Adaptive PPG Sensor Selection for Motion-Robust Wearables
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Solution Overview
Problem
Existing wearable devices face challenges in accurately collecting photoplethysmogram (PPG) data due to factors such as motion, ambient light, and varying skin properties, which affect signal quality.
Innovation Solution
A configurable PPG system that selects transmitter-receiver combinations based on signal strength, quality metrics, user movement, temperature, and ambient light, and adjusts wavelengths over time to optimize signal acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single transmitter-receiver combination is used, then the device complexity is reduced, but the signal quality deteriorates under varying conditions
Solution Approach 1:
The wearable device incorporates multiple transmitter-receiver combinations that can function in different orientations (e.g., vertical, horizontal, diagonal). Each combination serves as a potential PPG sensing path, allowing the system to adapt to various wearing positions and skin types while maintaining measurement precision without requiring a completely different device configuration.
Solution Approach 2:
The system dynamically selects and switches between different transmitter-receiver combinations based on real-time signal quality assessment. The controller evaluates metrics such as signal strength, noise levels, and motion artifacts, then activates the optimal combination, making the sensing configuration adaptive rather than static.
2Measurement precision
If multiple transmitter-receiver combinations are used, then the PPG signal quality is improved, but the device complexity increases
Solution Approach 1:
The PPG sensing system is segmented into multiple independent transmitter-receiver combinations, each capable of operating autonomously. This segmentation allows the controller to activate only the necessary subsets of sensors based on current conditions, reducing the effective complexity while maintaining the capability for high-quality signal acquisition when needed.
Solution Approach 2:
The system includes automatic signal quality assessment and combinatorial selection functionality that operates without user intervention. The controller autonomously evaluates the performance of different transmitter-receiver combinations and switches between them based on predefined criteria, eliminating the need for manual configuration and reducing operational complexity.
3Stability of the object's composition
If the wearable device remains stationary, then the PPG measurement stability is improved, but the user mobility is restricted
Solution Approach 1:
The system continuously monitors signal quality metrics and motion characteristics, using this feedback to dynamically adjust the selected transmitter-receiver combination. When motion artifacts degrade signal quality, the system switches to combinations less affected by the current motion pattern, maintaining measurement stability during user mobility activities such as walking, exercising, or changing positions.
4Measurement precision
If the sampling rate is increased, then the PPG signal resolution is improved, but the energy consumption increases
Solution Approach 1:
The system applies partial action by activating only the necessary number of transmitter-receiver combinations required to achieve adequate signal quality. Rather than continuously operating all sensors at maximum sampling rates, the controller selectively engages subsets of sensors and adjusts sampling rates based on current signal conditions, reducing energy consumption while maintaining sufficient measurement precision.
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
Ensures high-quality PPG signal capture across different orientations and conditions, providing accurate physiological data including heart rate, HRV, and sleep stage classification.
Implementation Method 1
The PPG system may include one or more optical transmitters and one or more optical receivers. In some examples, the optical transmitters (e.g., light-emitting diodes (LEDs)) may transmit one or more wavelengths of light
Implementation Method 2
the optical receivers may generate a PPG signal in response to the transmitted light
Data Source
AI summary
Methods, systems, and devices for optical signal measurement are described. A wearable electronic device may activate a first combination of optical sensors, the first combination of optical sensors including a set of transmitter sensors and a set of receiver sensors. In some cases, one or more optical sensor of the first combination of optical sensors may be positioned under a protrusion on an inner surface of the wearable electronic device. The device may measure, at the set of receiver sensors at a first time, one or more signals from the set of transmitter sensors, determine a signal quality metric associated with the one or more signals, and select a second combination of optical sensors for use at a second time based on the signal quality metric.