OSENGINEER

Blended MBDyn utilizes Blender (an open-source, 3D computer graphics and modeling software package) as a graphical user interface (gui) for MBDyn (an open-source, multi-body dynamics solver used to model mechanical systems). One does not need to be an expert user of Blender to use Blended MBDyn, but the more skilled one is at using Blender, the better looking the models and animations will be. The examples on this website demonstrate only a basic use of Blender, tutorials can be found on Blender's website.

Blended MBDyn creates meshes in Blender which correspond to bodies in MBDyn and connect them with joints, beams and/or other forces. Once the meshes/bodies are connected, information is transfered back and forth between Blender and MBDyn. The location and orientation of the connections are defined in Blender as empties. These empties must be children of the meshes, i.e. the meshes must be parents of the empties. To make an empty the child of a mesh, right select the empty, hold down shift, right select the mesh, let up on the shift, then hold down <Ctrl> and type "p". It might be more helpful to look at a very simple tutorial before reading through the user's guide: tutorial.

Blended MBDyn is currently implemented using python scripts in Blender.

These scripts are accessible in the Blender "Window Type" menu

Window Type Menu

Scripts Window

In the "Scripts Window" there is a menu from which the Blended MBDyn panels can be accessed. For example, the beam, bodies and joint panels can be accessed from the under the heading "Misc"

Body

Body Panel

By default Blended MBDyn produces a body for every mesh in the Blender model. Each body can be selected and a mass and inertia matrix defined. Initial conditions for the body's translational and rotational velocities are also definable in this panel. The "Show Axis" button will display the axis (Blender refers to these as empties) which defines the center of mass for the body, however, for the button to work the mesh must be selected. For example, to show the axis, right click on the mesh, and then click the "Show Axis" button.

Planned improvements: Eliminate the necessity for every mesh in Blender to be seen as a body in MBDyn. For example, a stationary object can currently be "clamped" with a joint so it will not move. But, it would be faster, computationally, not to include it in the analysis.

Beam

(Link to MBDyn Input Manual)

Beam Panel

The beam is used to connect two bodies. The attachment location is defined by the empty.The user can define a 2 or 3 node beam. Each element in the stiffness matrix is defined in this panel.

Export

Export MBDyn Menu Location

The Export MBDyn Menu is located ...

Export Panel

The export panel has two purposes:

1. Translate the model into an MBDyn input file and start the MBDyn solver.

The following paramaters are written to the MBDyn input file as solver parameters: Start time, End time, Step time, Derivative Tolerance, Derivative Coefficient. To start MBDyn using this model as the input, select "Start Solve." The default name for the MBDyn input file is shown below. If the user wants to change that name, select "Choose New Filename." Once "Start Solve" is selected, the panel will go away, regardless of whether or not the model finishes successfully. To determine if the solver is done, look at the MBDyn output files or look at the process (in linux: "ps-ef|grep mbdyn").

2. Save the Blended MBDyn model information to a "pic" file.

Selecting "Save" will store the Blended MBDyn data. To open the Blended MBDyn file, the Blender model must be opened and the .pic file imported.

Planned Improvements: Add more solver parameters. Automatically have the MBDyn data saved to the Blender file.

Import

Import Menu

Import Panel

Similar to the export panel, the import panel has two purposes:

1. To import the results of the MBDyn run (".mov" file)

2. To import the .pic file.

"Import File" imports the file specified in the white text below the button. To change this name, select "Choose Input File". To open the ".pic" file select "Open".

Joint

Joint Panel

Joints relate directly to joints in MBDyn. When the type of joint is selected the required information for that joint appears. "Select Joint" allows the user to edit the existing joints. The name is changed in the "Name" field. The empties, when required, will appear below their parent node/body. "Accept" saves the entered data without closing the window.