How to stop a runaway Prius

All Toyota hybrid cars have the override. It was easy to include, due to the electronic controls used in HSD.

Toyota will be adding override to other cars in the future; all Prius already have them.

Mechanical systems are more prone to failure than electronic systems. Why would you want to use a system more likely to fail?

Tom

 

Mechanical systems being more prone to failure is a general, nearly meaningless statement. The reliability of systems varies based on circumstances. The number and simplicity of components are major factors in reliability of systems, such as override systems. Electronic systems often are more complicated, have more parts and can be more prone to fail in different situations.

A simple mechanical system, such as over-engineered piece(s) of metal that go from the brake pedal or pedal housing to a gas or acceleration shut off, could override electronic systems and be more reliable in a greater number of situations.

Electronics are much harder to diagnose. Apparently, there still is no definitive proof that there isn't some flaw in the Prius electronics that causes the car to sometimes unintentionally accelerate. If it was a mechanical system, it would be much easier to say with certainty that this isn't happening.

I'm not suggesting getting rid of the electronics, but rather using mechanical safety systems to override electronic systems when this is the safest, simplest and most reliable option.

 

You are right. My Prius is susceptible to fail in the event of airburst nuclear device! But then so is every car using an EFI or Electronic ignition system.

How many miles do we as a forum family have on our Prii? Millions upon millions perhaps? The errors and failures for those total miles are very small.


and yes you could say my post is meaningless too. But I trust Toyota and have since my first one in 1972. I trust my Prius enough to let my wife drive hers daily without fear.

 

The main lack of redundancy is still the wetware.... When are they going to require a co-pilot and a second set of controls? We already have more braking systems than other cars out there.... regen and friction. Still fed from one brake pedal though, and controlled by one human.

 

If you understood how the Prius drivetrain works, you would know that even if the gasoline engine is stuck in acceleration mode, you can still come to a stop by engaging the front disc brakes, and it will be a PERMANANT stop, i.e. the car will NOT be able to move again unless you get the transaxle replaced.

Fully engaging the friction brakes while the gasoline engine is running wild will destroy the Prius transaxle.

The MECHANICAL design of the planetary gearset ensures this will happen in the event of a runaway gasoline engine in the Prius, if the brakes are functional.

How? Look at the Prius Power Split Device Transaxle simulator: Toyota Prius - Power Split Device

If you hold the MG2/outer ring gear/drive wheels to 0 RPMs using the friction brakes while revving the gasoline engine up to its maximum 4500 RPM (to simulate a runaway gas engine), the gear ratio of the planetary gearset will result the center sun gear (MG1 electric motor) to rev up to 16,000 RPM-- That's 6,000 RPM past its safety limit. MG1 burns out from the overload, and the transaxle is destroyed. The car comes to a stop. PERMANENTLY.

So to have an unstoppable Prius, BOTH the HSD computer will have to be on the fritz (runaway gasoline engine), AND the front disc brakes would have to be totally non-functional.

 

I guess that would depend on the crisis....

The "shift" lever is right there on the dashboard of the G2. If you hold the steering wheel at the 2 o'clock position with your right hand, you can just extend your fingers and almost touch the shift lever without taking your hand off of the steering wheel. You can actually just grab it by feel once you familiarize your right hand with its position on the dashboard. Just push it straight "left", hold it for a split second, and you are in neutral.

And the "gear" indicator is right on the LED display at eye level, making it easy to immediately know what "gear" you are in. I don't see how it could get any easier. But that's just me, I guess.

With most "normal" cars with automatic transmission shift levers on the steering wheel, you would have to look at the shift lever (and steady your hand movement) to make certain that you didn't unintentionally throw the car in Park or Reverse when trying to find Neutral (which could literally destroy an automatic transmission if the car is travelling at speed). To me the Prius shift lever is a model of simplicity.

Just like any car, if you put the Prius into Neutral, you disconnect the "motive" power from the drive wheels (via a different means with the Prius, but the effect is the same). So putting the Prius in Neutral would keep power to the brakes and steering active.

And just like a "normal" car, if you turn the power off, the power is off. No motive power, no power brakes, no power steering.

Since you would have to actually "hold" the Power button for 3 seconds to get the Prius to turn "off", it would be better for you to learn how to hold the shift lever in Neutral for a split second to get the car to go into Neutral. And then you would keep your brakes and power steering.

Or you could use the "Park" button method as others have stated. Just don't do it at slow speeds, or the parking pawl may engage and lock up the drive wheels.

Best wishes,

 

Tom:

I propose that Toyota provide provide a large, red "In the event of emergency button" on the dashboard that is covered by a clear, hinged cover.

When the cover is flipped open and the button is pressed, all 20 something ECUs (with maybe the exception of the Skid Control unit) would immediately blow up, rendering the car inoperable.

This could be called the "Ultimate Override Button" (or "UOB"). That should take care of it.

 

so does TOYOTA get to sue SIKES if all his claims are FOS?

 

If Toyota chooses not to sue, then I hope every newspaper runs a banner headline on the front page, and every TV news program runs a lead story that Sikes has been charged with fraud. I say "charged" because getting a conviction could take years, if at all.

Oh well, I also believe in the Tooth Fairy, Easter Bunny, etc.

 

I like this idea. It wouldn't take much of a charge, just a small squib in each ECU, and perhaps two in each MG for safety. Flip the cover, press the button three times, BLAMO, the car coasts to a stop in a cloud of smoke.

It's a good plan. Let's try to sell it to Toyota.

Tom

 

I agree with your first paragraph. The reliability of any system is highly dependent on complexity and circumstances. I was considering an apples to apples comparison, where the mechanical system and electronic system are being used to accomplish the same function. In this apples to apples comparison, a properly designed electronic system is almost always more reliable than a properly designed mechanical system.

Obviously you can poorly design any system, be it mechanical or electronic. Likewise you can take something like a kill switch and compare it to the Space Shuttle guidance system and correctly point out that the mechanical kill switch is more reliable. It's hard to argue with that point. However, if you try to replace the Space Shuttle guidance system with a mechanical computer the results are much different.

I think this is problem with your argument. You envision a very simple mechanical device to replace the "complex" electronic override on the Prius. Exactly how would this simple mechanical override work? Would it kill all power any time you step on the brake, or would it have to couple with the gas pedal? What if you press both just a little bit? Exactly how does it kill power? How does it reset after being triggered? Can it be reset under way after an accidental trigger? How do you make sure it hasn't rusted into place from lack of use?

The trouble is that it is very easy to envision a "simple" mechanical override, but in reality, any acceptable working system would not be all that simple. But just for the sake of argument, let's say a simple solution is all that is really required. In that case we can use a very simple piece of dedicated electronic hardware to do the job and get rid of all of the moving parts of the mechanical system. If it is simple in one modality it can be simple in the other.

I wouldn't be against a simple kill switch. That would be simple, which would in turn make it reliable. It's the same reason all of my bench power tools have big red power buttons.

Tom

 

...which is every car sold in California since the introduction of mandatory on-board diagnostics in 1994, in the USA since 1996, and in Europe since 2001. Bosch introduced LH-Jetronic, the first digitally-controlled fuel injection system, in 1982.

If there were general electromagnetic interference issues with the engine management computers of all these cars, we would have known about it by now. I simply do not believe that Toyota could have been unaware of the problem and not done something about it.

Hobbit has documented a case where his own additional electronic instrumentation went screwy in a large electromagnetic field (search for 'Buffalo Bill'). The car itself was absolutely fine.

 

I heard that there is an after market device that you can put in the back of the car that releases an anchor and a parachute to slow the car down.

Seriously, though I think even if you had failure of the front brake, the mechanical parking brake would stop the car even if it were at max rpm.

 

I of course was talking about apples to apples comparisons. You tried to weaken my argument by implying that I was suggesting comparing the space shuttle to a kill switch.

Everything I said is true when applied in apples to apples situations. The most effective option depends on circumstances. Sometimes mechanical systems will be the most reliable and inexpensive. Sometimes electronic systems will be the best option.

You mentioned problems with mechanical systems. All of them, such as rust, can be easily overcome (ie: don't use parts that rust). Electronic systems have their own problems. For example, they can lose power and become non-functional. Mechanical systems often don't need electricity.

This is a hypothetical conversation. There is no right answer, without focusing on a specific situation. I said that mechanical systems "SOMETIMES" are the best option. That is a non-debatable point. It is impossible to prove this point wrong, if you wish to remain within the realm of logic.

A main point that I was making is that it is much harder to diagnose whether unintended acceleration is happening in the Prius because of the complex electronics. A mechanical system often would be easier to diagnose.

Again, this is not to suggest that electronics should not be used. But rather that in SOME cases, a mechanical override to an electronic system MAY be the least complex, most reliable and most effective option.

 

I can just imagine a scene from the future. The year is AD 2310.

Father> The robots are malfunctioning. Quick hit the Sikes switch.

Son> Yeah that stopped them.
Son> Dad, why do they call it the Sikes switch?

Father> Hmmm, that's a good one. I don't really know, that's just what we've always called it.

 

Agreed. In a similar vein, the point I am making is that many uninformed people equate primitive systems with reliable systems. Just because a system is simple and easy to understand does not necessarily mean that it is reliable. We need to look no further than the humble carburetor to see a good example of this. The simple float carburetor works and requires no electricity, but is much more prone to fouling and failure than the much more complicated fuel injection systems.

Simple systems are great when you need to be able to repair them in the field with bailing wire and tape, but that doesn't mean they are always the best choice for high reliability.

As you said in your last post, it all comes down to the requirements of a particular problem.

Tom

 

I agree that complex electronic systems can be more reliable. I love my Prius for example, and it's got to be one of the most complex cars in the world.

My concern probably has to do with faith. I feel a little uncomfortable trusting the safety of my family and myself to a complex system that I do not understand.

For example, many people are saying that there is nothing wrong with the Prius acceleration. But because of the complex electronics, it's difficult to trust this 100 percent.

Personally, I'd feel more comfortable if there was some simple mechanical system that would stop the car no matter what when I slam on the brakes. Weird things can happen to electronics.

But I am not an engineer. So this may be irrational, non-expert fear on my part. I suppose in this world of high technology, we must just go along for the ride sometimes. Otherwise, we'd probably never leave our homes. Even then, there probably are some dangerous electronics lurking within...

 

Sure can't argue with that point. The folks who used a horse and buggy never blamed the buggy for leaving them stranded. They knew where to place the blame.

 

Presumably, they'd blame the buggy if the wheel fell off. But that's irrelevant. You're implying that I was suggesting that functionality should be traded off for simplicity or safety. But that is not what I said. As someone else mentioned, we were discussing apples to apples comparisons, meaning that there is no loss of functionality.

All I was saying is that mechanical systems can provide equivalent functionality and greater reliability in some situations.