The aim of the present paper is that of building a mathematical model of a two wheeled vehicle which can be used to assess the driveability even in the early design stages. The simplified theoretical formulation requires a limited number of data and allows the user to consider many possible design choices. The vehicle and the tyres are assumed to be rigid and the tyre-road contact zone reduces to a single point. A total number of 4 degrees of freedom is sufficient to study the directional behaviour of the vehicle. Due to the complexity of the equations of motion so obtained, the model is linearized about the equilibrium position. This is also consistent with the main aim of investigating the how much demanding for the driver is the task of achieving sufficient stability. The model of the vehicle is coupled with a linear model of driver, whose parameters are obtained by imposing predetermined manoeuvres. This does not allow the simulation of the behaviour of any actual driver, but generates a control system which achieves the required stability. The integration in time of the model generates a time history of the control parameters (mainly of the torque exerted by the driver on the handlebar) from which comparative assessments on the driveability are readily drawn.
Abstract