Page 85 - Automotive Engineering Powertrain Chassis System and Vehicle Body

Digital engine control systems CHAPTER 4.1

ROM
TABLES

CONTROLLER

TPS
IGNITION
MIXTURE
FUEL MIXTURE
MAP INJEC-
TION 3WCC
THROTTLE ENGINE
HEGO DP
EGR
VALVE
EGR
SIGNAL

Fig. 4.1-4 Engine control system using the speed–density method.

physical system is susceptible to changes with either for those variables. In the case of fuel control, the vari-
operating conditions (e.g., temperature) or with time ables being regulated are exhaust gas concentrations of
(aging or wear of components). HC, CO, and NO x . Although direct measurement of
In any closed-loop control system a measurement of these exhaust gases is not feasible in production auto-
the output variables is compared with the desired value mobiles, it is sufficient for fuel control purposes to

ROM ROM
LOOKUP TABLE LOOKUP TABLE
MAP MAP
T I MAP D A CONTROLLER MAP RPM N V
T I RPM

D A N V
DP EGR R E
ROM
LOOKUP TABLE
DP EGR R E

Fig. 4.1-5 Lookup table determination of d a , R E , and n v.

83