Toyota learns the tyranny of software complexity

A good column about Toyota’s acceleration mess. The author is a former electrical engineer at Ford, and discusses the complexity of the software that runs modern cars. He compares this problem with previous major recalls by other vendors. The comments to the post are good, too. Here’s an excerpt:

The system level error that Toyota made is not letting a brake signal override a throttle signal. I designed speed control systems at Ford, and everything was dependent on having a tap on the brake cancel any speed control function. A throttle-by-wire car like Toyota makes is almost free to add speed control, you just have to have a button to tell the ECU (engine control module) to hold speed and a brake signal,

and that is probably already sent to the module. So it was just software, a couple lines of typing, that means that once a car accelerates a brake input will send the throttle angle to zero. I have to assume that Toyota engineers talked themselves into thinking there are times when you want to hit the throttle and brake at the same time. Motorcycle racers do this to put torque loads on the frame so when they do let off the brake coming out of a corner, the bike is already “bent” by the chain loads and then handles more predictably. I can’t think of a reason a car needs to have brake and throttle on at the same time, but somebody must have dreamed it some sports-car-dork reason to not have the brake single cancel the throttle signal.

via Toyota learns the tyranny of software complexity – Anablog – Blog on EDN – 1700000170.

CNN  has an informative visit to a Toyota dealer, discussing how they are handling the repair. According to the mechanic they interview, every fix includes re-flashing the engine control software!  I have not seen that discussed elsewhere, and to me it’s a bigger deal than the mechanical fix. (Which as far as I can see is a kluge.)

By the way, the dealer says they have done 800 cars in the last ten days, and it’s a 45 minute repair. They are working long hours, so 80 cars per day, 16 hours per day….. 5 cars an hour… They need about 8 mechanics working JUST on this problem. I guess normal business at Toyota dealers is down the tubes, so they have the time.

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