A Constant radius event simulates a vehicle driving in a circular path.
The Constant radius event maintains a constant turn radius and varies the vehicle velocity
to produce increasing amounts of lateral acceleration. Steering and torque controllers
maintain the path and the speed of the vehicle through the event. A plot template is
available to plot the results. The Constant radius event is used to characterize the roll
and understeer characteristics of a vehicle.
The event at a steady state speed or at an increasing speed (and as a result, increasing
lateral acceleration). Figure 1.
The parameters available in the Constant Radius event are detailed in the following
table.
Parameter
Description
Units
Length unit selection (Model, m, ft).
Velocity unit selection (Model, m/s,
km/h, mph).
Acceleration unit selection (Model, m/s2, g’s).
Radius
The radius of the circle that the vehicle CG will follow during the constant
radius portion of the event.
Initial straight
Vehicle is driven straight this distance, to attain steady state.
Initial velocity
Initial vehicle velocity.
Final velocity
Final velocity desired in the simulation.
Initial lateral acceleration
Estimated initial lateral acceleration, calculated using the initial speed
and the turn radius.
Final lateral acceleration
Estimated final lateral acceleration, calculated using the initial speed and
the turn radius.
Turn direction
Direction the vehicle turns during the event (as seen by the driver).
Transient time
Time duration for which vehicle accelerates/decelerates after achieving
steady state.
Look ahead time
Look ahead time, used by the Driver feedforward steering model.
Time in circular track
The time spent in the circular track.
Prediction step size
Maximum step size, used by the Driver feedforward steering model.
Print interval
Time interval of data output to the plot file (.plt) and graphics file
(.h3d).
References
ISO +4138-2004 - Passenger cars — Steady-state circular driving behavior — Open-loop test
methods.
