[HN Gopher] The motor turns too much
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The motor turns too much
Author : mooreds
Score : 147 points
Date : 2024-10-28 12:29 UTC (5 days ago)
(HTM) web link (www.projectgus.com)
(TXT) w3m dump (www.projectgus.com)
| Animats wrote:
| This shows why BYD developed their "e-axle" system.[1] The drive
| axle, differential, and motor are an integrated unit. There's an
| electronics box that connects the battery, the e-axle, and the
| charging port. It's controlled over CANbus. So there's a coherent
| standalone component BYD can reuse in many different vehicles.
| Which they are doing, and clobbering Detroit on price.
|
| [1] https://www.yolegroup.com/technology-outlook/whats-in-the-
| bo...
| weaksauce wrote:
| how repairable is such a design?
| dghlsakjg wrote:
| It isn't inherently more difficult to make it more or less
| repairable.
|
| Repair ability is a design attribute that is planned for.
| magicalhippo wrote:
| I guess a repair could mean swap it out, and the unit would
| get sent back to get refurbished, like what's commonly done
| with say alternators.
| Animats wrote:
| There's an e-axle repair kit from Germany.[1] This kit is for
| a Schaeffler e-axle, and contains all the bearings and seals.
| If you have to take the axle apart to replace any of those,
| you may as well replace all of them.
|
| Third party E-axles are mostly for trucks, where power trains
| and truck bodies come from different manufacturers. Heavy
| trucks can be maintained for decades, and that market wants
| repair parts available. For a car, the powertrain bearings
| tend to outlast the useful life of most cars.
|
| [1] https://www.repxpert.com/en/eaxle
| wakawaka28 wrote:
| >Which they are doing, and clobbering Detroit on price.
|
| Let's be real, their prices are lower because Chinese labor is
| cheaper. US companies have to pay US rates and import as much
| as they can rather than having it all made in the US.
| bryanlarsen wrote:
| Labor is under 10% of the cost of an electric car.
| 0l wrote:
| Is there a source on this? And is this the labor cost for
| the final product, or also that of all components?
| Cthulhu_ wrote:
| I'm sure that's a factor, but probably not for long - Chinese
| wages are on the rise along with China's economy, still a
| long way from US wages but they doubled in the past decade
| according to [0].
|
| But one thing that's hard to deny is that US and European car
| manufacturers are still building on top of previous
| iterations of their vehicles, swapping out a ICE with an
| electric system but keeping the existing systems,
| frankensteining the two together. The article itself makes
| note of it:
|
| > More than five separate CAN buses, ten or more kilograms of
| low voltage wiring, probably over one hundred electronic
| modules (most with their own CPU and firmware), etc.
|
| I don't know cars, granted, nor legislation, but surely a car
| engineered from scratch would be much simpler and thus
| cheaper to build? How does Tesla do this?
|
| [0] https://tradingeconomics.com/china/wages
| cwalv wrote:
| > So the controller only ever increased the torque request, or
| kept it at the same level. Even when I simulated pressing the
| brake it was like "Nothing needs to change, we're not even
| moving!"
|
| So wheel speed sensors drop out and the car will accelerate
| uncontrollably? I love EVs, but with all this complexity I wish
| there's some kind of mechanical disconnect or a big red STOP
| button somewhere.
| trhway wrote:
| >the car will accelerate uncontrollably?
|
| https://en.wikipedia.org/wiki/2009-2011_Toyota_vehicle_recal...
|
| 'Michael Barr of the Barr Group testified[30] that NASA had not
| been able to complete its examination of Toyota's ETCS and that
| Toyota did not follow best practices for real time life-
| critical software, and that a single bit flip which can be
| caused by cosmic rays could cause unintended acceleration. "
| cwalv wrote:
| Yeah, maybe not particular to EVs. I do remember wondering
| back during the Toyota "uncontrolled acceleration" epidemic
| why people wouldn't just put the cars in neutral
| Syonyk wrote:
| Because the vast majority of people driving cars don't have
| enough of a mental model of the vehicle systems to consider
| such a thing, especially in a panic situation such as
| unintended acceleration.
|
| If you've driven rattletrap manuals for most of your life,
| and have worked on cars, rebuilt engines, replaced
| clutches, rewired things that failed, yeah. That's an
| obvious conclusion, and I expect some people without doing
| that will have enough sense of what's going on to consider
| a drop to neutral (and letting the rev limiter handle
| keeping the engine intact).
|
| But go ask most people, even in technical fields, about the
| details of a car, and you'll struggle to get much beyond "I
| press the gas and it goes." You run into this constantly if
| you're a "car guy" and people ask you questions about why
| their car isn't going. "It turns over but doesn't start!"
| can mean anything from "the lights are barely on and
| nothing happens" to "the starter relay clicks but nothing
| happens" to what I would consider that to mean, "the engine
| is rotating under the starter's power but is not engaging
| in sustained internal combustion."
|
| Neutral isn't a thing most people even think about,
| unfortunately. Park, Drive, Reverse, and some oddball other
| positions that you don't want to end up in accidentally.
| Yes, they're useful, and yes, they solve problems, but it's
| not something that a lot of people would consider. Neither
| do they seem to consider "Stand on the brakes until the car
| comes to a stop. No, really, _stand_ on them! " - because
| I've yet to meet a moderately well maintained vehicle that
| can't come to a stop with the gas floored and the brakes
| applied firmly (yes, I've tried, it's a standard test of
| mine after brake work). But if you only apply partial brake
| pressure, or have a vacuum brake booster, you only get a
| few attempts before the booster has lost vacuum (won't get
| any more, because wide open throttle), and if you've heated
| up your brakes trying without succeeding, you may very well
| have no usable brakes left. Passenger car brakes are
| adequate, but you can easily overheat them and fade them if
| you try, or boil the fluid, or... etc. Again, not something
| you'll find many people aware of these days.
|
| I wish it were different, but "magic box I put gas into and
| it goes" is closer to the reality of how many people
| consider cars these days.
| Arch-TK wrote:
| Even people who know about the solution might find it
| drops out of their brain in a moment of panic.
|
| I locked myself out of my house recently, and it was only
| after scaling to the 1st floor, breaking in through an
| open window, and breaking through a locked interior door
| (the house had been secured as I was going on a trip, and
| the only things I forgot were my keys and that window),
| that I remembered that there was a spare key in my car
| (which was open). This moment of clarity coincided with
| the stress going away.
| Syonyk wrote:
| Again, it depends a lot on your experience with vehicles.
| I expect someone who had driven a manual for a long while
| (or even learned on one but hadn't driven one recently)
| would be radically more likely to come to "Oh, select
| neutral" as a solution than someone who has only ever
| driven automatics. "Neutral" is far more part of "life
| with a manual" than it is with automatics - I would be
| willing to bet that a substantial fraction of automatic
| transmissions have never been deliberately put in
| neutral.
|
| My daily driver has an archaic manual sequential
| transmission (2005 Ural - sidecar motorcycle sort of
| thing), and I select neutral at every stoplight I'm
| likely to be at for a while to avoid wearing the clutch
| bearings. Also, I have to most of the way double clutch
| my shifts on that bike (pause in the false neutral
| between gears) to avoid too much clashing. If I had a
| runaway throttle condition (certainly possible), I have
| at least three instant methods I'd use (kill switch,
| clutch, and rock it into a false neutral). But I've spent
| most of my driving career with such things, and vehicles
| that _don 't_ have those are a bit of a novelty to me.
| mkesper wrote:
| Also my Toyota Auris Hybrid has a weird kind of joystick
| for changing gear and putting it into neutral position
| requires holding that position for some time. Gave me an
| unpleasant (but luckily harmless) event in a car wash
| where you're required to have power on but use neutral
| position with automatic gearing.
| cwalv wrote:
| That makes sense in most cases, but I remember there
| being multiple cases where people had the composure to
| call 911 and report the situation.
| eru wrote:
| Compare https://en.wikipedia.org/wiki/2009%E2%80%932011_T
| oyota_vehic...
|
| If people think they are hitting the brakes (but are
| accidentally hitting the gas), then hitting the 'brakes'
| harder will make the problem worse.
| idunnoman1222 wrote:
| People that did put their car in neutral didn't make the
| news
| bsder wrote:
| 1) Because panic is a thing.
|
| You need _training_ to guarantee correct reaction when
| things go wrong.
|
| Here's an anecdote: I used to drive a car with a standard
| transmission in Los Angeles. In quite a few places, the
| parking spots have a "trench" in the front for drainage.
| So, you can place your car in reverse, release the brake
| and have your car roll forward quite a bit (the trench
| makes an even stronger downward slope on a hill that is
| already pointing downward) before the clutch engages. A bit
| surprising but nothing that weird for someone who drives a
| stick.
|
| Now, have that sequence happen to someone driving a car
| with an automatic transmission. They shifted to reverse,
| the car is rolling forward more than they expect and is on
| a hill, they hit the gas to arrest the roll, the
| transmission engages and the car _shoots_ in reverse. Pray
| that there isn 't anything close behind them or they're
| going to run over a pedestrian, put their car through a
| wall, etc.
|
| 2) Because the majority of the people who had "uncontrolled
| acceleration" were old.
|
| The vast majority of the cases were very likely driver
| error by older drivers who had incorrect habits ingrained.
| Toyota probably would have won the case if this was the
| only issue.
|
| Alas, Toyota lost the case because their processes for
| safety were such a complete shitshow that they were going
| to get _destroyed_ in court.
| Doxin wrote:
| If the wheel speed sensors drop out they put nothing on the CAN
| bus, not a "0 speed" message. I think it's pretty safe to
| assume the controller logic here has a fairly strict timeout on
| how often it wants to see wheel speed messages.
| Retr0id wrote:
| There is presumably still _some_ possibility of them failing
| in an "always reports 0" way
| lostlogin wrote:
| ...Like when dismembered and spread across a bench.
| Arch-TK wrote:
| It's not unthinkable that whatever transducer takes
| rotation and turns it into a signal which is processed by
| an MCU and translated into CAN messages could get stuck
| producing one signal and trigger such a scenario without
| the car's control system needing to be on a bench.
| 0_____0 wrote:
| There are some parts of engineering in safety systems where
| you have a single thing that could go wrong that would have
| serious consequences, and the result of the FMEA is that
| "it has to not do that".
| zardo wrote:
| I don't think you'll find a wheel speed sensor without a
| few "outputs incorrect speed" failure modes.
| qingcharles wrote:
| This is a video of a driverless car getting rear-ended, and
| doing who-knows-what damage to its electronics; it then goes
| rogue at max speed through the streets smooshing whatever is in
| its path:
|
| https://x.com/PicturesFoIder/status/1832940173400699255
|
| (apologies -- not sure of the best Twitter passthrough to use)
| ZeroGravitas wrote:
| Seems only a matter of time until Chinese manufacturers start
| providing kits for EV conversions. Can they compete on price and
| convenience with equipment rescued from scrapped EVs? Would EV
| tariffs apply?
| sandermvanvliet wrote:
| Check out what https://www.edisonmotors.ca/edison-pickup-kit is
| doing
| spockz wrote:
| Very nice. I really would like to get a replacement kit of my
| XC90 battery and electric engine. Especially one that doesn't
| cost more than half of the remainder of the economic value of
| the car. This is my second second hand plug in hybrid that
| loses battery capacity rapidly and the battery is crazy
| expensive to replace. Moreover, newer generations have
| stronger electric motors giving wider range of use and better
| regen.
| ggreer wrote:
| It's quite difficult to convert a combustion engine vehicle to
| an EV.
|
| - EVs need significant volume for batteries. The only places
| available in a combustion vehicle are the engine bay and the
| gas tank. If you put batteries in the engine bay, you'll mess
| up the weight distribution. The volume occupied by the gas tank
| isn't nearly large enough to house a battery for decent range.
|
| - The extra weight of the batteries requires changes to the
| suspension and tires.
|
| - EV motors have lots of torque. If you use the original
| transmission, you'll need to limit torque based on which gear
| it's in. Any replacement transmission will need to be designed
| for that car chassis. It's not easily adapted to other models.
|
| - Combustion vehicles are designed with an accessory belt in
| mind. The air conditioning, power steering, and many other
| components are run off of these belts. An EV motor doesn't spin
| while idling. These components will need another power source,
| or they'll have to be replaced with EV-specific components.
|
| - Combustion vehicles use waste heat from the engine to heat
| the cabin. Unless you live in a mild climate, a retrofit will
| need electric heating coils (or a heat pump for maximum
| efficiency).
|
| And after making all of these modifications, you'll need to
| deal with regulations around making sure the vehicle is street
| legal. Those can differ greatly based on the state and the
| model year of the vehicle you're converting. Considering all
| that, it's unlikely that you'd save money by converting an
| existing vehicle.
|
| An EV kit car might make more sense, but the market for those
| is quite small.
| Cthulhu_ wrote:
| That would be a major operation, basically a rebuild of a car,
| plus you'd need all the relevant controls etc rewired too. It
| wouldn't be worth it, not when this same China is investing
| heavily in affordable EV mass production.
| schiffern wrote:
| If you're interested in this check out the previous posts:
|
| Part 1 https://www.projectgus.com/2023/03/ev-conversion-one/
|
| Part 2 https://www.projectgus.com/2023/03/ev-conversion-two/
|
| Part 3 https://www.projectgus.com/2023/10/kona-can-decoding/
|
| ...and the follow-up posts:
|
| Part 5 https://www.projectgus.com/2024/04/unremarkable/
|
| Part 6 https://www.projectgus.com/2024/10/simplifying-bench-kona/
| krisoft wrote:
| I heard a similar story from a coworker. They were interfacing
| with a car via CAN. They had an engineer from the manufacturer
| telling them the details of the message they should be sending to
| demand a certain speed. Turns out the description wasn't quite
| right. The message ID was correct, but not the endianness of the
| speed demand signal.
|
| Thus when they tried to test it they thought they requested a
| stately 5m/s, but the vehicle thought they were asking it to
| exceed the speed of sound. Which of course it wasn't designed to
| be able to do, but it still tried.
|
| That's why i prefer to have nice hardware e-stops on prototype
| vehicles.
| m463 wrote:
| > That's why i prefer to have nice hardware e-stops on
| prototype vehicles.
|
| Yeah, I kind of wonder if lawsuits/regulation might be the way
| to get those.
|
| Because there will always be some sort of cost with that kind
| of thing.
|
| I'm pretty sure a major reason garage doors have limit and
| occlusion sensors is because of regulation. (and even those
| suck - it is common for garage doors to incorrectly sense
| occlusion in bright sunlight)
| bewaretheirs wrote:
| Something similar was at work in the 2018 natural gas
| explosions in and around Andover, MA:
| https://en.wikipedia.org/wiki/Merrimack_Valley_gas_explosion...
|
| "According to the NTSB's preliminary report, customers in the
| accident area received gas from a low-pressure (0.5 psi)
| distribution network which, in turn, was fed from a high-
| pressure (75 psi) main pipeline via regulators controlled by
| sensors measuring pressure in the low-pressure pipes. At the
| time of the accident, workers were replacing some of the low-
| pressure piping, but the procedure set out by Columbia Gas for
| doing this failed to include transfer of a regulator's pressure
| sensor from the old, disused piping to the new. As a result,
| when the old pipe was depressurized, the regulator sensed zero
| pressure on the low-pressure side and opened completely,
| feeding the main pipeline's full pressure into the local
| distribution network."
| aetherspawn wrote:
| EV software engineer here.
|
| Your hypothesis is basically correct. Since the motor is under no
| load, it will appear to spin out of control even with the
| smallest torque application, but in reality the torque being
| applied is very small... probably around 5Nm.
|
| Trust me if it was truly spinning out of control with no load
| you'd know... it would reach max speed in 0.1 seconds and
| probably start tearing through the floor.
|
| Most likely what's happening is that the creep torque is applying
| a constant small torque and the wheel sensors are reading 0
| continuously, so it continues to apply a constant small torque.
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