When and why does embedded Electronic Control Unit(ECU) use default calibration values?

[jani12]

Typical embedded ECU stores real calibration values and default calibration values in Non-Volatile Memory(NVM).

Let's say ECU is Steering Controller and it's primary function is Lane Keep Assist(LKA). It is mounted in a commercial truck. It programs camera's real and default calibration values in NVM.

Mostly, real calibration values are used. When and why are default calibration values used?

 

[Nigel Goodwin]

Fairly obviously, when it's first powered up - as is clear from 'default'. If something happens that trashes the current settings, I'd like to assume that the defaults are restored to regain operation.

 

[Pommie]

I'm guessing there is some kind of learning algorithm that gradually improves the system. If the "latest" values are lost then start again with the default (start) values.

Mike.

 

[KeepItSimpleStupid]

In the case of an engine ECU, you need default values in case a sensor is bad. An oxygen sensor needs time to warm up, so it needs a value to keep the car running. The car runs in a "open loop" condition typically a certain engine temperature is reached.

Some information can be gotten from the "drive cycle". https://epa.ohio.gov/Portals/27/echeck/docs/OBDReadinessDriveCycles.pdf
This is part of the tuning process.

A crank position sensor failure, you can't not have. You can approximate a MAF, a Mass Air Flow sensor. I had a case where the sensor was bad, but the car would not continue running. It did, when the connector was pulled.

 

[DrDoggy2]

i had a 2019 with LKA, atuo pilot works great until there was oncomeing traffic, then it would drift in to the other lane and disengage to manual control, I also enjoyed how it would lock up the breaks and jerk me around if i didn't squeeze the steering wheel tight enough.