Xsens releases wireless 3D motion tracker
October 25, 2010

Xsens releases wireless 3D motion tracker

Enschede, Netherlands – Xsens Technologies B.V., a leader in professional 3D tracking systems, announced the availability of the MTw miniature wireless inertial motion tracker for ambulatory 3D kinematic measurements. The Xsens MTw wireless body-area network system will be shown for the first time at the Neuroscience 2010 conference (November 13-17, 2010) in San Diego, USA at booth #2635.
The MTw is a small, highly accurate, wireless inertial 3D motion tracker. It sets a new standard for ambulatory 3D kinematic measurement systems - building on Xsens’ 10 years of leadership in inertial sensor technology for measuring real-time 3D motion. One of the unique features of the MTw is the Awinda radio protocol which ensures highly accurate time synchronization within the wireless network. In fact, the time synchronization is so accurate that it is comparable to the wired measurement systems from Xsens currently in use at hundreds of research institutes around the world. The importance of accurate time synchronization can be explained looking at the arm movement when playing tennis - both the upper and lower arm can move at angular velocities easily reaching 1000 deg/s. When tracking the 3D elbow joint angle, any error in timing, even of just a few milliseconds, would give rise to errors of several degrees.

The Xsens MTw brings the unobtrusiveness and ease of use of wireless technology to inertial 3D motion tracking. “The goal we have with this product is to further enhance the freedom of movement that inertial sensor technology brings to the field of 3D kinematics measurement systems by making our sensors wireless” says Colleen Monaghan, Product Manager Movement Science of Xsens. “Losing the cables makes the system easier to put on and more comfortable to wear; something that is essential when working with patients outside laboratory settings. However, while making the product wireless, there was no question on compromising on accuracy - at any level. In fact, the MTw is our smallest and most accurate motion tracker ever.”

Per Slycke, CTO of Xsens explains; “Measuring 3D motion accurately in biomechanics research, sports, and ergonomics is already challenging – you do not want time synchronization between multiple sensors to be a potential cause of measurement errors. While time synchronization is relatively easy to address in wired systems, it is not trivial for a wireless sensor network. In order to really tackle this issue at a fundamental level Xsens’ R&D team has developed a unique, patent pending radio protocol we call Awinda, based on standard low-cost 2.4 GHz ISM chipsets, that takes care of time synchronization of up to 32 MTw’s across the wireless network to within 10 μs.” Fred Dijkstra, system architect at Xsens adds; “Wireless data transmission is great because of the freedom it gives the user - but from a technical point of view you have to deal with data packets being lost during transmission. Traditional radio protocols reserve a lot of time for acknowledgement of data packet reception and re-transmission of data, which means the network throughput will drop dramatically. With Awinda, specifically developed for inertial sensors, we took a new approach – if a data packet from the sensor is lost in transmission the sensor will not re-transmit that packet but use the embedded processor to integrate the information from the “lost” data packet into the next one. This way, you can keep the accuracy in real-time motion tracking, without any impact on radio network throughput. The benefit for the user is that you do not have to worry about the accuracy of your measurement varying with the quality of the radio link.”
The MTw Development Kit includes; multiple MTw’s, a combined wireless receiver and charging dock, MT Manager, an easy to use Windows software for recording and real-time visualization of data and an SDK compatible with amongst others C/C++, MATLAB, LabVIEW. Using the specially designed click-in straps ensures efficient and secure fastening to the body.

The MTw is available for ordering with shipments in place in December 2010. For a preview of the MTw, visit Xsens at the Neuroscience 2010 conference November 13-17, 2010 in San Diego, USA at booth #2635.