Computer Model to Simulate the Vehicle Longitudinal Dynamics

Abstract

To determine the traction or braking performances of a motor vehicle or to know the dynamic behaviour and the stress level of the drivetrain parts, the study of the vehicle longitudinal dynamics is the first step to be done. Together with experimental research, the model based computer simulation represents one of the most important tools for the automotive specialist. The paper presents some models imagined and used by the authors to simulate the functioning of drivetrain subassemblies. The models were realized in Matlab-Simulink. The major design idea was to obtain sub-models that can be easily modified or included in new models. Other aim was to group the input data only in few blocks – for vehicle parameters, initial kinematics values, road conditions, driver actions (and control systems, if they exist). Assembling sub-models – for engine, clutch, synchromesh, gear, shaft, differential and wheel – was possible to study the dynamics of some vehicle types (car, 4WD SUV, tractorsemitrailer) in different travelling conditions: standing start, gear shifting, engine braking, travel on uneven road, tire friction variations. In addition, sub-models realised for actuation cylinder, solenoid or electronic control devices permitted to simulate the behaviour of vehicle having automated systems.