Throttle-off Turn-in

A Throttle-off turn-in event simulates a vehicle driving straight at constant speed, turning on to a constant radius, then after reaching steady state the throttle is closed and the steering is ramped to tighten the turn.

The event includes a short straight section to allow the vehicle to come to steady state, the constant radius circle, and throttle removal. It is designed to simulate a highway exit ramp maneuver. Appropriate vehicle and tire output requests are included.

The Throttle off cornering 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 Throttle off cornering event follows the ISO 9816-2006 Passenger cars — Power-off reaction of a vehicle in a turn.
Figure 1. Throttle-off Turn-in Event


Parameters

Parameter Name Description
Units Describes the Length, Velocity, and Acceleration units.
  • Length unit selection (Model, m, ft)
  • Velocity unit selection (Model, m/s, km/h, mph).
  • Acceleration unit selection (Model, m/s2, g’s).
Radius The radius of the circle that the vehicle CG follows during the constant radius portion of the event.
Initial straight The distance the vehicle is driven straight and corners in a given radius to attain the steady state.
Velocity The velocity of the vehicle during the event.
Initial lateral acceleration Estimated initial lateral acceleration, calculated using the velocity and the turn radius.
Turn direction Direction the vehicle turns during the event (as seen by the driver).
Throttle step duration Time duration the throttle controller takes to completely remove the drive torque.
Steer ramp rate* Rate at which steering is ramped up after the drive torque goes to zero.
Lean ramp rate** Rate at which lean angle is ramped up after the drive torque goes to zero.
Transient time Time duration for which the vehicle makes the drive torque zero and ramps up the steering.

*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
LATERAL – STEERING CONTROLLER SETTINGS
  • Altair Driver uses Feedforward steering controller for non-leaning vehicles like Cars and Trucks. The following settings can be edited by the user.
    Look ahead time Look ahead time for the feedforward model to evaluate future states of the vehicle
    Prediction step size Maximum step size, used by the Driver feedforward steering model
For more information see the Altair Driver Mathematical Methods topic.
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
LATERAL – STEERING CONTROLLER SETTINGS
  • The Lean PID and Lateral Error PID controllers only apply to leaning vehicles (for example, motorcycles and scooters).

    Steer control: Control mode for steering can be switched between ‘MOTION’ and ‘TORQUE’

    Lean control
    The Lean PID takes as input a demand lean angle and outputs front fork (steering) angle. For open loop events the lean angle demand is a function of time. For closed loop path following events the demand lean angle is computed based on the vehicle speed and the path curvature with a correction for lateral path error.
    Kp Proportional gain for the lean controller
    Ki Integral gain for the lean controller
    Kd Derivative gain for the lean controller
    Lateral error control
    The Lateral Error PID takes as input the predicted lateral path error and outputs an increment to the demanded lean angle. The lateral error is computed by predicting the vehicle’s lateral position relative to the path by the look ahead time in the future. The Lateral Error PID acts to lean the vehicle toward the path.
    Look ahead time Look ahead time for the feedforward model to evaluate future states of the vehicle
    Kp Proportional gain for the lateral error controller
    Ki Integral gain for the lateral error controller
    Kd Derivative gain for the lateral error controller
    For more information see the Leaning Two and Three Wheeler Vehicles and Gain Tuning for Leaning Two and Three Wheeler Vehicles topics.

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 Throttle off turn in event report are as follows:
Report Name Report Signals
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
Axle Loads
  • Front Axle Load vs. Lateral Acceleration
  • Rear Axle Load vs. Lateral Acceleration
Steering Input and Acceleration
  • Steering Wheel Angle vs. Time
  • Steering Wheel Torque vs. Time
  • Lateral Acceleration vs. Time
  • Roll Angle vs. Time
  • CG Sideslip Angle vs. Lateral Acceleration
  • Understeer vs. Lateral Acceleration
Front Axle Sideslip vs. Lateral Acceleration
  • Rear Axle Sideslip vs. Lateral Acceleration
Lateral Load Transfer
  • Front Load Transfer vs. Lateral Acceleration
  • Rear Load Transfer vs. Lateral Acceleration
Engine Torque vs. Time
  • Longitudinal Velocity vs. Time
Vehicle CG Displacement vs. Time
  • Vehicle CG Displacement vs. Time