Tractrix

Module(s): Tractrix

You can use the Tractrix tool to simulate the path covered by a vehicle you specify.

To create a path

1. Click Tractrix (How).
   

   Activate Tractrix in one of the following ways

   • Menu bar: Create Road Details Tractrix

   • Palette: Tools Create area in the following module(s):

   Tractrix

   The name and group of the selected vehicle are displayed in the title bar of the dialog box.

2. Click the box with the graphic preview to select a vehicle. Here you can also see the vehicle’s abbreviation.

   You can use the Vehicle filter to specify how many and which vehicles are presented for selection. Click Vehicle catalog to define properties for the vehicles.

3. Enter the speed of the vehicle. The speed affects the length of the clothoid when the path is created.
4. Specify the start angle of the vehicle. To do this, you can select a value in the list box or enter any value at the keyboard.

   Note: The angle set is only taken into account when the Vehicle angle button is activated (pressed in!). Otherwise, you enter the orientation of the vehicle after you have specified the start point.

5. Make Path settings. You can also change these settings while you are creating the path.
6. Click in the workspace to mark the beginning of the path and enter the orientation of the vehicle if the Vehicle angle button is not pressed in.
   Use the options in the dialog line.
7. Define the vehicle’s direction of movement by clicking the corresponding icon. The arrow shows the direction of movement.
   • indicates a forward direction.
   • indicates a backward direction.
8. Define whether and how the clothoids are to be created for the individual sections of the path. When the icon is pressed in, the corresponding clothoid is not used.
   

   The curvature within the clothoid changes linearly. This ensures a smooth transition from the radius of the initial element to the radius specified. In addition, this causes the centrifugal acceleration to change continuously.

   The default is one clothoid at the start and no clothoid at the end.

   • Clothoid at start: at the start of a section, one clothoid is always used to obtain a smooth transition to the defined radius.
     Disabling the clothoid at start (icon is pressed in!) makes sense only if the vehicle stops and starts again with the steering wheel being locked at an angle. A possible application would be to back the vehicle into a driveway, for example.
   • Clothoid at end: by default, there is no clothoid at the end of a section as the next section usually starts with a clothoid.
     When the clothoid at end (icon is not pressed in!) is enabled, a straight path is created at the end of the section; in other words, there is a smooth transition from the defined radius to a radius specified as being infinite.
9. Define the individual sections of the path. The following options are available:
   • Disable the Radius and Angle buttons and define the path intuitively using the mouse.
   • Enable the Radius button, enter a value for the radius and specify the direction and position of the vehicle using the mouse.
     If you want to define a straight section of the path, enter 0.00 for the radius.
   • Enable the Angle button, enter a value for the angle and specify the direction and position of the vehicle using the mouse.
   • Activate the Define the radius and angle for the next section button (this automatically enables the Radius and Angle buttons), enter a value for the radius and angle and specify the direction using the mouse.

     Notes:

   • You can use Undo to undo every entry made without having to quit the function.
   • When you use clothoids, you can see in the preview whether the desired position of the vehicle can be used with the radius and/or angle you have specified.
   • The program determines the minimum radius based on the radius for the turning circle and the track width of the vehicle.