Quote:
Originally Posted by Calum
Tuning gain is great, but a system like this would require the ability to correct offset as well. Otherwise the system could settle out at the wrong boost pressure and as long as the error signal (feedback compared to setpoint) is steady then the system wouldn't correct for it.
I've calibrated and rebuilt more then my fair share of pneumatic controllers that can do this, but I have no idea how to do it in the digital world. Basically for this to work well a controller that can do both proportional and integral adjustment is what to look for. A full PID wouldn't be required though, I don't think.
Or am I an idiot and that's already in the code above?
Also, I really think we need to get past the idea of boosting to the back of a partially closed throttle. That's inefficient and with a setup like this shouldn't be required. If BRZ edit could be used to remap the throttle plate vs. pedal maps, then you could just set WOT to something lower in the pedals travel range then 100% and then use the rest of the pedal's travel to increase boost pressure to a max.
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The code above, as over-simplified as it is, will not settle outside of the target unless the target is unreachable due to a hardware limitation. It's pretty simple, basically says "keep increasing motor speed by x until map == target boost, them quit, if map >= target boost, reduce motor speed by x". Rinse and repeat. Again very simplified and not representative of a full implementation, but that's the idea, and it works well enough to control head speed to within 1 or 2 rpm @ 3k rpm.
Certainly there are improvements to be made, just advocating the general idea of using a boost target and a feedback loop.