Introduction

The behaviour of the creep forces between a air-filled rubber tire and ground is more complex than the creep forces between wheel and rail. The behaviour of a rubber tire is different than a steel tire. A road vehicle can steer freely, it doesn't need to follow a certain track. A wheel made of steel is very stiff in all directions. In an air-filled rubber tire, the flexibility in the rubber walls must be taken into account.
The properties of a rubber tire can measured in a test rig, and the data can be used as input data to the Magic Formula tire models

• List the contents of the tar-file with: tar -tvzk --file=road_vehicle_4.tgz
• Extract the contents of the tar-file with: tar -xvzk --file=road_vehicle_4.tgz

Input data model

The model describes a car-body standing on 4 wheels.
The 4 wheels are connected to the car-body via four springs: spring1l, spring1r, spring2l and spring2r.
In parallel with the springs there are four dampers: damper1l, damper1r, damper2l and damper2r.
The tires are connected to ground with the four couplings: whe_grd_1l, whe_grd_2l, whe_grd_1r and whe_grd_2r.

Test example 1: Constant yaw torque on the two leading wheels

The yaw torque on the leading wheels, makes the vehicle to run in circles.
Friction loss in the couplings between tire and ground, makes the vehicle speed gradually lower and lower.

• Example: runf/car_Vo15_left.06.tsimf
Initial speed of the vehicle is 15[m/s].
Applied yaw torque gives the leading tires an angle of attack of 0.060[Rad].
The yaw torque is applied as a prestress torque on the two springs spring1l and spring1r.

Inspect the results in program Mplot.
Animate the results in program Glplot.

Test example 2: Leading wheels steers in a sinusoidal motion

The steering motion is creates by adding a yaw torque as a prestress force between car and the two leading tires. The frequency of the steering torque is varied from 0.10[Hz] up to 2.0[Hz].

• runf/car_Vo15_ampl.10_sin_0.10.tsimf
Initial speed of the vehicle Vo= 15 [m/s].
Steering frequency yaw_freq= 0.10 [Hz].
• runf/car_Vo15_ampl.10_sin_0.50.tsimf
Initial speed of the vehicle Vo= 15 [m/s].
Steering frequency yaw_freq= 0.50 [Hz].
• runf/car_Vo15_ampl.10_sin_2.00.tsimf
Initial speed of the vehicle Vo= 15 [m/s].
Steering frequency yaw_freq= 2.00 [Hz].