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The Toyota Witch Hunt

businessweek.com

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Re: The Toyota Witch Hunt

#31

Post by jonknee »

cryptnoob wrote: post #29
jonknee wrote: post #18

Earlier quoted context omitted.

> The accelerator pedal would have to be immovable, frozen in place. In recent Toyota vehicles the pedal isn't connected to the throttle--it's drive by wire. In theory the computer could continue accelerating regardless of the gas pedal's position.

I've designed systems like this. You use redundant potentiometers to sense throttle position. If they don't match within 5%, you power down. You also toggle bits in your code. One in the main loop, another in any interrupt service routine that you are dependent upon. These bits then go to a GPIO so that the GPIO toggles. If the ISR freezes or the main loop freezes, the GPIO quits toggling. You then have an hardware,…

... And yet there are out of control cars without the pedal being stuck.

"Well, I have many models of Prius that got recalled, but I have a new model that didn't get recalled. This new model has an accelerator that goes wild, but only under certain conditions of cruise control. And I can repeat it over and over and over again--safely."

"This is software. It's not a bad accelerator pedal. It's very scary, but luckily for me, I can hit the brakes," he said.

-- Steve Wozniak

http://news.cnet.com/8301-13924_3-10445564-64.html

Re: The Toyota Witch Hunt

#32

Post by cryptnoob »

lallysingh wrote: post #23
cryptnoob wrote: post #19

Earlier quoted context omitted.

Please forward your proof of this to Toyota and the congressional committee to which Toyota swore this was not the case. It's tempting to blame drive by wire, since electronics is black magic to most people. Keep in mind that most passenger jets in the sky are fly by wire, these days. For you to point blank claim this to be true, when it's been flatly denied several times, seems a bit over the top, don't you think?

Really? I think it was an article here (maybe, maybe not, I'm pretty hung over today) that mentioned that the problem was that the primary and backup pedal position sensors' wires could short and max out.

You usually design so that a single point of failure can't hurt you. If one position sensor (they use pots, since they're practically indestructable and not vulnerable to ESD, power transients, etc) fails, you sense the problem with the other sensor. They're not "primary and backup", they're both equally important.

You postulate that both sensors short out at the exact same instant, since any other scenario would power down the vehicle. They did it within milliseconds of each other, and they did it at some intermediate, yet believable level. (They didn't "peg at maximum", as that would also alert the software there was a problem. Instead they pegged, identically, at some believable value.

I'll take the other side of that bet any day.

Re: The Toyota Witch Hunt

#34

Post by cryptnoob »

jonknee wrote: post #31
cryptnoob wrote: post #29

Earlier quoted context omitted.

I've designed systems like this. You use redundant potentiometers to sense throttle position. If they don't match within 5%, you power down. You also toggle bits in your code. One in the main loop, another in any interrupt service routine that you are dependent upon. These bits then go to a GPIO so that the GPIO toggles. If the ISR freezes or the main loop freezes, the GPIO quits toggling. You then have an hardware,…

... And yet there are out of control cars without the pedal being stuck. "Well, I have many models of Prius that got recalled, but I have a new model that didn't get recalled. This new model has an accelerator that goes wild, but only under certain conditions of cruise control. And I can repeat it over and over and over again--safely." "This is software. It's not a bad accelerator pedal. It's very scary, but luckily…

This is more believable to me, as the "set-point" for cruise control is not dependent upon throttle position, but instead, is remembered by the computer. There's nothing to check against to insure believability.

More suspect, in my opinion, is that in a cruise control, you have a feedback system, based on car speed. The car speed is almost certainly redundantly sensed, so that's no worries, but the feedback loop itself could potentially go oscillatory if there were other variables introduced that hadn't been designed for. Those variables could be pretty subtle. For example, maybe the gear motor that you use to mechanically control the engine gets sourced from another distributor, and they give you a better one, that has more torque. Perhaps that throws off the stability analysis that you had done. Tons of things could change somewhere between the 500K's car and 1M's car you produced, lots of different vendors and permutations could come into play that could throw off the stability of a cruise control, I would think.

EDIT: They're probably using feedback in the control motors as well (servos), so that's a non-realistic example, but it illustrates the problem.

Re: The Toyota Witch Hunt

#35

Post by Sthorpe »

groaner wrote: post #14
erlanger wrote: post #8

I hold the conspiracy theory that these issues are being so aggressively sought out in an attempt to bring Toyota's image down to the level of American auto manufacturers.

I have to agree; I can sense the schadenfreude all over the place and it's getting annoying.

Hacker News is great. I had been thinking this exact same thing but then realized I was being ridiculous. However, isn't it a little scary to realize how no one is in control of us? I noticed this when I was riding on Bart. Everyone acts a particular way based on what other people expect them to act like. We all operate with so much order and yet no one is telling us to. Just thought this was cool.

Re: The Toyota Witch Hunt

#36

Post by idoh »

zzzmarcus wrote: post #25

Can someone explain to me why Congress gets involved in investigating things like Toyota's manufacturing defects or the way college football teams are ranked? Does Congress have a legal mandate to investigate anything it deems to be interesting/fishy/a potential target for legislation? Has Congress always conducted these types of investigations or is it a modern phenomenon?

Don't hate the players, hate the game. They do what they do to get reelected.

Re: The Toyota Witch Hunt

#37

Post by pohl »

Sthorpe wrote: post #35
groaner wrote: post #14

Earlier quoted context omitted.

I have to agree; I can sense the schadenfreude all over the place and it's getting annoying.

Hacker News is great. I had been thinking this exact same thing but then realized I was being ridiculous. However, isn't it a little scary to realize how no one is in control of us? I noticed this when I was riding on Bart. Everyone acts a particular way based on what other people expect them to act like. We all operate with so much order and yet no one is telling us to. Just thought this was cool.

I'm pretty sure the news media doesn't decide which drum to beat every night based upon which drum people expect them to beat.

Re: The Toyota Witch Hunt

#38

Post by Estragon »

mawhidby wrote: post #30
erlanger wrote: post #8

I hold the conspiracy theory that these issues are being so aggressively sought out in an attempt to bring Toyota's image down to the level of American auto manufacturers.

I've been beginning to suspect this as well, mainly because of all the media coverage this has been getting. If this theory is true, it's saddening because Toyota's image is completely tarnished in many people's eyes, and they won't be able to recover from this for years (if ever).

The really saddening part will be when the rest the world does it to the US. And they will have a much easier time finding things to beef about.

Re: The Toyota Witch Hunt

#40

Post by whyenot »

zzzmarcus wrote: post #25

Can someone explain to me why Congress gets involved in investigating things like Toyota's manufacturing defects or the way college football teams are ranked? Does Congress have a legal mandate to investigate anything it deems to be interesting/fishy/a potential target for legislation? Has Congress always conducted these types of investigations or is it a modern phenomenon?

cynic: Congress' mandate is to investigate anything that will get votes, or campaign funds.

Wikipedia: Investigative hearings share some of the characteristics of legislative and oversight hearings. The difference lies in Congress’s stated determination to investigate, usually when there is a suspicion of wrongdoing on the part of public officials acting in their official capacity, or private citizens whose activities suggest the need for a legislative remedy. Congress’s authority to investigate is broad and it has exercised this authority since the earliest days of the republic. Its most famous inquiries are benchmarks in American history: Credit Mobilier, Teapot Dome, Army-McCarthy, Watergate, and Iran-Contra. Investigative hearings often lead to legislation to address the problems uncovered. Judicial activities in the same area of Congress’s investigation may precede, run simultaneously with, or follow such inquiries.

It's not a recent phenomenon at all. For example, the Crédit Mobilier hearings were in 1872.

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