HAS-Motion Software Documentation

User Tools

Site Tools

You are here: Main Page » visual3d » documentation » pipeline » model_based_data_commands » Joint Angle
visual3d:documentation:pipeline:model_based_data_commands:joint_angle

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision		Previous revision
visual3d:documentation:pipeline:model_based_data_commands:joint_angle [2024/07/03 17:42] – created sgrangervisual3d:documentation:pipeline:model_based_data_commands:joint_angle [2024/08/26 19:47] (current) – [Examples] wikisysop
Line 1: Line 1:
-====== Joint_Angle ======+====== Joint Angle ======
  
 Joint angles represent a conceptual challenge to many users. Part of the challenge is related to the fact that joint angles are not vectors (unlike every other Kinematic variable in Visual3D). This means that they can't be added or subtracted, which makes the specification of a reference angle awkward. Another part of the challenge is related to the fact that there are a number of clinical/sports related conventions that specify a reference angle that is often not consistent with the definition of the segment coordinate systems in Visual3D, which usually requires Visual3D users to create [[Visual3D:Documentation:Modeling:Segments:Virtual_Segments|Virtual Segments]] whose segment coordinate systems are consistent. Joint angles represent a conceptual challenge to many users. Part of the challenge is related to the fact that joint angles are not vectors (unlike every other Kinematic variable in Visual3D). This means that they can't be added or subtracted, which makes the specification of a reference angle awkward. Another part of the challenge is related to the fact that there are a number of clinical/sports related conventions that specify a reference angle that is often not consistent with the definition of the segment coordinate systems in Visual3D, which usually requires Visual3D users to create [[Visual3D:Documentation:Modeling:Segments:Virtual_Segments|Virtual Segments]] whose segment coordinate systems are consistent.
Line 50: Line 50:
 The typical kinetic foot is displayed here: The typical kinetic foot is displayed here:
  
-{{tutorial1_16.jpg}}+{{:tutorial1_16.jpg}}
  
 For this representation of the foot segment the z-axis is directed from the metatarsals to the ankle center. For this representation of the foot segment the z-axis is directed from the metatarsals to the ankle center.
Line 64: Line 64:
 A common kinematic only foot is displayed here: A common kinematic only foot is displayed here:
  
-{{RFT_2_Rotated.jpg}}+{{:RFT_2_Rotated.jpg}}
  
 For this representation of the virtual foot segment the y-axis is directed from the heel to the toe. For this representation of the virtual foot segment the y-axis is directed from the heel to the toe.
Line 84: Line 84:
 The result of this decision is that flexion/extension has the same sign for left and right legs, but inward/outward rotation and abduction/adduction have opposite signs. The result of this decision is that flexion/extension has the same sign for left and right legs, but inward/outward rotation and abduction/adduction have opposite signs.
  
-The user can change this by negating the necessary terms when the joint angle is defined in the **Compute Model Based Items** Dialog. Refer [[Visual3D:Tutorials:Kinematics_Kinetics:Model_Based_Computations#Understanding_the_Knee_Angle_Signal|here]] for an example.+The user can change this by negating the necessary terms when the joint angle is defined in the **Compute Model Based Items** Dialog. Refer [[Visual3D:Tutorials:Kinematics_and_Kinetics:Model_Based_Computations#Understanding_the_Knee_Angle_Signal|here]] for an example.
  
 ==== The Joint Coordinate System ==== ==== The Joint Coordinate System ====
Line 140: Line 140:
 Note: In Visual3D joint angles are simply the transformation from one segment coordinate system to another segment coordinate system, so it follows that the definition (e.g. orientation) of the segment coordinate systems matters. For example, if two segment coordinate systems are aligned perfectly (even though they may be displaced from each other) the resulting joint angle signal is zero. Note: In Visual3D joint angles are simply the transformation from one segment coordinate system to another segment coordinate system, so it follows that the definition (e.g. orientation) of the segment coordinate systems matters. For example, if two segment coordinate systems are aligned perfectly (even though they may be displaced from each other) the resulting joint angle signal is zero.
  
-[[Visual3D:Documentation:Modeling:Segments:Normalizing_the_Pelvis_Segment_Angle_Example|Normalizing the Pelvis Angle]] 
 |     **Deprecated examples**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              | |     **Deprecated examples**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
 |**These examples are not recommended for use and are included for backwards compatibility only.**\\ \\ In early version of Visual3D, using default normalization of the knee causes the RKNEE_ANGLE signal to be zero in all 3 components when the subject is in the standing posture. This has not affect on the segment coordinate system definitions, so normalizing the joint angle does not "clean up" any errors in the definition of the segment. It simply sets the posture in which the joint angle is zero.\\ \\ We don't recommend using this normalization because there are situations in which the intermediate pose in the calculations will be in gimbal lock and the normalized angle will be undefined. In addition, it was sensitive to the subject's orientation relative to the lab, and was often being used incorrectly.\\ \\ As of version 5, the **Normalization** option for **Joint_Angle** was removed from the **Compute_Model_Based_Data** drop down list because it was sensitive to the subject's orientation relative to the lab, and was often being used incorrectly.  | |**These examples are not recommended for use and are included for backwards compatibility only.**\\ \\ In early version of Visual3D, using default normalization of the knee causes the RKNEE_ANGLE signal to be zero in all 3 components when the subject is in the standing posture. This has not affect on the segment coordinate system definitions, so normalizing the joint angle does not "clean up" any errors in the definition of the segment. It simply sets the posture in which the joint angle is zero.\\ \\ We don't recommend using this normalization because there are situations in which the intermediate pose in the calculations will be in gimbal lock and the normalized angle will be undefined. In addition, it was sensitive to the subject's orientation relative to the lab, and was often being used incorrectly.\\ \\ As of version 5, the **Normalization** option for **Joint_Angle** was removed from the **Compute_Model_Based_Data** drop down list because it was sensitive to the subject's orientation relative to the lab, and was often being used incorrectly.  |
Line 147: Line 146:
  
 === Pelvis Segment Angle === === Pelvis Segment Angle ===
 +
 +The [[visual3d:documentation:modeling:segments:pelvis_segment_angle|Pelvis Angle]] typically refers to the orientation of the Pelvis relative to the Laboratory.
  
 === Normalizing the Pelvis Angle === === Normalizing the Pelvis Angle ===
  
-Normalizing the Pelvis Segment Angle. The Coda and Helen Hayes pelvis are tilted forward approximately 20 degrees from the horizontal. In describing the orientation of the pelvis or for describing the hip joint angle, it is often convenient to define a pelvis angle that has a coronal plane parallel to the floor (eg a vertical segment with zero tilt).+[[Visual3D:Documentation:Modeling:Segments:Normalizing_the_Pelvis_Segment_Angle_Example|Normalizing the Pelvis Angle]]. The Coda and Helen Hayes pelvis are tilted forward approximately 20 degrees from the horizontal. In describing the orientation of the pelvis or for describing the hip joint angle, it is often convenient to define a pelvis angle that has a coronal plane parallel to the floor (eg a vertical segment with zero tilt).
 === Shoulder Angle === === Shoulder Angle ===
  
Line 160: Line 161:
  
 === Computing the Range of Motion === === Computing the Range of Motion ===
 +The range of motion of the pelvis angle is commonly defined as the range of each component of the segment angle. While this isn't mathematically correct because joint angles are not vectors, it is still quite common. 
  
 === Creating a Virtual Laboratory: Example 1 === === Creating a Virtual Laboratory: Example 1 ===
visual3d/documentation/pipeline/model_based_data_commands/joint_angle.1720028529.txt.gz · Last modified: 2024/07/03 17:42 by sgranger