wash effects
that the boom placement nozzle spacing
and also placement on the booms become very very different
in terms of how we're gonna try to set that up.
Also for unmanned or drone deer aircraft applications.
We're generally looking at very low volumes compared
to what we would a typical ground application.
Which have a ground application,
we might be looking at anywhere from a five to 20
or 25 gallon per acre or row crops.
For an unmanned drone applications,
we're gonna be looking at,
is somewhere from a quarter up to maybe a gallon per acre
at the most.
So very very different in terms of volumes there.
And that's gonna affect that the droplet size
and distribution pattern.
Effective swath width versus the uniformity and rate,
it we'll get into this.
But today with the knowledge we have the equipment
that we have, this is a very imprecise science compared
to what a ground or aerial application might be.
I say all of the above for different UAS or unmanned drones,
because every single drone is gonna be set up differently,
different miles, different booms, a different number
of rotors, different application speeds, boom heights.
And so there's a lot of different combinations
that we really don't understand what those interactions
are between those different combinations.
Now, I'm gonna spend the pretty much the rest of the time
that we have talking about the swath width
and how we set this up for uniformity coverage
and more or less how difficult
that is to get a uniform pattern.
So, I won't go into lots of detail
but just to give you a feel for what it looks like
this top part of the figure up here is what we get
in terms of distribution across that boom for a single pass,
the black box that you see as the,
what we would consider the optimum distance to optimize
that swath width, we're looking at,
in this case at a 5.5 meter, roughly 16 to 17 foot swath.
And if we look at that CV value,
and I talked about them being between 25 and 75%,
here we're right at 55% with a mean coverage of 10%.
You can see also inside this,
the distribution of the droplet sizes
across that spray swath
and the green representing the largest droplets
that we see in this particular application
or the extra course.
The blue being the very course, the yellow being the course.
And so you can see that those extra course drops
are deposited right underneath the equipment.
Maybe with just a little bit of shift to the left side
of that sprays wall, the larger droplets,
the smaller droplets getting pushed out away from the center
of the unmanned aircraft.
And then smallest droplets are those core droplets being
on the very outside edges of that.
Now the next figure down shows the,
what nine overlapping patterns
would be with that 5.5 meter swath width
and the red bar now represents
what the optimum coverage should look like.
This is for 10% coverage
and where you see gaps below that red bar,
that's a lower dose than what we were targeting,
where you see the spikes,
those green spikes sticking up above the red bar.
This is where we're getting more output than what we desire
and what this starts to lead to is potential for where we
get higher doses or improper injury
or damaging desirable vegetation
or where we see gaps down below,
this is potentially an ineffective dose,
which could lead to selection, pressure for resistance.
So, as you can see here,
should we start to set this up,
this scenario where we really aren't getting
a nice clean application.
Now, real briefly with the last minute or two,
I just wanna show you what that looks like in terms
of modelling this out.
So this is what the EPA would look at for risk assessments.
And I don't, won't go into details here,
but what you see are a number
of different drone applications
and those blue lines that you see swirling
across each of those four figures,
are the airflow coming
off of in this case at multi-rotor drone.
And you can see as we change the application speed,
we change different practices
in that application in this example,
two meter, three meter, five meter, a boundless height.
You can see how much that air flow dynamics changes
as we're spraying or releasing spray into that.
You can imagine how difficult that then becomes
to get those droplets to the ground in a uniform way.
So we'll just skip forward here.
This is us modeling done by Milton Teske and his group.
This is another multi-rotor air flow dynamics team.
And you can see that air flow coming off that drone.
Now, when it's in flight and the prediction
of what that release would look like,
and you can see,
just imagine if we're releasing droplets into this,
where those droplets might go, and it's all over the board,
which leads to those high CV values
and very imprecise applications that we're talking about.
So once we start to think about the future of our program,
now we're gonna be doing a lot of work looking
at field efficacy, pairing different nozzles
and product combinations,
continuing to do work on deposition
and swath width,
as you can see,
we're nowhere close to what a ground
of aerial application would be.
So the question becomes,
what we do to start to make it look more like that?
Definitely need to work
on getting standard application parameters,
including the heights and application speeds.
And then the other thing that we didn't even touch on today
is understanding pesticide drift
and where these products are gonna drift to.
So with that, I'm gonna wrap up,
we'll open things up for questions.
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