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.

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.

Bertec Customers

In addition to the Peripheral Device module, you also need to install the Digital Acquire™ 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.

• 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.

1. Start Motive

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.

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.

Motive with force plates and camera calibration.

3. Setup CS-400

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.

4. Place CS-400 on force plate

Place the calibration wand on the force plate so that the wand vertex is located at the right-hand corner of the side where the cable input is located (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

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.

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. The number label on the force plate is inverted because the force plate position and orientation has not been calibrated yet.

6. Zero force plates

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 the force plates.

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.

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.

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.

eSync synchronization settings.

Ethernet System Force Plate without eSync Configuration

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.

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 Devices pane or the perspective view, and select Resynch from the context menu to realign the sampling timing of both systems.

Note: Bertec digital force plates can collect data up to a maximum of 1000 Hz sampling rate.

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.

If you wish to double check the force plate position calibration, you may create a long trackable 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.

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.

Playback of recorded force plate data in Motive.

Visual3D biomechanics analysis software provided by C-Motion

The MotionMonitor biomechanics analysis software.

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

• Visual3D

• The MotionMonitor

• MATLAB

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.

Common Conventions

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

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.

Data Streaming

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.

Visual3D Streaming

For streaming into Visual3D, set the 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