This presentation is about the development of Instabeat, an innovative swimming tracker, it's sensors, horizon detection and swimming data analysis. Presentation by Orest Hera (Senior Software Engineer, GlobalLogic, Lviv), delivered at GlobalLogic Lviv Mobile TechTalk, November 13, 2014. More details - http://www.globallogic.com.ua/press-releases/lviv-mobile-2014-coverage

1. ©2014 GlobalLogic Inc.
Sensors data processing for
innovative swimming tracking device
Orest Hera

2. MEMS Sensors
Horizon plain detection
Magnetic field of the Earth
Swimming data analysis
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©2014 GlobalLogic Inc.

3. MEMS (MicroElectroMechanical System)
Sensors:
● 3D accelerometer
● 3D gyroscope
● 3D magnetometer
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4. 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

5. MEMS Sensors
Raw sensor data processing

6. Horizon plain detection:
● Gravity force detection by accelerometer
● Rotation speed by gyroscope
● Complementary filter
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7. Horizon plain detection
Angle by vector of gravity force
Advantages:
● Direct measurement without error
accumulation
Disadvantages:
● System own acceleration should be
filtered
● Relaxation time due to Low-pass
filter

8. Horizon plain detection
Angle by rotation speed integration
Advantages:
● Can be used during accelerated motion
Disadvantages:
● Integration error accumulation

9. 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

10. Magnetic field of the Earth:
● Binding coordinate system to horizontal
azimuth angle
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11. Magnetic field of the Earth
Magnetometer raw data
Expected
Reality

12. Magnetic field of the Earth
Magnetometer calibration
Ellipsoid equation:
The least-squares problem Pseudo-inverse matrix

13. Swimming data analysis:
● Calculate device orientation by raw sensor
data stream
● Dynamics of device orientation during
swimming
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14. Swimming data analysis
Raw sensor data processing

15. Swimming data analysis
X-,Z-axes horizontal direction (yaw)

16. Swimming data analysis
X-,Y-,Z-axes vertical direction (pitch)

17. ©2014 GlobalLogic Inc.
Thank You