Time Domain Motion Artifact Removal for PPG Heart Rate
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Solution Overview
Problem
Motion artifacts caused by body movement compromise the accuracy of heart rate determination from photoplethysmogram (PPG) signals, making it difficult to obtain reliable heart rate data.
Innovation Solution
A device that includes a heart rate sensor, an accelerometer, and processing circuitry to remove motion artifacts from PPG signals in the time domain. The processing circuitry uses acceleration signals and integrated acceleration signals to identify and subtract motion artifacts using algorithms such as least squares, allowing for accurate heart rate determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If motion artifacts are present in PPG signals during user movement, then the PPG signal can still be obtained, but the accuracy of heart rate determination deteriorates
Solution Approach 1:
An accelerometer is introduced as an intermediary device to detect motion artifacts separately. The accelerometer signals serve as a mediator that characterizes the motion state, which is then used to guide the removal of motion artifacts from the PPG signal through adaptive filtering or signal processing techniques.
Solution Approach 2:
The motion artifact component is extracted from the PPG signal using the accelerometer data as a reference. By identifying and separating the motion-related components from the original PPG signal, the clean cardiac signal can be obtained for accurate heart rate determination.
2Reliability
If traditional frequency domain methods are used to remove motion artifacts, then some artifact removal can be achieved, but computational complexity and processing time increase
Solution Approach 1:
The patent replaces complex frequency domain processing with simplified time domain processing. By working directly in the time domain using accelerometer-triggered filtering or time-domain deconvolution, the computational complexity is reduced while maintaining effective motion artifact removal capability.
3Productivity
If motion artifacts are present in PPG signals, then continuous monitoring can be maintained, but the reliability of heart rate data deteriorates
Solution Approach 1:
The accelerometer continuously provides feedback about the user's motion state. This feedback is used in real-time to adjust the signal processing parameters and apply appropriate motion artifact removal techniques, enabling continuous monitoring while maintaining accuracy even during movement.
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 solution effectively removes motion artifacts from PPG signals, enhancing the accuracy of heart rate determination and providing reliable heart rate data even during user movement.
Implementation Method 1
an accelerometer configured to generate one or more acceleration signals
Implementation Method 2
mean-centered, variance-scaled integrated acceleration signals
Data Source
AI summary
An algorithm for removing motion artifacts from the PPG signal in the time domain to determine heart rate is disclosed. A device for determining a heart rate of a user can include a heart rate sensor configured to generate heart rate signals when positioned on or adjacent to a user's skin, an accelerometer configured to generate one or more acceleration signals, and processing circuitry configured to remove, in a time domain, motion artifacts from the heart rate signals based on the acceleration signals. In some examples, the removal of motion artifacts can also be based on mean-centered, variance-scaled integrated acceleration signals. In some examples, the processing circuitry can be configured to remove motion artifacts using a least squares algorithm to identify a best representation of acceleration and integrated acceleration signals in the heart rate signals.