Codamotion 3D Measurement Instruments

Codamotion’s measurement technology uses miniature infra-red ‘active’ markers, each with their own unique identity, to track the three-dimensional (3D) positions of the human body in real time.

‘Active’ markers are those which generate their own light, they flash (as opposed to reflect). VES has 56 tracking markers on their disposal in the laboratory.

The motion of active markers is recorded using CODA sensors (also called CX1 units). A single sensor is a stand-alone measurement unit, capable of tracking 3D marker positions in real time.

Multiple CODAs can be easily aligned as a single framework to extend the measurement volume covered.

Codamotion 3D Measurement Instruments
Codamotion Sensor CX1
The Codamotion CX1 unit, known as a CODA. It only weighs 5kg, so it is readily portable.
Codamotion Markers and Marker Drive Boxes
Standard Marker
The standard active marker for use with the CX1 system can be powered by any of the marker drive boxes in the standard range. Each marker is given a unique identity by the drive box it is connected to.
2-Marker Drive Box
Contains the battery and optical synchronisation for up to two markers. Markers are time-multiplexed by these boxes so that every marker has a unique identity. Boxes are usually placed mid-segment so that no marker wires should cross any joints. Boxes are self-powered and fully independent.
8-Marker Drive Box
Contains the battery and optical synchronisation to for up to eight markers.
Codamotion Hubs

Active Hub with Quad UART
A rack-mountable industrial computer unit. Quad UART gives combined power and data connections for Cx1 units, plus sync input/output connectivity. The sync input connection can be used to control the timing of Codamotion acquisition using external devices, whilst sync output can be used to trigger external devices to run synchronously with the Codamotion system. Optional analogue and digital interfaces allow synchronous acquisition of data from other devices, and real-time triggering.

For more information visit www.codamotion.com/

Application of Codamotion system in Vibration Engineering research is presented in a journal article by Racic et al. (2010) doi:10.1016/j.jsv.2010.02.021

Force plate

Force plates, also known as force platforms, are devices designed to measure forces (loads) generated by people standing and moving on them or moving across them. VES has an AMTI strain gage force plate.

In 3D space the resultant force and moment vectors can be resolved into six components acting along three-axial orthogonal coordinate system – three forces Fx, Fy, Fz and three moments Mx, My and Mz. When designing structures which are predominantly occupied by active humans, civil structural engineers typically need only vertical Fz and/or lateral Fx force components (e.g. in the case of footbridges).

Because of its limited size, the force plate is typically used in VES to measure forces due to activities performed on a spot, such as jumping and bouncing:

An example of bouncing force record: An example of jumping force record:
Instrumented Treadmill

In VES, an ADAL3D instrumented force measuring treadmill is used for continuous measuring of time-varying walking and jogging forces during a large number of successive steps and over a wide range of steady-state gait speeds.

To measure independently the left and right footfalls, double belt design splits the walking surface into two identical treadmills - left and right, placed close together. Each treadmill belt is driven by a brushless servomotor equipped with internal velocity controllers to maintain the speed as constant as possible. Velocity of treadmill belts in the range 0.1-10 km/h can be controlled and monitored remotely either with a control panel or with ADAL3D-F software, Adisoft2000 (HEF Medical Developpement 2009), run from the data acquisition PC. Similar to fitness treadmills, both the FMIT and the remote control panel are equipped with a safety stop switch.

A pair of Kistler piezoelectric force transducers on each side of the treadmill are connected to signal processing units providing one vertical and two horizontal analog force signals per side. In total six force analog signals are sent from the four sensors to the charge amplifiers, then to a 16 channel, 12 bit, A/D card in the data acquisition PC. Usual sampling rates are between 100 and 1000 Hz.

Two more channels are used to monitor the instantaneous velocity of left and right treadmill belts measured by optical transducers. Finally, Adisoft2000 stores the data. Extra channels of the A/D card could be used to synchronise measurements between the treadmill data and other third party equipment, such as Codamotion.

Force records in a) vertical, b) lateral and c) longitudinal direction for a single test subject measured by the ADAL3D-F during one walking exercise. Left (red) and right (blue) individual steps are overlapped using Adisoft2000:;

a b c
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