OT: Thoughts on Toyota Recall, Safety Circuits Design

I am sure that everyone have heard about the big Toyota mass recalls of recent model cars and light trucks. I have participated in other forums but they usually degenerate into flame war and a lot of FUDs.

With the know-how in this forum I thought we would have some enlightening discussion on this technical topic.

My thought so far based on publiclly available information:

• This is a recall without a fix thus far, correct me if I'm wrong on this. But they don't know what the problem is. Floormat have been ruled out and Gas paddel design is still under investigation.
• there's claim out there that someone the "computer" screw up and won't brake or disengage gas. that's been strongly denied by Toyota and I tend to agree based on what I know. As far as I know, the brake does not need the "computer" ok to apply.
• I think there's a component of mass hysteria in play as well.
• Toyota will put a "brake override" that disengage gas if brake is applied. This is a good control safety design, ie, idiot proofing. But does it explain all the incidents thus far?

So far, it sounds like it's combination of floor mat, gas padel design (CTS made padel), and hysteria.

What say you?

Toyota talking about a brake override that will 'disengage' the accelerator while at the same time strongly denying possibility of a software issue seems to be an incongruous position. Ok, that might be a bit strong. It is possible their failure analysis was just seriously flawed. Wouldn't you think someone would have already said "What happens if the accelerator gets stuck down?"?

This is already a throttle-by-wire system. Anything mechanical you put in would be subject to the same failure possiblility the current mechanical system might be encountering. This has to be a command side error since either a fuel injection or throttle plate error on it's own would ultimately choke the motor.

I would agree that there is some measure of hysteria involved. The concept that pressing the brake makes the vehicle pick up speed (which I have heard) seems pretty far fetched. When something doesn't act as expected your perception of reality can get pretty skewwed.

Keith

My thoughts
......
....'Sounds like a tactic against Toyota
.......If problem with brakes
.........Else if problem with gas pedal
............Else if convince Americans to keep buying there gas guzzlers
...............Else PANIC
.......
'End of thought

There may be a problem with either a stuck pedal or a software issue but drivers are either uninformed or just stupid as that cop in California. All you have to do is take it out of gear. There is a rev limiter and often a backup. When the driver applies the brakes with the throttle open the vacuum is gone and the boost does not work....no brakes. That idiot was talking on the phone while the car accelerated. This guy was trained by a police dept to operate a car at high speed. What didn't he get? Besides dead.

I sure hope Toyota did not allow for anything to interfere with brake actuation ie step on brake pedal and it is a completely independent system and will always apply brakes (with exception of empty master cylinder or broken brake line). Brake system may be sensed only to allow or require shutdown of other systems of course.

At least that is how I would do it.

What the problem with throttle control is I have no idea but it sure makes an argument for mechanical throttle system. But in this age and day of "computer engine control" the mechanical is still turned over to the chips.
Have had a mechanical throttle stick open but the brake and key switch were able to handle that problem.

Maybe an E stop type fuel shut off?

I had this same type of issue with an American made truck about 4 years ago. I was going to a customer site with the company vehicle and the 'throttle' would take off on me and the engine would rev really high. Granted, I had to hit the brakes much harder to stop, and I put it into nuetral at the intersections (this happened in a city) at which I peeled out pretty good when I dropped it back into gear. I finally got to pull over to a shoulder and got it towed.

Turns out when I got to the dealer service garage, it was a known issue with the truck. When I called back into the office and relayed that information, there was no mention that our company had gotten any recall notice about the issue. This of course doesn't mean that we never received anything, we all know how paper trails work around the office sometimes.

Here is the best part. Remember I had this vehicle towed to a DEALER garage. After quite the repair bill for the service, someone else took the vehicle out on another call and the same thing happened to them!!! This was after the known problem was fixed of course by the dealer certified technicians.

I suppose being technically oriented it seems that it wasn't a big deal when it happened to me, but I guess there are lots of people out there that might freak out. I would never believe if they stepped on the brake though that the vehicle wouldn't stop. This happeded to me in a truck with some serious torque and I didn't have any problem using the brakes to stop the vehicle (granted I could smell them heating up when I got to pull off the road finally).

I find it interesting that Toyota is at least making people aware of the issue (and causing a huge panic with it)when this is clearly something that happened to an American Auto maker and never received media attention like the Toyota problem has.

By the way, since the dealer fix on the company car didn't solve the issue, I believe the company 'got rid' of that vehicle. Wonder where it is now........

Interesting article,

"Elkhart, Ind.-based CTS Corp., which made the parts, is cranking out redesigned gas pedal assemblies that fix the problem, which is caused by condensation around an arm attached to the pedal and springs that send the pedal back to the idle position."

http://www.manufacturing.net/article.aspx?id=238548

Andy


And another:

http://www.manufacturing.net/article.aspx?id=238470

gas said:

There may be a problem with either a stuck pedal or a software issue but drivers are either uninformed or just stupid as that cop in California. All you have to do is take it out of gear.

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That's fine if you are on the highway, but a few months ago someone was pulling into an ATM when the accelerator stuck, and in just a couple of seconds she had veered out of control and pinned someone against a wall. In a perfect world we all should be able to think quick enough, but in the real world we sort of expect the car to start coasting when we take our foot off the gas.

Heck, I've driven over 30 years without an accident, but I'm not sure what I would do if the car acted flaky in the middle of a parking lot.

thiem said:

I find it interesting that Toyota is at least making people aware of the issue (and causing a huge panic with it)when this is clearly something that happened to an American Auto maker and never received media attention like the Toyota problem has.

Click to expand...

Actually, Toyota has managed to keep their recalls "under the radar" for years. And I've been told that a couple of years ago they had more cars recalled that year than they made that year, but I'm not going to do the math to figure it out.

What I can do is to direct you to: http://www-odi.nhtsa.dot.gov/downloads/ where you can download "FLAT_RCL.zip" for yourself.

I didn't look too far into the file, I didn't need to. I came up with problems that could lead to wheels falling off, airbags deploying in such a way that the steering wheel cover comes off and strikes the driver, the parking lock on the transmission breaking allowing the car to roll away, under hood fire risks, and rollover fire risks.

So, you (and others) might be correct in that a few cars running away with their owners is just a tempest in a teapot. But then how would one explain away the lack of press on the issues that I listed? Odd...

As for American manufacturers not getting the attention that they deserve, when Saturn received defective antifreeze from Texaco which caused water pumps to go out at a much higher rate than normal, we "bought back" over 1800 cars, and gave the owners loaner cars to drive while we built new ones for them.

Those 1800+ cars were never resold, they were parked onsite for years until the decision was made to shred each and every one of them.

In both of these cases the manufacturers (Toyota and Saturn) received bad parts from their suppliers, so it isn't fair to place all of the blame on the manufacturer. Actually, it happens to every manufacturer at some point.


And just to present both sides of the Saturn experience, not all of Saturn's recalls were positive. The Vue's CVT transmission was a piece of junk and we knew it from the beginning.

However, by then GM had borg'ed us and they were calling all of the shots. They stubbornly insisted on continuing to use the CVT despite overwhelming evidence that it was a load of ****.

The story at the time was that the test drivers at Milford would draw straws to see who was going to have to test the Vue with the CVT in it, and send the loser off with a radio so that they could call for help when it broke down. Early on in the development cycle this was usually around the 50 mile mark or so.

In the regular consumer forum, I'm in the weird position of defending Toyota against all the allgation of "electronic module" problem where I usually tell people about the good quality car US Maker vs foreign makers....sigh...

I would say that a brake overide is a good design practice, what i can't stand is all these talk about phantom in the "kumputer" rumor.

I find the terminology used to describe the problem to be misleading. I've seen the phenomenon called "sudden acceleration". To me, that implies the gas pedal being depressed by something other than the driver's foot. Either that or the engine is being commanded to run at a speed faster than would be expected based on the position of the pedal

Toyota appears to be claiming that the problem is the failure of the pedal to retract when the driver's foot is removed. Does anyone know for sure what the true circumstances are?

That's the funny thing, Steve. I'm not 100% convinced that Toyota is sure what the problem is. The plan appears to be to change accelerator pedal assemblies so I have to suspect that they believe something is failing during/after a push and the pedal is either not coming back up or is disconnecting from the pedal position sensor.

I thnk the thing to keep in mind is that these analyses are being performed by a group of engineers under incredible time pressure. This isn't like an NTSB evaluation that can drag out for a year and every conceivable possibility is examined, tsted and either accepted or rejected. The Toyota brass wants these guys to figure out what is going on and they want an answer yesterday. The pedal fix is coming from the same guys who swore up and down that floormat anchors would correct the exact same symptom.

As engineers they can only work off the information given to them. They are generally unable to recreate the circumstances of the problem. So they need to determine causes in the order of most to least reasonable, just like the rest of us. However, that doesn't mean the evaluation is right. It just means it is the next most reasonable.

Keith

kamenges said:

That's the funny thing, Steve. I'm not 100% convinced that Toyota is sure what the problem is.
Keith

Click to expand...

This article seems to confirm Keith's thinking

http://www.designnews.com/article/446480-Toyota_s_Problem_Was_Unforeseeable.php?nid=4871&rid=1654365

ABC News just reported that the problem now looks related to electronics/software.

My thoughts:

Drive by wire is always a bad idea.

I worked in a plant that put drive by wire steering on some tow vehicles to make them easier to turn, thereby reducing sprains and strains. Sure they were easier to turn, and made for less work on the drivers, but more work for facilities maintenance fixing holes in block walls, and repairing the trucks...One broken coupler or wire and the truck steering would go in a random direction.

What do they gain by drive by wire throttle? Simplified cruise controls? Fewer (cheaper) parts in the throttle linkage? I bet they wish they stuck with the good old fashioned cable and spring returns on the both pedals and throttle plates now.