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Comment by MarkusWandel | Hacker News Reader

Whoa. My own car already has throttle-by-wire i.e. no mechanical linkage for that. Brakes is debatable; I assume if the ABS unit fails they revert to "dumb" hydraulic brakes with the usual rendundancy (pairs of wheels fail independently plus you still have some backup from the parking brake).

But steering by wire? That's what the article implies, though another comment already debunks it. I hope there are exactly no cars on the road today that are steering-by-wire. I.e. they all degrade to non-power, mechanical steering if the electronic or hydraulic gimcrackery fails.

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As described in the article, it's the self-driving computer who is "steering by wire", not the human driver.

If the powered steering fails, then the computer cannot steer. Therefore, there was redundancy in the powered steering system. The redundancy was removed because of a chip shortage, and this was considered acceptable because the self driving feature still requires the driver to keep hands on the steering wheel anyway.

>The redundancy was removed because of a chip shortage, and this was considered acceptable because the self driving feature still requires the driver to keep hands on the steering wheel anyway

But aren't we pretending that this year the autopilot /FSD will actually live to their names? Or will Tesla put the chip back later this year ?

It's only in the Chinese market where FSD isn't offered.

Infiniti produces steer-by-wire cars that have been on the road for awhile now.

Considering that some cars can change how much the wheels turn based on the speed you're driving, we know it must have been approved for road use.

BMW does this (it's great), and they did not remove the physical linkage to do it. It's done with a planetary gear system: https://en.wikipedia.org/wiki/Active_steering

I guess the cheap variant of this is reduced power steering at higher speeds.

Creative gear tooth geometry lets manufacturers offer steering that's slow near the center and fast near the ends at far less cost.

Yes, that's the cheaper version they have on the BMW 3 and 4 series. Purely mechanical, but then also not speed dependent.

Does this actually change how much the wheel turns or just the level of power steering? The wiki seems to suggest it does, though this seems dangerous to me. You don't drive the same on the highway as you do in a parking lot.

It changes how much the wheel turns, but it's subtle / intuitive so you don't notice it's there. Unless you drive the same kind of car without the option, then you notice the steering seems not as nice.

It is also used by stability control to counter-steer small amounts of oversteer. But it can only do so for a relatively small amount of wheel angle change, not turn the wheel 90 degrees or something like that.

That is a really clever solution.

Electric power steering / steer by wire systems still have a backup mechanical link. This issue here is the backup when in self-driving mode, where nobody would have their hands on the wheel so you couldn't rely on that link. So instead you have to have a second system as a backup instead.

> Electric power steering / steer by wire systems still have a backup mechanical link.

Electric power steering and steer by wire are two different things. A steer by wire system does not have a "mechanical link" backing up the function of the electronics.

I assume if the ABS unit fails…

If your Antilock Braking System fails, then your brakes will continue to work as they always did, save the fact that they’ll lock the wheels if you press too hard. If there weren’t a light on the dashboard, it is unlikely one would notice ABS failure (unless, of course, one is in a situation where ABS would come in handy, like an ice-covered road).

Citroen high-end cars got hydraulic systems that decoupled the steering wheel from the wheels in the seventies: https://en.wikipedia.org/wiki/DIRAVI

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