Normalized Joint Angle - Method 1

From Visual3D Wiki Documentation
Jump to: navigation, search
Language:  English  • français • italiano • português • español 

One method for setting the Ankle Joint Angle to Zero degrees in the standing trial is to define the Segment Coordinate System for the Virtual Foot Segment to be aligned precisely with the Segment Coordinate System for the Shank. This can be accomplished by using the same proximal and distal targets.

This example uses Tutorial2.cmo from the Visual3D Tutorial Files page. Download this file and follow the steps below.

Open the Tutorial2.cmo file, click on the Model tab. The model has been completely constructed.

Step 1: Construct Right Shank Segment

Create Right Shank Segment:

  1. In the Segments tab, from the Segment Name pulldown select Right Shank.
  2. Click on the Create Segment button.
  3. In the Right Shank tab, enter these values:

       Define Proximal Joint and Radius
       Lateral: RLK     Joint: None     Medial: RMK     
       Radius: numbers grayed out

       Define Distal Joint and Radius
       Lateral: RLA     Joint: None     Medial: RMA     
       Radius: numbers grayed out

       Extra Target to Define Orientation
       Location: None     None

       Select Tracking Targets:
         Check RSK1, RSK2, RSK3, RSK4

  4. Click on Build Model. A 3D image of the shank will appear
  5. Click on Close Tab before proceeding.

Right Shank Segment Normalized Joint Angle Method 1.png

Step 2: Construct Right Virtual Foot Segment

Create Right Virtual Foot Segment:

  1. In the Segments tab, type Right Virtual Foot in the Segment Name box.
  2. Check Kinematic Only
  3. Click on the Create Segment button.
  4. In the Right Virtual Foot tab, enter these values:

       Define Proximal Joint and Radius
       Lateral: RLK     Joint: None     Medial: RMK     
       Radius: numbers grayed out

       Define Distal Joint and Radius
       Lateral: RLA     Joint: None     Medial: RMA     
       Radius: numbers grayed out

       Extra Target to Define Orientation
       Location: None     None

       Select Tracking Targets:
         Check RFT1, RFT2, RFT3

  5. Click on Build Model. Since it is a Kinematic Only segment, no new image will be appear. Note that the coordinate system for the right virtual foot segment is the same as the right shank segment.
  6. Click on Close Tab before proceeding.

Right Virtual Foot Segment Normalized Joint Angle Method 1.png

Note: that having the two segment coordinate systems perfectly aligned means that the segments have identical orientation in the standing trial and hence have a joint angle of zero degrees.

Step 3: Plot Angles for Comparison

Let's plot both ankle joint angles (shank with respect to foot and shank with respect to virtual foot) to see the difference.

Create the angles

First, let's create the angles:

Create Right Ankle Angle - Right Foot with respect to Right Shank:

  1. In the Model menu, select Compute Model Based Data.
  2. In the dialog enter the following:

       Data Name
       Right Ankle Angle

       Model based Item Properties
       Joint_Angle

       Segment
       Right Foot

       Reference Segment
       Right Shank

  3. Click on Create
  4. Click on Close before proceeding.
Right Ankle Angle Normalized Joint Angle Method 1.png

Create the Normalized Right joint angle - Right Virtual Foot with respect to Right Shank:

  1. In the Model menu, select Compute Model Based Data.
  2. In the dialog enter the following:

       Data Name
       Right Ankle Angle Virtual Foot

       Model based Item Properties
       Joint_Angle

       Segment
       Right Virtual Foot

       Reference Segment
       Right Shank

  3. Click on Create
  4. Click on Close before proceeding.
Right Ankle Angle Virtual Foot Normalized Joint Angle Method 1.png]

Graph the Angles for Comparison

Now let's graph the two angles and compare their signals.

Graph the Right Ankle Angle and Right Ankle Angle Virtual Foot
  1. Graph the Right Ankle Angle
    1. In the Signal and Events tab, make the Walking Trial 1.c3d active
    2. Select the Link_Model_Based to expand the folder
    3. Right-click on the Right Ankle Angle to bring up the submenu
    4. From the submenu, select Graph X,Y, and Z to plot all three components of the right ankle angle.
    5. Another submenu will appear, select New Graph to plot all 3 components in the pane to the right.
  2. Add the Right Ankle Angle Virtual Foot to the Graph
    1. In the Signal and Events tab, select the Link_Model_Based folder.
    2. Right-click on the Right Ankle Angle Virtual Foot to bring up the submenu
    3. From the submenu, select Graph X,Y, and Z to plot all three components of the right ankle angle virtual foot.
    4. Another submenu will appear, select Add to Existing to add all 3 components to the existing graph.
Graphs Normalized Joint Angle Method 1.png

The top graph represents ankle dorsi/plantarflexion angle. Two signals are shown. The top most signal is right ankle angle and the bottom signal is the normalized angle angle (wrt to virtual foot).

Other Normalization Methods

For another normalization method, go to Normalized Joint Angle - Method 2. In addition, there is a great tutorial Tutorial: Foot and Ankle Angles that discusses normalization.

Retrieved from ""