Browsing by Author "Nurmi, Marko"
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- Dynamic control algorithm for an analog front end in a wearable optical heart rate monitoring device
Sähkötekniikan korkeakoulu | Master's thesis(2016-06-13) Nurmi, MarkoOptical heart rate monitoring is an established technology based on photoplethysmography measurements from the surface of the skin. It has recently gained popularity among many companies in consumer targeted applications. Even though the principles of optical heart rate monitoring are fairly simple, the inherent problems of the technology and often challenging operating conditions pose serious issues for the PPG signal acquisition and consequent HR estimation. This thesis investigates the challenges of a PPG front end in a consumer targeted wrist-worn optical heart rate monitor and proposes a method for improving the measurement resolution. The goal of this thesis is to develop an embedded real-time control algorithm to optimally adjust the parameters of the two chosen PPG front ends, AFE4400 and AFE4404. The main requirement for the control algorithm is to acquire good quality PPG signal in a wide range of ambient light conditions while maintaining low power consumption. The developed control algorithm was optimized with simulations using 228 recordings form various activities with a total length of 280 hours. The algorithm performance was compared against the thesis starting point with an apparatus that simulated PPG signal in different lighting conditions. As a result, the saturation illuminance was increased notably and the PPG signal was still usable at 20 klux illuminance, whereas without the controller the signal saturated at 13 klux. Moreover, the signal quality determined by AC/DC ratio was increased tenfold for normal lighting conditions. Additionally, carefully selecting the LED sampling timings reduced ambient light artifacts visibly and power consumption by 85 %. The algorithm was implemented to the commercially available PulseOn wrist device and P-OHR1F module. The performance and functionality of the PulseOn device has been verified with multiple recordings in both controlled and real use cases. - Sairauksiin liittyvät systeemidynamiikan sovellukset
Sähkötekniikan korkeakoulu | Bachelor's thesis(2012) Nurmi, Marko