Difference between revisions of "AMTI Force Plate Setup"

Revision as of 21:52, 1 December 2015

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Step 1: Hardware Setup

(As of Motive 1.9.0 we only support systems with AMTI Gen 5 amplifiers)

To install plug each force plate into a separate Gen 5 amplifier, plug a USB 2.0 type B to A cable from each amplifier to your computer, then set up the camera system as normal (see Hardware Setup page).

Prime System + Force Plate

For better sync using an Ethernet based prime series camera system, connect an eSync2 to your camera system, then connect the eSync2 and your Gen 5 amplifer(s). To connect the two use one of the “50 Ohm BNC Male to 75 Ohm RCA Jack Adapters” included with the eSync as well as an RCA male to male cable in one of the four output ports of the eSync to the sync port of the Gen 5 amplifier.

Diagram for Prime Camera System with integrated force plates.

Flex System + Force Plate

For better sync using a USB 2.0 based flex series camera system you can do one of two things. Connect a “50 Ohm BNC Male to 75 Ohm RCA Jack Adapters” into the output port on your OptiHub(s) and connect each OptiHub to a corresponding force plate using a male to male RCA cable. (Note: you need an OptiHub for each force plate this way.) Alternately you may use a BNC splitter to use one OptiHub as a master sync for your force plates. (Note: you may need to use an active BNC splitter because you lose some power each time you passively split the signal.) Without the presence of an eSync your motion capture and force plate data may be as much as 1-2 frames off.

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Step 2: Software Setup

• Install Motive (see the Quick Start Guide for more help).

• Your force plates should come with installation files. For AMTI force plates, these file are contained on a disk. Install the program Netforce because it contains the configuration program, which can be used to validate that the force plates are working. (Note: The force plate drivers should install automatically, but you may need to manually point to the Gen 5 device drivers.)

• Run either the system configuration program AMTISystemConfig.exe or the same app through Netforce detect your force plates and press save. (Note: If you have multiple hard drive you may need to move the configuration file to C:\AMTI\CFG\AMTIUsbSetup.cfg. Motive should alert you if this has not been done properly.)

Step 3: Motive Setup

1. Start Motive. If you set up the hardware and software correctly, then when you open motive you will see force plates with the numbers 1, 2, etc.. depending on how many force plates you have connected. If you did not set up the hardware and software correctly Motive will notify you if it detects a force plate, and an incorrect or nonexistent calibration file.

Motive with force plates.

2. Calibrate cameras. Calibrate the volume as normal to get the orientation of cameras (see the Quick Start Guide or Calibration page for more information). The position of the force plate is relative to the center of the volume. So if you re-calibrate 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. Pull the force plate alignment tabs out and put the force plate levelings jigs on the bottom of your CS-400 calibration square. The leveling jigs align force plate 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 with the corner of the force plate to the right of where the cable input is located. The direction matters, because it give you the proper orientation and some force plates are rectangular.

Force plate with CS-400 aligned properly.

5. Set force plate position in Motive. Select the CS-400 markers in Motive then right click the force plate you want to assign to that position, and click Set position. To figure out which force plate the calibration square is on you can step on the force plate. A force vector will appear on the force plate you stepped on.

Setting the position of a force plate in Motive.

6. Zero force plates. After you have set all of your force plate’s with steps 4 and 5, remove the CS-400 from your force plates. Right click one of your force plates and click "Zero (all)". This will set the current force on the plate data to 0. This helps account for small constant amount that the force plate will be off by. Remember that it zeros all of the force plates at once. So make sure there are no objects on the force plates.

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

Step 4: Recording Force Plate Data in Motive

To view live force plate data open the project pane (or cameras pane) and timeline pane, then open the editor in the timeline pane. Select your force plate in the project pane (or cameras pane). Then select one of Fx, Fy, Fz, Mx, My, or Mz to view the live force plate data. This is a good way to confirm that your force plates are working.

Graph of live force plate data.

Note: The frame rates supported by your force plates may will depend on the manufacturer. So for the most up to date rates consult their documentation. For AMTI the supported frame rates: 2000, 1800, 1500, 1200, 1000, 900, 800, 600, 500, 450, 400, 360, 300, etc...

Ethernet System Force Plate Sync Configuration

Open the cameras Pane and the Synchronization Pane. In the synchronization pane select “Custom Synchronization” set sync input > Source = Internal Clock. Set sync input > Clock Freq = 1000. Set Sync input > Input divider = 10. Set Sync output 1-4 > Type =Record Start/Stop Pulse; click apply. In the cameras pane select the force plates group and double check that the Sync Source is set to Free Run. These settings should sync your force plate and motion capture data very well in Motive for regular recordings. The settings should look something like the following:

Example settings in the cameras and synchronization panes for eSync.

Replace this image with 100fps!

USB System Force Plate Sync Configuration

Open synchronization pane select “Custom Synchronization” set External Sync Output > Type = Recording Level. Make sure that in the cameras pane that the force plate rate is a multiple of the tracking frames per second (fps), ex 100 fps and 2000 fps. This can be done in the cameras pane. (The sync for the OptiHub may not give as true of a sync as the eSync.). It should look something like the following:

Example settings in the cameras and synchronization panes for OptiHub.

Ethernet System Force Plate without eSync Configuration

If you are not using the eSync, but are using a prime system: Ignore the Synchronization pane. Just make sure that in the cameras pane that the force plate rate is a multiple of the tracking frames per second (fps), ex 100fps and 1000fps. The issue with this method is that because there is no master synchronization device there might be drift in the data and the data will not trigger at the same time. This can be an issue for longer takes and if you want your system to be timed perfectly. Motive should alert you if your cameras and force plates do not have rates that work.

This is what it will look like if you don’t have the force plate sample rate as an integer multiple of the frame rate,

Graph of bad data.

Step 5: Exporting/Streaming Force Plate Data

1. Streaming data is very easy to do on Motive’s side. Just open the Data Streaming Pane and turn on “Broadcast Frame Data”. Make sure that you are not streaming over the camera network. Then you are good to stream into another program. We recommend Visual3D for any bio-mechanics streaming or data reading.
   1. Real-time streaming into Visual3D uses Visual3DServer plugin provided by C-Motion: http://www.c-motion.com/v3dwiki/index.php/Visual3DServer_Overview

1. You may also export to C3D as long as there is at least one marker in your recording. This is just straight forward exporting. You can open the exported C3D files in Visual3D which is out recommended bio-mech analysis software.