Abstract
Keywords: cylinder pressure, load torque, engine speed
The limit values for combustion engine exhaust are steadily reduced by the legislator while the customer preference tends to an increased driving dynamics. These conflictive requirements force the car industry to design innovative strategies according the function and control of cars in particular the combustion engines. Besides of the reduction of car weight and an improved aerodynamic, constructive modifications to the power train in particular advanced combustion processes lead to the fulfilment of the conflictive requirements. The implementation of novel combustion processes calls for the acquisition of courses of thermodynamic state values with reference to the burned gas, e.g. the combustion pressure. Apart from a few exceptions the indication measurement technology is currently used only for scientific applications. Factors like the insufficient long-term stability of the pressure sensors, the extra required engine indicator access hole and the expensive sensor acquisition costs actually prevent the application of intrusive pressure sensors in common production engines. Thus new approaches were developed to model the in cylinder pressure or the engine torque based on common sensor signals. In 1991 Fehrenbach used the measured engine rotational speed of a single cylinder diesel engine to model the course of the in cylinder pressure, see (Fehrenbach, 1991). Afterwards new approaches were investigated to model the courses of the in cylinder pressure or the engine torque using multi-cylinder engines, see (Henn, 1995), (Gyan et al., 2000), (Eriksson et al., 2002) and (Zeng et al., 2004). All these approaches are based on the knowledge of the engine load torque. In fact the engine load torque is not a measurement in common production cars. Thus other approaches were investigated to obtain the engine load torque based on the measured engine rotational speed, see (Rizzoni et al., 1995), (Fam et al., 2004), (Isermann et al., 2000), (Lee et al., 2001) and (Isermann et al., 2002). Within this paper two novel approaches were presented. The first presented approach models the engine- and load torque based on the measured engine rotational speed considering the dynamics caused by the dual-weighted flywheel. The second approach determines the pressure inside the firing cylinder based on the torque estimation of the first approach.