Activity recognition using multiple accelero sensors

The activity recognition concept of VitaMove is based on accellero sensors. These wireless sensors are placed on strategic body segments allow registration of both the angle of the sensor (with respect to the gravitational axis) as well as accelerations of the sensor at the same time.
After completion of the recording, these 2 components are separated via steep software filters to yield ‘Angle’ and ‘Motility’ for each sensor. Also, band-pass filtering followed by joint time-frequency domain techniques yield a possible cyclical ‘Frequency’ component in the signal, as seen during walking, bicycling or wheelchair driving. Even so, the ‘Phase’ angle between the sensors on the two legs can be computed to yield the symmetry of walking.
Such ‘Angle’, ‘Motility’ and ‘Frequency’ and ‘Phase’ features can be calculated at an effective rate of 1 per second. These features can statistically be combined to yield up to 30 classes of ‘Postures’ and ‘Motion’ (general and cyclical).

The concept in a 25 year old female displayed over a period of 25 hours. From the top going down:

 

  1. ‘Motion’ showing Bicycling, Wheelchair driving, Running, Walking (also staircase up and down, and general movement (as transitions of postures)
  2. ‘Posture’ showing Standing, Sitting and Lying on side, supine and prone
  3. Heart rate in beats per minute and its variability in terms of the Standard Deviation
  4. Breath rate (periods per minute) and Standard Deviation (not supported in this KINS version)
  5. Walking frequency from 0 – 120 steps per minute.

 

For ‘Posture & Motion’ analysis, the following minimum set of sensors should be recorded:

  • ‘TruSag’:  Sensor ‘Sagittal’ / perpendicular to sternum / trunk
  • ‘UllSag’ or ‘UlrSag’: Sagittal / perpendicular to ‘l’eft (or ‘r’ight) ‘U’pper ‘l’eg

To increase the accuracy of the analysis, the following sensor is normally added:

  • ‘TruLon’:  ‘Longitudinal’ / parallels the trunk; the sensitivity axis points down

So the default set of sensors that come with the body activity and motion comprise at least 3 sensors:

  • 2 on the trunk:   ‘TruSag’ and ‘TruLon’
  • 1 leg sensor:   ‘UllSag’ or ‘UlrSag’

 

Extra accelero sensors and ECG

To be able to discriminate between lying on the left or on the right-hand side (for instance in hypertensic patients while in bed), the following sensor can be added optionally:

  • ‘TruTra’:   ‘Transversal’ to the trunk; sensitivity axis points from right to left

To yield information on the phase angle between the legs during walking (for instance in amputees) one extra sensor is optionally attached to the other upper leg:

  • ‘UlrSag or ‘UllSag’: Sagittal / perpendicular to ‘r’ight (or ‘l’eft)’U’pper ‘l’eg

The body activity and motion analysis program will also analyze the activity or ‘Motility’ of sensors on the hand. One or two sensor(s), distal to one of (or both) the wrists:

  • ‘LalTra’:  Transversal to the sides of the ‘l’eft ‘L’ower ‘a’rm
  • ‘LarTra’:  Transversal to the sides of the ‘r’ight ‘L’ower ‘a’rm

An ECG can be registered and heart rate and variability (St. Dev. of HR) will be computed automatically.