LifeModeler.com
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Overview
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Modeling
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Tutorials
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Appendix
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| What's New |
| Program Setup |
| Quick Start |
Quick Start
This chapter is a quick startup modeling guide. Simple steps to create three types of human models are presented as an introduction to modeling. For more advanced functionality see the tutorials section.
Sections
Starting LifeMOD™
After the product installation process, the icon pictured in Figure 1 will appear on the desktop. This icon starts LifeMOD.
When LifeMOD first appears on the screen the program will open a modeling window and a splash screen as depicted in Figure 2. The splash screen is a portal to explore functions and training functions of the program. It also allows the user to begin creating a new model or to read in a previously created model. The user may skip this splash screen by unchecking the box "Show this dialog at startup." The splash screen may be recalled at any time by selecting the LifeMOD button in the lower left corner of the modeling window.
Figure 2: Selecting the "LifeMOD" icon in the bottom left corner brings up the LifeMOD™ splash screen again.
LifeMOD Control Panels
LifeMOD provides a very intuitive graphical user interface. Very detailed human models are created via control panels. These control panels enable the user complete functionality to generate, display, analyze, animate and plot data.
Access to the control panels may be achieved by selecting "New Model", "Open Existing Model" or "Close" is selected on the splash screen the three main LifeMOD panels will be displayed. Figure 3 displays the main modeling panel, the display toolbox and the automated tutorial control panel.
Figure 3: The three main LifeMOD panels.
Main Modeling Panel
Figure 4: LifeMOD™ main modeling panel displaying the commands (main-menu) and actions (sub-menu) and toolbox access.
Figure 4 displays the LifeMOD™ main modeling panel. This is the main model building command structure. Under each selection is a sub-menu which contains the actions for each main command. The toolboxes on the far right include the LifeMOD Display Toolbox, the Table Editor, the Automated Tutorial Panel, and access to this manual and to the user's forums. This panel also contains a context sensitive help button which accesses the on-line manual section current for the selection in the main-menu and the sub-menu.
LifeMOD Display Toolbox
Figure 5: LifeMOD Display Toolbox
Figure 3 displays the LifeMOD Display Toolbox used to manipulate the display of the model. Though no longer physically present on the display panel, the view manipulation tools remain the same:
- f - fit in view
- z - zoom view
- w - zoom in window
- r - rotate
- t - translate
- c - center view
- S - toggle between solid and wireframe representation
- v - turn icons on/off
The user may use these keyboard shortcuts to alter the items listed in the pull-down menu:
- Whole Body
- Joints
- Motion Agents
The middle section of the panel includes an entity manipulation section. The entities include:
Body
- Body CM tracker
- Vision Cones
- Foot graphics
- Grip graphics
Tissues
- Muscles
- Ligaments/Tendons
- Tissue Icons
Joints
- Graphics
- Axis-Major
- Axis-Minor
Motion Agents
- Segment CG Set
- Davis Set
- Plugin Set
- Golf Set
- Motion Matrix Set
- Tracker Set
Misc. Items
- Markers
- Constraints
- Forces
The panel offers controls for body internal/external representation display functions. Bodies may be represented as a combination of external and internal representation. When an internal representation is used other than "none" the external representation will change to semi-transparent. The user may affect the control of the external and internal transparencies using the sliders at the bottom of the panel.
The bottom of the panel also offers control of the ADAMS icons and components. These include markers, constraints, forces, parts, and geometry.
Automated Tutorial Control Panel
Figure 6 displays the Automated tutorial control panel. This panel automatically steps through any of the available tutorials in LifeMOD. The tutorials themselves are designed as self-training tools. The best way to use the tutorials is by following the manual (select the question mark for the specific tutorial document) while stepping through the tutorial. The panel displays the current chapter and step of the tutorial and controls to single step through or fast forward to a specific step.
Introduction to Modeling
Modeling Paradigm
The core modeling methodology in LifeMOD is to start as basic as possible, and then to refine and enhance the model to produce the desired accuracy. For the apects of the human model created in LifeMOD, there is a base level configuration. There is a base level of human segments, human joints and human muscles. Each human segment may be further discretized by creating single elements such as individual cervical vertebra segments in the single base-level neck segment. Single joints may then be used to join each of the single vertebra segments. The base-level muscle set consists of 118 generalized muscles. For certain activities, additional muscles can be added to the model for increased fidelity.
Types of Models
There are three basic types of human modeling in LifeMOD: passive jointed, recording jointed, muscled. Each model can dynamically react to the environment, via contact forces.
Passive Jointed - models are used to simulate passive injury evaluation activities such as a car crash, falls, collisions, sporting activities, etc. The passive joints are built using properties from the Hybrid III crash dummy, including non-linear stiffness, damping, joint friction and joint limits with hysteresis.
Recording Jointed - models are used to simulate any human activity. The first step in the process is to move the segments of the model in the desired motion pattern using user-input trajectories or motion capture data. The second step involves using the joint angle histories to drive the joints with torques (PD-control) to enforce the recorded displacements.
Trainable Muscled - models are used to simulate any human activity. The first step in this process is to move the segments of the model in the desired motion pattern using user-input motion patterns or motion capture data. The second step involves using the muscle contraction histories to drive the muscles with forces generated from PD-controllers to enforce the recorded contractions. During this process, the muscles are continually monitored to make sure the generated force does not exceed the specific muscle tissue force generating capabilities.
Modeling steps
Figure 7 illustrates the modeling procedure described below.
Step 1: Generating the Model
The process begins by creating a base level of body segments scaled using the data from the internal anthropometric databases. The base level segment set includes:
- Head
- Neck
- Upper_Torso
- Central_Torso
- Lower_Torso
- Right_Scapular, Left_Scapular
- Right_Upper_Arm, Left_Upper_Arm
- Right_Lower_Arm, Left_Lower_Arm
- Right_Hand, Left_Hand
- Right_Upper_Leg, Left_Upper_Leg
- Right_Lower_Leg, Left_Lower_Leg
- Right_Foot, Left_Foot
Once the segments have been created, they are held together using LifeMOD joints. Once the joints are installed, the user can begin running simulations on the model, or may install soft tissues for additional data-collection.
Soft tissue forces, including ligaments, tendons and muscles, contribute additional data input and allow for more realistic modeling of the human body.
Step 2: Positioning the Model in the Environment
Posing the model in a starting configuration is optional, however, it usually lends well to the progression of a simulation if the model is placed in a position appropriate to the task it is simulating. LifeMOD contains a standard library of postures from which to upload a posture. If the target posture is not in the library, however, the user may design his/her own by affecting each joint angle with graphical tools.
Contact forces are then created between the segments of the human model and the geometry of the environment, vehicle, mechanical system, etc.
Step 3: Running the Simulation
Passive Simulation
Once the model is generated and in position, either passive or active simulations may be run. A passive simulation relies on external forces acting on the body, while the model records the reactions of the joints and muscles to the applied force. The most common forms of this type of simulation are injury-based -- falls, crashes, etc.
Inverse Dynamics Simulation
Most active simulations require two steps, the first of which "trains" the joints and soft tissues and records the data that they playback later to drive the motion. This type of simulation is called an inverse dynamics simulation. Motion trajectories, either user-generated, or based on motion-capture data, move the segments in the desired motion pattern. During this process, joint angles (for Recording Jointed models) or muscle contraction histories (for Recording-to-Active Muscled models) are recorded. These will serve to drive the model.
Forward Dynamics Simulation
The forward dynamics simulation uses the recorded joint angles or muscle contractions to generate torque and force that will produce the appropriate internal reactions needed to move the model consistently with the motion from the inverse dynamics simulation.
Step 4: Validate
After running any of the simulations, the user can import the test data and determine whether the desired results have been achieved.
Step 5: Refine
If the results do not quite meet expectations, the user can return to change the fidelity of specific joints/segments/soft tissues or the environment before running the simulation again as many times as necessary.
Step 6: Optimize
If no adjustments are needed, or if the simulation achieves the desired results, it can then be optimized through studies in design sensitivity, experiment design, etc that will help the user to extract as much valuable information as possible.
Creating a Human Model with Passive Joints
This simple example outlined below illustrates one type of human modeling with LifeMOD. The human model with passive joints is used to model situations where a "crash dummy" model reacts to environment forces such as with a car crash, a fall, etc.
For more elaborate development of this type of analysis see the following tutorials:
Step 1: Creating the Body Segments
The first step in the process is to create the segments of the human body. Segment dimensions and mass properties are scaled based on the GeBOD anthropometric database.
- Bring up LifeMOD by selecting the desktop icon.
- Referring to the screen in Figure 2, select New Model.
- Select "Segments" in the main-menu and "Create Base Set" in the sub-menu
- On the main modeling control panel, keep the defaults and select GeBOD for the anthropometric library.
- Select "Median" and select "Apply" next to Create Body Measurement Table.
- Select "Apply" next to generate the body segments.
Step 2: Creating the Joints
After the body segments are created the segments must be joined together with human joints. The joints for this example will be kinematic joints with passive torque functions. The torque functions are derived from the internal Hybrid III crash dummy database and include nonlinear stiffness, damping, friction, and joint limits with hysteresis effects.
- Select "Joints" in the main-menu and "Create Base Set" in the sub-menu
- Select the light bulb next to "Prepare Joints with Hybrid III Crash Dummy Strength Elements"
- When the sub-panel opens, select "Select All"
- Select Execute to create the complete joint set.
Step 3: Posing the Human Model
After the joint are created, the human model may be posed in any configuration by accessing the library of standard postures or by adjusting the joint angles individually.
- Select "Posture" in the main-menu and "Configure Base Model" in the sub-menu
- Select "Load Library Posture" to bring up the posture library
- Select "Sitting" as the posture from the library
Step 4: Creating Environment Forces
With the model posed in position, environment contact forces between the segments of the model and the geometry of the environment may be created. LifeMOD contains a generalized surface contact algorithm which generates contact forces between any segment and any geometric entity.
- Select "Contacts" in the main-menu and "Create Base Set" in the sub-menu
- Select Barefoot-Hard Floor as the contact condition
- Select the Ellipsoid-Plane contact method
- For the surface marker, right click in the field to pop up the marker creation dialog box
- Enter .World.ground.ref as the marker name, 0,-20,0 for location and 0,-90,0 for the orientation. Select OK to create the marker.
- Enter 100 for both the Surface X and Y length
- Toggle Create Contact Surface Plane
- Enter 1 for the thickness
- Check Right_Foot_Single, Left_Foot_Single and Lower_Torso
- Select Apply to create the contact forces
Step 5: Running a Simulation
With environmental contact forces created on the model and inverse dynamics simulation may be performed.
- Select "Analyze" in the main-menu and "Dynamics" in the sub-menu
- Check the gravity box and select -Y for the gravity vector
- Enter 2 for end time and 100 for time steps
- Select Analyze to run the simulation
Step 6: Examining the Results
After the simulation is performed, the results may be reviewed in a variety of ways. This section illustrates how head acceleration data may be animated with the skeleton animation.
- Select "Results" in the main-menu and "Data Display" in the sub-menu
- Bring up the post processor window by selecting the graph button at the top of the panel
- Select Body Motion as the data type.
- Select Issac_Head as the segment, CM_Accleration as the characteristic and the Y component.
- Select Create Full Plot
- Select Animation on the sub-menu
- Check divide window, select left view and select the arrow button to animate
Creating a Human Model with Recording Joints
This simple example illustrates one type of human modeling with LifeMOD. In this example the human joints are "trained" by using motion agents to move the segments of the body in an inverse dynamics analysis. When the joints are trained, or the joint angle histories obtained, the joints are changed from trainable (passive) elements to trained (active) elements. The motion agents are then removed and the model is driven with torques from the model.
For more elaborate development of this type of analysis see the following tutorials:
Step 1: Creating the Body Segments
The first step in the process is to create the segments of the human body. Segment dimensions and mass properties are scaled based on the PeopleSize anthropometric database.
- Bring up LifeMOD by selecting the desktop icon.
- Referring to the screen in Figure 2, select New Model.
- Select "Segments" in the main-menu and "Create Base Set" in the sub-menu
- On the main modeling control panel, keep the defaults and select PeopleSize for the anthropometric library.
- Specify a 5th percentile Japanese female
- Select Apply to create the body measurement table.
- Select Apply next to Create Human Segments.
Step 2: Creating the Joints
After the body segments are created the segments must be joined together with human joints. The joints for this example will be kinematic joints with passive torque functions.
- Select "Joints" in the main-menu and "Create Base Set" in the sub-menu
- Select the light bulb next to "Prepare Model with Recording Joints "
- When the sub-panel opens, select "Select All"
- Select Execute to create the complete joint set.
Step 3: Posing the Human Model
After the joints are created the human model may be posed into any configuration using by accessing the library of standard postures or by adjusting the joint angles individually.
- Select "Posture" in the main-menu and "Configure Base Model" in the sub-menu
- Select "Load Library Posture" to bring up the posture library
- Select "MuscleRelocation" as the posture from the library
Step 4: Creating the Motion Agents
With the model posed, motion agents can be created and positioned on the model. Motion agents move the segments of the model and can be based on displacement trajectories -- either entered manually or derived from motion capture equipment. The motion agents themselves are attached to the body segments with springs.
- Select "Motion" in the main-menu and "Create Individual Motion Agent" in the sub-menu
- Right click in the Body Segment field, select part - pick and click on the left_lower_leg in the modeling window.
- Select Manually select location either pick a point on the leg or enter 3,-12,14
- Set x_dof as fixed and Rx_dof, Ry_dof and Rz_dof as free.
- For the Y_dof and the Z_dof select driven
- Right click in the Y_dof field and select Spline - Create
- Enter 0,1,2,3,4 for the x values and 0, 0.5, 1, 0.5, 0 for the y values (when creating the spline, keep in mind the unit of measurement in which the body is functioning. To check, go to Segments -> Create Base Set and the Unit menu is in the top left section of the panel)
- Select Apply to create the spline.
- Right click in the Z_dof field and select Spline - Browse and select .World.Spline_1
- Select Apply to create the motion agent
Step 5: Running the Inverse Dynamics Simulation
With the motion agent created on the leg, the model is then secured to ground by using a fixed joint between the lower_torso and ground. A simulation is then performed with the motion agent moving the leg up and down. During this phase the joint angles are being recorded.
- In the ADAMS/View main toolbox right click on the fixed joint icon in the first row, third column.
- With the cursor click on the lower_torso and anywhere on the screen for ground, then select anywhere on the screen to create the fixed joint (the location will not affect the simulation results).
- Select "Analyze" in the main-menu and "Dynamics" in the sub-menu
- Check the gravity box and select -Y for the gravity vector
- Enter 4 for end time and 100 for time steps
- Select Analyze to run the simulation
Step 6: Running the Forward Dynamics Simulation
After the inverse dynamics simulation has been performed, the joint angles are now recorded for the activity. In this step the motion agent is rendered inactive and the joints are updated to trained elements. The trained elements are controller functions which will produce a torque to minimize the difference between the instantaneous joint angle and the desired joint angle from the previous analysis.
- Select "Joints" on the main-menu and "Training" on the sub-menu
- Select the light bulb next to Install Trained Driver Rotational Elements to bring up the sub-panel.
- Leave the default values and select Apply. The joint graphics will change color indicating the trained elements
- Select "Analyze" in the main-menu and "Dynamics" on the sub-menu.
- Check Disable Motion Agents
- Select 4 seconds for the end time and 100 time steps.
- Select Analyze to run the simulation
Step 7: Examining the Results
After the simulation is performed, the results may be reviewed in a variety of ways. This section illustrates how hip torque data is presented with an animation of the human model with joint graphics which scale as a function of torque magnitudes.
- Select "Results" in the main-menu and "Data Display" in the sub-menu
- Bring up the post processor window by selecting the graph button at the top of the panel
- Select Joints as the data type.
- Select Issac_Left_Hip as the joint, torque as the characteristic and the sagittal component.
- Select Create Full Plot
- Select "Animation" in the sub-menu (change from "Data Display").
- Check Scale Joint/Tissue Graphics, select joints, scale globally and the light bulb
- Check divide window, select left view and select the arrow button to animate
Creating a Human Model with Muscles
This simple example illustrates the third type of human modeling with LifeMOD. In this example recording muscle elements are created on the body and a motion agent is used to move the passive limb through a certain motion pattern. During the inverse dynamics simulation, the muscle contractile histories are recorded. Next, the motion agents are rendered inactive and muscle forces based on the recorded contractile histories are used to drive the model. The forces generated in the model are based on creating forces to track the contractile histories while maintaining the limitations of the individual muscle physiological limitations. The user may also impose additional limitations on the individual muscle.
For more elaborate development of this type of analysis see the following tutorials:
- Bicycle
- Muscle Relocation
- Hip Replacement
- Knee Replacement
- Detailed Spine
- Rehabilitation Machine
- Grasping
Step 1: Creating the Body Segments
The first step in the process is to create the segments of the human body. For this example a lower body model is created. In LifeMOD, any configuration of segments may be modeled. Segment dimensions and mass properties are scaled based on the GeBOD anthropometric database.
- Bring up LifeMOD by selecting the desktop icon.
- Referring to the screen in Figure 2, select New Model.
- Select "Segments" in the main-menu and "Create Base Set" in the sub-menu
- Select Lower Body
- On the main modeling control panel, keep the defaults and select GeBOD Database for the anthropometric library.
- Select Median.
- Select Apply to create the body measurement table.
- Select Apply next to Create Human Segments.
Step 2: Creating the Joints
After the body segments are created the segments must be joined together with human joints. The joints for this example will be kinematic joints with passive torque functions. The passive torque functions are created to stabilize the model during the "training" or inverse dynamics phase.
- Select "Joints" in the main-menu and "Create Base Set" in the sub-menu
- Select the light bulb next to "Prepare Model with Recording Joints "
- Select the right leg and the left leg
- Select Execute to create the complete joint set.
Step 3: Posing the Human Model
fter the joints are created the human model may be posed into any configuration using by accessing the library of standard postures or by adjusting the joint angles individually.
- Select "Posture" in the main-menu and "Configure Base Model" in the sub-menu
- Select "Load Library Posture" to bring up the posture library
- Select "BicycleRiding" as the posture from the library
Step 4: Creating the Muscles
With the model posed, recording muscles are created for the body. LifeMOD contains a library of muscles for the body representing a sub-set of actual human muscles. If more muscles are necessary for simulation accuracy, they can be created as single muscles. Muscles may also wrap around structures in the model in "tissue wrapping." However, for this simple example, only the base set of muscles are generated.
- Select "Soft Tissues" in the main-menu and "Create Base Set" in the sub-menu
- Select the light bulb next to Prepare Model with Recording Muscle Elements to bring up the sub-panel.
- Select only the left leg and the right leg
- Select Execute to create the complete body muscle set.
Step 5: Creating the Motion Agents
With the model posed, motion agents can be created and positioned on the model. Motion agents move the segments of the model and can be based on displacement trajectories -- either entered manually or derived from motion capture equipment. The motion agents themselves are attached to the body segments with springs.
- Select "Motion" in the main-menu and "Create Individual Motion Agent" in the sub-menu
- Right click in the Body Segment field, select part - pick and click on the left_lower_leg in the modeling window.
- Select Manually select location either pick a point on the leg or enter 0,12,8
- Set x_dof as fixed and z_dof fixed and Rx_dof, Ry_dof and Rz_dof as free.
- For the Y_dof select driven and right click in the window to create a data spline.
- Enter 0,1,2,3,4 for the x values and 0,3,6,3,0 for the y values (when creating the spline, keep in mind the unit of measurement in which the body is functioning. To check, go to Segments -> Create Base Set and the Unit menu is in the top left section of the panel)
- Select Apply to create the motion agent on the left leg
- Enter Right_Lower_Leg as the body segment
- Enter 0,11,-6 as the location of the motion agent
- For the Y_dof select driven and right click in the window to create a data spline.
- Enter 0,1,2,3,4 for the x values and 0,-3,-6,-3,0 for the y values
- Select Apply to create the motion agent on the right leg
Step 6: Running the Inverse Dynamics Simulation
With the muscles created on the body, create a fixed joint between the lower_torso and the ground. A simulation is then performed with the motion agent moving the leg up and down. During this phase the individual muscle contractions are being recorded.
- In the ADAMS/View main toolbox right click on the fixed joint icon.
- With the cursor click on the lower_torso and anywhere on the screen for ground, then select anywhere on the screen to create the fixed joint (the location will not affect the simulation results).
- Select "Analyze" in the main-menu and "Dynamics" in the sub-menu
- Check the gravity box and select -Y for the gravity vector
- Enter 4 for end time and 100 for time steps
- Select Analyze to run the simulation
Step 7: Running the Forward Dynamics Simulation
After the inverse dynamics simulation has been performed, the individual muscle contractions are now recorded for activity. In this step, the motion agent is rendered inactive and the muscles are updated to trained elements. The trained elements are controller functions which will produce a force to minimize the difference between the instantaneous muscle contraction and the desired contractions from the previous analysis, while maintaining the muscle output within physiological constraints.
- Select "Soft Tissues" in the main-menu and "Training" in the sub-menu
- Select the light bulb next to "Install Trained Closed-loop Contractile Elements" to bring up the sub-panel.
- Leave the default values and select Apply. The muscle graphics will change color indicating the trained elements
- Select "Analyze" in the main-menu and "Dynamics" on the sub-menu.
- Check Disable Motion Agents
- Select 4 seconds for the end time and 100 time steps.
- Select Analyze to run the simulation
Step 8: Examining the Results
After the simulation is performed, the results may be reviewed in a variety of ways. This section illustrates how the iliacus muscle tension of the left leg is presented with the animation of the human model with muscles graphics scaling as a function of muscle tension magnitudes.
- Select "Results" on the main-menu and "Data Display" on the sub-menu
- Bring up the post processor window by selecting the graph button at the top of the panel
- Select Soft Tissues as the data type.
- Select Issac_Iliac_Ltiss as the soft tissue and tension as the characteristic.
- Select Create Full Plot
- Select Animation on the sub-menu
- Check Scale Joint/Tissue Graphics, select tissues, scale globally and the light bulb
- Check divide window, select left view and select the arrow button to animate
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