Create a Belt-Pulley Subsystem

In a belt-pulley system, a long flexible belt is used to transmit mechanical power by wrapping the belt around rotating pulleys. The power is transmitted due to friction between the belt and pulley surface. The belt-pulley subsystem in MotionView helps assemble such a system very quickly with a minimal inputs such as pulley center position, radius, and belt properties.

A belt-pulley needs the following entities to be present in the model.
  • A reference marker, such as that the XZ plane of the marker coincides with the plane formed by the pulley, centers when the belt-pulley system lies in a plane other than the global XZ. In the case of an NLFE belt formulation, the XZ plane has to be parallel to the global XZ plane.
MotionView offers two types of belt-pulley systems:
  • Nonlinear Finite Element (NLFE) based – The belt is modeled as a series of connected nonlinear finite element beams. Use this model if you are interested in a high fidelity model that returns accurate belt stresses and strains.
    Note: These simulations can take a long time.
  • Discretized rigid bodies – The belt is modeled as a series of rigid bodies connected by bushings. Use this model if you are interested in the overall motion of the belt-pulley system. These simulations are usually faster than similar ones with NLFE belts.

In both cases, the system is modeled in such a way that the pulley centers lie in the XZ plane of the reference marker used to model the system.

Note: An NLFE belt currently can only be modeled such that the Y-axis of belt-pulley system marker reference is parallel to the global Y. This limitation will be removed in a later release.
  1. From the Assembly ribbon, click the Belt/Pullies icon.
    The Add a Belt-Pulley Subsystem dialog is displayed.
  2. Click the System collector and decide which system the belt/pulley needs to be created in.
  3. Specify a variable name and label for the belt/pulley.
    By default, variable names of entities in MotionView follow a certain convention. For example, all belt/pulley entities have a variable name starting with bp_. This is the recommended convention to follow when building models in MotionView since it has many advantages in model editing and model manipulation.
  4. Select the type of belt formulation to represent the belt using the drop-down menu.
  5. If a reference frame other than global frame is to be used, select the reference marker for pulley coordinates by double-clicking on the Marker collector (located in the lower, left of the dialog).
    The belt-pulley system will be created such that the assembly lies within the XZ plane of the reference frame.
  6. By default, two pulleys are available. To add or delete a pulley, use the right-click option on a row item indicating the pulley number.
  7. Enter values for the X and Z coordinates of the pulley center in the reference marker coordinate frame.
  8. Enter a value for the radius of the belt and specify which side (inner or outer) of the belt loop the pulley is positioned from the drop-down menu.
  9. Specify the total number of pulleys to create.
    As the pulley is added/deleted, this field will be automatically updated.
  10. Enter values for the belt width and belt thickness in the text boxes on the right side of the dialog.
  11. A linear elastic Belt Rubber material is available in MotionView and is selected by default. To use a different material, double click on the MaterialProperty collector and select a different material from the list.
  12. To create an NLFE belt formulation, complete the steps below:
    1. In the NLFE Belt Component area, the minimum number of NLFE beam elements required to accurately represent the belt based on the calculated belt profile is displayed in blue. By default, the minimum number of required elements is used. To use more elements, deactivate the Use minimum required option and specify the number of NLFE beam elements to be created.
    2. The effective diameter based on the calculated profile length of the belt in the installed position is also displayed in blue. By default, the dialog sets a value for the free diameter by a known amount of offset from the installed free diameter. Deactivate the Use calculated value option to provide a different value for the belt free diameter.
      Note: This number should be smaller than the installed belt diameter, so that the belt is sufficiently pre-tensioned. The greater the difference between the free diameter and the Installed diameter, the more pretension is induced.
  13. To create a Discretized rigid bodies belt formulation, complete these steps:
    1. In the Belt Stiffness Properties section of the dialog, enter tensile stiffness and tensile damping values along the longitudinal direction of the belt.
    2. Enter bending stiffness and bending damping values along the bending direction of the belt.
    3. Enter a value for the pre-tension of the belt.
    4. For the Belt Contact Properties (Impact) section, the parameters are the same as that found in the Contact panel with Impact method. Refer to the Contacts tool topic to learn more about each of the parameters.
  14. Once all the above information is entered, click OK to create the belt-pulley system and exit the dialog.
    The NLFE belt-pulley system that is created has the following architecture:
    Entity Description
    Bodies Rigid pulley bodies and an NLFE belt body consisting of a series of nonlinear beam finite elements are created.
    DataSet A dataset where all editable values are stored. After the creation of the belt-pulley system, you can change the free diameter and width of the belt through this dataset.
    Points The points that define the uninstalled belt profile and the pulley centers. These are hidden by default.
    Graphics The graphics for the pulleys.
    Joints Revolute joints between the pulley and attaching body. In addition, there are joints that connect the pulley and belt body that help in transmitting motion.
    Markers A reference marker to define the uninstalled configuration of the belt (hidden by default).
    Template Includes NLFE statements that are currently not supported by MotionView. These include GRIDS at the periphery of the pulley, LINE2 elements that model contact between belt GRID and pulley GRID, and CONN1 elements that restrain the belt with the pulley along normal of the belt-pulley plane.
    The discretized rigid bodies belt-pulley has the following architecture:
    Entity Description
    Bodies Rigid pulley bodies and a belt body consisting of a series of connected rigid bodies is created.
    DataSet A dataset where all editable values are stored. After the creation of the belt-pulley system, you can change the free diameter and width of the belt through this dataset.
    Points The points that define the uninstalled belt profile and the pulley centers. These are hidden by default.
    Graphics The graphics for the pulleys and belt.
    Joints Revolute joints between pulley and attaching body. In addition there are joints that connect the pulley and belt that hold the belt in the system plane.
    Markers A reference marker to define the uninstalled configuration of the belt (hidden by default).
    Template Includes MotionSolve command statements to hide the graphics used in contact.
Tip:
  • Select Show additional parameters to specify variable names and labels for the points that are to be created.
  • As the pulley X, Z, radii, and the belt side parameters are set, the preview image shows the belt-pulley system configuration. The line joining the pulleys tangentially represents the belt. For any incompatible information (for example, overlapping locations of the pulleys, distance between two pulley centers smaller than the summation of their radii) the belt line will not be visible. Cross belt and out of plane pulley configurations are not supported.
  • To return to default settings, click Reset to Defaults.

Edit a Belt-Pulley System

Change the Pulley Mount Bodies

The pulleys, by default, are connected to ground body via revolute joints. To change this attachment to a different body, select the belt-pulley system in the Project Browser and change the attachments in the Attachments tab, as shown below:


Figure 1.

Change the Belt Material

Once the belt-pulley system is built, the material of the belt can be changed through the material attachment to the belt-pulley system in the Attachments tab:


Figure 2.

Change the Pulley Material

The pulley material can be changed by selecting the graphic system of the pulley and changing the material attachment in the Attachments tab:


Figure 3.

Change the Belt Parameters

Belt parameters can be changed through the dataset Parameters DataSet available within the belt-pulley system.

The parameters that are active can be changed, while those that cannot be changed are grayed out.


Figure 4.

In the case of a discretized rigid bodies belt, the stiffness parameter and belt tension can be changed using the dataset Parameters Stiffness DataSet:



Figure 5.