RM0020 datasheet(33/69 Pages) STMICROELECTRONICS

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RM0020

Function API

33/69

Arguments:

Description:

Pressure sensing function 1. The function is used for in-cylinder pressure sensor

management. For each cylinder and every engine revolution, there is calculated the

mass fraction burned function (MFB), MFB50 value and PMH torque index. As inputs

there are used vector of in-cylinder pressure values P_MFB, vector of cylinder volume

values V, and constant K. The function returns the MFB50 value, mass fraction

burned function (MFB) is returned in P_MFB vector and PMH index in a variable

addresses by PMH pointer.

Algorithm:

Calculation of MFB and MFB50 value:

Aquisition of in-cylinder pressure at any sampling position

[i] (aquisition window

ranges from -180

 before TDC to 180 after TDC): P[0] P[1] ... P[N-1]

Calculation of cylinder volume V[i] at any sampling position

[i], V[i] can be

precalculated and stored in a calibration vector: V[0] V[1] ... V[N-1]

Calculation of heat release rate (QIST), (supposed delta

 is constant e.g. 0,5), for

each i = 1,2 ... N-2:

Equation 29

Note: The function calculates the heat release rate without multiplication with constant

in both QV and QP equations.

Calculation of mass fraction burned MFB (integration of heat release rate), initial

condition is MFB[1] = 0, then for each i = 2,3...N-2:

Equation 30

Note: The function calculates the mass fraction burned without multiplication with constant

Table 15.

mfb50_pmh arguments

Nin

length of pressure vector P_MFB and volume vector V, N-2 must be

multiple of 8, N must be greater than or equal to 18

P_MFB(1)

Both pressure and volume vector must be double word aligned.

in/out

pointer to the input pressure vector of length N, input memory layout

is P(0) P(1) ... P(N-1), output memory layout is MFB(1) MFB(2) ...

MFB(N-2) MFB(N-1) 0

V(1)

pointer to the input volume vector of length N, memory layout is V(0)

V(1) ... V(N-1)

constant related to engine setup

PMH

out

pointer to variable where PMH index is returned

K P i

 Vi 1

–



–

 2







----------------------------------------------



V i

 Pi 1

–



–

 2







----------------------------------------------



QIST i



–

 2







-------------------------------------

MFB i



MFB i

–



QIST i

 QIST i 1

–









------







------

RM0020 Datasheet(PDF) 33 Page - STMicroelectronics

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