Inertial sensor measurement systems

An inertial measurement unit (IMU) is a device consisting of an accelerometer, gyroscope, and often a magnetometer. By combining the information from the accelerometer – gravitational acceleration – with the data from the gyroscope – rotational velocity -, the orientation of the device can be determined (M Brodie, Walmsley, & Page, 2008). The magnetometer is used to track the magnetic-north, to determine the heading of the IMU. There are many commercially available IMUs on the market.

As stand-alone system, the device cannot determine its (global) position, and therefore is not added to the chart. In principle, the accelerometer could be used to determine position by performing a double integration, but the data will suffer from large integration drifts. The systems do appear in the table as fusion motion capture system (see discussion). The position in global space can for example be estimated when an IMU is combined with a rigid-body model of a human (Neuron, 2017; Xsens, 2017). Hereby the IMUs are placed on body segments to determine the global orientation. IMUs do not have a base station and are therefore the most mobile of all available measurement systems. Additionally, the system is capable of detecting very rapid motion (Zohlandt, Walk, & Nawara, 2012) and is non-invasive for the user, which makes it an attractive system in sports (e.g. gymnastics (Zohlandt et al., 2012), swimming (James Bruce Lee, Burkett, Thiel, & James, 2011)). A drawback is that the system is susceptible to measurement errors due to nearby metal (experimental set-up). Moreover, the gravity-based algorithms are sensitive to linear accelerations.

Video: The work presented was conducted by Sebastian O.H. Madgwick during his Ph.D research at the University of Bristol. For more information and source code, see: http://www.x-io.co.uk/gait-tracking-w…

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