©2014 GlobalLogic Inc.

Sensors data processing for innovative swimming tracking device

Orest Hera

©2014 GlobalLogic Inc.

MEMS Sensors

Horizon plain detection

Magnetic field of the Earth

Swimming data analysis

01

02

03

04

MEMS (MicroElectroMechanical System) Sensors:

● 3D accelerometer● 3D gyroscope● 3D magnetometer

01

MEMS Sensors

Applications

● Mobile devices (Android, iOS)○ Display/map orientation

○ Step counter, Compass applications

○ Augmented reality

● Small custom devices○ Small vehicle navigation and stabilization (quadcopter)

○ Industrial automation

○ Innovative smart systems

MEMS Sensors

Raw sensor data processing

Horizon plain detection:● Gravity force detection by accelerometer● Rotation speed by gyroscope● Complementary filter

02

Angle by vector of gravity force

Horizon plain detection

Advantages:● Direct measurement without

error accumulation

Disadvantages:● System own acceleration should

be filtered● Relaxation time due to Low-pass

filter

Horizon plain detection

Angle by rotation speed integration

Advantages:● Can be used during accelerated motion

Disadvantages:● Integration error accumulation

Horizon plain detection

Complementary filter

● High frequency by gyroscope● Low frequency by gravity force vector

Disadvantages:● Cannot compensate error accumulation drift of rotations around vector of

gravity force

Magnetic field of the Earth:● Binding coordinate system to horizontal

azimuth angle

03

Expected

Magnetometer raw data

Magnetic field of the Earth

Reality

Magnetic field of the Earth

Magnetometer calibrationEllipsoid equation:

The least-squares problem Pseudo-inverse matrix

Swimming data analysis:● Calculate device orientation by raw sensor

data stream● Dynamics of device orientation during

swimming

04

Swimming data analysis

Raw sensor data processing

Swimming data analysis

X-,Z-axes horizontal direction (yaw)

Swimming data analysis

X-,Y-,Z-axes vertical direction (pitch)

©2014 GlobalLogic Inc.

Thank You