Step Steer

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.
The parameters available in the Step Steer event are detailed in the following table:
Parameter Description
Steer input start time Initial Steer start time (absolute time in seconds).
Steer input end time Ending time for application of the step steer in seconds (absolute time).
Maximum steer Steering angle is rapidly increased from 0 to the Max Steering value (default 60 degrees) using the entered function types.
Function type Sine, step or ramp function, used to transition from 0 degrees steer to the maximum steer value.
Velocity Velocity of the vehicle during the event in meters/sec.
End time Absolute end time of the event, in seconds.
Print interval Data is output to the plot files and graphics file at this time interval (seconds).

References

ISO +7401-2003 - Road vehicles - Lateral transient response test methods - Open-loop test methods.