PPG Heart Rate Detection Using Motion Denoising
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Solution Overview
Problem
Conventional pulse oximeters struggle to accurately detect heart rate in non-static conditions due to disturbed signals caused by relative movement between the device and the user, leading to incorrect heart rate calculations.
Innovation Solution
A heart rate detection module incorporating an optical sensor, a motion sensor, and a processor that converts PPG signals and acceleration signals into frequency domain information, identifies spectrum peaks, and uses a denoising parameter to remove noise from the PPG signals, allowing for accurate heart rate calculation even in non-static states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a pulse oximeter is adapted to a portable or wearable electronic device for non-static state monitoring, then the device can be worn during movement and daily activities, but the relative movement between the device and skin causes disturbed signals and incorrect heart rate detection
Solution Approach 1:
The patent introduces an acceleration sensor as an intermediary device to detect motion artifacts separately. The processor then uses this acceleration information to identify and remove motion-related noise from the PPG signal, allowing accurate heart rate measurement even during movement. This mediator approach enables the system to distinguish between physiological signals and motion-induced disturbances.
Solution Approach 2:
The patent extracts motion artifact information from the acceleration sensor and separates it from the PPG signal processing chain. By identifying frequency components in the acceleration signal that correspond to motion noise, the system removes these specific frequency components from the PPG spectrum, leaving only the pure physiological heart rate information.
2Measurement precision
If motion denoising is applied to remove noise from PPG signals, then heart rate calculation accuracy improves in dynamic conditions, but the device complexity increases due to additional motion sensor and processing requirements
Solution Approach 1:
The acceleration sensor serves multiple functions: it detects motion artifacts for denoising, provides activity recognition data, and enables posture detection. This multi-functionality justifies the added device complexity by providing additional valuable health monitoring capabilities beyond just heart rate measurement.
Solution Approach 2:
The system uses the acceleration sensor data to automatically adjust the PPG signal processing parameters and noise removal strategies based on the detected motion state. The device self-regulates the denoising intensity and frequency range based on the actual motion conditions, eliminating the need for manual configuration or complex adaptive algorithms.
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 denoises PPG signals to improve heart rate calculation accuracy in dynamic conditions, enabling reliable heart rate monitoring in wearable devices like smart watches and wristbands.
Implementation Method 1
detects an intensity variation of the penetrating light based on the feature that the oxyhemoglobin and the deoxyhemoglobin have different absorptivities in particular spectrum
Implementation Method 2
The motion sensor is configured to output an acceleration signal corresponding to the detection period
Data Source
AI summary
A heart rate detection module including a PPG measuring device, a motion sensor and a processing unit is provided. The PPG measuring device is configured to detect a skin surface in a detection period to output a PPG signal. The motion sensor is configured to output an acceleration signal corresponding to the detection period. The processing unit is configured to respectively convert the PPG signal and the acceleration signal to first frequency domain information and second frequency domain information, determine a denoising parameter according to a maximum spectrum peak value of the second frequency domain information to denoise the first frequency domain information, and calculate a heart rate according to a maximum spectrum peak value of the denoised first frequency domain information.