This information is part of the Modelica Standard Library maintained by the Modelica Association.

This is a simple model of a ground vehicle, comprising the mass, the aerodynamic drag, the rolling resistance and the inclination resistance (caused by the road grade). For all particular resistances, significant variables can be either given by a parameter or input by a time-variable signal.

The vehicle can be driven at the rotational flange flangeR, e.g. by an electric motor and a gearbox. It is possible to use the vehicle as a passive trailer, leaving the rotational flange flangeR unconnected.

At the translational flange flangeT the vehicle can be coupled with another vehicle, e.g. as a trailer or to pull a trailer. It is possible to leave the translational flange flangeT unconnected.

The velocity v and the driven distance s of the vehicle are provided as variables; the vehicle can be initialized using these variables.

Mass and inertia

Both the translational vehicle mass and the rotational inertias (e.g. the wheels) are accelerated when the vehicle is accelerated. This nature is usually put into account for fundamental vehicle analyses done either in the rotational or translational domain, e.g. when analysing vehicle's driveline. Then, the vehicle mass m can be expressed as an additional equivalent inertia J_eq = m * R2 or vice versa rotational inertia J as an additional equivalent mass m_eq = J/R2, where R is the wheel radius. Since this model introduces rolling resistance and inclination resistance as well where just the vehicle mass plays a role, the approach of equivalent mass/inertia would lead to incorrect simulation results and shall therefore not be applied here.

Drag resistance

fDrag = Cd*rho*A*(v - vWind)^2/2

Wind velocity is measured in the same direction as velocity of flangeT. Wind velocity is either constant or prescribed by the input vWind.

Rolling resistance

fRoll = Cr*m*g*cos(alpha)

Rolling resistance coefficient Cr is either constant or prescribed by the input cr. Rolling resistance has a crossover from positive to negative velocity within [-vReg, vReg].

The inclination angle α is either constant or prescribed by the input inclination = tan(α). This corresponds to the road rise over running distance of 100 m which, in general, is written as a percentage. For example for a road rising by 10 m over 100 m the grade = 10 % and, thus, the parameter inclinationConstant = 0.1. Positive inclination means driving uphill, negative inclination means driving downhill, in case of positive vehicle velocity.

Inclination resistance

fGrav = m*g*sin(alpha)

With the inclination angle α described above.

m	Value: Type: Mass (kg) Description: Total mass of vehicle
g	Value: Modelica.Constants.g_n Type: Acceleration (m/s²) Description: Constant gravity acceleration
J	Value: Type: Inertia (kg·m²) Description: Total rotational inertia of drive train
R	Value: Type: Length (m) Description: Wheel radius
A	Value: Type: Area (m²) Description: Cross section of vehicle
Cd	Value: Type: Real Description: Drag resistance coefficient
rho	Value: 1.2 Type: Density (kg/m³) Description: Density of air
useWindInput	Value: false Type: Boolean Description: Enable signal input for wind velocity
vWindConstant	Value: 0 Type: Velocity (m/s) Description: Constant wind velocity
useCrInput	Value: false Type: Boolean Description: Enable signal input for Cr
CrConstant	Value: 0.015 Type: Real Description: Constant rolling resistance coefficient
vReg	Value: 1e-3 Type: Velocity (m/s) Description: Velocity for regularization around 0
useInclinationInput	Value: false Type: Boolean Description: Enable signal input for inclination
inclinationConstant	Value: 0 Type: Real Description: Constant inclination = tan(angle)