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--- visual3d:documentation:kinematics_and_kinetics:external_forces:force_structures [2024/07/03 17:37] – created sgranger
+++ visual3d:documentation:kinematics_and_kinetics:external_forces:force_structures [2025/09/12 19:04] (current) – [Structure consisting of 2 force platforms and 1 surface] wikisysop
@@ Line 1: / Line 1: @@
-====== Force_Structures ======
+====== Force Structures ======
 Force Structures were conceived as a mechanism for combining force platform data (e.g. treating several contiguous platforms as a single platform), and for accommodating structures that are attached to the force platform as a super-structure such as the stairs manufactured by AMTI.
@@ Line 9: / Line 9: @@
 External forces require the specification of 9 components
-Force= (Fx, Fy, Fz)
+Force= (Fx, Fy, Fz)\\
-Center of Pressure= (COPx, COPy, COPz)
+Center of Pressure= (COPx, COPy, COPz)\\
-Free Moment= (Tx, Ty, Tz)
+Free Moment= (Tx, Ty, Tz)\\
 Only 6 pieces of information, however, are available from a force platform, so it is necessary to specify (or assume) 3 components.
 For a typical platform:
-Tx and Ty are assumed to be zero. This means that we assume that the subject is **not** pulling up on the platform.
+Tx and Ty are assumed to be zero. This means that we assume that the subject is **not** pulling up on the platform.\\
-COPz is assumed to be on the top surface of the platform.
+COPz is assumed to be on the top surface of the platform.\\
 For a surface (e.g. a step) placed on top of the force platform, the COP is translated along the Force Vector to the new surface. (e.g. the intersection of the force with the new surface).
-{{Force_Structure.jpg}}
+{{:Force_Structure.jpg?500x}}
 This figure shows a picture of an oblique force applied to a step. This figure shows one type of force platform, but the concept applies equally to all platforms.
@@ Line 40: / Line 40: @@
 The edit dialog invoked either by selected Modify Force Structures under the Force Menu or by the Pipeline command [[Visual3D:Documentation:Pipeline:Force_Commands:Modify_Force_Structure_Parameters|Modify_Force_Structure_Parameters]] as follows.
-{{AMTI_steps2.jpg}}
+{{:AMTI_steps2.jpg}}
 Each structure is defined as a plane (or polygon) defined by four corners.
@@ Line 48: / Line 48: @@
 === Modify_Force_Structure_Parameters ===
-**Modify_Force_Structure_Parameters**
+<code>
+Modify_Force_Structure_Parameters
 /USED= Number of Force Structures Used
 ! /TYPE= Not currently used
@@ Line 63: / Line 64: @@
 /USE_FORCES_FOR_KINETICS= are forces kinematics only?
 /COMBINE_INPUT_FORCES= combine all forces for each structure into a single force
-! /[[Visual3D:Documentation:Pipeline:File_Commands:Update_C3D_File|Update_C3D_File]]=FALSE
+! /Update_C3D_File=FALSE
-**;**
+;
-For example, the following force structure has one surface attached to two force platforms.
+</code>
-{{ForceStructureDlg1x2.jpg}}
+For example, the following force structure has one surface attached to two force platforms.
-\\
+{{:ForceStructureDlg1x2.jpg}}
-**Modify_Force_Structure_Parameters**
+<code>
+Modify_Force_Structure_Parameters
 /USED=2
 /TYPE=0+0
@@ Line 88: / Line 90: @@
 /COMBINE_INPUT_FORCES=TRUE+FALSE
 ! /UPDATE_C3D_FILE=FALSE
-**;**
+;
+</code>
 See also [[Visual3D:Documentation:Pipeline:Force_Commands:Modify_Force_Structure_Parameters|Modify_Force_Structure_Parameters]]
@@ Line 95: / Line 98: @@
 The following dialog creates a force structure that is comprised of 2 surfaces attached to the same platform.
-{{AMTI_steps3.jpg}}
+{{:AMTI_steps3.jpg}}
 Visual3D creates two surfaces, so it creates two force signals.
@@ Line 111: / Line 114: @@
 **COP_1**, **FORCE_1** and **FREEMOMENT_1**
-{{ForceStructureDataTree.jpg}}
+{{:ForceStructureDataTree.jpg}}
 In the following figure the right foot makes contact with 2 steps
-{{ForceStructureGraph.jpg}}
+{{:ForceStructureGraph.jpg}}
 ==== Structure consisting of 2 force platforms and 1 surface ====
@@ Line 121: / Line 125: @@
 The following dialog creates a force structure that is comprised of 1 surface spanning 2 force platforms.
-{{ForceStructureDig1x2.jpg}}
+{{:ForceStructureDlg1x2.jpg}}
 The user has the option to treat each force independently, which means that each force FP1 and FP2 could be assigned to the same segment.
@@ Line 134: / Line 138: @@
   * solve the following 6 equations for the resultant force and moment
-{{ForceStructureEqn1.jpg}} solve for the 3 components of the force
+{{:ForceStructureEqn1.jpg}} solve for the 3 components of the force
-{{ForceStructureEqn2.jpg}} assume the resultant center of pressure lies on the output surface, and that the Free Moment is computed only about the normal to the surface
+{{:ForceStructureEqn2.jpg}} assume the resultant center of pressure lies on the output surface, and that the Free Moment is computed only about the normal to the surface
   * solve for the x and y component of the COP on the surface
@@ Line 142: / Line 146: @@
   * Transform these values back into the laboratory coordinate system
-If there are two force platforms, the resulting signal will appear in the data tree as
+If there are two force platforms, the resulting signal will appear in the data tree as:
 **FS1_1** and **FS1_2**
 This is interpreted as Force Structure 1 contribution from Force platform 1, and Force Structure 1contribution from force platform 2.
-\\
+If, for example, instead of FP1 and FP2, there was FP1 and FP3, the signals would be:
-If, for example, instead of FP1 and FP2, there was FP1 and FP3, the signals would be
 **FS1_1** and **FS1_3**
-\\
-if the option to combine all input forces is selected, there will be one resulting signal
+If the option to combine all input forces is selected, there will be one resulting signal:
 **FS1_1**