Wearable Sensor System for Heart Rate Motion Artifact Compensation
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Solution Overview
Problem
Motion artifacts during physical activities, such as walking or biking, interfere with the accuracy of heart rate data measured by photoplethysmography (PPG) sensors due to similar frequency ranges, affecting the reliability of heart rate monitoring in wearable devices.
Innovation Solution
A wearable sensor system that combines a PPG optical sensor with an accelerometer, where both share a linear configuration of light processing elements and a housing aligns these elements to match the accelerometer's orientation, allowing for active motion artifact compensation by discarding data points that match motion and heart rate data criteria, thereby improving heart rate data accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a PPG sensor is used for heart rate measurement, then heart rate data can be obtained, but motion artifacts interfere with accuracy due to similar frequency ranges
Solution Approach 1:
The patent introduces an accelerometer as an intermediary device that measures motion artifacts separately. The accelerometer data serves as a mediator to identify and compensate for motion interference in the PPG heart rate measurements, allowing the system to distinguish between actual heart rate signals and motion-induced artifacts.
Solution Approach 2:
The patent changes the approach from directly using PPG signals to using a combination of PPG and accelerometer parameters. By analyzing multiple parameters (PPG waveform characteristics and accelerometer motion data) together, the system can identify motion artifacts and compensate for them, improving measurement accuracy during physical activity.
2Measurement precision
If motion artifact compensation is implemented using accelerometer data, then heart rate accuracy improves, but device complexity increases
Solution Approach 1:
The patent makes the accelerometer serve multiple functions: it not only measures motion artifacts for compensation but also provides activity recognition data and enables motion-corrected heart rate monitoring. This multi-functionality justifies the added complexity by extracting maximum value from a single additional sensor.
Solution Approach 2:
The system implements feedback by continuously comparing accelerometer data with PPG data to identify motion artifacts. The accelerometer provides real-time feedback about motion states, which is used to adjust and compensate the heart rate measurements dynamically, creating a closed-loop system that improves accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively compensates for motion artifacts, enhancing the accuracy of heart rate measurements by correlating and synchronizing data from both sensors, resulting in more precise and reliable heart rate data even during physical activities.
Implementation Method 1
PPG is an optical measurement technique in which light is directed towards the skin, and changes in blood volume pulsing under the skin are correlated to changes in reflected light
Implementation Method 2
an accelerometer for providing accelerometer measurements for at least one accelerometer axis of orientation
Data Source
AI summary
Technology is described for a wearable sensor system including an accelerometer and a PPG optical sensor having light processing elements including at least one photodetector in at least one linear configuration sharing an axis of orientation with the accelerometer. Heart rate measurements determined from reflected light detected by a photodetector of the light processing elements in a linear configuration are co-sampled with accelerometer measurements for one of its axes sharing its orientation with the linear configuration, thus providing per axis measurements which provide more precise data points for more easily compensating for motion artifacts in heart rate data. A wrist wearable biometric monitoring device is also described which embodies the wearable sensor system and performs active motion artifact compensation.