Transmission Models

The take-off manoeuvre of a vehicle was studied in Section 23.9 using a simple model where the inertia of both engine and vehicle were modelled as two flywheels connected to each other by a rigid shaft and a friction clutch. This model can be made more realistic by adding the torsional compliance of the shaft, of the joints and possibly the gear wheels, as well as the rotational inertia of the various elements of the driveline. A model of the whole driveline is thus obtained, with the engine and vehicle modelled as two flywheels located at its ends.

However, the engine shaft is itself a compliant system. Moreover, its pistonconnecting rod-crank systems should be modelled as systems with variable inertia in time. At the other end of the driveline, the dynamics of the transmission and the longitudinal dynamics of the vehicle are coupled by the tires, which are themselves compliant in torsion. The longitudinal compliance of the suspensions may affect the dynamics of the driveline and couples with the dynamics of the vehicle, which is in turn coupled with comfort dynamics.