
Darpa Shows Off Some Things You Can Do with Distributed Electric Propulsion - godelmachine
https://spectrum.ieee.org/tech-talk/transportation/advanced-cars/darpa-vehicle-technologies
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TaylorAlexander
If any of y’all like this, I am building an open source 3D printed off road
robot with in wheel motors and transmissions, and I post regular updates on
the project on YouTube. The transmission is currently an 11:1 two stage
planetary gearbox that is almost entirely 3D printed (aside from some
bearings, screws, and metal pins). I recently drove 2.2 kilometers with it but
I’m shooting for 20km and hopefully 50+kms between gearbox services. Can be
made on a $1k printer and it’s all CC0 open source. Code is python on
Raspberry Pi.

Please check it out if that sounds cool!

[https://youtu.be/cU_0M1_TvD0](https://youtu.be/cU_0M1_TvD0)

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arketyp
I liked that part of the DARPA-demo the best for sure. It seems obvious that
vehicle suspension should be dynamically controlled by software anticipating
the terrain. (Maybe cars already have this technology to some extent? I'm not
sure.) What's the soft tech in your robot?

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Already__Taken
> Maybe cars already have this technology to some extent?

It was banned in F1, that combined with the skirts for downforce meant for
insane low ground clearances with grip off the scales. You could see cornering
speeds going up seemingly without end.

context: [https://www.racefans.net/2007/05/17/banned-active-
suspension...](https://www.racefans.net/2007/05/17/banned-active-suspension/)

~~~
intruder
Even non-computer aided active suspension was banned. Good readup:
[https://www.autosport.com/f1/news/127638/f1-latest-
suspensio...](https://www.autosport.com/f1/news/127638/f1-latest-suspension-
row-explained)

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black_puppydog
1st thought: wow, cool stuff!

2nd thought: too bad it's gonna be military use first. I've often heard the
argument being made that military applications (and even war itself) somehow
drive innovation. While that may be true to an extent, it always rang hollow
to me as an argument. Why should civil life always just get the "crumbs" of
science and engineering? Why not turn it around, spend most of the research
money _and brain time_ on things that benefit everyone (in the US, and
worldwide) and then see which of those technologies can be repurposed for the
military, not the other way around?

DARPA alone has a bigger budget than NASA, and I just googled "us military
research budget" and the numbers for all the arms of the US military are quite
staggering, really.

~~~
cabalamat
> Why not turn it around, spend most of the research money and brain time on
> things that benefit everyone (in the US, and worldwide)

[http://slatestarcodex.com/2014/07/30/meditations-on-
moloch/](http://slatestarcodex.com/2014/07/30/meditations-on-moloch/) is why
not

~~~
swebs
>8\. Arms races. Large countries can spend anywhere from 5% to 30% of their
budget on defense. In the absence of war – a condition which has mostly held
for the past fifty years – all this does is sap money away from
infrastructure, health, education, or economic growth. But any country that
fails to spend enough money on defense risks being invaded by a neighboring
country that did. Therefore, almost all countries try to spend some money on
defense.

>From a god’s-eye-view, the best solution is world peace and no country having
an army at all. From within the system, no country can unilaterally enforce
that, so their best option is to keep on throwing their money into missiles
that lie in silos unused.

Funnily enough, we can come full circle and say that many developed nations
can survive these days with very little military spending just because
America's massive military is enough of a deterrent.

[https://en.wikipedia.org/wiki/Pax_Americana](https://en.wikipedia.org/wiki/Pax_Americana)

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baybal2
One advantage of electric transmission for military vehicle is that you don't
have a single driveshaft to fail on you rendering you immobile, nor clutches,
nor a chance that a single broken wheel will jam the rest of powertrain.

The last point is the biggest advantage of many wheels vehicles over tracks. A
detracked tank is a sitting duck, but an 8x8 without a single wheel will
happily run away after taking damage

~~~
cm2187
How easy is it to insulate the electric motors? My thinking is electric motors
in the wheels while crossing a river, opportunity for short circuits.

~~~
jasonjs
These are probably brush-less motors, so in theory, they shouldn't pose any
specific challenges in that scenario, as there are no exposed conductors, only
sets of insulated coils/windings and permanent magnets that would end up being
immersed in a river.

~~~
justinclift
EMP sensitive?

~~~
Nokinside
Not the motors. They are designed to withstand high currents.

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arketyp
Technology is naturally more augmentation than automation. This is closer to
the future of driving than the self-driving AI solutions. Our senses will be
aided and some tasks out-sourced. This is already happening, has always been
happening, e.g. anti-lock braking system or proximity detection with auditory
feedback.

~~~
pineaux
How are self-driving vehicles NOT an augmentation? We are not talking about
self-living bodies here. Self driving vehicles augment our ability to
transport ourselves and our stuff without the use of a part of our mental
system. It's like walking on the automatic pilot, like in your home, except
faster.

~~~
arketyp
Yeah, it is certainly not a clear cut distinction. You know, I initially
listed _automatic_ transmission as an example of augmentation. So it goes both
ways too. Anyway, they highlight different aspects and I find the notion
elucifying.

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Nokinside
Darpa should have open betting market for these concepts.

Only thing I might moderately bet on is electric motors inside wheels.
Electric motors can be more durable, require less maintenance and perform
better.

That shaping wheel concept is obvious no go. I would bet serious money against
it. Tank tread is the weak point even in modern main battle tank. Their design
is simpler but they have problems with mechanical complexity and short
lifespan and reliability. Tracks getting jammed or thrown track is relatively
common.

Just take a that wheel to a drive across mud, sand and bushes with lots of
sticks and stones and see how it goes. Low maintenance and reliability are
high on military priorities.

~~~
Retric
The advantage over tracks is you can lock everything and use the wheel anyway
over relatively short distances. So, you trade increased complexity for a
vastly better failure mode.

Yea it's bad for the car and passengers, but being able to move even 1 mile
after failure is a huge advantage.

~~~
Nokinside
You may not be able to lock it after you drive in dirt for some time or have
any kind of failure where you lose the track.

Having tires with adjustable air pressure, or just adding extra pair of wheels
(you may lift them up) to the vehicle seems like simpler idea.

~~~
Retric
Losing track on one wheel is not going to stop one of these things from moving
in an emergency. Plenty of videos of people driving even normal cars on rims.
ex:
[https://www.youtube.com/watch?v=-1BgwX3hHgo](https://www.youtube.com/watch?v=-1BgwX3hHgo)

~~~
Nokinside
You are focusing on very narrow concept and scenario.

The overall maintainability, durability and cost is the issue. The ability of
brigades to operate long time independently with minimal maintenance logistics
is essential.

~~~
Retric
I worked in Logistics simulation for a little while.

Humvee armor was a huge issue as it reduced speeds and increased fuel
consumption. However, more armor on a small percentage of them was still
extremely useful.

IMO, these are of similar value. You don't replace all wheels, but assuming
they mostly worked you could swap them in a few vehicles during a monsoon for
example then take them out.

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DanielBMarkham
That extreme suspension vehicle looks like something out of Batman. Bet it's a
hoot to drive.

I thought it was interesting that while they're doing a ton of research, it's
all one-off stuff. In other words, they could have required all of the
experiments to ter with one another using some standard framework. Then they
could mix-and-match various experiments to see how well they work with one
another. Instead, it looks like they're evaluating each one separately -- with
some huge integration nightmare up head if any of them ever make it into the
field. I wonder why they do it that way.

~~~
solidr53
Im not sure that RD works that way. Innovate, time and compatibility, pick
two.

~~~
DanielBMarkham
I don't know. I know that some mention was made of the pieces fitting already-
existing army wheel specs. So obviously for some groups integration was a
consideration.

And it's a mistake to think in all-or-nothing thinking here. I didn't say you
needed to design a rock-solid integration system, only that it looked like
integration was a minimal concern -- and that was an interesting choice.

I come from the tech community. The longer we put off integration, the more
expensive things become.

~~~
hedvig
This sub-thread reminds me of the monolith vs microservices kernel discussion
I see a lot here. Doesn't Linux benefit from specialized pieces being piped
together at will?

~~~
DanielBMarkham
Yep. It's a spectrum and a scale. On various scales you want to apply various
paradigms. It's not a yes/no thing.

We know for a fact that no matter what they pentagon does with wheels, they
need to fit on a body and cost less than a million bucks or so. Even giving
the R&D teams wide latitude for they're playing around in, we can start
setting some reasonable guardrails up.

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mrfusion
I hope cars will do this once we’ve gone electric. Imagine how long you could
keep a car if you can swap out a motor with a jack and a socket wrench.

~~~
dsfyu404ed
The unsprung mass of hub motors makes them terrible for handling, especially
at speed (military vehicles top out at "slow person in the right lane"
speeds). When you've got a teardrop shaped turd (or economy car, whatever your
preferred pronoun is) that's riding 2in off the ground (because how else are
you going to be aerodynamic enough to deliver reasonable range) and nearly nil
suspension travel (relative to anything expected to operate off road) drive-
train and power transmission packaging isn't really an issue (whereas that was
the primary issue solved here by going electric).

You should expect to see centrally mounted motors driving the wheels via CV
shafts as the dominant EV power-train for the foreseeable future.

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karambahh
The video states a 100kw motor per wheel.

Wikipedia states the humvee has a 142kw motor.

Not only the vehicle would probably be lighter (batteries vs motor, gearboxes,
etc) but it would have 2.81 more power, so it would probably vastly
overperform current vehicles?

~~~
goodcanadian
Batteries are heavy. It is not immediately clear to me that the overall
vehicle would be lighter.

~~~
samatman
This is true, but I would expect a military vehicle to be a diesel-electric
hybrid.

As a general rule, diesel-electric is lighter than pure diesel for a given
rating, because the generator doesn't need a powertrain.

~~~
SigmundA
That has not been my experience. Diesel generator-motor sets are much heavier
than a diesel engine with mechanical transmission and are less efficient. That
does not even take into account a buffer battery weight which you pretty much
need for power draw spikes and regenerative braking.

Just look at say a Cummins ISB with Allison transmission at 300hp, that's
around 225 kilowatts. That combo weighs around 1500 lbs, maybe closer to 2000
with running gear if your comparing to hub motors. A bare frame generator
putting out 200+ kw its going to be well over 4000lbs plus whatever hub motors
and motor controllers and power systems and batteries weigh.

You can go smaller on the generator and make it up on the battery which means
more weight, but even a 100kw generator is going to be around 3000lbs and you
won't be able to utilize full power for long periods (long grades).

Perhaps some advanced generator might be lighter, but it essentially the
engine with the same size and weight generator attached to it as needed for
motors of equivalent power output. Mechanical transmission on the other hand
are pretty light comparatively and have much less losses than the mechanical-
electrical-mechanical double conversion.

~~~
samatman
This isn't a fair comparison, because you're considering a generator that's
intended for stationary use.

Of course this is going to be heavier than one intended for a vehicle, because
the weight isn't a consideration, and lighter is more expensive (more precise,
higher-quality materials).

What you'd want to be looking at is train powertrains, which are uniformly
diesel-electric, because this is the most efficient power configuration.

Or the Chevy Volt, for a smaller example which happens to run on gasoline.

~~~
SigmundA
Can you point me to a light weight 100kw or 200kw genset that is under 1500
lbs? Bottom line even if a 200kw genset plus motors and controllers was the
same weight as a 200kw engine hooked to a transmission, it would have lower
efficiency due to conversion losses unless we get practical superconductors.

Trains do not use diesel electric drives trains for efficiency or weight, the
need precise traction control to prevent the steel wheels from slipping on the
tracks to get moving, the electric drive train gives them that. The actual
efficiency is lower than a mechanical transmission once up to speed due to
double conversion losses. Modern mechanical transmissions are actually very
efficient with very low losses.

The Chevy volt also bypasses the electric system at highways speeds due to the
inefficiency of converting mechanical energy to electrical and back to
mechanical as most (all?) production hybrids. The Gen 2 Volt actually more
aggressively move to mechanical drive at lower speed as it was found to be
more efficient. The Volt is also heavier then the Cruze even though they share
the same platform.

This is an excellent breakdown of the Volt operating modes, in CS2 and CS3
mode the engine is driving the wheels mechnically: [https://gm-
volt.com/2015/02/20/gen-2-volt-transmission-opera...](https://gm-
volt.com/2015/02/20/gen-2-volt-transmission-operating-modes-explained/)

Gasoline hybrids like the volt also typically rely on the Atkinson cycle to
get better highway efficiency at the expense of torque which is made up for by
the electric drivetrain. Diesels are even more efficient and have plenty of
torque but also heavier due to a more robust design, this is why they are much
less popular in hybrid configurations except in specialized applications like
city buses with extreme urban start stop usage.

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stealthcat
Since this is version 1.0, expect lots of failure in the field then lots of
fixes for 2.0

~~~
RugnirViking
Heck this isn't even version 1.0 - more like version 0.1 It's the first
functioning prototype of what will later become version 1.0

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dugluak
The sad part of building all this technology is they need a WAR to put it to
use.

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deepnotderp
Doesn't zoox use independent motors?

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readhn
i find it hilarious that this is a 118 year old technology!

Ferdenand Porsche in 1900 presented a sportscar fitted with four electric
wheel-hub motors, it was the first all-wheel drive passenger vehicle.

Where is the progress? The cars should have been flying by now.

~~~
wffurr
Physical limitations of batteries vs air oxidized fuel. Dragging around your
own oxidizer takes a lot of mass which severely limits power.

The real breakthrough will be a battery that can use atmospheric oxygen, like
a zinc-air battery. But it hasn't worked out in the last 100 years and it's
not clear if it ever will.

~~~
Nasrudith
Batteries appear to be operating on a vastly slower Moore's law at least. They
have been sinfully underfunded as a research field historically.

~~~
MrEldritch
It's not really a "Moore's law" thing at all - it's more that, like every
single other technology in history that isn't specifically semiconductors,
batteries don't follow an exponential improvement curve. They also evolve
slower than many other technologies even on a more typical growth trajectory,
because battery chemistry has _way_ less room for easy improvement. There's
only a few battery chemistries that could even theoretically offer much better
density than lithium-ion, and we've been trying to make them work for a long
time.

~~~
pineaux
My bet is on graphene capacitor batteries.

~~~
wffurr
I would bet on biodiesel for long distance highway transport, farm equipment,
and other heavy industry; and electric in a bewildering array of form factors
for short distance urban transport.

