Assigned Force Functions

The model based items GRF_DATA and COP Path are signals stored at the Motion Capture rate.

This is because these signals have the option to be resolved into a Segment Coordinate System and all Segment Coordinate Systems (except the default LAB) are at the motion capture rate.

There are times, however, when it would be useful to get the Force, CofP, and FreeMoment for the force assignment at the analog sample rate.

Forces

FORCE(segment)

Select the force assigned to the Left Foot segment (default segment name LFT).

Evaluate_Expression

/EXPRESSION=FORCE("LFT")

/RESULT_NAME=SCOTT

! /RESULT_TYPE=DERIVED

! /RESULT_FOLDER=PROCESSED

;

Center of Pressure

COFP(segment)

Select the center of pressure assigned to the Left Foot segment (default segment name LFT).

Evaluate_Expression

/EXPRESSION=COFP("LFT")

/RESULT_NAME=SCOTT

! /RESULT_TYPE=DERIVED

! /RESULT_FOLDER=PROCESSED

;

Free Moment

FREEMOMENT(segment)

Select the Free Moment assigned to the Left Foot segment (default segment name LFT).

Evaluate_Expression

/EXPRESSION=FREEMOMENT("LFT")

/RESULT_NAME=SCOTT

! /RESULT_TYPE=DERIVED

! /RESULT_FOLDER=PROCESSED

;

Error Messages

Error Messages

There are several possible error messages related to the Assigned Forces Function.

Evaluate_Expression

/EXPRESSION=FORCE(JUNK)

/RESULT_TYPE=DERIVED

/RESULT_FOLDER=PROCESSED

/RESULT_NAME=TEST

;

WARNING! No Segment Name was specified. Did you forget the quotes?

In order to ensure that a string containing the segment name is recognized quotes must be used.

Evaluate_Expression

/EXPRESSION=COFP("JUNK")

/RESULT_TYPE=DERIVED

/RESULT_FOLDER=PROCESSED

/RESULT_NAME=TEST

;

INFO! Segment Junk was not found

The segment was not part of the Link Model

Evaluate_Expression

/EXPRESSION=COFP("Right Foot")

/RESULT_TYPE=DERIVED

/RESULT_FOLDER=PROCESSED

/RESULT_NAME=TEST

;

WARNING! Evaluate_Expression requires default segment names. For Right Foot use RFT

Visual3D has a set of default segment names that must be used in expressions, so that the

expressions can be shared between users that have different config files.

Evaluate_Expression

/EXPRESSION=COFP("Right Fore Foot")

/RESULT_TYPE=DERIVED

/RESULT_FOLDER=PROCESSED

/RESULT_NAME=TEST

;

INFO! Segment Right Fore Foot is Kinematic Only, so there is no Force Assignment possible.

Only Kinetic segments can be assigned a force.