4 ms·

This doesn't sound like a big deal. Electronics normally can't function when system voltage is too low, and that can happen in a car if the battery is weak and

by magduf 7y ago

This doesn't sound like a big deal. Electronics normally can't function when system voltage is too low, and that can happen in a car if the battery is weak and the alternator isn't producing enough power (e.g., at very low speeds and with a high electrical load, such as making a sharp turn in a parking lot with a nearly-dead battery). This isn't very different from old hydraulic-assist cars that also had the assist die or be too low when there was some problem (fluid too low, pump failure, belt failure, etc.). Was it ever a big problem? No, not really. If your power steering fails in a parking lot, it's a pain, but you're already barely moving, so you just stop. At worst, you might have a minor fender-bender. I don't see how this is a software problem; this is an electrical problem. The only software issue here is the decision to shut down the EPS instead of bringing it back online when the system voltage goes high enough. Personally, I'd say the fundamental problem here is actually the fact that cars still have 12V electrical systems, and batteries that are really meant for starting only, not for continuously supplying heavy electrical loads (like EPS). Carmakers should have gone to 42V or 48V systems ages ago.

bumby 7y ago
To your point, the GM issue was involved in 30 accidents in a couple years but no fatalities. The problem is obviously not a failure in a parking lot, but at speed. I don’t know the specifics of the system safety analysis but if the software is used to mitigate a hazard, it’s usually considered safety critical. In this case, if it shuts the EPS off, or fails to bring it back online, it it would significantly affect the vehicle handling dynamics. Again, I don’t know their classification scheme but I would assume the steering is a safety critical system. Some reports claim the vehicle lost all handling control, but I’m a little skeptical of that claim. In any event, I wouldn’t consider it no issue. Recalls cost a lot of money. In the GM case it affected 1MM cars. I didn’t look up the cost of each fix, but I wouldn’t be surprised if it cost nine figures. I doubt they would go forward with a recall of that magnitude for a trivial issue. I could see the same rationalization for MCAS. The system safety analysis didn’t claim an MCAS failure was catastrophic and they already had a procedural mitigation in place if it did fail. It wouldn’t take much to convince someone that such a recall fix was no big deal. This is part of the problem with systems using safety critical software
- Gibbon1 7y ago
  There was a problem with GM ignition switches. The detent was too short and so it was possible for it to accidentally be switched to off. Bunch of people died as a result. Three problems. Power steering and brakes no longer work. Two the anti-theft device can lock the steering wheel. Third the airbags are disabled. It's a classic systems interaction issue. And is exactly the thing that shows up as the design processes becomes Balkanized.
  - magduf 7y ago
    I remember that one; that was absolutely criminal because they were informed there was a problem, and refused to do a recall because it would cost money. Instead, they quietly changed the ignition switch to fix the design defect, but without changing the part number or informing anyone. And, as you pointed out, it was a systems interaction problem. Losing power steering at speed isn't great, but it's recoverable (maybe less so if you're weak and you're driving some big stupid SUV, rather than a small economy car), and losing power brakes is also bad but recoverable because you have enough vacuum in the system to do a full stop (but only 1 usually), but tie them together, at speed, and also (worst of all) lock the steering wheel, and you have a recipe for disaster. This is far, far, far worse than losing your power steering assist at parking-lot speeds.
    - bumby 7y ago
      What you bring up in terms of cascading failures is termed the "swiss cheese model"[1] This is the traditional way to deal with system hazards. What has been talked about is the need for changing the way we think about software failures on safety critical systems, distinct from traditional failure mode approaches. "The result is that software-related accidents involve a new type of accident, which can be called a component interaction accident: None of the components fail (all satisfy their specified requirements) but the problems arise from dysfunctional interactions among the components."[2] [1] https://en.wikipedia.org/wiki/Swiss_cheese_model https://en.wikipedia.org/wiki/Swiss_cheese_model [2] https://dspace.mit.edu/handle/1721.1/58930 https://dspace.mit.edu/handle/1721.1/58930
- 7y ago

by magduf 7y ago

bumby 7y ago

To your point, the GM issue was involved in 30 accidents in a couple years but no fatalities. The problem is obviously not a failure in a parking lot, but at speed. I don’t know the specifics of the system safety analysis but if the software is used to mitigate a hazard, it’s usually considered safety critical. In this case, if it shuts the EPS off, or fails to bring it back online, it it would significantly affect the vehicle handling dynamics. Again, I don’t know their classification scheme but I would assume the steering is a safety critical system. Some reports claim the vehicle lost all handling control, but I’m a little skeptical of that claim. In any event, I wouldn’t consider it no issue. Recalls cost a lot of money. In the GM case it affected 1MM cars. I didn’t look up the cost of each fix, but I wouldn’t be surprised if it cost nine figures. I doubt they would go forward with a recall of that magnitude for a trivial issue. I could see the same rationalization for MCAS. The system safety analysis didn’t claim an MCAS failure was catastrophic and they already had a procedural mitigation in place if it did fail. It wouldn’t take much to convince someone that such a recall fix was no big deal. This is part of the problem with systems using safety critical software

Gibbon1 7y ago
There was a problem with GM ignition switches. The detent was too short and so it was possible for it to accidentally be switched to off. Bunch of people died as a result. Three problems. Power steering and brakes no longer work. Two the anti-theft device can lock the steering wheel. Third the airbags are disabled. It's a classic systems interaction issue. And is exactly the thing that shows up as the design processes becomes Balkanized.
- magduf 7y ago
  I remember that one; that was absolutely criminal because they were informed there was a problem, and refused to do a recall because it would cost money. Instead, they quietly changed the ignition switch to fix the design defect, but without changing the part number or informing anyone. And, as you pointed out, it was a systems interaction problem. Losing power steering at speed isn't great, but it's recoverable (maybe less so if you're weak and you're driving some big stupid SUV, rather than a small economy car), and losing power brakes is also bad but recoverable because you have enough vacuum in the system to do a full stop (but only 1 usually), but tie them together, at speed, and also (worst of all) lock the steering wheel, and you have a recipe for disaster. This is far, far, far worse than losing your power steering assist at parking-lot speeds.
  - bumby 7y ago
    What you bring up in terms of cascading failures is termed the "swiss cheese model"[1] This is the traditional way to deal with system hazards. What has been talked about is the need for changing the way we think about software failures on safety critical systems, distinct from traditional failure mode approaches. "The result is that software-related accidents involve a new type of accident, which can be called a component interaction accident: None of the components fail (all satisfy their specified requirements) but the problems arise from dysfunctional interactions among the components."[2] [1] https://en.wikipedia.org/wiki/Swiss_cheese_model https://en.wikipedia.org/wiki/Swiss_cheese_model [2] https://dspace.mit.edu/handle/1721.1/58930 https://dspace.mit.edu/handle/1721.1/58930
7y ago