Difference between revisions of "Bertec Force Plate Setup"

(Prime Series Force Plate Sync Configuration)
(Peripheral Device Module)
 
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[[Category: Peripheral Devices]]
 
[[Category: Peripheral Devices]]
 
[[Category: Device Synchronization]]
 
[[Category: Device Synchronization]]
  [[OptiTrack Documentation Wiki|Back to the Main Page]]
+
  [[Main Page]] → [[Bertec Force Plate Setup]]
 
----
 
----
  
 +
'''Scope'''
 +
<div class="padded">
 +
This page provides instructions on how to integrate a Bertec force plate system with an OptiTrack motion capture system.
 +
</div>
  
 
'''Overview'''
 
'''Overview'''
 
<div class="padded">
 
<div class="padded">
When a motion capture system is used in conjunction with force plates, they work together as a powerful tool for various research applications including biomechanical analysis, clinical gait analysis, physiology research, sports performance research, and much more. An OptiTrack motion capture system can synchronize with force plates to obtain both kinematic and kinetic measurements. Force plate integration is supported only with a Prime camera system using the eSync synchronization hub. For Bertec force plate integration support, you must use '''Motive 1.10 or above'''. This page provides guidelines for setting up and configuring Bertec force plates — with digital outputs — along with the OptiTrack motion capture system.
+
{{ForcePlateIntro}}
 
+
For detailed information on specifications and configurations on the force plates, refer to the documentation provided by the force plate manufacturer.
+
 
</div>
 
</div>
 
  
 
'''Requirements'''
 
'''Requirements'''
 
<div class="padded">
 
<div class="padded">
 
* Supported Amplifier Models: AM6800
 
* Supported Amplifier Models: AM6800
* For synchronization support, firmwares on Bertec amplifiers must be updated to its most recent version (above June 2016 release).
+
* Firmware Version: For synchronization support, the Bertec amplifiers must be installed with firmware version 4.5.2 or above. The current firmware version gets displayed on the 7-segment display when first powering up the amplifier. Please check this and make sure the firmware is updated to the supported versions.
* Prime series Ethernet camera system with the eSync synchronization hub for outputting ''Recording Gate'' signal.
+
* Prime series Ethernet camera system with the eSync synchronization hub.
 
* Motive 1.10 or above.
 
* Motive 1.10 or above.
 
</div>
 
</div>
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<div class="padded">
 
<div class="padded">
==Component Wiring (Bertec)==
 
 
====Bertec Force Plate System Setup====
 
====Bertec Force Plate System Setup====
 
:Refer to the respective Bertec system user documentation for detailed information on setting up the force plate system and connecting to the host PC.
 
:Refer to the respective Bertec system user documentation for detailed information on setting up the force plate system and connecting to the host PC.
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====Wiring the eSync with the Amplifier====
 
====Wiring the eSync with the Amplifier====
* Bertec AM 6800 amplifiers: Use the provided female 15-pin D-Sub connector to get the '''ZERO''' signal and the '''SYNC''' signal from the '''ANALOG OUTPUT''' port of the amplifier.
+
<tabs>
* The ZERO cable from the amplifier needs to be connected to the output port of the eSync for synchronization with the camera system.
+
<tab name="Triggered Sync" class="padded">
* The SYNC cable from the amplifier needs to be interconnected between the force plate amplifiers for their internal sync.
+
'''Triggered Sync Cabling'''
 +
:* Bertec AM 6800 amplifiers: Use the provided female 15-pin D-Sub connector to get the '''ZERO''' signal and the '''SYNC''' signal from the '''ANALOG OUTPUT''' port of the amplifier.
 +
:* The '''ZERO''' cable from the amplifier needs to be connected to the output port of the eSync for synchronization with the camera system.
 +
:* The '''SYNC''' cable from the amplifier needs to be interconnected between the force plate amplifiers for their internal sync. When using more than one plates, a BNC connector or a BNC splitter will need to be used to interconnect the SYNC cables between multiple amplifiers.
  
 +
<center>
 +
<li class="thumblist">[[Image:Bertec_Ethernet_Triggered.png|thumb|750 px|Bertec force plate + Prime system setup diagram for triggered sync.]]</li>
 +
<li class="thumblist">[[Image:Bertec_Sync_Zero.jpg|thumb|550 px|Zero cable from the amplifier]]</li>
 +
</center>
 +
</tab>
 +
<tab name="Reference Clock Sync" style="padding: 1em;">
 +
'''Reference Clock Sync'''
 +
:*The '''SYNC''' cable from the amplifier needs to be connected to the output port of the eSync for synchronization with the camera system.
  
 
<center>
 
<center>
<li style="display: inline-block; vertical-align: text-top;">[[Image:Bertec_Ethernet_Updated.png|thumb|750 px|Bertec force plate + Prime system setup diagram.]]</li>
+
<li class="thumblist">[[Image:Bertec_Ethernet_ClockSync.png|thumb|750 px|Bertec force plate + Prime system setup diagram for reference clock sync.]]</li>
<li style="display: inline-block; vertical-align: text-top;">[[Image:Bertec_Sync_Zero.jpg|thumb|550 px|Zero cable from the amplifier]]</li>
+
 
</center>
 
</center>
 +
</tab>
 +
</tabs>
 +
 +
====Hot Plugging====
 +
{{Indent|{{HotPlugging}}}}
 
</div>
 
</div>
  
 
=Software Setup=
 
=Software Setup=
 
----
 
----
 
<div class="padded">
 
 
==Peripheral Device Module==
 
==Peripheral Device Module==
 
<section begin=peripheralmodulesetup/>  
 
<section begin=peripheralmodulesetup/>  
 
<div class="padded">
 
<div class="padded">
In order to integrate force plate systems with Motive, you will need to setup the required drivers and plugins. Motive installer is packaged with the Peripheral Device module which can be added during the Motive installation process. This module includes all necessary drivers and plugins for integrating external devices including force plates (AMTI and Bertec) in Motive. During the Motive installation, a list of program features will be shown in the Custom Setup section. Here, change the setting for the ''Peripheral Device'' module, as shown in the below image, so that the module is installed along with Motive Files.
+
In order to integrate force plate systems with Motive, you will need to setup the required drivers and plugins. Motive installer is packaged with the Peripheral Device module which can be added. During the Motive installation, a list of program features will be shown in the Custom Setup section. Here, change the setting for the ''Peripheral Device'' module, as shown in the below image, so that the module is installed along with Motive Files.
 
{{Info|'''Note''' : Even if you are not using NI-DAQ, it is still necessary to install NI-DAQmx drivers that come up next in the installer.}}
 
{{Info|'''Note''' : Even if you are not using NI-DAQ, it is still necessary to install NI-DAQmx drivers that come up next in the installer.}}
 +
 +
{{Warning|
 +
'''Installation Note:''' For integration into Motive, the NI-DAQmx 15.1.1 or later runtime driver must be installed. If you are already using an older version of the NI-DAQmx runtime and Motive is having problems recognizing the connected device, update the driver or uninstall and re-install the packaged version of the driver before contacting [http://optitrack.com/contact/ Support]. In Motive, you can inspect device connection status via the [[#Troubleshooting|Status Log]] panel which can be accessed under the View tab in Motive.
 +
}}
 +
 +
{{Warning|'''Notes on NI-DAQmx version 19.x:''' There is a known issue with the latest NI-DAQmx version (19.x) where it crashes Motive on startup. If you have this version of the driver installed, please reinstall with the recommended version (15.1.1) provided with the Motive installer.}}
 +
  
 
<center>[[Image:ND_OPMinstall.png|450 px|Installing OptiTrack Peripheral Module.]] [[Image:DAQmxInstall.gif|450 px]]</center>
 
<center>[[Image:ND_OPMinstall.png|450 px|Installing OptiTrack Peripheral Module.]] [[Image:DAQmxInstall.gif|450 px]]</center>
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<div class="padded">
 
<div class="padded">
 
====Bertec Customers====
 
====Bertec Customers====
:In addition to the Peripheral Device module, you also need to install the '''Digital Acquire&trade;''' from Bertec. Visit the below webpage to download the software, and follow the respective instructions to install. This software installs remaining resources for connecting the Bertec force plates.
+
:In addition to the Peripheral Device module, you may also want to install the '''Digital Acquire&trade;''' from Bertec to verify that the force plates are properly working. Visit the below webpage to download the software, and follow the respective instructions to install. This software installs remaining resources for connecting the Bertec force plates.
  
 
:* Link: http://bertec.com/downloads/
 
:* Link: http://bertec.com/downloads/
  
:'''Note:''' You cannot run Digital Acquire and Motive together and have them connected to the plate(s) at the same time.  
+
{{Indent|{{Warning|'''Note:''' You cannot run Digital Acquire and Motive together and have them connected to the plate(s) at the same time.}}}}
 
</div>
 
</div>
  
 
==Force Plate Setup in Motive==
 
==Force Plate Setup in Motive==
 
 
<div class="padded">
 
<div class="padded">
 
====1. Start Motive====
 
====1. Start Motive====
 
<section begin=setupstepone/>
 
<section begin=setupstepone/>
:If the hardware and software for the force plates are configured and successfully recognized, Motive will list out the detected force plates with number labels (1, 2, etc..). Motive will notify you of incorrect or nonexistent force plate calibration files. When the devices are properly instantiated in Motive, the following status messages will be shown under that [[Status Log]].
+
<div class="padded">
 +
If the hardware and software for the force plates are configured and successfully recognized, Motive will list out the detected force plates with number labels (1, 2, etc..). Motive will notify you of incorrect or nonexistent force plate calibration files. When the devices are successfully instantiated in Motive, the [[Status Log]] will indicate that the device has been created and loaded.
  
 
<center><ul>
 
<center><ul>
<li style="display: inline-block; vertical-align: text-top;">[[Image:FP_FirstOpened.png|thumb|alt=Initial view in Motive after setting up force plates.|450px|center|Motive with force plates.]]</li>
+
<li class="thumblist">[[Image:FP_FirstOpened.png|thumb|alt=Initial view in Motive after setting up force plates.|450px|center|Motive with force plates.]]</li>
 
<section end=setupstepone/>
 
<section end=setupstepone/>
<li style="display: inline-block; vertical-align: text-top;">[[Image:Bertec_StatusLog.png|thumb|Status Log pane in Motive.]]</li>
+
<li class="thumblist">[[Image:Bertec_StatusLog.png|thumb|Status Log pane in Motive.]]</li>
 
</ul></center>
 
</ul></center>
 +
</div>
  
 
====2. Calibrate Cameras====
 
====2. Calibrate Cameras====
:Calibrate the capture volume as normal to get the orientation of the cameras (see the [[Quick Start Guide]] or [[Calibration]] page for more information). The position of the force plate is about the center of the volume, and when you recalibrate or reset the ground plane, you will need to also realign the position of your force plates for best results.
+
<div class="padded">
 +
Calibrate the capture volume as normal to get the orientation of the cameras (see the [[Quick Start Guide]] or [[Calibration]] page for more information). The position of the force plate is about the center of the volume, and when you recalibrate or reset the ground plane, you will need to also realign the position of your force plates for best results.
  
 
[[Image:FP_CaibCameras.png|thumb|alt=Motive after setting up force plates and calibration.|450px|center|Motive with force plates and camera calibration.]]
 
[[Image:FP_CaibCameras.png|thumb|alt=Motive after setting up force plates and calibration.|450px|center|Motive with force plates and camera calibration.]]
 +
</div>
  
 
====3. Setup CS-400====
 
====3. Setup CS-400====
:On the [[Calibration Squares|CS-400 calibration square]], pull the force plate alignment tabs out and put the force plate leveling jigs at the bottom. The leveling jigs align the calibration square to the surface of your force plate. The alignment tabs allow you to put the CS-400 flush against the sides of your force plate giving the most accurate alignment.
+
<div class="padded">
 +
On the [[Calibration Squares|CS-400 calibration square]], pull the force plate alignment tabs out and put the force plate leveling jigs at the bottom. The leveling jigs align the calibration square to the surface of your force plate. The alignment tabs allow you to put the CS-400 flush against the sides of your force plate giving the most accurate alignment.
  
 
[[Image:FP_WandAlignment.png|thumb|alt=CS-400 calibration square with force plate force plate parts.|600px|center|CS-400 calibration square with force plate force plate parts.]]
 
[[Image:FP_WandAlignment.png|thumb|alt=CS-400 calibration square with force plate force plate parts.|600px|center|CS-400 calibration square with force plate force plate parts.]]
 
+
</div>
  
 
====4. Place CS-400 on force plate====
 
====4. Place CS-400 on force plate====
 
<section begin=setupstepfour/>  
 
<section begin=setupstepfour/>  
:Place the calibration wand on the force plate so that vertex of the wand is located at the right-hand corner of the side where the cable input is located (as shown in the image below). A correct placement of the calibration square is important because it determines the orientation of the force plate and its local coordinate axis within the global system. The coordinate systems for force plates are independent of the system used Motive.
+
<div class="padded">
 +
Place the calibration wand on the force plate so that vertex of the wand is located at the right-hand corner of the side where the cable input is located (as shown in the image below). A correct placement of the calibration square is important because it determines the orientation of the force plate and its local coordinate axis within the global system. The coordinate systems for force plates are independent of the system used Motive.
 +
</div>
 
<section end=setupstepfour/>  
 
<section end=setupstepfour/>  
:Bertec force plates use the right-hand system. The longer arm of CS-400 will define the Y axis, and the shorter arm will define the X axis of the force plate. Accordingly, Z axis is directed downwards for measuring the vertical force.
+
<div class="padded">Bertec force plates use the right-hand system. The longer arm of CS-400 will define the Y axis, and the shorter arm will define the X axis of the force plate. Accordingly, Z axis is directed downwards for measuring the vertical force.
  
 
<center>
 
<center>
<li style="display:inline-block; vertical-align:text-top;">[[Image:Bertec_CalSquare.png|thumb|350px|Bertec force plate with CS-400 aligned properly.]]</li>
+
<li class="thumblist">[[Image:Bertec_CalSquare.png|thumb|350px|Bertec force plate with CS-400 aligned properly.]]</li>
<li style="display:inline-block; vertical-align:text-top;">[[Image:FP_ForcePlateCoordinateAxis.png|thumb|300 px|Calibrated force plate position and orientation. X and Y axis is shown.]]</li>
+
<li class="thumblist">[[Image:FP_ForcePlateCoordinateAxis.png|thumb|300 px|Calibrated force plate position and orientation. X and Y axis is shown.]]</li>
 
</center>
 
</center>
 +
</div>
  
 
====5. Set force plate position in Motive====
 
====5. Set force plate position in Motive====
:After placing the calibration square on the force plate, select the CS-400 markers in Motive. Right click on the force plate you want to locate, and click '''Set Position'''. When there are multiple force plates in a volume, you may need to step on the force plate to find which platform the calibration square is on. In Motive, uncalibrated force plates will light up in green and a force vector will appear when you step on the plate.  Repeat step 4 and 5 for other force plates as necessary.
+
<div class="padded">
 +
After placing the calibration square on the force plate, select the CS-400 markers in Motive. Right click on the force plate you want to locate, and click '''Set Position'''. When there are multiple force plates in a volume, you may need to step on the force plate to find which platform the calibration square is on. In Motive, uncalibrated force plates will light up in green and a force vector will appear when you step on the plate.  Repeat step 4 and 5 for other force plates as necessary.
  
:Referencing to the markers on the calibration square, Motive defines the location of the force plate axis within the global coordinate system. When setting the position, the previously defined force plate dimension values and mechanical-to-electrical center offset values will be applied and reflected in the [[View pane|Perspective View]] pane.  
+
Referencing to the markers on the calibration square, Motive defines the location of the force plate axis within the global coordinate system. When setting the position, the previously defined force plate dimension values and mechanical-to-electrical center offset values will be applied and reflected in the [[View pane|Perspective View]] pane.  
  
<div class="padded">
 
 
{{Info|'''Tip:''' To double check that the dimensions are modified properly, you can place extra retroreflective markers on each corner of the platform and monitor the coincidence of the markers position with the force plate assets from the perspective view.}}
 
{{Info|'''Tip:''' To double check that the dimensions are modified properly, you can place extra retroreflective markers on each corner of the platform and monitor the coincidence of the markers position with the force plate assets from the perspective view.}}
 
  
 
[[Image:FP_SetPosition.png|thumb|alt=Setting the position of a force plate in Motive.|600px|center|Setting the position of a force plate in Motive. The number label on the force plate is inverted because the force plate position and orientation has not been calibrated yet.]]
 
[[Image:FP_SetPosition.png|thumb|alt=Setting the position of a force plate in Motive.|600px|center|Setting the position of a force plate in Motive. The number label on the force plate is inverted because the force plate position and orientation has not been calibrated yet.]]
 +
</div>
  
====6. Zero force plates====
+
====6. Set the Force Plate Dimension====
 +
<div class="padded">
 +
If the force plate dimensions are not automatically configured, you need to enter the dimensions of the force plate in the force plate properties after calibrating its positions. Go to the [[Devices pane]] and select the force plate, and its properties will get listed under the [[Properties pane]]. Enter the length and width (in meters) values for the corresponding plates as reported in the specifications.
 +
</div>
 +
 
 +
====7. Zero force plates====
 
<section begin=setupstepsix/>  
 
<section begin=setupstepsix/>  
:After you have calibrated each of your force plates, remove the CS-400 from the volume. Right click one of your force plates in Motive and click '''Zero (all)'''. This will tare the scale and set the current force on the plate data to 0. This will account for a small constant amount of measurement offset from the force plate. Remember that it zeros ''all'' of the force plates at once. So make sure there are no objects on any of the force plates.
+
<div class="padded">
 +
After you have calibrated each of your force plates, remove the CS-400 from the volume. Right click one of your force plates in Motive and click '''Zero (all)'''. This will tare the scale and set the current force on the plate data to 0. This will account for a small constant amount of measurement offset from the force plate. Remember that it zeros ''all'' of the force plates at once. So make sure there are no objects on any of the force plates.
 +
</div>
 
<section end=setupstepsix/>  
 
<section end=setupstepsix/>  
 
<div class="padded">
 
<div class="padded">
 
{{Info|'''Note:''' Zeroed scales of Bertec force plates are saved within their software driver, and each time the driver restarts, these settings are refreshed. This means that the force plate zero setting will be refreshed each time you start Motive, or each time the device is disabled and enabled back again in Motive. Please be aware of this behavior and zero your plates when necessary. In Motive, there is a '''Zero On Enable''' property setting for Bertec force plates under the [[Devices pane]], and enabling this setting will automatically zero your plate each time the device is enabled or when Motive restarts. The '''Zero On Enable''' setting is enabled by default.}}
 
{{Info|'''Note:''' Zeroed scales of Bertec force plates are saved within their software driver, and each time the driver restarts, these settings are refreshed. This means that the force plate zero setting will be refreshed each time you start Motive, or each time the device is disabled and enabled back again in Motive. Please be aware of this behavior and zero your plates when necessary. In Motive, there is a '''Zero On Enable''' property setting for Bertec force plates under the [[Devices pane]], and enabling this setting will automatically zero your plate each time the device is enabled or when Motive restarts. The '''Zero On Enable''' setting is enabled by default.}}
 
</div>
 
</div>
 
  
 
[[Image:FP_Zero.png|thumb|alt=Set the force plate data to zero for more accurate data.|600px|center|Set the force plate data to zero for more accurate data.]]
 
[[Image:FP_Zero.png|thumb|alt=Set the force plate data to zero for more accurate data.|600px|center|Set the force plate data to zero for more accurate data.]]
  
 
+
====8. Set Sampling Rate ====
</div>
+
 
+
==Synchronization Configuration==
+
When synchronizing through the eSync, use the following steps for configuring the sync settings in Motive. This will allow both systems to be triggered simultaneously with reference to the master synchronization device. The '''Recording Gate''' signal must be sent out from the eSync and inputted into the Bertec force plate system for synchronization.
+
 
+
{{Warning|'''IMPORTANT NOTE:''' For this synchronization setup to work properly, the Bertec amplifier firmware must be updated to its most recent version (above June 2016 release). Contact Bertec for instructions on updating the firmware.}}
+
 
+
[[Image:BertecSyncEthernet.png|thumb|400 px|eSync synchronization settings.]]
+
 
+
 
+
 
<div class="padded">
 
<div class="padded">
====Sync Configuration Steps: eSync & Bertec Force Plate====
+
The sampling rate of force plates is configured through the synchronization setup, which will be covered in the next section. The eSync is required in order to synchronize the two systems together. It will be configured to send out either the reference clock signal or the recording trigger signal to the force plate amplifier. Depending on which type of signal is used for the synchronization, supported sampling rates may vary.  
# Open the [[Devices Pane]] and the [[Synchronization]] pane.  
+
# In the [[Synchronization]] pane, select the [[Custom Synchronization Settings: eSync|Custom Synchronization mode]] from the dropdown menu.
+
# Set the ''Sync Input &rarr; Source'' to Internal Clock.
+
# Set the ''Sync Input &rarr; Clock Freq'' to 1000 Hz, and set the ''Sync Input &rarr; Input divider'' to 10.  
+
# Set the ''Sync Output 1-4 &rarr; Type'' to [[Custom Synchronization Settings: eSync#Outputs|Recording Gate]] triggered sync.
+
# Click ''Apply'' from the Synchronization pane.
+
# In the [[Cameras_pane#Properties:_Force_Plate_Group|Cameras Pane]], select the force plates group and double check that the Sync Source is set to Free Run for the force plates.
+
 
+
====Validating your Synchronization====
+
<div class="padded">
+
Before you start recording, you may want to validate that the camera and force plate data are in sync. There are some tests you can do to examine this.
+
 
+
The first method is to record dropping a retroreflective ball/marker onto the platform few times. The bouncing ball produces a sharp transition when it hits the surface of the platform, and it makes the data more obvious for validating the synchronization. Alternately, you can attach a marker on a tip of the foot and step on and off the force plate. ''Make sure that your toe &mdash; closest to the marker &mdash; strikes the platform first, otherwise the data will seem off even when it is not.'' You can then monitor the precise timing of the ball or the foot impacting the force plate and compare them between the mocap data and the force plate data. [[#top|↑]]
+
  
 +
{{Info|
 +
'''Supported Force Plate Sampling Rates'''
 +
* '''Reference Clock Signal Sync: ''' When using the reference clock signal from the eSync to synchronize the force plates, the force plate will basically run at the same rate as the received clock signal. You can also apply either the multiplier or the divider to the outputted clock signal to make additional adjustments.
 +
* '''Recording Trigger Sync: ''' When using the recording signal from the eSync to trigger-sync the force plates, the force plates will be running at their own ''free run'' sampling rate.  In this case,  only 1000 Hz sampling rate is supported, and you will need to adjust the camera frame rate in the [[Devices pane]] and apply framerate-multipliers to set the 1000 Hz sampling rate on the force plates. 
 +
}}
  
The following is an example of validating both good and bad synchronizations using these methods:
+
[[Image:Bertec_Device_Multiplier_21.png|thumb|center|Configuring force plate sampling rate from [[Devices pane]].]]
 
</div>
 
</div>
 
</div>
 
</div>
  
 +
=Synchronization Configuration=
 +
----
 +
There are two synchronization approaches you could take:  Synchronization through '''clock signal''' or through '''recording trigger signal'''.
  
<div class="padded"><center><ul>
+
Synchronization via clock signal utilizes the internal clock signal of the eSync to synchronize the sampling of the force plates on per-frame basis. However, when there is another device (e.g. NI-DAQ) being synchronized to the clock signal frequency, the sampling rate cannot be set for each individual device. In that case, triggered sync must be used for synchronizing the initial recording trigger. Synchronization via trigger signal utilizes the recording trigger in Motive to align the initial samples from both systems. After the initial sync, both systems run freely at their own sampling rate. If the force plates are running at whole multiples of the camera system, the collected samples will be aligned. However, since the sampling clocks are not perfectly accurate, alignment of the samples may slowly drift over time. Thus, when synchronizing via recording trigger, it is better to keep the record times short.
<li style="display:inline-block; vertical-align: text-top;">[[Image:FP good-sync-mixed.png|thumb|alt=Graphs of good data.|450px|center|Example of good sync using tests described]]</li>
+
<li style="display:inline-block; vertical-align: text-top;">[[Image:FP bad-sync-mixed.png|thumb|alt=Graphs of bad data.|450px|center|Example of bad sync using tests described]]</li>
+
</ul></center></div>
+
  
 +
When synchronizing through the eSync, use the following steps to configure the sync settings in Motive. This will allow both systems to be triggered simultaneously with reference to the master synchronization device, the eSync. 
  
<div class="padded">
+
{{Warning2|'''IMPORTANT NOTE:''' For this synchronization setup to work properly, the Bertec amplifier firmware must be updated to firmware version 4.5.2 or above. Currently installed firmware version gets displayed on the 7-segment display when first powering up the amplifier. Please check this and make sure the firmware is updated to the supported versions. If an older version is installed, please contact Bertec for instructions on updating the firmware.}}
====Ethernet System Force Plate without eSync Configuration====
+
<div class="padded">
+
First of all, it is important to note that without a master synchronization device, recording for the camera system and the force plates will not be triggered precisely at the same time. Also, for longer takes the sampling timing of mocap data and the force plate data will eventually deviate from each other. If you want your system to be timed perfectly, we recommend synchronizing through the eSync 2.  
+
  
If you are using an Ethernet system without an eSync, ignore the synchronization configuration options. From the [[Cameras Pane]], make sure that that the force plate sampling rate is a multiple of the tracking frames per second (e.g. 100 Hz and 1000 Hz). Motive will alert you if the sampling rates of cameras and force plates disagree. When the force plate sampling rate is not set to an integer multiple of the camera frame rate, force plate data may record improperly and cause an error.
+
==Sync Configuration Steps: eSync==
 
+
<tabs>
Also note that this mode will introduce a gradual drift between the two data sets, and the offset will be increasingly significant for longer recordings. To zero out the drift, the '''ReSynch''' feature can be used. Right-click on force plates from either the [[Cameras pane|Devices pane]] or the [[View pane#3D Perspective View|perspective view]], and select Resynch from the context menu to realign the sampling timing of both systems.
+
<tab name="reference clock Sync" style="padding:0 1em 0 1em;">
 
+
====Reference Clock Sync Setup Steps====
{{Info|'''Note:''' Bertec digital force plates can collect data up to a maximum of 1000 Hz sampling rate.}}
+
# Open the [[Devices pane]] and the [[Properties pane]].  
</div></div>
+
# In the [[Devices pane]], select the eSync among the listed devices. This will list out the synchronization settings in the properties pane for the selected eSync.
 +
# In the [[Properties pane]], under '''Sync Input Settings''' section, set the '''Source''' to '''Internal Clock'''.
 +
# Next, to the '''Clock Frequency''' section, input the sampling rate that you wish the run the force plates in. This clock signal will be eventually outputted to the force plate system to control the sampling rate. For this guide, let's set this to 1000 Hz.
 +
# Once the clock frequency is set, apply the '''Input Divider/Multiplier''' to the clock frequency to set the framerate of the camera system. For example, if you input 10 to the '''Input Divider''' section with internal clock frequency running at 1000 Hz, the camera system will be running at 100FPS. The resulting frame rate of the camera system will be displayed in the '''Camera Rate''' section.
 +
# Next step is to configure the output signal so that the clock signal can be sent to the force plate system. Under the ''Outputs'' section, enable the corresponding output port of the eSync which the force plate system is connected to.
 +
# Set the ''Output 1-4 &rarr; Type'' to [[External_Device_Sync_Guide:_eSync#Gated_Internal_Clock|Gated Internal Clock]].
 +
# Now that the eSync has been configured, you need to configure the force plate properties in Motive. While the force plate(s) is selected in Motive, access the Properties pane to view the [[Properties: Force Plates|force plate properties]]. Here, set the following properties:
 +
::*Record Trigger &rarr; ''False''
 +
::*Reference Clock Sync &rarr; ''True''
 +
::*eSync Output Channel &rarr; output port used on the eSync.
  
 +
::Once this is set, the force plate system will start sampling at the frequency of the clock signal configured on the eSync, and this rate will be displayed on the [[Devices pane]] as well.
  
 
<center><ul>
 
<center><ul>
<li style="display:inline-block; vertical-align: text-top;">[[Image:Bertec_SamplingRate.png|thumb|A sample free Run configuration with a camera system running at 200 Hz frame rate and the force plates sampling at 1000 Hz (X5).]]</li>
+
<li class="thumblist">[[Image:Bertec_eSyncClockSyncProperties_21.png|thumb|370px|Example eSync properties for clock sync. Make sure the eSync is selected in the [[Properties: eSync|Properties pane]].]]</li>
<li style="display:inline-block; vertical-align: text-top;">[[Image:ForcePlate_ReSynch.png|thumb|400 px|Re-aligning initial sampling timing of the force plate.]]</li>
+
<li class="thumblist">[[Image:Bertec_FPClockSyncProperties_21.png|thumb|370px|Example force plate properties for clock sync. Make sure the Force Plate is selected in the [[Properties: Force Plates|Properties pane]].]]</li>
 
</ul></center>
 
</ul></center>
</div>
 
  
=Force Plate Data in Motive=
+
{{Indent|{{Info2|'''Live Data'''
----
+
:When force plates are synchronized through ''Gated Internal Clock'', the force data may not be available in the Live mode because the signal gets outputted only when Motive is recording. If you need to see the data in Live mode, use the triggered sync setup.
 
+
}}}}
<div class="padded">
+
</tab>
To view and confirm the live force plate data, open the editor from the [[Timeline Pane]]. Then, open the [[Project Pane]] (or [[Cameras Pane]]) and select one of the force plates. A list of available channels will appear under each force plate instance. Here, you can confirm that your force plates are working properly. Select Fx, Fy, Fz, Mx, My, or Mz channels to view the live force plate data from the timeline. Multiple channels can be displayed at once. Both reconstructed markers and force plate channels can be selected to display two different plots on the timeline. In live sampling, the force plot will be sub-sampled when plotted along with trajectory data, but all of the recorded samples will be fully resolved in the playback mode.
+
<tab name="Triggered Sync" style="padding:0 1em 0 1em;">
 +
====Triggered Sync Setup Steps====
 +
#  Open the [[Devices pane]] and the [[Properties pane]].  
 +
#  The final frame rate of the camera system will be displayed at the very top of the [[Devices pane]].
 +
#  In the [[Devices pane]], select the eSync among the listed devices. This will list out the synchronization settings in the Properties pane for the selected eSync.
 +
#  Set up the output signal so that the recording trigger signal can be sent to the force plate system. In the ''Outputs'' section, enable and configure the corresponding output port of the eSync which the force plate system is connected to.
 +
#  Set the ''Output 1-4 &rarr; Type'' to [[External_Device_Sync_Guide:_eSync#Recording_Gate_.26_Recording_Start.2FStop_Pulse|Recording Gate]].
 +
#  Now that the eSync has been configured, you need to configure the properties of the force plates. While the force plate(s) is selected in Motive, access the Properties pane to view the [[Properties: Force Plates|force plate properties]]. Here, set the following properties:
 +
::*Record Trigger &rarr; ''Device''
 +
::*Reference Clock Sync &rarr; ''False''
 +
::*eSync Output Channel &rarr; output port used on the eSync.
  
If you wish to double check the force plate position calibration, you may create a long trackable [[Rigid Body Tracking|rigid body]] and use it to apply force against force plate. If the force plate location is precisely calibrated in Motive, the force vector will go right through the rigid body.
+
::Once this is done, the force plate system will synchronize to the recording trigger signal when Motive starts collecting data, and the force plates will free-run after the initial sync trigger. You can configure the sampling rate of the force plates by modifying the ''Multiplier'' values in [[Devices pane]] to sample at a whole multiple of the camera system frame rate.
  
 
<center><ul>
 
<center><ul>
<li style="display: inline-block; vertical-align: text-top;">[[Image:FP_FPGraph.png|thumb|alt=Graph of live force plate data.|700px|center|Graph of live force plate data.]]</li>
+
<li class="thumblist">[[Image:Bertec_eSyncTrigSyncProperties_21.png|thumb|370px|Example eSync properties for clock sync. Make sure the eSync is selected in the [[Properties: eSync|Properties pane]].]]</li>
<li style="display: inline-block; vertical-align: text-top;">[[Image:Bertec_Press.png|thumb|A resultant force vector displayed in Motive.]]</li>
+
<li class="thumblist">[[Image:Bertec_FPTrigSyncProperties_21.png|thumb|370px|Example force plate properties for clock sync. Make sure the Force Plate is selected in the [[Properties: Force Plates|Properties pane]].]]</li>
</ul></center></div>
+
</ul></center>
  
 +
{{Indent|{{Info2|
 +
====Sampling Rate====
 +
* '''Supported Frame Rate:''' When synchronizing two systems via recording trigger, the force plates will be running at their own ''free-run'' frame rate. In this case, only ''1000 Hz'' sampling rate is supported for Bertec force plates. If you wish to sample at a different rate, please use the reference clock sync approach.
 +
* '''Setting Framerate Multiplier:''' For free run sync setups, sampling rates of force plates can be set from the [[Devices pane]], but the sampling rate of force plates must be configured to a whole multiple of the camera system's framerate. By adjusting the ''Rate Multiplier'' values in the [[Devices pane]], sampling rates of the force plates can be modified. First, pick a frame rate of the camera system and then adjust the rate multiplier values to set force plates to the desired sampling rate.}}
  
 +
{{Info|
 +
====ReSynch====
 +
[[Image:ForcePlate_ReSynch.png|thumb|300 px|Re-aligning initial sampling timing of the force plate.]]
 +
:When two systems are synchronized by recording trigger signals (Recording Gate or Recording Pulse), both systems are in ''Free Run Mode''. This means that the recording of both the mocap system and the force plate system are triggered simultaneously at the same time and each system runs at its own rate.
  
=Data Playback=
+
:Two systems, however, are synchronized at the recording trigger but not by per frame basis. For this reason, alignment of the mocap data and the force plate data may gradually drift from each other for longer captures. But this is not a problem since the sync chain will always be re-synchronized each time recording in Motive is triggered. Furthermore, ''Takes'' in general do not last too long for this drift to take effect on the data.
----
+
 
 +
:However, this could be an issue when live-streaming the data since recording is never initiated and two systems will be synchronized only when Motive first launches. To zero out the drift, the '''ReSynch''' feature can be used. Right-click on force plates from either the [[Devices pane|Devices pane]] or the [[View pane#3D Perspective View|perspective view]], and select Resynch from the context menu to realign the sampling timing of both systems.
 +
}}}}
 +
</tab>
 +
</tabs>
  
 +
==Validating Synchronization==
 
<div class="padded">
 
<div class="padded">
When playing back a ''Take'' with force plate data, integrated devices will appear under the assets group in the [[Project pane]]. When a force plate is selected, available channels will be listed at the bottom of the pane. You can select data channels and respective signals will be graphed in the [[Timeline pane]], as shown in the image below.
+
Before you start recording, you may want to validate that the camera and force plate data are in sync. There are some tests you can do to examine this.  
  
 +
The first method is to record dropping a retroreflective ball/marker onto the platform few times. The bouncing ball produces a sharp transition when it hits the surface of the platform, and it makes the data more obvious for validating the synchronization. Alternately, you can attach a marker on a tip of the foot and step on and off the force plate. ''Make sure that your toe &mdash; closest to the marker &mdash; strikes the platform first, otherwise the data will seem off even when it is not.'' You can then monitor the precise timing of the ball or the foot impacting the force plate and compare them between the mocap data and the force plate data. [[#top|↑]]
  
[[Image:Bertec_Editmode.png|thumb|center|800 px|Playback of recorded force plate data in Motive.]]
+
The following is an example of validating good synchronization outcomes:
 +
 
 +
[[Image:AMTI_Goodsync_20.png|thumb|center|600px|Good synchronization]]
 
</div>
 
</div>
  
 
+
=Device Settings Profile=
=Data Export=
+
 
----
 
----
 +
All of the configured device settings, including the calibration, get saved on ''Device Profile'' XML files. When you exit out of Motive, updated device profiles will be saved under the program data directory (<code>C:\ProgramData\OptiTrack\Motive\DeviceProfiles</code>), and this file gets loaded again when you restart Motive. The persistent settings folder can be accessed through '''''Help &rarr;  Application Folders &rarr; Persistent Setting'''''. This XML file ensures that all of the device settings are persisted each time you close and restart Motive.
  
<div class="padded">
+
[[Image:ApplicationFolder_PersistantSettings.png|thumb|center|Direct access to the persistent settings folder. In this folder, license files as well as XML files for persistent configurations are stored.]]
[[Image:Visual3D.png|thumb|350 px|[http://www.c-motion.com/products/visual3d/ Visual3D] biomechanics analysis software provided by [http://www.c-motion.com/ C-Motion]]]
+
[[Image:TMM.png|thumb|350 px|[http://www.innsport.com/ The MotionMonitor] biomechanics analysis software.]]  
+
  
 +
=Force Plate Data in Motive=
 +
{{#lsth:AMTI Force Plate Setup|Force Plate Data in Motive}}
 +
 +
=Data Export=
 +
----
 +
[[Image:TMM.png|thumb|350 px|[http://www.innsport.com/ The MotionMonitor] biomechanics analysis software.]]
 +
[[Image:Visual3D.png|thumb|350 px|[http://www.c-motion.com/products/visual3d/ Visual3D] biomechanics analysis software provided by [http://www.c-motion.com/ C-Motion]]]
 
We recommend the following programs for analyzing exported data in biomechanics applications:
 
We recommend the following programs for analyzing exported data in biomechanics applications:
  
Line 225: Line 278:
 
* [http://www.mathworks.com/products/matlab/ MATLAB]
 
* [http://www.mathworks.com/products/matlab/ MATLAB]
  
 
+
==C3D Export==
====C3D Export====
+
 
:Motive exports tracking data and force plate data into C3D files. Exported C3D files can then be imported into a biomechanics analysis and visualization software for further processing. See the [[Data Export]] or [[Data Export: C3D]] page for more information about C3D export in Motive. Note that the coordinate system used in Motive (y-up right-handed) may be different from the convention used in the biomechanics analysis software.
 
:Motive exports tracking data and force plate data into C3D files. Exported C3D files can then be imported into a biomechanics analysis and visualization software for further processing. See the [[Data Export]] or [[Data Export: C3D]] page for more information about C3D export in Motive. Note that the coordinate system used in Motive (y-up right-handed) may be different from the convention used in the biomechanics analysis software.
<div class="padded">{{#lsth:Data Export: C3D|C3D Axes|MotionBuilder Compatible Axis Convention}}</div>
 
  
====CSV Export====
+
<div class="padded">
:Force plate data and the tracking data can be exported into CSV files as well. When a ''Take'' file is exported into a CSV file. Separate CSV files will be save for each force plate and it will contain the force, moment, and center of pressure data. Exported CSV file can be imported for analysis.
+
====C3D Axes====
 +
{{#lsth:Data Export: C3D|C3D Axes|MotionBuilder Compatible Axis Convention}}</div>
 +
</div>
  
====Data Streaming====
+
==CSV Export==
:To stream tracking data along with the force plate data, open the Data Streaming Pane and check the ''Broadcast Frame Data'', and make sure that you are not streaming over the camera network. Read more about streaming from the [[Data Streaming]] workflow page.
+
<div class="padded">
 +
Force plate data and the tracking data can be exported into CSV files as well. When a ''Take'' file is exported into a CSV file. Separate CSV files will be saved for each force plate and it will contain the force, moment, and center of pressure data. Exported CSV file can be imported for analysis.
 +
</div>
  
:Motive can stream the tracking data and the force plate data into various applications &mdash; including Matlab &mdash; using [[Data Streaming#NatNet Streaming|NatNet Streaming]] protocol. Find more about [http://www.optitrack.com/products/natnet-sdk/ NatNet streaming] from the User's Guide included in the download.  
+
==Data Streaming==
 +
<div class="padded">
 +
To stream tracking data along with the force plate data, open the Data Streaming Pane and check the ''Broadcast Frame Data'', and make sure that you are not streaming over the camera network. Read more about streaming from the [[Data Streaming]] workflow page.
  
====Visual3D Streaming====
+
Motive can stream the tracking data and the force plate data into various applications &mdash; including Matlab &mdash; using [[Data Streaming#NatNet Streaming|NatNet Streaming]] protocol. Find more about [http://www.optitrack.com/products/natnet-sdk/ NatNet streaming] from the User's Guide included in the download.
  
:For streaming into Visual3D, set the [[Data Streaming Pane#OptiTrack_Streaming_Engine|Visual3D Compatible setting]] to true from the Data Streaming pane. Real-time streaming into Visual3D uses Visual3DServer plugin provided by C-Motion. For more information on the Visual3DServer, refer to the C-Motion Documentation Wiki: http://www.c-motion.com/v3dwiki/index.php/Visual3DServer_Overview
+
{{Warning|'''Number of Force Plates'''
</div>
+
  
----
+
:At the time of writing, there is a hard limit on the maximum number of force plate data that can be streamed out from Motive. Please note that only up to 8 force plate data can be streamed out from Motive and received by a [[NatNet]] application.}}
 +
</div>

Latest revision as of 17:28, 2 December 2019

Main PageBertec Force Plate Setup

Scope

This page provides instructions on how to integrate a Bertec force plate system with an OptiTrack motion capture system.

Overview

When a motion capture system is used in conjunction with force plates, they work together as an efficient tool for various research applications including biomechanical analysis, clinical gait analysis, physiology research, sports performance research, and many more. An OptiTrack motion capture system can synchronize with force plates to obtain both kinematic and kinetic measurements. Note that force plate integration is supported only with a Prime camera system using the eSync synchronization hub. This page provides quick guidelines for setting up and configuring force plates — with digital outputs — along with the OptiTrack motion capture system.

For detailed information on specifications and configurations on the force plates, refer to the documentation provided by the force plate manufacturer.

Info2.png

Analog Platforms

Analog force plate devices can only be implemented via DAQ devices. Incoming voltage signals can be detected through the data acquisition channels, but force plate related software features (vectors, position calibration, etc.) will not be supported in Motive for the analog platforms. Refer to the NI-DAQ Setup page for detailed instructions on integrating analog devices.

Requirements

  • Supported Amplifier Models: AM6800
  • Firmware Version: For synchronization support, the Bertec amplifiers must be installed with firmware version 4.5.2 or above. The current firmware version gets displayed on the 7-segment display when first powering up the amplifier. Please check this and make sure the firmware is updated to the supported versions.
  • Prime series Ethernet camera system with the eSync synchronization hub.
  • Motive 1.10 or above.


Hardware Setup[edit]


Bertec Force Plate System Setup[edit]

Refer to the respective Bertec system user documentation for detailed information on setting up the force plate system and connecting to the host PC.

Camera System Setup[edit]

Set up an OptiTrack system. Connect the camera system to the same host PC. For more information, refer to the Quick Start Guide: Getting Started page or the Hardware Setup pages.

Wiring the eSync with the Amplifier[edit]

Triggered Sync Cabling

  • Bertec AM 6800 amplifiers: Use the provided female 15-pin D-Sub connector to get the ZERO signal and the SYNC signal from the ANALOG OUTPUT port of the amplifier.
  • The ZERO cable from the amplifier needs to be connected to the output port of the eSync for synchronization with the camera system.
  • The SYNC cable from the amplifier needs to be interconnected between the force plate amplifiers for their internal sync. When using more than one plates, a BNC connector or a BNC splitter will need to be used to interconnect the SYNC cables between multiple amplifiers.
  • Bertec force plate + Prime system setup diagram for triggered sync.
  • Zero cable from the amplifier
  • Reference Clock Sync

    • The SYNC cable from the amplifier needs to be connected to the output port of the eSync for synchronization with the camera system.
  • Bertec force plate + Prime system setup diagram for reference clock sync.
  • Hot Plugging[edit]

    Warning2.png

    Hot plugging is not supported with the integration. When a new device is connected to the system, you must re-start Motive to instantiate it.

    Software Setup[edit]


    Peripheral Device Module[edit]

    In order to integrate force plate systems with Motive, you will need to setup the required drivers and plugins. Motive installer is packaged with the Peripheral Device module which can be added. During the Motive installation, a list of program features will be shown in the Custom Setup section. Here, change the setting for the Peripheral Device module, as shown in the below image, so that the module is installed along with Motive Files.

    Info2.png

    Note : Even if you are not using NI-DAQ, it is still necessary to install NI-DAQmx drivers that come up next in the installer.

    Warning2.png

    Installation Note: For integration into Motive, the NI-DAQmx 15.1.1 or later runtime driver must be installed. If you are already using an older version of the NI-DAQmx runtime and Motive is having problems recognizing the connected device, update the driver or uninstall and re-install the packaged version of the driver before contacting Support. In Motive, you can inspect device connection status via the Status Log panel which can be accessed under the View tab in Motive.

    Warning2.png

    Notes on NI-DAQmx version 19.x: There is a known issue with the latest NI-DAQmx version (19.x) where it crashes Motive on startup. If you have this version of the driver installed, please reinstall with the recommended version (15.1.1) provided with the Motive installer.


    Installing OptiTrack Peripheral Module. DAQmxInstall.gif


    Bertec Customers[edit]

    In addition to the Peripheral Device module, you may also want to install the Digital Acquire™ from Bertec to verify that the force plates are properly working. Visit the below webpage to download the software, and follow the respective instructions to install. This software installs remaining resources for connecting the Bertec force plates.

    Warning2.png

    Note: You cannot run Digital Acquire and Motive together and have them connected to the plate(s) at the same time.

    Force Plate Setup in Motive[edit]

    1. Start Motive[edit]

    If the hardware and software for the force plates are configured and successfully recognized, Motive will list out the detected force plates with number labels (1, 2, etc..). Motive will notify you of incorrect or nonexistent force plate calibration files. When the devices are successfully instantiated in Motive, the Status Log will indicate that the device has been created and loaded.

    • Initial view in Motive after setting up force plates.
      Motive with force plates.
    • Status Log pane in Motive.

    2. Calibrate Cameras[edit]

    Calibrate the capture volume as normal to get the orientation of the cameras (see the Quick Start Guide or Calibration page for more information). The position of the force plate is about the center of the volume, and when you recalibrate or reset the ground plane, you will need to also realign the position of your force plates for best results.

    Motive after setting up force plates and calibration.
    Motive with force plates and camera calibration.

    3. Setup CS-400[edit]

    On the CS-400 calibration square, pull the force plate alignment tabs out and put the force plate leveling jigs at the bottom. The leveling jigs align the calibration square to the surface of your force plate. The alignment tabs allow you to put the CS-400 flush against the sides of your force plate giving the most accurate alignment.

    CS-400 calibration square with force plate force plate parts.
    CS-400 calibration square with force plate force plate parts.

    4. Place CS-400 on force plate[edit]

    Place the calibration wand on the force plate so that vertex of the wand is located at the right-hand corner of the side where the cable input is located (as shown in the image below). A correct placement of the calibration square is important because it determines the orientation of the force plate and its local coordinate axis within the global system. The coordinate systems for force plates are independent of the system used Motive.

    Bertec force plates use the right-hand system. The longer arm of CS-400 will define the Y axis, and the shorter arm will define the X axis of the force plate. Accordingly, Z axis is directed downwards for measuring the vertical force.
  • Bertec force plate with CS-400 aligned properly.
  • Calibrated force plate position and orientation. X and Y axis is shown.
  • 5. Set force plate position in Motive[edit]

    After placing the calibration square on the force plate, select the CS-400 markers in Motive. Right click on the force plate you want to locate, and click Set Position. When there are multiple force plates in a volume, you may need to step on the force plate to find which platform the calibration square is on. In Motive, uncalibrated force plates will light up in green and a force vector will appear when you step on the plate. Repeat step 4 and 5 for other force plates as necessary.

    Referencing to the markers on the calibration square, Motive defines the location of the force plate axis within the global coordinate system. When setting the position, the previously defined force plate dimension values and mechanical-to-electrical center offset values will be applied and reflected in the Perspective View pane.

    Info2.png

    Tip: To double check that the dimensions are modified properly, you can place extra retroreflective markers on each corner of the platform and monitor the coincidence of the markers position with the force plate assets from the perspective view.

    Setting the position of a force plate in Motive.
    Setting the position of a force plate in Motive. The number label on the force plate is inverted because the force plate position and orientation has not been calibrated yet.

    6. Set the Force Plate Dimension[edit]

    If the force plate dimensions are not automatically configured, you need to enter the dimensions of the force plate in the force plate properties after calibrating its positions. Go to the Devices pane and select the force plate, and its properties will get listed under the Properties pane. Enter the length and width (in meters) values for the corresponding plates as reported in the specifications.

    7. Zero force plates[edit]

    After you have calibrated each of your force plates, remove the CS-400 from the volume. Right click one of your force plates in Motive and click Zero (all). This will tare the scale and set the current force on the plate data to 0. This will account for a small constant amount of measurement offset from the force plate. Remember that it zeros all of the force plates at once. So make sure there are no objects on any of the force plates.

    Info2.png

    Note: Zeroed scales of Bertec force plates are saved within their software driver, and each time the driver restarts, these settings are refreshed. This means that the force plate zero setting will be refreshed each time you start Motive, or each time the device is disabled and enabled back again in Motive. Please be aware of this behavior and zero your plates when necessary. In Motive, there is a Zero On Enable property setting for Bertec force plates under the Devices pane, and enabling this setting will automatically zero your plate each time the device is enabled or when Motive restarts. The Zero On Enable setting is enabled by default.

    Set the force plate data to zero for more accurate data.
    Set the force plate data to zero for more accurate data.

    8. Set Sampling Rate[edit]

    The sampling rate of force plates is configured through the synchronization setup, which will be covered in the next section. The eSync is required in order to synchronize the two systems together. It will be configured to send out either the reference clock signal or the recording trigger signal to the force plate amplifier. Depending on which type of signal is used for the synchronization, supported sampling rates may vary.

    Info2.png

    Supported Force Plate Sampling Rates

    • Reference Clock Signal Sync: When using the reference clock signal from the eSync to synchronize the force plates, the force plate will basically run at the same rate as the received clock signal. You can also apply either the multiplier or the divider to the outputted clock signal to make additional adjustments.
    • Recording Trigger Sync: When using the recording signal from the eSync to trigger-sync the force plates, the force plates will be running at their own free run sampling rate. In this case, only 1000 Hz sampling rate is supported, and you will need to adjust the camera frame rate in the Devices pane and apply framerate-multipliers to set the 1000 Hz sampling rate on the force plates.
    Configuring force plate sampling rate from Devices pane.

    Synchronization Configuration[edit]


    There are two synchronization approaches you could take: Synchronization through clock signal or through recording trigger signal.

    Synchronization via clock signal utilizes the internal clock signal of the eSync to synchronize the sampling of the force plates on per-frame basis. However, when there is another device (e.g. NI-DAQ) being synchronized to the clock signal frequency, the sampling rate cannot be set for each individual device. In that case, triggered sync must be used for synchronizing the initial recording trigger. Synchronization via trigger signal utilizes the recording trigger in Motive to align the initial samples from both systems. After the initial sync, both systems run freely at their own sampling rate. If the force plates are running at whole multiples of the camera system, the collected samples will be aligned. However, since the sampling clocks are not perfectly accurate, alignment of the samples may slowly drift over time. Thus, when synchronizing via recording trigger, it is better to keep the record times short.

    When synchronizing through the eSync, use the following steps to configure the sync settings in Motive. This will allow both systems to be triggered simultaneously with reference to the master synchronization device, the eSync.

    Warning2.png

    IMPORTANT NOTE: For this synchronization setup to work properly, the Bertec amplifier firmware must be updated to firmware version 4.5.2 or above. Currently installed firmware version gets displayed on the 7-segment display when first powering up the amplifier. Please check this and make sure the firmware is updated to the supported versions. If an older version is installed, please contact Bertec for instructions on updating the firmware.

    Sync Configuration Steps: eSync[edit]

    Reference Clock Sync Setup Steps[edit]

    1. Open the Devices pane and the Properties pane.
    2. In the Devices pane, select the eSync among the listed devices. This will list out the synchronization settings in the properties pane for the selected eSync.
    3. In the Properties pane, under Sync Input Settings section, set the Source to Internal Clock.
    4. Next, to the Clock Frequency section, input the sampling rate that you wish the run the force plates in. This clock signal will be eventually outputted to the force plate system to control the sampling rate. For this guide, let's set this to 1000 Hz.
    5. Once the clock frequency is set, apply the Input Divider/Multiplier to the clock frequency to set the framerate of the camera system. For example, if you input 10 to the Input Divider section with internal clock frequency running at 1000 Hz, the camera system will be running at 100FPS. The resulting frame rate of the camera system will be displayed in the Camera Rate section.
    6. Next step is to configure the output signal so that the clock signal can be sent to the force plate system. Under the Outputs section, enable the corresponding output port of the eSync which the force plate system is connected to.
    7. Set the Output 1-4 → Type to Gated Internal Clock.
    8. Now that the eSync has been configured, you need to configure the force plate properties in Motive. While the force plate(s) is selected in Motive, access the Properties pane to view the force plate properties. Here, set the following properties:
    • Record Trigger → False
    • Reference Clock Sync → True
    • eSync Output Channel → output port used on the eSync.
    Once this is set, the force plate system will start sampling at the frequency of the clock signal configured on the eSync, and this rate will be displayed on the Devices pane as well.
    • Example eSync properties for clock sync. Make sure the eSync is selected in the Properties pane.
    • Example force plate properties for clock sync. Make sure the Force Plate is selected in the Properties pane.

    Info2.png

    Live Data

    When force plates are synchronized through Gated Internal Clock, the force data may not be available in the Live mode because the signal gets outputted only when Motive is recording. If you need to see the data in Live mode, use the triggered sync setup.

    Triggered Sync Setup Steps[edit]

    1. Open the Devices pane and the Properties pane.
    2. The final frame rate of the camera system will be displayed at the very top of the Devices pane.
    3. In the Devices pane, select the eSync among the listed devices. This will list out the synchronization settings in the Properties pane for the selected eSync.
    4. Set up the output signal so that the recording trigger signal can be sent to the force plate system. In the Outputs section, enable and configure the corresponding output port of the eSync which the force plate system is connected to.
    5. Set the Output 1-4 → Type to Recording Gate.
    6. Now that the eSync has been configured, you need to configure the properties of the force plates. While the force plate(s) is selected in Motive, access the Properties pane to view the force plate properties. Here, set the following properties:
    • Record Trigger → Device
    • Reference Clock Sync → False
    • eSync Output Channel → output port used on the eSync.
    Once this is done, the force plate system will synchronize to the recording trigger signal when Motive starts collecting data, and the force plates will free-run after the initial sync trigger. You can configure the sampling rate of the force plates by modifying the Multiplier values in Devices pane to sample at a whole multiple of the camera system frame rate.
    • Example eSync properties for clock sync. Make sure the eSync is selected in the Properties pane.
    • Example force plate properties for clock sync. Make sure the Force Plate is selected in the Properties pane.

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    Sampling Rate

    • Supported Frame Rate: When synchronizing two systems via recording trigger, the force plates will be running at their own free-run frame rate. In this case, only 1000 Hz sampling rate is supported for Bertec force plates. If you wish to sample at a different rate, please use the reference clock sync approach.
    • Setting Framerate Multiplier: For free run sync setups, sampling rates of force plates can be set from the Devices pane, but the sampling rate of force plates must be configured to a whole multiple of the camera system's framerate. By adjusting the Rate Multiplier values in the Devices pane, sampling rates of the force plates can be modified. First, pick a frame rate of the camera system and then adjust the rate multiplier values to set force plates to the desired sampling rate.

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    ReSynch

    Re-aligning initial sampling timing of the force plate.
    When two systems are synchronized by recording trigger signals (Recording Gate or Recording Pulse), both systems are in Free Run Mode. This means that the recording of both the mocap system and the force plate system are triggered simultaneously at the same time and each system runs at its own rate.
    Two systems, however, are synchronized at the recording trigger but not by per frame basis. For this reason, alignment of the mocap data and the force plate data may gradually drift from each other for longer captures. But this is not a problem since the sync chain will always be re-synchronized each time recording in Motive is triggered. Furthermore, Takes in general do not last too long for this drift to take effect on the data.
    However, this could be an issue when live-streaming the data since recording is never initiated and two systems will be synchronized only when Motive first launches. To zero out the drift, the ReSynch feature can be used. Right-click on force plates from either the Devices pane or the perspective view, and select Resynch from the context menu to realign the sampling timing of both systems.

    Validating Synchronization[edit]

    Before you start recording, you may want to validate that the camera and force plate data are in sync. There are some tests you can do to examine this.

    The first method is to record dropping a retroreflective ball/marker onto the platform few times. The bouncing ball produces a sharp transition when it hits the surface of the platform, and it makes the data more obvious for validating the synchronization. Alternately, you can attach a marker on a tip of the foot and step on and off the force plate. Make sure that your toe — closest to the marker — strikes the platform first, otherwise the data will seem off even when it is not. You can then monitor the precise timing of the ball or the foot impacting the force plate and compare them between the mocap data and the force plate data.

    The following is an example of validating good synchronization outcomes:

    Good synchronization

    Device Settings Profile[edit]


    All of the configured device settings, including the calibration, get saved on Device Profile XML files. When you exit out of Motive, updated device profiles will be saved under the program data directory (C:\ProgramData\OptiTrack\Motive\DeviceProfiles), and this file gets loaded again when you restart Motive. The persistent settings folder can be accessed through Help → Application Folders → Persistent Setting. This XML file ensures that all of the device settings are persisted each time you close and restart Motive.

    Direct access to the persistent settings folder. In this folder, license files as well as XML files for persistent configurations are stored.

    Force Plate Data in Motive[edit]


    Force plate data can be monitored from the Graph View pane. You will need to configure a custom graph layouts to show force plate data. As shown in the images, make sure the desired force plate data channels (Fx, Fy, Fz, Mx, My, or Mz) are selected to be plotted. Then, when you select a force plate in Motive, and the data from the corresponding channels will be plotted on the graphs. When both reconstructed markers and force plate channels are selected, the force plot will be sub-sampled in order to be plotted along with trajectory data. For more information about how to configure graph layouts, read through the Graph View pane page.

    Live Force Plate Data[edit]

    For plotting live force plate data, the graph View Style of the corresponding graph must be configured to Live.

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    Notes

    • The force and moment data reflects the coordinate system defined by the force plate manufacturer, which is typically the Z-down right-handed coordinate system. Note: This convention is independent of the global coordinate system used in Motive. Thus, the Fz components represent the vertical force. For more in-depth information, refer to the force plate specifications.
    • Graph of live force plate data.
      Graph of live force plate data.
    • Layout configuration.
      Graph view pane layout configuration.


    Data Export[edit]


    The MotionMonitor biomechanics analysis software.
    Visual3D biomechanics analysis software provided by C-Motion

    We recommend the following programs for analyzing exported data in biomechanics applications:

    C3D Export[edit]

    Motive exports tracking data and force plate data into C3D files. Exported C3D files can then be imported into a biomechanics analysis and visualization software for further processing. See the Data Export or Data Export: C3D page for more information about C3D export in Motive. Note that the coordinate system used in Motive (y-up right-handed) may be different from the convention used in the biomechanics analysis software.

    C3D Axes[edit]

    Common Conventions[edit]

    C3D export setting for applications using z-up right-handed coordinate systems.

    Since Motive uses a different coordinate system than the system used in common biomechanics applications, it is necessary to modify the coordinate axis to a compatible convention in the C3D exporter settings. For biomechanics applications using z-up right-handed convention (e.g. Visual3D), the following changes must be made under the custom axis.

    • X axis in Motive should be configured to positive X
    • Y axis in Motive should be configured to negative Z
    • Z axis in Motive should be configured to positive Y.

    This will convert the coordinate axis of the exported data so that the x-axis represents the anteroposterior axis (left/right), the y-axis represents the mediolateral axis (front/back), and the z-axis represents the longitudinal axis (up/down).

    CSV Export[edit]

    Force plate data and the tracking data can be exported into CSV files as well. When a Take file is exported into a CSV file. Separate CSV files will be saved for each force plate and it will contain the force, moment, and center of pressure data. Exported CSV file can be imported for analysis.

    Data Streaming[edit]

    To stream tracking data along with the force plate data, open the Data Streaming Pane and check the Broadcast Frame Data, and make sure that you are not streaming over the camera network. Read more about streaming from the Data Streaming workflow page.

    Motive can stream the tracking data and the force plate data into various applications — including Matlab — using NatNet Streaming protocol. Find more about NatNet streaming from the User's Guide included in the download.

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    Number of Force Plates

    At the time of writing, there is a hard limit on the maximum number of force plate data that can be streamed out from Motive. Please note that only up to 8 force plate data can be streamed out from Motive and received by a NatNet application.