Posted on 11/01/2013 10:04:04 AM PDT by Freeport
Somthing that is absolutely not somthing one does not do in safety-critical applications.
Always, sensor sample is decoupled from other processes. Always, safty timmers are decoupled from other processes and it's usually one thread/task (Different code/data space.) per safety timer.
All single point failures are to be mittigated. No fewer than TWO failures are ever allowed before a safety-critical fault is created: It takes two faults before trouble happens.
There's no information, but it appears there was no task monitor or continuous built-in-test task...
This is a horible system design and I suspect most vendors are no better.
So... let those google cars free! I'll be walking...
My Yoyoda has 5 speed standard transmission so a problem like that is not nearly as dangerous as it is with automatic transmission. My left foot is always tapping the clutch.
But finding cars with standard 5 speed is harder and harder here.
Toyoda cites low demand.
Ever have a noisy volume pot on a stereo? I always wondered what would happen if you had a similar noisy pot on the throttle sensor of a drive-by-wire system.
Then about an hour later on the way to get it cleaned up before taking it back to the dealership, it almost ran us into the gas pumps at the car wash, stopped it with inches to spare . We called a wrecker had had it towed to the dealership.
They found nothing wrong with it and put it on their lot. A few months later we saw on the local news a dark red Ford 150 plowed into a house. The kid driving said “I couldn't stop it!”
Couldn’t you do the same thing with an auto, grab the column or console shifter and bump it into neutral? The majority, if not all of the automatic shifter gate/detents that I’ve come across allow the driver to go from drive to neutral without engaging anything.
Real time code can’t be checked just by inspection. There can be hardware interactions and execution time availability and phasing and interactions with other s/w modules that can have big impacts on correct operation.
Maybe, but its more natural to hit the clutch while the car is moving then to change the automatic trans shifter isnt it?
Do drivers usually touch that control when the car is moving and foot is on gas? I bet few do.
it’s a required safety feature to be able to bump the transmission to neutral on the shifter for an auto transmission - so yes you can do it.
I would have followed up with the cops about it. See if it was your truck and explain to them what happened. May save the kid's family a bunch of hurt financially.
Sure, but his point is that the code wasn’t design in such a way as to minimize the impact of that kind of failure. In the early days of electronic engine control the throttle position sensor was a big failure item, but the vehicle was capable of slow but safe operation in “limp home” mode. Inconvenient, but not deadly.
No. I do, and my kids will, when they get older. I really want to get them manually-shifted cars, though. Primarily as a theft deterrent (little buggers are getting dumber and don't know how to shift 'em), but also as a way to ensure they understand just how much they have to pay attention to their driving. I always feel much more in tune with what's going on when I have to shift it. Plus, takes a hand away from being able to talk/text while driving in traffic.
Ping for later.
I like manual transmissions the best, cheaper and more reliable, never had one go bad. Unfortunately American consumers are like kids and want more and more expensive gadgets in cars that break,
see #2
What vehicle testing? All I read about is a code review.
The pedal end at least (and maybe the throttle/fuel injector) has two variable resistors operating in opposite sense. While one is going up, the other is going down.
Careful. That is one of the major contributors to accelerated crankshaft thrust bearing wear.
“A dozen embedded systems experts were allowed to review Toyota’s electronic throttle source code in a secure room in Maryland — described as the size of a small hotel room. The room, with a guard at the door, was disconnected from the Internet. No cellphones, paper, belts, or watches were allowed inside. The experts viewed Toyota’s code on five computers in cubicles.”
I have this terrible mental picture of a dozen Nerds wearing only Speedos crammed into a small room reviewing code.
The volume knob on the factory stereo in my wife’s Chrysler acts very strangely. Turning the knob in the appropriate direction sometimes does nothing, or turns the volume way up or down.
I would NOT want a throttle-by-wire system failing in that fashion.
I’m also a big fan of the traditional H-pattern gearbox. The box in my Miata has a bad 4th-gear synchro (and has since early 2000), but it was really easy to work around. If I have to downshift into 4th, I either double-clutch or nudge the lever up toward 3rd before dropping into 4th. And if I’ve slowed down sufficently, I just drop it straight into 3rd.
297,000 miles on that transmission, and it’s now on its third clutch.
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