AutoDamper

The AutoDamper entity is a force-velocity model designed to easily simulate a shock absorber used in ground vehicles. The AutoDamper entity reads force-velocity data from a file written in the TeimOrbit format.

Some advantages of the AutoDamper entity include the following:

The damper properties are defined in a readable ASCII format file.
The damper file can be referenced multiple times in the model (for symmetric dampers and for dampers that are used in more than one location).
The data file format is used in other MBD codes, such as SIMPACK and ADAMS.
The math that defines the Force-velocity relationship is contained in a subroutine, instead of in the user interface.

The Autobush uses a Force_Scalar_Twobody XML statement in the MotionSolve deck, along with a subroutine to calculate the force in the bushing.

Damper Graphic

A Damper graphic appears when an AutoDamper is added. The graphic includes two cylinders (shown in Figure 1).

The gray cylinder is attached to Body 1 and will move with that body. The red graphic is associated with Body 2 and will move with Body 2. Graphic sizes are calculated automatically and can be modified by expert users by editing the damper system definition.

The blue and pink arrows shown in the picture below are the MotionView Implicit graphics associated with the Force created by the AutoDamper:

Connecting an AutoDamper

From the Connectivity tab, select the first body to connect.
- Click Body 1 and select a body from the modeling window.
- Double click Body 1 and select the required body from the dialog.
Similarly, select the second body to connect by clicking the Body 2 input collector.
Select the first point.
Similarly, select the second point by clicking the Point 2 input collector.
The AutoDamper generates a damping force that acts on a line between points 1 and 2. Point 1 moves with Body 1 and Point 2 moves with Body 2.
Use the Scale force and Scale velocity fields to enter the damper scale factors. These numbers apply a scale factor to the damper curves. They are typically used to convert data from one unit set to another. Factors are supplied for force and velocity to simplify the scale input.
In the Body-1 Cyl. Dia and Body-2 Cyl. Dia fields, enter the damper dimensions.
Use the Property file field to browse and select the damper property file. The file should be in the TeimOrbit format.
Click View file to display a browser view of the property file. The file can be viewed, however it cannot be edited or saved.

If desired, check the Output box to add an output request for the Damper length, length-rate-of-change, the Damper force, and the direction cosines of the line passing through Point 1 and Point 2.

The Damper length and length-rate-of-change is measured along the line between Point 1 on Body 1 and Point 2. The Damper force also acts along the same line. A positive Damper force acts to repel the bodies, while a negative Damper force acts to attract the bodies.

The table below summaries the output channels in the MotionSolve .mrf file.

Type	Component	Quantity
REQSUB	RESULT(2)	Damper Length
-	RESULT(3)	Rate-of-change-Damper-length
-	RESULT(4)	Damper Force
-	RESULT(6)	Global X direction cosine of Damper
-	RESULT(7)	Global Y direction cosine of Damper
-	RESULT(8)	Global Z direction cosine of Damper

Sample TeimOrbit Damper File

A sample Sample TeimOrbit Damper File format damper text file is shown below. Enter the damper curve data in ascending order.

$----------------------------------------------HEADER
[HEADER]
 FILE_TYPE     =  'dpr'
 FILE_VERSION  =  4.0
 FILE_FORMAT   =  'ASCII'
$----------------------------------------------UNITS
[UNITS]
 LENGTH =  'mm'
 ANGLE  =  'degrees'
 FORCE  =  'newton'
 MASS   =  'kg'
 TIME   =  'second'
$----------------------------------------------CURVE
[CURVE]
{   vel    force}
-4916.935 -8.889
-1000.0   -3.0
 -500.0   -1.5
 -250.0   -0.75
 -100.0   -0.3
    0.0    0.0
  100.0    0.3
  250.0    0.75
  500.0    1.5
 1000.0    3.0
 4914.298  9.0416