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Table 2 Summary of IMUs

From: The role of wearables in spinal posture analysis: a systematic review

Components

 Accelerometer

Measure proper acceleration

 - I.e. gravitational force (static) and sensor movement (dynamic)

 - At least one 1D accelerometer

 Gyroscope

Measure angular velocity

 - At least one 1D gyroscope

Magnetometer

Measure all magnetic fields

 - Optional

Degrees of Freedom (DoF)

 9 DoF

3D accelerometer, 3D gyroscope & 3D magnetometer:

 - Most accurate type of IMU as able to measure proper acceleration, angular velocity and magnetic fields in three axes

 - Used in: PostureMonitor [34]; Zishi [39]; Xu’s wearable system [33]; Hermanis’ Wearable Sensor Grid [23]; LumoLift [46]; BodyMonitor [22]

 6 DoF

3D accelerometer & 3D gyroscope:

 - Less accurate than 9 DoF IMUs as no magnetometer, therefore lower accuracy in determining sensor orientation

 - Used in: Giansanti’s wearable system [3]; SPoMo [6]; Wong’s wearable system [12]; Miyajima’s wearable system [20]

 5 DoF

3D accelerometer & 2D gyroscope:

 - Less accurate than 6 DoF IMUs as gyroscope cannot measure in the third dimension

 - Used in Lou’s Smart Garment [44]

 4 DoF

3D accelerometer & 1D gyroscope:

 - Less accurate than 5 DoF IMUs as gyroscope can only measure in one dimension

 - Used in DorsaVi’s ViMove [35]