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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
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©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
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