Power-off in a Straight Line

The Altair Driver maintains the straight line path and controls the throttle. Engine motoring torque is not applied after the throttle torque is removed.

The Power off in straight line event is supported by the Cars & Small Trucks, Heavy Trucks, and Two-Wheeler vehicle libraries. Automated output reports are available to plot the results.

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 initial speed of the vehicle during the steady state driven portion of the event.
Throttle step begin	The absolute time, in seconds, when the throttle torque begins to be removed.
Throttle step duration	The length of the time the throttle controller takes to remove all torque from the drivetrain using a step function.
End time	Absolute end time of the event, in seconds.

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 Step steer event report are as follows:


Report Name	Report Signals
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. Longitudinal Acceleration Rear Axle Load vs. Longitudinal Acceleration
Vehicle Angles	Pitch vs. Longitudinal Acceleration Front Drive vs. Longitudinal Acceleration Rear Lift vs. Longitudinal Acceleration
Steering Wheel Angle vs. Time	Vehicle CG Displacement vs. Time