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The calculation of a functional joint is based on the movement of one segment relative to another segment. This allows to estimate knee- and elbow joint axes, hip- and glenohumeral joint centers.
The calibrations movements should have sufficient range of motion that the computation statistics produce a reasonable stationary point, but the range of motion should not be too large because soft tissue artifact (e.g. movement of markers relative to the underlying skeleton) should be minimized.
Typically specific calibration trials have to be executed.
Several cycles of movement should be included, but there is no study which analyses how many cycles is best. We recommend more than 3 cycles, others recomment a minimum of 5. The optimal number may depend on many issues, including the joint and the amount of soft tissue artfeacts. Each user should experiment with his own measurement procedure.
|name||name of the element||Yes|
|coordinateSystem||The name of the base coordinates system the moving marker is defined in.||Yes|
|biasCompensation||false||Switch bias compensation on or off.||No|
|biasCompensationIterations||3||If bias compensation is used with this attribute the number of iterations can be defined.||No|
|biasCompensationMaximumChange||10||If bias compensation is used and the different between the last two iteration is bigger than the given value in at least one component a warning is given.||No|
|Condition||A formula, which defines which frames are included in the functional calibration. If the formula value is 1 the frame is used.||No|
|phase||The name of the phases used for functional calibration. If this and the attribute Condtion are both not used the complete trials are used.||No|
|<name>OriginLocal||3d vector||CoR in local coordinates of the parent system.|
|<name>Radius||Double||Radius of the estimated sphere.|
|<name>FramesCount||Integer||Number of frames used for calibration.|
|<name>RadiusStd||Double||Std of the estimated radius of the sphere.|
<Phase name="RAbduk" startEvent="RHS" endEvent="RTO" process="post" calibrateIncludes="dynamic_calibrate_right_shoulder" includes="dummy"/> <CoRGamage2002 name="RGHJC" coordinateSystem="Right_Acromion" phase="RAbduk" biasCompensation="true" biasCompensationIterations="5" calibrateIncludes="dynamic_calibrate_right_shoulder" includes="dynamic,static">RHUMS</CoRGamage2002>
|name||name of the element||Yes|
|condition||If the attribute phase is not used and if it is set to a mathematical formula which is 1 or 0 it is used instead of defined events||No|
|phase||phase name, used if the phases are calculated elsewhere||No|
|<name>OriginLocal||3d vector||CoR in local coordinates of the parent system|
|<name>FramesCount||double||count of frames used for the estimation|
|<name>Radius||double||radius of the sphere around the origin of the parent coordinate system on which the origin of the child coordinate system is assumed to move around.|
|<name>RadiusStd||double||standard deviation of the radien|
<CoRSCoRE name="RGHJC" condition="RAbdukAngle<30.0" parentCoordinateSystem="RClavicle" childCoordinateSystem="RHumerus"/>
A warining is given, if the count of frames selected by the defined phases is smaller than 30. Keep in mind that even 30 frames typically are too less to get a „good“ estimation of a center of rotation. In this case the frames of the complete trial are used, which also typically does not result in an good estimation.