A Step steer event simulates vehicle response to a sudden step input to the steering
wheel.
The steering input is a rotational motion or torque at the steering wheel or the input
shaft to the steering gear. The standard output requests are included to measure vehicle
response. Tire requests are included to understand tire forces during the event. The Altair
Driver model maintains constant speed during the event. A plot template is available to plot
the results.
A series of step steer tests (in both the left and right turn direction) at increasing
steer angles can be used to characterize the vehicle understeer and lateral response. Figure 1. Step Steer Event
The parameters available in the Step Steer event are detailed in the following table:
Parameter
Description
Units
Velocity unit selection (Model, m/s, km/h, mph).
Velocity
Velocity of the vehicle during the event.
Steer input start time
Initial Steer start time (absolute time in seconds).
Lean input start time*
Initial Lean start time (absolute time in seconds).
Steer input end time
Ending time for application of the step steer in seconds (absolute
time).
Lean input end time*
Ending time for application of the step lean in seconds (absolute
time).
Maximum steer
Maximum Steering input value (default 60 degrees).
Function type
Sine, step or ramp function (used to transition from 0 degrees steer to the
maximum steer value).
End time
Absolute end time of the event, in seconds.
Print interval
Time interval of data output to the plot file (.plt) and graphics file
(.h3d).
*Applicable only for Two-wheeler events.
References
ISO +7401-2003 - Road vehicles - Lateral transient response test methods - Open-loop test
methods.
