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posted by hubie on Thursday May 12 2022, @12:08AM   Printer-friendly
from the that's-the-brakes dept.

No more brakes for cars of the future:

Electric cars of the future could be able to ditch conventional brake technology in favour of powerful regeneration by battery-powered motors.

[...] Electric cars already use a combination of conventional friction braking and brake regeneration. The latter slows down vehicles using resistance from the same electric motor that propels the car, feeding that energy into the car's battery to extend its range.

DS, Citroen's luxury arm, said it is "exploring whether regenerative braking alone could eventually be the sole method to slow cars down, helping to better recharge the battery in the process, and doing away with conventional brake discs and pads".

[...] [Conventional brake pads and drums] produce "brake dust", fine particles of metallic material that separates from the pad and disc as part of the braking process.

[...] Dr Asma Beji, a non-exhaust particles expert, said in June 2021 that "the impact on health of brake wear particles is undeniable and cannot be neglected".

[...] Environmental researcher Dr Liza Selley, published a paper for the MRC Centre for Environment and Health at King's College London and Imperial College London in 2020 that suggested "diesel fumes and brake dust appear to be as bad as each other in terms of toxicity in macrophages".

[...] "Macrophages protect the lung from microbes and infections and regulate inflammation, but we found that when they're exposed to brake dust they can no longer take up bacteria.

"Worryingly, this means that brake dust could be contributing to what I call 'London throat' – the constant froggy feeling and string of coughs and colds that city dwellers endure – and more serious infections like pneumonia or bronchitis which we already know to be influenced by diesel exhaust exposure."

DS and other manufacturers including Jaguar and Porsche participate in Formula E electric car racing. The series will eliminate rear disc brakes from its next-generation machines in a bid to improve real-world research into the performance potential of purely regenerative braking.


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  • (Score: 5, Insightful) by Immerman on Thursday May 12 2022, @04:55AM (12 children)

    by Immerman (3985) on Thursday May 12 2022, @04:55AM (#1244298)

    I agree with the sentiment, but burning rubber means you're significantly below your maximum acceleration. It means your tires are skidding, and thus exerting considerably less force than they would if they still had traction. Hence the existence of anti-lock brakes.

    Beyond that, so long as your regenerative braking is powerful enough to lock up the wheels if you wanted to, it's as good as it gets. And since it (presumably) uses the same motor as accelerating, that means that you'd also able to burn rubber when mashing the accelerator. At cruising speed. (barring software limiters)

    The actual risk is in system failures - mechanical brakes are a completely independent system that will work even if almost everything else has failed. Regenerative braking fails if there's a failure anywhere in the drive train: the transmission, the motor, the battery, the power controller, the computer, the brake pedal sensor, or the wiring for any of those.

    Now, such failures may be rare, but for something as critical as stopping I'd prefer to have a simple mechanical backup system. Even if it's just a pair of cheap drum brakes on one axle that only kicks in when you completely floor the brake pedal, and aren't strong enough to lock up except in the most contrived circumstances - you're still *far* better off than trying to coast to a stop.

    That said, I'm all in favor of rarely/never *using* that backup system. Brake pads end up in the air we breathe, and even the ones that don't contain asbestos still aren't exactly lung-friendly.

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  • (Score: 3, Touché) by ewk on Thursday May 12 2022, @07:18AM (1 child)

    by ewk (5923) on Thursday May 12 2022, @07:18AM (#1244319)

    While acceleration technically can be correct (since it can be negative after all :-) ), I believe the common term is 'deceleration' when we refer to braking :-)

    --
    I don't always react, but when I do, I do it on SoylentNews
    • (Score: 2) by Immerman on Thursday May 12 2022, @01:17PM

      by Immerman (3985) on Thursday May 12 2022, @01:17PM (#1244372)

      Ack, it seems I accidentally outed my physics background.

  • (Score: 4, Interesting) by inertnet on Thursday May 12 2022, @08:23AM (2 children)

    by inertnet (4071) on Thursday May 12 2022, @08:23AM (#1244333) Journal

    I completely agree, but would add that a backup system might fail if it is used only once in a blue moon. And that would be right when you need it most. So I would advise to build the backup system in a way that it automatically gets applied once in a while instead of the regenerative brake, without using emergency level braking of course.

    • (Score: 3, Insightful) by maxwell demon on Thursday May 12 2022, @04:19PM

      by maxwell demon (1608) on Thursday May 12 2022, @04:19PM (#1244447) Journal

      Isn't that what inspections are for?

      --
      The Tao of math: The numbers you can count are not the real numbers.
    • (Score: 0) by Anonymous Coward on Thursday May 12 2022, @07:06PM

      by Anonymous Coward on Thursday May 12 2022, @07:06PM (#1244501)

      Tell that to my air bags

  • (Score: 2) by mcgrew on Thursday May 12 2022, @08:57PM (3 children)

    by mcgrew (701) <publish@mcgrewbooks.com> on Thursday May 12 2022, @08:57PM (#1244575) Homepage Journal

    Regenerative braking fails if there's a failure anywhere in the drive train: the transmission...

    Electric motors have the greatest torque at zero RPM and need no transmissions. That's one main reason I want an EV; no oil, tranny fluid, coolant, or gasoline you have to stand there in below freezing weather to fill.

    An internal combustion engine and transmission is a primitive Rube Goldberg machine with gears, pumps, pulleys, belts, etc, while an electric motor is sophisticated, having only one moving part. That said, I imagine they'll have some sort of emergency brake, probably friction.

    --
    mcgrewbooks.com mcgrew.info nooze.org
    • (Score: 2) by Immerman on Thursday May 12 2022, @10:03PM

      by Immerman (3985) on Thursday May 12 2022, @10:03PM (#1244600)

      That's true of an idealized electric motor - it's a little more complex than that for real ones.

      Most electric vehicles (such as the Teslas) have single-speed transmissions - presumably to map the optimal motor speed to a typical car speed. Electric motors tend to like spinning *fast* - far faster than you'd want your wheels to spin. I believe I recall that the Tesla Roadster actually had a two-speed transmission originally, which was eventually abandoned as it kept being destroyed by the incredible torque from the motor.

    • (Score: 2) by ChrisMaple on Friday May 13 2022, @03:06AM (1 child)

      by ChrisMaple (6964) on Friday May 13 2022, @03:06AM (#1244658)

      Calling the rotor of an electric motor a "single part" is an exaggeration. In addition to a shaft, it may have permanent magnets, windings, a commutator or slip rings, and magnetic laminations, depending upon the design.

      • (Score: 2) by mcgrew on Friday May 20 2022, @12:45AM

        by mcgrew (701) <publish@mcgrewbooks.com> on Friday May 20 2022, @12:45AM (#1246445) Homepage Journal

        True, but they're all connected together and move as one thing. That's far different than all the valves and pistons moving differently from each other in a gas engine, not to mention... well, I'm pretty sure I made my point. I've only had one motor fail that I remember, in my 70 years. I was in the Air Force, and it was the motor in my cassette deck quit. The plastic that had held the rotor's shaft had broken. A little super glue and it was as good as new.

        --
        mcgrewbooks.com mcgrew.info nooze.org
  • (Score: 2) by bussdriver on Friday May 13 2022, @01:03AM (2 children)

    by bussdriver (6876) Subscriber Badge on Friday May 13 2022, @01:03AM (#1244636)

    I have parking brakes on my rear Nissan Leaf's wheels. It has it's own special pedal which is a bit high up but thankfully exists. It is not quite enough to replace normal brakes but it really should be made to do so.

    Make the parking brakes a bit stronger and easier to trigger and that would be enough of a backup. It doesn't make dust unless there is an emergency and parking with it shouldn't make any. Even now, brakes last incredibly long with regen doing most the work.

    • (Score: 2) by Immerman on Friday May 13 2022, @02:06AM (1 child)

      by Immerman (3985) on Friday May 13 2022, @02:06AM (#1244643)

      Yeah, a simple mechanical parking brake would get the job done. Even if it's not as powerful as your normal brakes, it's a huge improvement over nothing. Add in a kill switch that physically cuts power to the motor when the parking brake is engaged (in case of any sort of stuck-on malfunction) and you're golden.

      • (Score: 2) by bussdriver on Monday May 30 2022, @05:56PM

        by bussdriver (6876) Subscriber Badge on Monday May 30 2022, @05:56PM (#1249009)

        Yes, a good point-- my electric motor can pretty easily grind past the parking brakes given it's high torque. I'm on my 2nd set of drum brakes because of that; previous owner somehow didn't notice... and after they wear down there is nothing to notice.

        that said, nissan has some funky stuff going on with braking to try to make the regen and disc brakes blend so it's not jarring when it transitions to physical brakes. I've once had the computer mess up and lost brakes and the regen is not strong enough on it's own -- not even close! I figure these newer e-brakes must be sizable and add cost somewhere to replace physical brakes. You've at least got to bulk up the electronics to use the motor to brake because that has to be some huge power spikes you go past generation and start to spend energy to brake. Not just a high power generation positive spike but reversing to a huge negative spike to actively brake.