Development of Prototypal Engine Management System for a Vvt Engine
Published May 23, 2004 by Society of Automotive Engineers of Korea in South Korea
The modern automotive requirements are very stringent in particular in terms of emissions (in order to guarantee the respect to emissions legislation) and fuel consumption. Sometimes in order to satisfy these hard requirements, mechanical modifications must be introduced. The EVO Engine is a traditional speed density engine with a Variable Valve Timing (VVT) system. This system has the capability to vary the valve timing and so the percentage of Exhaust Gas Recirculation (EGR), in order to maximize the performance or to minimize the fuel consumption. In a torque-based architecture, from the control point of view, the presence of VVT introduces a further degree of freedom for the torque actuation. The introduction of VVT has an impact on a lot of parts of control. The greatest influence is on air mass flow estimation (direct and inverse model), spark advance calculation and torque estimation.
The air mass flow estimated (in function of manifold pressure, engine speed, temperatures and ambient pressure) must be corrected to take into account the current EGR.
The spark advance calculation must be modified to introduce the dependence on the VVT position: a greater EGR amount makes the combustion slower.
A different VVT position modifies the pumping torque and so the torque losses.
So it has been necessary to introduce heavy modifications on Engine Control Unit to manage efficiently the capability coming from the presence of this component. In order to validate the control solutions directly on the system a prototypal control has been implemented with the bypass techniques. So starting from the normal production ECU a functional bypass has been implemented for the interested parts of control on a Rapid Control Prototyping system.
The prototypal control has been validated first in a PC simulation with the engine model (Software In the Loop), then with the ECU hardware on the EVO 2 engine model (Hardware In the Loop) and finally on the engine in an engine test-bench.
The results of the validation phases that demonstrate the effectiveness of the designed control are presented.