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ecu redundancies?

Discussion in 'Gen 2 Prius Main Forum' started by kenmac, May 22, 2004.

  1. kenmac

    kenmac New Member

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    Hi folks,
    As a person associated with computers I am familiar with their tendancies to do the unexpected, sometimes from a program bug and other times from external interferences. (e.g. RFI)
    I ask the following:
    The only direct physical control we have over the Prius is brakes and steering - do the important ECU systems have built in redundancies? - in other words some duplication of control to allow for failures.
    Hyperthetical:
    What happens if the ECU misreads the throttle input as "maximum" - can the car take off out of control?

    There is no way to turn off the system except at low speed - I believe the Power switch is inhibited at normal speeds .
    Does anyone here have the technical info re the computer/s design?

    Aircraft "fly-by-wire" systems have heavy redundancy built in, with most triplicated and some 5 times - extreme example of course.


    Regards,
    kenmac
     
    #1 kenmac, May 22, 2004
  2. KMO

    KMO Senior Member

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    I can only offer a few points.

    1) The brakes, which are electrically pumped, have a backup power store in the form of a capacitor pack in case the HV circuit fails.

    2) If the throttle input jammed, you could switch to Neutral. I suspect pressing the brake would also override the throttle input - they're both feeding into the same ECU (anyone want to try that?).

    3) The power button can be held down for a few seconds to force a shut-off (much like an ATX PC).
     
    #2 KMO, May 22, 2004
  3. kenmac

    kenmac New Member

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    Yes, the Power button can be pressed for >3 seconds to shutdown - assuming the problem computer is not part of the shutdown process of course - the program may have crashed!
    If the power off function is completely independant (e.g. hardware driven) all should be OK.
    Anyway, as they say " it may never happen".

    kenmac
     
    #3 kenmac, May 24, 2004
  4. assagor

    assagor New Member

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    i am sure there are redundency measures in the system, as anthing otherwise would be suicide for the car company. On the software point, sure there are bugs, but a system as important as the brake and throttle control is tested over and over again until there are NO bugs. Also, ECU's don't operate on a window's paltform :) so we can be relieved somewhat.
     
    #4 assagor, May 24, 2004
  5. Mike N

    Mike N New Member

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    If the system is forced to shutdown by a prolonged power button press, does the parking gear lockup engage like during a normal power off? That could be pretty catastrophic to lock the tranny at 50 MPH.
     
    #5 Mike N, May 24, 2004
  6. aarons12

    aarons12 New Member

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    oh my god? can you imagine?? you would have to pull over after every few hours and reboot the car!!??

    wonder how many other bad jokes can be made here...
     
    #6 aarons12, May 24, 2004
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