[Terr_]

> Steer-by-wire

Thinking back to case-studies around the Therac-25 [0], I would like to pre-emptively highlight the differences between:

1. Technique X is unsafe.

2. Technique X is unsafe because too much can go wrong even with the best intentions.

3. Technique X is unsafe without strong QA and interlocking safety measures, and there's too much economic pressure for the manufacturer to cut corners.

[0] https://en.wikipedia.org/wiki/Therac-25

[AnthonyMouse]

The obvious problem with steer-by-wire is that in the traditional design, it's not uncommon to lose power assist but not the mechanical connection to the wheels, so you can still steer the car. To completely lose steering control you'd need significant mechanical damage.

If the whole thing goes through the computer then there are lots of new ways to fail. Steering wheel position sensor goes bad on the highway? Computer gets bad data. Control wires get disconnected or damaged? No data. Completely unrelated wires get shorted and fry the computer? No steering. Anything pops the wrong fuse? No power, no computer or steering motors.

Some of those can be mitigated with redundancy but you're still vulnerable to common causes. You have three position sensors and someone dumps their beverage down the steering column, are there any left and do you have any good way to determine which one(s)? The vehicle took some minor damage allowing water to get somewhere it's not intended to, any way to guarantee you're not about to lose both sides of a redundant electrical system the next time it goes through a puddle infused with conductive road salt?

[spwa4]

Of course, a counterpoint is what's been happening in aviation. Autopilot became a thing. Autoland became a thing. And, to keep improving planes (first military planes, then commercial aircraft), it was much easier to drop the mechanical connection to the wings.

Autopilot started as a help to pilots, and evolved to something that is a necessity and pilot control inputs are "suggestions" or "goals", not inputs like turning the wheel on a bike. To be followed in what you might refer to as "the long term" from the perspective of controlling the aircraft, but in the short term, the computer is to fly the plane in a way IT thinks is reasonable. An extreme example would be to enforce the flight envelope. But today there exist autoland-only airports (as well as huge airports that go autoland-only if things are too hard for humans, like LHR)

Most of today's passenger aircraft cannot be flown if fly-by-wire is not operational. Most of today's aircraft actually used for passenger transport cannot land without fly-by-wire.

A number of military aircraft, and rocket planes and rockets, even the ones carrying humans, and more and more passenger planes cannot be flown by humans, not just because the mechanical force humans can generate cannot move the control surfaces (which "can be fixed" with hydraulics, if you don't mind serious caveats), but because the human brain is incapable of generating sufficient control inputs at a fast enough rate, or just can't keep stable flight going.

Hilariously, this also goes for hobby quadcopters. They are flown by algorithms. Humans can't do it. Not fast enough. Humans provide direction. Algorithms, even AI algorithms that aren't even guaranteed to succeed at all (in professional/military drones), actually fly the thing.

But, yes, you're entirely correct by saying "then there are lots of new ways to fail". It also works better, cheaper, faster, safer, more comfortable, ... if it doesn't fail.

And ... robotaxis are already far safer than even a good human driver. So whatever the problems ... they don't actually make things worse.

Also you should check out geohot's business. A lot of cars already are "fly-by-wire". Their solution? They now have 2 CAN buses instead of one. One for the critical stuff. Cylinder timings. Checking the oil levels. Turning the wheels. Actuating the brakes. That sort of stuff. A second CAN bus for your bluetooth music, and displays and what have you. I hear a certain new Mercedes now has like 7 buses. We are making things safer.

We can make this work. We will make this work.

[Scholmo]

Planes are probably the most controled machines we have. Everything gets checked twice or more, everything gets tracked and there is a clear requirement to do it like this because, as you said, its not possible for humans to control a fighterjet or a big plane.

Cars are non of that and we have billions of them on the street.

Cars also became a lot more expensive due to their complexity which def creates problems for a lot of people who can't afford all of that. I'm really torn by this because I think its very good that my side mirror shows me if there is a car next to me but in our capitalistic economy, we are excluding a lot of people from affordable cars. Drive by wire needs to be cheaper and easier to fix/repair.

Btw. Waymos are slowly learning to drive on highways so I might agree that they drive saver than humans in certain controlled envs. For sure not in any environment.

[spwa4]

But that is the "tradeoff" people are going for. What irritates me about Waymos is that they are not really cheaper than taxis and Uber. If we want people to become more mobile ... Waymo does not appear to be the answer.

And that was always the trade that was proposed. Sure, Waymo's (and Uber) will displace a LOT of taxi jobs, but they'll be way cheaper than taxis. Well ... they're not. And at that point, from an economic perspective, this is just taking things away for not much in return.

Once again people get a lot of possible choices and once again they choose for the more expensive one, putting more people out of business, out of a job, and as you say out of society. Now they're saying "yeah but this is good for autistic people and women, who can now travel by taxi without ever seeing anyone". How, exactly, does anyone think that's a good thing for society? Seriously?

Plus I'm a bit of the opinion, if Waymo is already breaking their own proposed social contract now ... imagine what they'll do in 10 years.

[jillesvangurp]

Safety is a great reason to not do something. Utility and enhanced safety are great reasons to override that reflex. A lot has happened since the Therac 25 incident in the medical world with AI, machine learning, robotic neuro surgery, all sorts of computer aided diagnostics, etc. This stuff undeniably saves lives. The incident did inspire some level of scrutiny of course. But compared to modern medical equipment, that machine is from the stone age.

Steer by wire (which the article highlights) is common on all modern airbus planes for decades. The first ones flew shortly after the Therac incident. Boeing has also started implementing that on their newer models. And of course most of the vtol planes/drones currently starting to operate and progress through certification programs also commonly use steer by wire. Several of these flew without pilots before their first manned test flights. These are computer controlled, pilot directed pretty much by default with that part being optional by design.

Beyond Tesla, there are now several other manufacturers implementing steer by wire in the car industry. Nio, Lexus, Toyota, Mercedes, and a few others each either already have cars on the road for this or are working on new ones. And while Tesla has received quite a bit of criticism on their FSD system, I don't think there have been a lot of incidents implicating the steer by wire in Cybertrucks. It seems to work and drivers seem to mostly like it once they get used to it. The car is controversial of course. But there's a lot of cool tech inside that is being copied across the industry now.

The implied warning "we should be careful with this stuff because Therac-25" is a bit of a cliche at this point. Yes, we need lots of checks and balances when using automation in safety critical systems. And that has been common for decades.

[psd1]

All analysis should also keep in mind the "who", no matter how logically separable it is.

I put this less strongly since boeing contracted MBA cancer and yolo'd the 737-max, but that aside, the civil aviation engineering field controls risks to a fault. Commercial pilots are selected to follow checklists without deviation. I allow them the grace to implement steer-by-wire.

Ford kept selling Pintos with exploding fuel tanks, Toyota sold priuses with runaway acceleration defects, and depending on region maybe the worst twenty per cent of drivers ought to be operating nothing more dangerous than shirt buttons. No matter how good the plan is, those people shouldn't be anywhere near it.

[cyberax]

Moreover, Technique X does not actually provide any significant value.

The whole steer-by-wire in CT happened because Musk wanted a yoke as the control system. And a yoke requires progressive steering which is impractical without steer-by-wire.

[rootusrootus]

> does not actually provide any significant value

If that were true, it would not explain why other manufacturers are headed the same direction. The CT is not the only steer-by-wire vehicle.

[michaelt]

Vehicles include low-utility features for market positioning all the time.

Do buyers need a motorised hood ornament? A tiny vase built into the dashboard? A built-in champagne chiller? Gull wing doors? A spoiler and a 300-horsepower engine?

If it boosts sales by giving the vehicle a distinctive character, though, there's a place in the market for that tiny vase.

[nickff]

The motorized hood ornaments on Rolls Royce vehicles were a solution to the problem of people being injured by, or stealing the (Spirit of Ecstasy) ornaments.

https://en.wikipedia.org/wiki/Spirit_of_Ecstasy

[soopypoos]

How does it being motorized prevent injury?

[sarchertech]

> Today's Spirit of Ecstasy, from the 2003 Phantom model onward, stands at 3 inches (7.6 cm) and, for the safety of any person being accidentally hit, is mounted on a spring-loaded mechanism designed to retract instantly into the radiator shell if struck from any direction.

[cyberax]

What other manufacturers? There's Mercedes EQS and Geely. Both are trialing it in one model each as luxury gimmicks.

[rconti]

steer-by-wire makes safety nannies way easier, eg, the ones that jerk the wheel out of your hands when they decide you're too close to a line on the road.

[Scholmo]

I don't think thats true.

Its power steering already and cars use that to turn a wheel when you are not driving.

So why would that make it safer?

[rconti]

I didn't say safer, I said easier.

https://ddl.stanford.edu/publications/thesis/steer-wire-impl...

https://www.reddit.com/r/MVIS/comments/1qnkxpz/reason_for_ad...

[Scholmo]

Yeah sry but I meant easier.

But why do you think it would make it easier? Power-steering doesn't mean there are sensors build in or more precise ones.

Your reddit comment references autonomes vehicle and in that case it shouldn't matter if the car also moves a steering wheel no one is using while it moves the wheels which is a lot heavier.

And in case of your nanny, the main argument of your referenced paper are issues with the hands of the driver. In that case it could make it better for the driver, I might agree, but I would then question how the driver acts if the wheel is suddenly / temporarily not aligned with the wheel. I might also argue that in such a case were my thumb gets in the way, it might be an emergency and i wouldn't worry then?

[wat10000]

Other models got the yoke but not the steer by wire.

[cyberax]

Yes. And it was a disaster without progressive steering, they quietly switched back to the round wheel.

[ErroneousBosh]

> And a yoke requires progressive steering which is impractical without steer-by-wire.

But also look at Citroën's DIRAVI system, used on the CX, SM, and some XMs. There's no direct mechanical link between the steering wheel and the rack when the system is pressurised. When you turn the wheel a kind of dogbone link thing pushes a spool valve one way or the other allowing hydraulic fluid to push the rack along, which pushes the other end of the link back to shut the fluid off again.

So far, so similar to the Danfoss valve in a conventional power-assisted steering system, except that uses a rotary valve and a big torsion spring in the steering rack (that's why your steering wheel feels springy with the engine off).

But DIRAVI is fully powered with no mechanical link, so how do you get increasing resistance with increasing speed? Well, there's a governor on the gearbox that allows hydraulic fluid into a little cylinder that pushes a spring-loaded roller against a heart-shaped cam attached to the steering wheel shaft. This will try to spring back to the middle, and the faster you go the harder it springs back. At 70mph you can barely move the steering wheel, but it will flick a large heavy car from lane to lane with fingertip pressure.

You have to get used to this and for the first few miles you'll be zig-zagging down the road like you're tacking a dinghy, but after that you'll get used to just thinking about your right pinky finger being a gram heavier and going round a corner. I've driven some seriously high-end sports cars with legendary handling and performance and they feel pretty rough and tractory now ;-)

If the pressure fails of course then there's no powered steering (notice I say powered, not power-assisted), although in practice what tends to happen is that the "resistance" part goes first giving you very sensitive steering.

What happens once there's no pressure is that the steering wheel moves about 20° before you run the valve to its end and then the dogbone pushes directly on the drive gear for the rack. So the steering is very loose and wobbly but you can at least steer well enough to get it out of the parking space and into the workshop. You still have brakes for an hour or so if the pump belt breaks, and enough steering to get safely to the side of the road, or at least out of the fast lane.

In the 1960s they had a prototype Citroën DS controlled by a joystick using pretty much the same setup (hydraulic valve to push the rack around, heart-shaped cam to apply resistance). Apparently it was very comfortable and natural to drive but ultimately a bit to weird even for Citroën.

Not a scrap of electronics in it, unless you count the pressure switch and dashboard lightbulb.

[psd1]

TIL! I love old Citroëns, but i never knew about that steering design.

Have you experienced that failure mode yourself? How alarming was it? Do you think it's a reasonable trade-off for the benefits?

[ErroneousBosh]

I had the hydraulic pump belt break when I was about 30 or 40 miles from home, and of course I had a water pump belt and an alternator belt, but not the hydraulic pump belt.

The brake and regulator accumulators were both nice and new though so the "low brake pressure stop immediately" warning only came on about two or three miles from home (once there's no pressure at all, there's no brakes at all, but this is pretty difficult to achieve in practice) and I just had to cope with the twitchy steering through the difficult part - driving through town at 15-20mph in rush hour traffic anyway.

[cyberax]

That is truly steampunk! Overengineered and crazy but cool!

[ErroneousBosh]

It would only be overengineered if it was not necessary, and once you drive one you'll realise that all cars should have it.

You can actually get pretty close with electric power steering but that's a lot more involved than a few dozen incredibly finely machined parts and a bunch of thin oil at 180 times atmospheric pressure.