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
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.
Turn direction
Direction the vehicle turns during the event (as seen by the driver).
Initial velocity
Initial vehicle velocity (meters/second).
Final velocity
Final velocity desired in the test (meters/second).
Time in circular track
The time spent in the circular track.
Initial lateral acc
Estimated initial lateral acceleration, calculated using the initial speed
and the turn radius.
Final lateral acc
Estimated final lateral acceleration, calculated using the initial speed and
the turn radius.
Look ahead time
Look ahead time, used by the driver model.
Prediction step size
Maximum step size that the solver can take, in seconds (if the number is .02,
maximum step size is .02 seconds).
Print interval
Data is output to the plot file and graphics file at this time
interval.
References
ISO +4138-2004 - Passenger cars — Steady-state circular driving behavior — Open-loop test
methods.
