This paper describes the development of a mathematical model which allows the simulation of the Internal Combustion Engine (ICE), the transmission and the vehicle dynamics of a motor vehicle equipped with a Continuously Variable Transmission (CVT) system. The aim of this work is to realize a simulation tool that is able to evaluate the performance and the operating conditions of the ICE, once it is installed on a given vehicle.
Since the simulation has to be run in real-time for Hardware In the Loop (HIL) applications, a zero-dimensional (filling and emptying) model is used for modeling the cylinder thermodynamics and the intake and exhaust manifolds. The combustion is modeled by means of single zone model, with the fuel burning rate described by Wiebe functions. The gas proprieties depend on temperature and chemical composition of the gas, which are evaluated at each crank-angle. An automatic procedure for identifying the unknown parameters of the model by using experimental data has also been developed. The experimental data needed for model identification are the crank-angle resolved in-cylinder pressure and the measurements performed during typical engine-dynamometer steady state tests: rotational speed, load, fuel consumption, Air Fuel Ratio (AFR)… The transmission and vehicle systems have also been modelled: both clutch and CVT models have been fully described through physically-based equations and geometric characteristics. The CVT model evaluates the gear ratio, once the engine speed and torque are known. The clutch model is able to describe, with a single model, both the situations of engaged and disengaged clutch. The vehicle is modeled as a body subject to the engine tractive force, aerodynamic force and the tires friction force, with an equivalent inertia that takes into account the vehicle mass and the inertia of the engine and transmission elements.
Finally, the model has been validated on the basis of experimental data.