[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Race condition...

On 19 Mar 2010, at 17:55, Tony Gore wrote:

Not on this one, but the original Toyota accelerator problem does appear to have been a poor piece of software. It is normal when writing an engine controller to take account of other inputs. Thus, if the brake is pressed (in my days, detected by the same switch that puts the brake light on) then you cut the fuel injection down to a small level to sustain combustion and keep the engine ticking over and this also helps keep emissions down.
This makes the brake light switch into a safety-critical component!

In the case of Toyota, they do not appear to have done this, or if they have, the conflict between the signals has been mismanaged. This is why the engine can have full throttle and is not overridden by the brake. Modern engines (especially in US cars) are more powerful than the brakes, and this is why people are finding it impossible to stop the car in some circumstances.

Is it not the case that the accelerator pedal is now used as a "speed control", telling the fuel management system the acceleration the driver wants?
If so, the software will simply ramp up the power when the brake is applied, assuming it is unaware (or takes no account) of that.

Can it really be that simple?


Ian East
Open Channel Publishing Ltd.
(Reg. in England, Company Number 6818450)