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| UAS Sprayer 1 (Agricultural UAV, 2016) |
Problem:
A UAS is to be designed
for precision crop-dusting. In the middle of the design process, the system is
found to be overweight.
- Two subsystems – 1) Guidance, Navigation & Control [flying correctly] and 2) Payload delivery [spraying correctly] have attempted to save costs by purchasing off-the-shelf hardware, rather than a custom design, resulting in both going over their originally allotted weight budgets. Each team has suggested that the OTHER team reduce weight to compensate.
- The UAS will not be able to carry sufficient weight to spread the specified (Marketing has already talked this up to customers) amount of fertilizer over the specified area without cutting into the fuel margin. The safety engineers are uncomfortable with the idea of changing the fuel margin at all.
My Response:
My priority for this
issue is to ensure we deliver the end product that marketing has promised, we
can precisely deliver the allotted volume of fertilizer in the correct location
with the needed endurance for the UAS.
My second and third priorities are to ensure we are within budget by a
few percent and within the promised time frame within reason. If a UAS is delivered as promised but a few
percent more in cost is better than a UAS that doesn’t deliver as marketed but
costs what was promised. The initial purchase is a onetime pain for the end
user, and can be overcome when the seasonal use of the UAS goes off as
promised. Same thing with the timeline.
If it is late by a small amount of time, say within a month, then the repeated
seasonal use of a functioning product will most likely overcome the late
delivery. Of course, all attempts will
be made to deliver on budget, time, payload and endurance. “Build the right
system, and build the system right” (Cantor & Roose, 2006).
I would go to the lead
Guidance, Navigation & Control engineer and lead Payload delivery engineer
in two separate meetings, both with the same structure. I’d like to see the weight roll up of all
parts they are responsible for. Using
this we would go after the heaviest parts first, and go from there. Assuming
the heaviest part is the off the shelf purchase I would ask the engineer to talk
to the supplier. If the supplier knows
our requirements, they may have alternative solutions that do not come with the
same weight. The main competitors of the suppliers should
also be contacted. If they also know our requirements, to include cost and
timeline, they may have a solution the current supplier does not.
What are the options for
creating our own systems that are not off the shelf? Again, the suppliers would
need to be contacted and a discussion had.
Most likely their parts have some ability to be interchanged within
themselves. If we don’t purchase a box
full of electronic components from the supplier, but instead we purchase only
some of the electronics inside we may have an opportunity for weight reduction.
They have a packaged product that delivers to all of the end users, which may
have features we do not need.
I would also let every
engineer on the project know we are having weight issues. Perhaps another
system has a means to reduce weight which will offset the added weight from
these two systems. An example of saving weight is to look at something simple
such as brackets and hardware. Let’s take a simple L bracket and discuss ways
to reduce weight. If you have two flat
plates that are welded to form the L a flat plate bent into an L would be
lighter. It’s also likely a bent bracket would be cheaper as there is less
labor and handling on the manufactures end. Assuming the L bracket has holes
for mounting if we add welded nuts to it that would reduce the total part count
for hardware required, by eliminating the washer that would go under a loose
nut. One washer is not significant, but
if you do that all over the UAS is does start to add up. This would also reduce
labor time on our end for assembly as well as less total parts that need to be
stored along the assembly line.
Is there a place to use rivets instead of
bolts/nuts/washers? Is there places to use bends instead of welds? Working with
the suppliers of any mounting brackets they would be able to offer solutions to
save weight or cost. Can we change the material? If it’s currently steel is
there an option to make it out of some form of plastic? An L bracket is straight
forward and not likely to save much, however a fully enclosed box with mounting
hardware in it starts to open possibilities. I spent years as an engineer and would work
with suppliers often to reduce weight and cost, they normally had ideas since
they built the parts for us. The ideas
varied from changing steel types, removing extra gussets or decreasing their sizes,
changing hardware configurations, riveting not bolting or bending instead of
welding.
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| UAS Sprayer 2 (Agricultural UAV, 2016) |
Making any changes to
hardware or the electronics would have benefits down the line. In the future
generations of our product we have already started to customize the “off the
shelf” products to our needs. We started the relationship with the supplier
now, and any future programs can be started with the supplier from the beginning,
instead of later on into the project as is the case now. Working with suppliers to possibly modify
brackets and mounting hardware also educates our engineers on this topic and
they can start to design hardware more intelligently. Which would reduce design
iterations and save on cost of the engineer’s time.
There is a balance to
strike with cost and timeline, however in the end we have to deliver a usable
product. A systems engineer can’t deliver
everything required. The “job is not to satisfy all needs, but to select a
profitable and practical subset of those needs and attempt to deliver” (Gilb,
2006). If we focus on delivering the
right product, this will pay off in the long run for our company.
References
Agriculture UAV Crop Dusters Agriculture UAV Sprayers
Platforms. (2016, December 21). Retrieved from
http://www.uavcropdustersprayers.com/
Glibb, T. (2006). Some Powerful Systems Engineering
Heuristics. SE Heuristics.
Cantor, M., & Roose, G. (2006, March 18). The Six
Principles of Systems Engineering. Retrieved from
http://websphere.sys-con.com/node/196077
