Tutorials

Bed Settling

Injury Evaluation Application - Bed Settling

This demonstration problem will illustrate the combination of a mechanical model (bed) from the model library with a human model (patient) for a bed settling analysis to determine the final resting configuration for models with two different sets of joint stiffnesses.

Features of this model include:

Combining ADAMS model with human body model
Importing SLF file for anthropometric, joint and posture data.
Creating human/bed contact forces
Running parametric variation simulation

Generating the Bed Model

In this phase, the previously built ADAMS model of the bed is imported into the database.

Figure 1: Imported mechanical model (bed).

Figure 2: Panel used to import the mechanical environment (bed).

Step 1: Bring up the import mechanical environment panel
Select XCHANGE in the main-menu and IMPORT MECHANICAL ENVIRONMENT in the sub-menu.

Step 2: Import the bed model from the mechanical environment library
Select Mechanical Environment Library and Bed as the Model Library SLF File. Select Apply to create the bed model. Select the "S" icon on the BodySIM display Toolbox to shade the view of the bed.

Import the Body Model

In this phase, the human body is created using data contained in the SLF file. The file, Patient.slf contains body anthropometric data, joint data and posture data.

Figure 3 Body with joints and posture imported from the model library.

Figure 4: Body import panel

Step 3: Bring up the import model
Select IMPORT on the main-menu and IMPORT SLF MODEL FILE from the sub-menu.

Step 4: Import the body, joints and posture from the library
Select Model Library and Full Body Bed Settling as the Model Library File. Body, Joints and Posture should be checked in the Build section indicating the presences of these items. Select Apply to create the model.

Creating Contact Forces

The contact ellipsoids automatically created at the time of segment generation, will now be used to create the foot-floor contact elements. For information on selecting specific model parameters for this section see Choosing Model Parameters.

Figure 5: Human model displayed as ellipsoids. The ellipsoids represent contact elements to be used between the model and the bed.

Figure 6: Contact set creation panel

Step 5: Bring up the contact panel
Select CONTACTS on the main-menu and CREATE BASE CONTACT SET on the sub-menu.

Step 6: Create the contact forces between the head/neck and pillow
Select Ellipsoid as the External representation and none as the Internal in the BodySIM Display Toolbox. Check force vectors to create scaled force graphics during animation. Provide the contact parameters as listed in Figure 6. Select the pillow as the contact solid. Select head and neck segments and select APPLY to create the pillow contacts.

Step 7: Create the contact forces between the body and the mattress
Check force vectors to create scaled force graphics during animation. Provide the contact parameters as listed in Figure 6. Select the mattress as the contact solid. Select right_lower_arm, left_lower_arm, right_hand, left_hand, lower_torso, central_torso, upper_torso, right_upper_leg, right_lower_leg, right_foot_Single, left_upper_leg, left_lower_leg, left_foot_Single segments and select APPLY to create the pillow contacts.

Running the Passive Simulation

With the body in position over the bed, a simulation is perform to "drop" the body into the bed to determine the resting (equilibrium) position for the human model.

Figure 7 Body before settling simulation (left) and after (right).

Step 8: Bring up analyze panel
Select ANALYZE on the main-menu and DYNAMICS on the sub-menu.

Step 9: Adjust the visualization parameters on the bed
Right click on the blanket. Select Shell:blanket and appearance. Adjust visibility using the slider.

Step 10: Run the dynamics simulation
Check gravity in the -Y direction and run the simulation for1.5 seconds and 150 time steps.

Step 11: Display simulation results
Display animation using the ADAMS/View toolbox.

Step 12: Save the first analysis
Select SAVE ANALYSIS and enter the name Stiff. Select OK.

Running the Parametric Study

The joint properties are adjusted by changing a global scale factor. In this phase, the hybrid III joint properties are scaled to .3 of the original value. For information on selecting specific model parameters for this section see Choosing Model Parameters.

Figure 8: Parameters window to adjust the joint parameters

Step 13: Bring up the parameters panel
Select PARAMETERS on the main-menu and JOINTS on the sub-menu.

Step 14: Increase the joint properties by .1 of the original value
Set the Hybrid III scale factor to .1 and select INSTALL VALUES.

Step 15: Bring up analyze panel
Select ANALYZE on the main-menu and DYNAMICS on the sub-menu.

Step 16: Run the dynamics simulation
Check gravity in the -Y direction and run the simulation for 1.5 seconds and 150 time steps.

Step 17: Display simulation
Use the ADAMS/View toolbox to animate the model.

Step 18: Display the animation with the skeletal/skin model
Set the external representation to Skin and the internal representation to Skeleton using the BodySIM Display Toolbox and use the ADAMS/View toolbox to animate the model.

Interrogating the Results

When the simulation is complete the model may be animated. To gain insight to the comfort level of each body stiffness profile, the contact force at the pelvis may be plotted and the animation for each case superimposed.

Figure 9: Panel set up to plot the lower torso contact force

Figure 10: Pelvis contact forces for the stiff model and the flexible model

Step 19: Bring up results panel
Set the external representation to none and the internal representation to Skeleton using the BodySIM Display Toolbox. Select RESULTS on the main-menu and DATA DISPLAY on the sub-menu. Select Contacts as the Data Type and select the post processor button.

Step 20: Plot the pelvis contact force for stiff model
Select "Diane_Lower_Torso_Con_1", magnitude component. Select the .World.Stiff as the analysis. Select Create Full Plot to create the data curve.

Step 21: Plot the pelvis contact force for flexible model
Select "Diane_Lower_Torso_Con_1", magnitude component. Select the .World.Last_Run as the analysis. Select Create Full Plot to create the data curve.

Step 22: Display simulation in iso view
Set the view to iso, divide window, and Play to view the animation.

Step 23: Animate superimposed models
Select Compare Cases with .world.stiff as case 1 and world.last_run as case 2. Select Play to animate both cases simultaneously.

Step 24: DEMO COMPLETE

Further

This model was put forth to demonstrate the capability of combining a human model with an ADAMS model by importing an external file. This model may be refined in many areas including:

Developing the bed model to include articulations (motorized bed).
Evaluating settling characteristics of various mattress foam types