Tutorial: Getting Started with Motion Analyst

Tutorial Level: Beginner Learn how to create connections, add a motion and spring damper force, create a flexible body and run a motion analysis.

In this lesson you will learn how to:
  • Ground a part
  • Create a rigid group
  • Connect parts with joints
  • Determine the direction of gravity
  • Add a motion to the model
  • Apply a spring-damper force
  • Add a flexible body
  • Review flexible body stress
  • Run a motion analysis

Open the CAD model

  1. Press F7 to open the Demo Browser.
  2. Double-click the M01_FourBar.x_t file in the Motion folder to load it in the modeling window.


  3. If not already visible, press F2 to open the Model Browser.
  4. Check that the display units are set to MKS.
  5. Under File > Preferences > Inspire Motion > Run Options change the solver units to MKS.
  6. To switch to the Motion Analyst ribbon, click the dropdown under Profile and select Analyst.

Ground a Part

  1. On the Motion ribbon, select the Ground tool from the Connections category.


  2. Select the Base part to ground it.
    The part turns red, and the part icon in the Model Browser changes to indicate that it is a ground part.


  3. Right-click and mouse through the check mark to exit, or double-right-click.

Create a Rigid Group

  1. Select the Rigid Groups tool.


  2. Select the Base, Mount Crank, and Mount Clevis parts in the bottom half of the mechanism.
    The parts turn red as you select them.


  3. Click the floating Create New Group icon to place the parts you selected into a new rigid group.


  4. Right-click and mouse through the check mark to exit, or double-right-click.

Run a Simple Motion Analysis

  1. Click the Quick Run button on the Analyze Motion tool to see the model in motion.


  2. Notice that the ground parts remain stationary and some of the unconnected parts fall due to gravity.
    Note: The Quick Run is a toggle button, so you can also use it to stop an analysis that is still running.
  3. After the analysis has stopped running, the icon appears and you are automatically placed into review mode. Click the Review Motion Results icon or double-right-click to exit review mode.


Connect Parts with Joints

  1. Select the Joints tool on the Motion Analyst ribbon.


    The joints dialog appears with Revolute as the default joint Type and Part 1 collector preselected.
  2. In the modeling window, click on the Link Crank part.
  3. Click on the Mount Crank part.
  4. Click the snap point at the center of the Mount Crank hole.
    Figure 1.


  5. To define the orientation, select the dropdown next to Method and select Vector.
  6. Click the Advanced Selector ... in the Vector collector.
  7. In the Advanced Selector window, select Global Y and click OK.
  8. Click Accept to create the joint.
  9. Right-click and mouse through the check mark to exit, or double-right-click.
    Note:
    • After clicking Accept, the context remains in edit mode where you are free to make changes to the joint definition by first clicking on the appropriate collector in the dialog and then selecting the entity from the modeling window.
    • Using geometry snap points to define entities such as Origin, Point or Vector results in the creation of a new entity in the model. These new entities can be re-used as references for defining other joints, forces, motions, etc.
    • If a collector is already populated with an entity, clicking on it will highlight the entity (part, point or vector) in the modeling window for visual clarification.
  10. Left-click in the modeling window to reset all collectors and begin creating a new joint.
    Notice the Label auto-indexes by 1 to now read Joint 1.
  11. Repeat the steps 3 through 8 and add a Revolute joint between the Link Crank and Link Single Slot parts. Use the hole center snap point, as shown, when defining the origin.
    Figure 2.


  12. Repeat steps 3 through 8 and add a Revolute joint between the Link Single Slot and Link Dual Slot.
    Figure 3.


  13. Repeat steps 3 through 8 and add a Revolute joint between the Link Dual Slot and Mount Clevis parts.
    Figure 4.


When finished, the model should appear as follows:
Figure 5.




Note: The scaling factor for joint graphics can be changed in Preferences > Inspire Motion > Visualization > Scaling factor for Analyst joints. In the image, the joints were scaled to 65.

Inspect the Gravity Direction

  1. Open the Gravity tool:
    1. On the Motion ribbon, under Forces, select the Gravity tool.


      If Gravity is not visible, use the dropdown under the Forces tool).
      By default, the gravitational acceleration (G) is set to 9.80665 m/s2 in the -z direction.
  2. Notice that a vector is displayed which indicates the direction of gravity.
    Figure 6.


  3. Right-click and mouse through the check mark to exit, or double-right-click.

Change the Run Settings and Rerun the Analysis

  1. Hover over the Analyze Motion tool, then click the Run Settings icon to open the Run Motion Analysis window.


  2. Change the Output Rate to 100 by entering the value in the field or clicking the 100 button.
    Figure 7.


  3. Expand the Gravity section and verify that the Yes radio button is selected.
    This is the default setting for a motion analysis.


  4. Close the Run Motion Analysis window.
  5. Click the Quick Run button on the Analyze Motion tool to see movement of the model with the joint connections in place.


    A message will appear warning of redundant constraints. This is because we have all rigid bodies in the model and the combination of four revolute with three rigid bodies is over-constraining the model. There are different ways to resolve redundant constraints, but shortly we will address it by replacing a rigid part with a flexible body.
    Figure 8.


  6. Click Continue.
  7. Click the Quick Run button again to stop the analysis.


  8. Double-right-click to exit review mode.

Add a Motion to Drive the Mechanism

  1. Select the Motions tool.


  2. In the dialog, set Define Motion to On Joint.
  3. Set the Type to Velocity.
  4. Click on the joint connecting the Mount Crank and Link Crank.
  5. Click Accept to create the motion.
    A microdialog will appear as well as a rotational arrow graphic on the joint.
    Figure 9.


  6. In the microdialog that appears, enter 60 rpm.

Add a Spring-Damper Force

  1. Select the Coil Spring tool.


  2. Select the Link Dual Slot part.
  3. Select the Base part.
  4. Click the Mid (middle) edge snap point of the Link Dual Slot part.
    The selected feature turns red.
    Figure 10.


  5. Click the Mid (middle) edge snap point of the Base part.
    Figure 11.
  6. Click Accept to create the spring.
    A coil spring appears and the microdialog shows the default settings.
  7. In the microdialog that appears, change the K stiffness value to 2500 N/m and C Damping to 1 N*s/m. Leave the Force and Length options as the defaults.
    Figure 12.


  8. Click and drag the white arrow manipulator to reduce the spring diameter to .01 m.


  9. Right-click and mouse through the check mark to exit, or double-right-click.

Change the Run Settings and Rerun the Analysis

  1. Click the Run Settings icon.


  2. Change the End Time to 2 s by entering the value in the field or clicking the 2 button.
  3. Close the window.
  4. Click the Quick Run button, then click Continue on the Redundant Constraint message dialog, to see movement of the model.


  5. After two seconds, the run will complete and you will automatically be placed into the Review Motion Results tool.
  6. Optional: Click the Play button on the animation toolbar to review the results.
  7. Left-click and swipe to exit the animation context.

Create a Flexible Body

One preferred way to remove redundant constraints from the model is to use flexible bodies in place of rigid bodies. In this four bar example, we only need to replace one of the links to break the redundancies in the system.

  1. Right-click on the Link single slot.
  2. Select Flexible for Motion from the panel.
    The part will turn light blue.
    Figure 13.


Rerun the Motion Analysis

  1. Click the Quick Run button.


    Prior to running the motion analysis, the flex body will be created, as shown by the Run Status window.
    Figure 14.


    Notice the Redundant Constraints warning message did not appear.
  2. 2. When the simulation is complete, click Close in the Run Status window.
  3. Under the Review tools in the Motion Analyst ribbon, click the dropdown menu.
  4. Select the Review Flexible Body Results tool.
    Figure 15.


    The Analysis Explorer will display.
  5. In the Analysis Explorer, change Result Types to VonMises Stress.
  6. In the color legend, click on the maximum value in the legend (8e5 Pa) and enter 7e5 (to better see stress contours).
  7. Drag the animation slider to replay the animation and see stress change during the mechanism movement.
    Figure 16.


  8. Left-click and swipe to exit the Analysis Explorer.

Plot the Motion Results

  1. Click on the blue check mark (Review Motion Results) next to the Analyze Motion icon.


  2. Change the Time on the animation toolbar to 0.73 s by dragging the slider bar.
    Figure 17.


  3. Select Coil Spring 0 in the modeling window to see a plot of the spring forces.
    Figure 18.


  4. Select Motion 0 from the Model Browser to see a plot of the motion's output.
    Figure 19.


  5. In the motion's plot, click the TX, TZ and TM to hide them and only show TY.
  6. In the Model Browser, select the pin connecting the Link Single Slot to the Link Dual Slot to view a force plot for the pin.
    Figure 20.


    Note: Right-click on the plot to view other components that can be plotted.
  7. Right-click and mouse through the check mark to exit, or double-right-click.