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This is correct, though some scanners, such as the one I use, report the data as sht term fu tr and lg term ft. so its good to know both. thanks for the clarification.,On TBIs it's INT (short term) and BLM (long term)
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This is correct, though some scanners, such as the one I use, report the data as sht term fu tr and lg term ft. so its good to know both. thanks for the clarification.,On TBIs it's INT (short term) and BLM (long term)
the system is continually attempting to achieve stoicometric efficiency within the parameters that the engine is operating in., the parameters change constantly due the barometric pressure changes , fuel octane, load, humidity , driving habits,, yes driving habits,,, more on this later... ect.. think of it as an adaptive learning system. The O2 sensor oscillates very rapidly on these trucks, as combustion gasses pass by it. its not sniffing anything, it is reactive to temperture changes. it is basically a thermistor that changes resistance with changes in temperture. these variations in resistance are continually sent to the ECM and the ECM makes adjustment to the timing and injector pulse width once the truck goes into closed loop. a truck that idles fine for a while then starts surging is usually in a "confused" state.. many times when a truck senses a lean condition, this looping surge will manifest... the coolant temp sensor is signalling the ECM that the truck is warmed up but the O2 sensor sees a continuous lean condition.,,. so the ECM tries to make adjustments in the timing and fuel for a while. when it cannot bring the engine in to acceptable parameters, it defaults back to open loop base timing and fuel trims..I apologize if taking this down the geek rabbit hole - but you started it!
I know a bit about control systems - ie. things that use feedback of something to control something to a target. eg. missile targeting, cruise control, and I assume this feedback loop controlling the TBI AFR.
You're right about the source of the terminology. Control systems can be of different "order" which means they use more info from the feedback signal(s). You can control something just with the difference between target and actual. You can do better controlling something with the difference between target and actual + the rate of change. You could also incorporate the 2nd derivative for even better performance.
A first order control system uses the first derivative of the signal. In a control system, this means the system contains an integrator (essentially the math which does the derivative and determines the correction needed).
The BLM block learn multiplier is not familiar to me but a "block diagram" is used as term to describe a control system diagram/design. So I'd guess the BLM is the steady state error or offset correction needed for the various AFR control cells. For example, the steady state fuel requirements @ high RPM/cruising is larger than at idle. When control system changes cells it uses that steady state value as "center point" and then zeros in to target A/F - seems like by watching Int and if it rails tweaking the BLM center. All this is a guess but how I think about the system.
a bit technical but may be interesting https://www.electrical4u.com/first-order-control-system/
from that article:
In a closed-loop control system, the system has the ability to check how far the actual output deviates from the desired output (as the time approaches infinity, this difference is known as the steady state error). It passes this difference as feedback to the controller who controls the system. The controller will adjust its control of the system based on this feedback.
..... We have two types of systems, first-order system, and second-order system, which are representative of many physical systems.
The first order of the system is defined as the first derivative with respect to time and the second-order of the system is the second derivative with respect to time.
A first-order system is a system that has one integrator. As the number of orders increases, the number of integrators in a system also increases. Mathematically, it is the first derivative of a given function with respect to time.