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Parameters
Various parameters are built into the model during its construction. These parameters may be altered periodically to change the performance of the model during the simulation. "Tuning" the model allows it to follow the observed (motion capture) motion data more closely. For information on data sources for the parameters see Choosing Model Parameters
Sections:
- Types of Parameters
- Tuning Body Segment Parameters
- Tuning Joint Parameters
- Tuning Soft Tissue Parameters
- Tuning Contact Parameters
- Tuning Motion Agent Parameters
Types of Parameters
Various model parameters may be used to alter the behavior of the model during the simulation. These tuning processes allow the model perform more in line with the observed conditions in MOCAP data by comparing model output data to experimental data such as force plates, EMG data, etc. The parameters available for tuning are listed below in Figure 1.
Figure 1: Model parameters available for tuning.
These parameters include:
| Body | Passive Joint Scale Factors |
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| Hybrid III Joint Parameters | Forward Dynamics Servo Parameters |
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| Tendon Scale Factors | Muscle Scale Factors |
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| Contact Force Scale Factors | Motion Agent Parameters |
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Tuning Body Segment Parameters
Parameters -> Geometry
This panel in Figure 2 adjusts the radii of the foot ellipsoids (see Figure 3). Separate values may be entered for the heel and the metatarsals. An ellipsoid may be edited individually by right-clicking on the specific ellipsoid and entering the desired value. In this example, the radii of the ellipsoids model foot-floor contact forces in walking simulations.
Figure 2: Panel used to adjust the foot ellipsoid parameters
Figure 3: Heel and metatarsals ellipsoids
Tuning Joint Parameters
Parameters -> Joints
Figure 4 displays the panel to modify the joint scale factors. The scale factors are multipliers used to increase or decrease specific joint parameters on a globally-proportionate scale. Figure 4 also displays the correspondence between the scale factor and the scaled value.
Figure 4: Relationship between the joint parameters and the joint matrix edit panel
Tuning Soft Tissue Parameters
Parameters -> Tissues
Figure 5 displays the soft tissue scale factors for the ligaments, Hill-based muscles, tissue wrapping parameters and trained muscle gains.
Figure 5: Soft tissues scale factors panel
Tuning Contact Parameters
Parameters -> Contacts
Figure 6 displays the panel to adjust the scale factors for the contact forces in the model.
Figure 6: Contacts scale factors panel
Tuning Motion Agent Parameters
Parameters -> Motion Agents
Figure 7 displays the panel to adjust the weights and the global scale factors on the motion agents.
Figure 7: Motion agent scale factors panel
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