Swept Sine

A Swept Sine event simulates a vehicle driving at a constant speed with a sinusoidal steering input of constant magnitude but increasing frequency applied.

Output Requests are included to measure the vehicle state variables, tire forces, and tire state variables. The Altair Driver steers the vehicle and maintains constant speed.

The Swept sine event is supported by the Cars & Small Trucks and Heavy Trucks vehicle libraries. Automated output reports are available to plot the results.

The Swept sine event follows the ISO +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.
  • Length (Model, m, ft)
  • Velocity (Model, m/s, km/h, mph).
  • Acceleration (Model, m/s2, g’s).
Velocity The constant speed that the vehicle attempts to maintain during the event.
Steer amplitude Amplitude of the steering input (degrees).
Frequency change rate The rate of change of frequency (hz/sec) of the sine wave function applied to the steering wheel.
Minimum frequency The minimum (initial) frequency sine wave that is applied to the steering wheel.
Maximum frequency The maximum (final) frequency sine wave that can be applied to the steering wheel.
Start time The start time of the sine wave.
End Time End time of the simulation (calculated using the start time, the frequency rate, and the max and min frequencies).

Controller Settings

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
For more information see the Altair Driver Mathematical Methods topic.

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

Three options are available to specify the road in the event, Flat Event, Road File, and Tires.
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.
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

The list of outputs present in Swept sine event report are as follows:
Report Name Report Signals
Steering Input and Acceleration
  • Steering Wheel Angle vs. Time
  • Steering Wheel Torque vs. Time
  • Lateral Acceleration vs. Time
  • Longitudinal Acceleration vs. Time
Vehicle Velocities
  • Yaw Rate vs. Time
  • Longitudinal Velocity vs. Time
  • Lateral Velocity vs. Time
Vehicle Slip Angles
  • Front Sideslip Angle vs. Time
  • Rear Sideslip Angle vs. Time
  • CG Sideslip Angle vs. Time
Roll Angle
  • Roll Angle vs. Time
Steer/Suspension Travel
  • Front Steer Angle vs. Time
  • Rear Steer Angle vs. Time
  • Front Suspension Travel-left vs. Time
  • Front Suspension Travel-right vs. Time
  • Rear Suspension Travel-left vs. Time
  • Rear Suspension Travel-right vs. Time
Steering, roll and torque
  • Steering Wheel Angle vs. Lateral Acceleration
  • Steering Wheel Torque vs. Lateral Acceleration
  • Roll Angle vs. Lateral Acceleration
  • Vehicle Path
Vehicle Slip vs. Acceleration
  • Front Axle Sideslip vs. Lateral Acceleration
  • Rear Axle Sideslip vs. Lateral Acceleration
  • CG Sideslip Angle vs. Lateral Acceleration
Steering Wheel Angle vs. Vehicle Sideslip Angle
Tire Lateral Slip
  • Left Front Tire Lateral Slip vs. Time
  • Right Front Tire Lateral Slip vs. Time
  • Left Rear Tire Lateral Slip vs. Time
  • Right Rear Tire Lateral Slip vs. Time
Vertical Tire Forces
  • Left Front Tire Vertical Force vs. Time
  • Right Front Tire Vertical Force vs. Time
  • Left Rear Tire Vertical Force vs. Time
  • Right Rear Tire Vertical Force vs. Time
Lateral Tire Forces
  • Left Front Tire Lateral Force vs. Time
  • Right Front Tire Lateral Force vs. Time
  • Left Rear Tire Lateral Force vs. Time
  • Right Rear Tire Lateral Force vs. Time
Longitudinal Tire Forces
  • Left Front Tire Longitudinal Force vs. Time
  • Right Front Tire Longitudinal Force vs. Time
  • Left Rear Tire Longitudinal Force vs. Time
  • Right Rear Tire Longitudinal Force vs. Time
Wheel Aligning Torques
  • Left Front Tire Aligning Torque vs. Time
  • Right Front Tire Aligning Torque vs. Time
  • Left Rear Tire Aligning Torque vs. Time
  • Right Rear Tire Aligning Torque vs. Time
Vertical Tire Forces vs. Lateral Acceleration
  • Left Front Tire Vertical Force vs. Lateral Acceleration
  • Right Front Tire Vertical Force vs. Lateral Acceleration
  • Left Rear Tire Vertical Force vs. Lateral Acceleration
  • Right Rear Tire Vertical Force vs. Lateral Acceleration
  • Yaw Rate vs. Lateral Acceleration
  • Understeer vs. Lateral Acceleration
Lateral Load Transfer
  • Front Lateral Load Transfer vs. Lateral Acceleration
  • Rear Lateral Load Transfer vs. Lateral Acceleration