Rivian reduced electrical wiring by 1.6 miles and 44 pounds

https://www.popsci.com/technology/rivian-zonal-electrical-architecture/

by addaon • 2 years ago

173 105 2 years ago

Couldn't they just use Wi-Fi? So much wiring..

Jtsummers2• 2 years ago

"just use Wi-Fi?", probably not. I don't think you'd want to create so many openings for attackers. Besides, EMI is a real issue and not something you want interfering with your critical systems too much.

dylan604• 2 years ago

EMI is a real issue

To the point they are wanting to eliminate AM radio because they've gotten to the point that the uncontrollable EMI makes AM "unlistenable". So move the goal posts, and make AM radio out-of-fashion and get rid of it rather than solving the EMI issues.

adrian_b• 2 years ago

So that anyone could crash your car with a jammer?

silisili• 2 years ago

Ignoring wifi as a poor use case here(you'd likely use something with much less interference and better latency), RF will still usually have more latency than a wire. It's more prone to interference from other random devices and even other cars. Canbus is typically shielded, which you obviously can't do with something relying on radio.

Then you have physical interference...imagine all your warning lights come on, wipers come on, and radio cuts off because your wife put her Stanley in just the wrong spot.

Gibbon12• 2 years ago

People don't like your comment but I have a side project that requires controlling 36 lamps in groups of 3. I rolled it over and I'm just going to slap a cheap radio on a PCB's and just daisy chain the power.

kkfx2• 2 years ago

I've built my "smart home" explicitly without wifi [1] to shield against any kind of "local exterior attack" and mere communication issues due to natural phenomenon. Even for light I decide for ShellyPro 4PM to avoid wireless...

Surely without cables it's far easier, but this easiness have a price.

[1] with the exception of the car charger since I wasn't able to find a damn cabled one (it's 230Vac, not CCS eh!)

gruturo• 2 years ago

Maybe you already completed your project, maybe you already knew about Charlieplexing (https://en.wikipedia.org/wiki/Charlieplexing), maybe it doesn't apply to your case as your controller didn't support tristate output, but, just in case you didn't know about it:

It's a technique for controlling (or reading) large numbers of LEDs, switches, etc, with surprisingly little wiring. Instead of the usual X/Y of multiplexed I/O, the wiring is diagonal. To control 12 outputs (36 in groups of 3) you'd need just 4 pins (if your lamps are not LEDs, though, you probably need to put some diodes in there)

daghamm4• 2 years ago

OP is heavily downvoted, but yes some ECU are moving to wireless communication although not WiFi.

It started with places where you simply can't have wires, for example tire pressure monitoring. But is now spreading to other simple ECUs. And yes, it can be jammed so obviously it's not for brakes and steering and things like that.

Gibbon12• 2 years ago

You can image the drivers side door has a module that senses the door switches and operates the drivers window and door locks. And communicates via RF to modules in the other three doors to control the windows and door locks.

Seriously why the heck not?

I've thought in the past what I want for trailer lights is a RF connection between the vehicle and the trailer. It can't be worse than the standard way that always fails.

janice1999• 2 years ago

It's a good question. Wireless is already replacing wiring inside the battery pack performing some of the most sensitive data transmission. See here for details: https://www.gm-trucks.com/explained-general-motors-wireless-...

PlunderBunny• 2 years ago

If my experience of trying to tether my laptop to my phone on a moving bus is any indication, I'm thinking that WiFi (as opposed to other wireless technologies) is a non-starter.

gorgoiler• 2 years ago

The before/after ECU layout diagram is very instructional.

I like to imagine some kind of engineering “meet cute” whereby, one random day, the headlights engineer and the parking radar engineer happen to be working on the front of the car together. Their eyes meet:

“hey, I’m John — I didn’t know you had an ECU here!”,

“hi, I’m Claire — wow, you have an ECU right up front too? It’s, like, right next to mine and we never knew!”

“I know, crazy right?! Hey this is going to sound really forward and I don’t normally do this but I’m only running at 70% compute capacity. I don’t suppose you need any real-time budget this evening?”

“So funny you should ask, I was just about to run a whole bunch of heavy new wiring to…”

And in a story as old as time they get ECU married and raise their control loops in the same front-of-vehicle ECU together instead of living their separate, lonely, ECU-right-next-to-each-other-and-they-didn’t-know-it lives.

jdiez17• 2 years ago

I ... am a bit speechless ...

I didn't know this was something I could be into so much, and yet here we are.

brundolf• 2 years ago

That's what they said

kevin_thibedeau2• 2 years ago

Ford did this with the cost reduced version of SYNC 3, merging two modules to form SYNC 2.5. The result is an unstable heap of trash.

dangus• 2 years ago

Well, it is Ford. You buy a Ford you should expect it to be trash.

plg94• 2 years ago

wow, you made hackernews turn into tumblr. Well done, great explanation.

gregmac• 2 years ago

It's interesting to think about the failure modes here.

With domain-based ECUs, a failure means your locks OR windows OR windshield wipers stop working.

With zone-based, it could be the entire "west" zone that stops, which means you can't unlock the driver's door, open the windows, adjust the seat, and maybe even the ventilation fans don't work

I actually thought a lot of that was already on the CAN bus anyway, but my knowledge of cars stops there so maybe someone can fill in the gaps. Seeing only three "zones" is actually surprising to me. As I was reading I started forming the idea of a single bus cable that went around the car, with I/O modules anywhere there were physical buttons/lights/etc. There would just have to be a cost+weight balance of where it makes sense to stick a small I/O module vs run individual wires back to a bigger module. My assumption is as technology advances it becomes cheaper to have more small I/O modules with very short wire runs to buttons, but it doesn't seem like this is what they're doing.

I am also making the assumption this is "dumb I/O", and somewhere there is a "door lock" program that handles all locks/buttons. In the main computer you'd run all the domain programs individually/isolated, but there would still be a single program responsible for each domain, eg: all the locks (eg: considering button presses, fob buttons, door state, moving or not, etc, and act on the locks accordingly).

From a pure software point of view, if the east/west/south ECUs are actually doing the logic for their respective parts of the car, that seems like a nightmare to build: the code would end up being all partial and distributed. In the worst case you end up with bizarre bugs like "if you open the passenger door, then open the tailgate, then close the passenger door and press the lock button, the driver's door will lock but the passenger won't until you first unlock then shut everything" (which gets reported as "the locks are unreliable, some will randomly just not work every few days").

edmundsauto• 2 years ago

Some door locks will trigger the servo every time you hit the heron (older-ish cars) and some have a sensor. Not clear to me if it’s a remote sensor or some sort of smarts in the local mechanism.

Given some of the chip shortages of recent year, I’m curious how the teams responsible for those trade offs made the balance.

Animats• 2 years ago

"if you open the passenger door, then open the tailgate, then close the passenger door and press the lock button, the driver's door will lock but the passenger won't until you first unlock then shut everything"

I have a Jeep where the dome light logic has a problem like that. If you open a door, the dome light comes on. When all doors are closed, but the engine is not running, the dome light dims out after a delay. If the engine is running or is started in the all doors closes, dome light on situation, the dome light goes out. If you open the tailgate, the dome light comes on as well. That's all normal.

But if I open a side door, then close it, and the light times out and dims, then, for some period of time thereafter, opening the tailgate will not turn on the light. I can just see some horrid mess of IF statements written in C behind this.

sdwr• 2 years ago

State management is the only difficult problem in computer science

Or something like that

euroderf• 2 years ago

Have they never heard of fuzzing.

Timshel• 2 years ago

They though of the failure mode opening doors should be part of the "vehicle access" which get its own ecu.

daghamm4• 2 years ago

There is a short answer to all this:

Distributed systems are hard, more so in a real-time environment. If you can reduce the number of components or the need for them to communicate they will almost always become more robust and also easier to code.

Rivian added some network redundancy and central monitoring to make this design safe, but otherwise the core design principle was basically KISS.

morning-coffee• 2 years ago

From the article:

The system includes an array of 11 internally developed cameras and five radars performing over 250 trillion operations per second, which Rivian says is an industry-leading statistic

I generally like what they are doing with their overall architectural simplifications, but gee-zus; the feeling of complexity I get from that one statement leaves me with the feeling of "it's just a car man... it takes us from point A to point B... is all that really necessary?"

moring3• 2 years ago

When I read this, my first thought was: Why do these ECUs have any deep logic at all? I would have expected all logic to be centralized at one point (or in a few points, but with each domain localized to one of them), and everything at the edge be dumb(1) port extenders. That's a single point of failure, of course, but as far as I understand the zonal approach has those too -- multiple SPOFs, actually. At least when it's a single SPOF, that problem can be better mitigated.

(1) "dumb" meaning no decision-making logic. It could still mean a lot of decision-less logic, from button debouncing to input signal filtering/processing and outputting compressed audio streams.

guai888• 2 years ago

Standard approach is following ISO 26262 development to deal with risk resulting from failure mode.

Lvl999Noob• 2 years ago

With zone-based, it could be the entire "west" zone that stops, which means you can't unlock the driver's door, open the windows, adjust the seat, and maybe even the ventilation fans don't work

From my reading, I thought the important parts were on their own dedicated ECUs (7 ECUs, 3 zones). Battery management, driving related stuff, infotainment, door mechanisms, etc have their own ECUs. The three zones are for smaller things that are probably important but not urgently important.

Moto7451• 2 years ago

Some cars work this way logically already. If you scan my Audi with a compatible tool it will read various functional modules. If one dies than that modules’ systems go down but other nearby functions work. Child locking is a separate unit from door locking and as a result in my car my driver side rear door will lock in such a way that only the inside manual latch will open the door.

The dealer can’t figure out the issue four years in.

techdmn• 2 years ago

Some days I'm really happy that I kept at least one analog car.

indoorcomic• 2 years ago

I love this. I hope this more manufactures go this route. I've always felt that having ~100 ECUs in a car is complete overkill.

Jtsummers2• 2 years ago

See gregmac's comment, it changes the failure modes and makes what could be isolated subsystem failures larger regional failures. However, components are also becoming much more reliable so this is an engineering tradeoff. Cases can be made in both directions.

EDIT: That's not the only tradeoff, but it is a key one.

metadat• 2 years ago

https://news.ycombinator.com/item?id=41207335

In the future, please include the actual link. It is 10x more useful.

AlotOfReading3• 2 years ago

I've been a (somewhat successful) advocate of similar approaches at the automakers I've worked for, but it's not as simple as the article makes it sound. Individual components in each "zone" can have different reliability requirements, for example. They also might be produced by different suppliers, or only be present on certain models / trims.

Rivian is able to do this because they're taking advantage of modern heterogenous processors and they haven't made the mistake of outsourcing almost all of their software capabilities to tier 1,2,3 suppliers. Legacy OEMs find it much more difficult to adopt, especially once the institutional inertia takes over.

Ekaros• 2 years ago

Replacing word ECU with micro-controller makes number seem less insane. Okay, PCs are having less and less components. But one might ask why do so many components have any logic at all? We got extremely insanely powerful central CPUs with loads of memory and storage space. So why not just do absolutely everything there?

Remove any logic and computing from screens, keyboards, mice, SSDs, HDDs, off load everything from network chips and sounds chips. Just move all of it to CPU?

moring3• 2 years ago

I think you'd want at least some "dumb" logic moved to the periphery, otherwise everything has to be conected directly to the CPU and you would still end up with tons of wiring. Also, some functions done in the periphery are ideal candidates for parallelization, such as the keyboard scanning the key matrix for pressed keys.

OptionOfT• 2 years ago

I think having multiple ECUs over time is a cost savings mechanism. You have a module that you can use in all your models because it works.

If Rivian wants to add a new feature that doesn't 'fit' on the AIO ecu, then what? Replace it and re-certify ALL of its functions?

A good example is the ABS controller which is usually just a Bosch COTS ECU.

You wouldn't even want to implement that for yourself.

daghamm4• 2 years ago

"four categories get their own ECUs: infotainment, autonomy, vehicle access, drive units, and its battery management system."

Am I reading this wrong, or are these actually five categories?

masklinn• 2 years ago

Given the wording of "drive units, and its battery management system" I'd think the BMS is linked to the drive units and under the same ECU. I'd assume the drive units and BMS are tightly integrated, as that's basically the entire high-voltage system and you have to manage the two-ways energy flow between the two (propulsion and braking / regen).

trainsarebetter2• 2 years ago

Not really, the FOC software that runs on the inverters is compute heavy and safety critical. It gets its own dedicated controller (they are actually running to cpus in parallel in case one fails) and same with the bms. They talk over can currently in teslas. bms states it’s max charge and discharge current, and everything else listens

schobi• 2 years ago

The diagrams for the new west south and east zones still show a lot of wires going all across the vehicle. This step might be a good first one to reduce the number of ECUs by combining them, but there is still the same cross-car wiring. You still seem to have a single ECU per function, but merged into a few dedicated boxes for example.

Next step: Each wire only goes to the nearest box. I'm curious how the Tesla unboxed architecture will eventually play out. I understand that eventually, the ECUs will be split up, so you have some aspect of each ECU in each corner of the vehicle. Part of the "lights" function is in front-left, part of it in the back. Wires only go to the nearest box.

A powerful vision, with the potential to further reduce wiring. Complex until you get a distributed brake ECU.

yc-kraln• 2 years ago

The electrical wiring in cars is Conway's law manifest in copper.

For those unfamiliar with Conway's law, I am arguing that how the car companies have organized themselves--and their budgets--ends up being directly reflected in the number of ECUs as well as how they're connected with each other. I imagine that by measuring the amount of excess copper, you´d have a pretty good measure for the overhead involved in the project management from the manufacturers' side.

(I previously worked for Daimler)

mensetmanusman• 2 years ago

Would be funny to have a ‘mm Cu / FTE’ scaling law.

throwaway484763• 2 years ago

Complexity is a function of the number and depth of suppliers.

westurner2• 2 years ago

The ohm*meter^3 is the unit of electrical resistance.

Electrical resistivity and conductivity: https://en.wikipedia.org/wiki/Electrical_resistivity_and_con...

Is there a name for Wh/m or W/m (of Cu or C) of loss? Just % signal loss?

"Copper Mining and Vehicle Electrification" (2024) https://www.ief.org/focus/ief-reports/copper-mining-and-vehi... .. https://news.ycombinator.com/item?id=40542826

There's already conductive graphene 3d printing filament (and far less conductive graphene). Looks like 0.8ohm*cm may be the least resistive graphene filament available: https://www.google.com/search?q=graphene+3d+printer+filament...

Are there yet CNT or TWCNT Twisted Carbon Nanotube substitutes for copper wiring?

lofaszvanitt2• 2 years ago

3rd generation: no wires from sensors to detectors.

twoWhlsGud• 2 years ago

4th generation: wires are back so the car doesn't stop working every time it drives by a source of RF noise...

lofaszvanitt2• 2 years ago

We'll see...

xbmcuser• 2 years ago

I recalled I read something similar before so I searched for it. It was Tesla doing something like this in 2019

https://electrek.co/2019/07/22/tesla-revolutionary-wiring-ar...

"In order to facilitate the automation of manipulating cables, Tesla has been reducing the length of wiring harnesses in its vehicles.

Musk said that Model S has about 3 kilometers of wiring harnesses and Tesla brought it down to 1.5 kilometers in length for the Model 3.

But that’s just the beginning. Tesla is working on a whole new wiring architecture for future vehicle platforms and they aim to bring it down to just 100 meters starting with the Model Y."

grecy2• 2 years ago

Tesla have taken it to a whole new level on cyber truck.

It is assumed this will continue in their next gen vehicles

theluketaylor2• 2 years ago

The legacy car makers have flirted with 48V components for decades but haven't been willing to do the hard work to realize all the benefits it brings. The germans in particular are stuck in limbo. For their PHEV and BEV cars they are shipping 12V for all traditional functions, 48V for advanced functions like active suspension and anti-roll bars, and high voltage systems for the traction motor. Complete mess.

It's frustrating to be a Tesla owner. For every great engineering choice they make like going all in on 48V they make a user hostile choice like removing stalks and selling "full self driving" that is downright dangerous.

quanto• 2 years ago

quick math check

1.6 miles and 44 pounds

pure copper density at 9000 kg/m3, wire diameter assumed at 1mm, length at 3000 m (1.8 mi, approx) gives 21 kg, approximately 46 lb. math checks out.

the company claims a 20 percent savings in material costs and 15 percent reduction in its carbon footprint between Gen 1 and Gen 2.

surely this is not just due to the reduction of copper. copper is around 10 USD/kg at bulk.

now let's see if we can address the copper length number. can 1.6 mi (< 3000 m) of copper be saved from wiring alone?

The car dimensions are 2m x 5m. That means, in the worst case, two ECUs placed at opposite ends will need 5m of wire (half of perimeter). There were 17 ECUs originally. Call it n = 20, and if we wire dense (in the graph sense), we get n^2 = 400. So, in the absolute worst case, the densest possible graph would have had 5m x 400 = 2000 m of wire. The claimed wire saving is significantly (but not by an order of magnitude) larger than this. I would say this passes the smell test (albeit barely), but original wiring must have been truly inefficient.

spydum• 2 years ago

maybe i missed in your estimate, but most circuits need more than one wire?

hn72774• 2 years ago

In a vehicle, the chassis is the negative wire in the circuit.

caleblloyd• 2 years ago

I didn’t completely follow either but I think the n^2 = 400 worked out to 20 ECUs each with 20 wires

thelastgallon• 2 years ago

Rivian can switch to 48V for more gains.

https://news.ycombinator.com/item?id=38576612: The move to 48V means much less power is lost (power loss = (IxI)xR ), cables can be much smaller, cables and terminals can be much lighter and much less copper can be used used.

Discussion: Tesla shares 48V architecture with other automakers: https://news.ycombinator.com/item?id=38557203

jondwillis• 2 years ago

Those are rookie numbers. Let’s bump it up to 96V while we are at it.

throwaway484763• 2 years ago

50V is the generally accepted safe cutoff. There are separate electrical certifications for 'low voltage' <50V.

maxerickson2• 2 years ago

60 volts DC is treated as a safety threshold. Human bodies start to conduct better about there.

amluto• 2 years ago

There are massively diminishing returns. 1kW at 12V is 83A, which needs a rather beefy wire that is expensive to buy, annoying to route, difficult to route, and needs careful termination with large tools. 1kW at 48V is ~20A, which can be done with 12 gauge wire, which is not bad at all to work with.

_heimdall• 2 years ago

I was expecting to see a mention of whether there were any safety concerns related to running fewer ECUs. I'd assume not since they chose to go this route, but the idea of the infotainment system going down and taking other systems offline with it seems like a risk they would have had to consider.

therealdkz• 2 years ago

There is nothing like perf improvement that removes sleep() put in earlier…

Rivian reduced electrical wiring by 1.6 miles and 44 pounds

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