Exactly.

Now throw in heavy highway or even worse city traffic.

It's easy to say what we'd do sitting at our keyboard.

They should have -always- had one.

34 Americans are dead because they didn't.

I don't mean to be insensitive, as I know what it's like to lose someone to an accident. Still, 40,000 people die every year on America's roads and I am quite sure you can attribute many more than 34 of these to identical causes.

The Toyota problem needs to be fixed but the media needs to put the story into perspective. In other words, they need to STFU and quit pandering to people that seem to enjoy reading the sensationalist crap they put out.

JR

There is no mechanical neutral. In both the manual and automatic transmissions, the gear selector can mechanically separate the engine from the wheels. That does not exist on the Prius

http://forums.pelicanparts.com/uploa...1268182976.gif

What you see in the car is in fact another electronic input device made to look like a mechanical system.

Since the brakes and the gas pedal and the transmission selector and the on/off switch are just computer inputs, it does not surprise me that we can have a failure like this. And the final point, the only thing that slowed the car down, was application of a MECHANICAL emergancy brake.

You're saying that a Prius doesn't have hydraulic brakes, actuated by a brake pedal, at either corner?

JR

I don't think that would be legal. My understanding is that cars with electric brakes (like Mercedes' SBC system) have to have a backup hydraulic system - you can't have a pure electric, non-mechanical braking system.

34 isn't a lot until it's your wife, or your sister, or your mother, or your daughter.

I understand what you're saying, statistically speaking you're correct. But dead loved ones are not a statistic when it's your (or my) dead loved ones.

Early F-16A's had the same sorts of problems with their FBW systems and there was a big media witch hunt, and it turned out that the USAF had also tried to cover up a known wire chaffing issue to get the plane into production.

There were fatalities, inquiries, 60 minutes stories and a made for TV movie over it.

But know what? It made the USAF actually admit and fix the problem. So sometimes a witch hunt can serve a very useful purpose.

If I had a Toyota (I wouldn't, EVER), I would still drive it, as I am pretty confident I could get it under control.

However, I would not let my wife drive it.

There's gotta be some karma and irony that that cars made for non-car people are killing and injuring those same people because they don't have the presence of mind to stop the crappy appliance when it decided to try to kill them.

Also, I am finding it quite hard to believe that Toyota is in denial that that its electronics are not to blame. Remember when Dell's were catching on fire? Was a floormat causing that?

That is precisely what I'm saying. The brakes are not connected to the pedal. They go through the computer. The brake pedal is connected to a pressure sensor.

That's an unbelievably unsafe design idea.

How does that even go into production?

I think many young designers do not understand the risks inherent with a computer mediating your interactions with machines. It is not a question of programming fail safe modes but ensure there are ways to bypass the controls if you need to shut down right now.

Look at any hazardous industry that uses automated controls. They all include hard wired systems to force a shutdown (emergency machine off - EMO function) if the controls fail. At some point, you need a direct physical means to make something stop.

At least the hand brake doesn't go through the computer.

EXACTLY!

You need an emergency IMMEDIATE cutoff on ANY machine that has the potential to cause serious injury.

That's next- along with the steering.

Prius braking system:

http://www.techno-fandom.org/~hobbit...BPP-system.gif

"In normal use, the hydraulic lines from the master brake cylinder go only to a 'stroke simulator' - a piston that permits the brake pedal to move and provides braking feel. The master cylinder pressure sensors, PMC1 and PMC2, measure the driver's braking pressure. SMC1 and SMC2 are closed, so for the moment ignore the lines leading from there to the wheel cylinders.

The Skid Control ECU takes those sensor values and computes how much braking force to apply to each wheel. It asks the HV ECU to provide as much of the braking force to the front wheels as possible through regeneration, and the HV ECU reports back how much it achieved (this is done via CAN). The Skid Control ECU then distributes the remaining braking force required across the friction brakes, turning on the SLAxx solenoid valve for each wheel to Apply the brake further (increase pressure) and the SLRxx valve to Release the brake (decrease pressure). For example, SLAFL and SLRFL control the Front Left wheel and SLARR and SLRRR control the Rear Right. It monitors the pressure achieved with each wheel's Pxx sensor (PFL, PFR, PRL, PRR).

Pressure changes are achieved by having a chamber (accumulator) that stores fluid at high pressure. When an Apply valve is opened, the high pressure fluid flows to the lower-pressure wheel cylinder, applying the brake. The Accumulator Pressure Sensor (PACC) measures the pressure in the cylinder so the ECU can decide when to run the pump motor, to keep the accumulator pressurised.

The reason that hydraulics are used in the sensing side is so that in fail-safe conditions, the master cylinder is connected to some wheel cylinders, operating them directly from pedal force. "

From the prius service manual:

"From the service manual:

2. FAIL-SAFE FUNCTION OF HYDRAULIC SYSTEM
(a) If a malfunction is detected in the brake booster with master cylinder (skid control ECU or brake actuator) or an individual sensor, control will be stopped and brake effort will be generated by the brake booster with master cylinder (hydraulic brake booster).

(b) If brake control is stopped due to a malfunction in the hydraulic pressure source, the pressure generated in the master cylinder by the driver is applied to the wheel cylinders to ensure braking force."

And when the computer doesnt realize it should cede control?

Then what?

That is exactly the issue happening. There is no "fault" being reported in the braking system so the computer doesn't go into "fail safe" mode.

My solution for this would be to have the brake pedal go straight to the master cylinder then put a pressure sensor on the back of the MC that engages regenerative braking. The actual force of the calipers can still be manually regulated by the operator and prevents said issues of the braking system failing to engage by computer control.

As for e-gas... WORST IDEA EVER! I can understand the desire for the engine to not over-rev, throttle to transition smoothly and prevent manual rapid acceleration but taking the stop and go control away from the driver leaves too much more to go wrong.