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 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.
The Step steer event is supported by the Cars & Small Trucks, Heavy Trucks, and Two-Wheeler vehicle libraries. Automated output reports are available to plot the results.
The Step steer event follows the +7401-2003 - Road vehicles - Lateral transient response test methods - Open-loop test methods.
Parameters
Parameter Name | Description |
---|---|
Units | Describes the Length, Velocity, and Acceleration units.
|
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. |
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. |
*Applicable only for Cars/Trucks i.e., Non-leaning events.
**Applicable only for Two-wheeler i.e., Leaning events.
Controller Settings
- Non-leaning events (Cars/Trucks)
- LONGITUDINAL – TRACTION CONTROLLER SETTINGS
- Use additional control: Enables the additional feedback control for the traction
control. The gains for the controller can be edited by toggling this check
box.
Kp Proportional gain for the feedback PID controller Ki Integral gain for the feedback PID controller Kd Derivative gain for the feedback PID controller
- Use additional control: Enables the additional feedback control for the traction
control. The gains for the controller can be edited by toggling this check
box.
- Leaning events (Two-wheelers)
- LONGITUDINAL – TRACTION CONTROLLER SETTINGS
- Use additional control: Enables the additional feedback control for the traction
control. The gains for the controller can be edited by toggling this check
box.
Kp Proportional gain for the feedback PID controller Ki Integral gain for the feedback PID controller Kd Derivative gain for the feedback PID controller
- Use additional control: Enables the additional feedback control for the traction
control. The gains for the controller can be edited by toggling this check
box.
Signal Settings
Use the signal settings to set minimum, maximum, smooth frequency and initial values for Steering, Throttle, Brake, Gear, and Clutch signals output by the driver.
The smoothing frequency is used to control how fast the Driver changes signals. Only closed loop control signals from the Driver are smoothed. Open loop signals are not smoothed.
Road Settings
- Flat Road
- Uses a flat smooth road for the event with no required road file.When the Flat Road is selected, the Graphics Setting option is available with the following parameters:
- View path centerline: Enables the visualization of the event path.
- This check box is disabled for open loop events without a path.
- View grid graphics: Enables the visualization of the road grid graphics.
- When view grid graphics check box is toggled, road grid parameters can be edited in the Grid Settings tab.
Grid length Defines the length of the road. Enter a positive value in the model units. Grid Width Defines the width of the road. Enter a positive value in the model units. Grid X offset Gives a distance offset to the road graphics in the longitudinal direction. Enter a positive value in the model units. Grid Y offset Gives a distance offset to the road graphics in the lateral direction. Enter a positive value in the model units.
- View path centerline: Enables the visualization of the event path.
- Road File
- The road file option enables the selection of a road file to be used in the event. Using this option, all tires in the model consider the event specified road file instead of the file included in the tire entities.
- Tires
- Using Tire as road selection option, the road file specified in the tire entity is used in the events simulation.
Automated Output Report
Report Name | Report Signals |
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Steering Input and Acceleration |
|
Vehicle Slip Angles |
|
Vertical Tire Forces |
|
Lateral Tire Forces |
|
Longitudinal Tire Forces |
|
Vertical Tire Forces vs. Lateral Acceleration |
|
Steering Wheel, Torque and Roll |
|
Vehicle Slip vs. Acceleration |
|
Lateral Load Transfer |
|