Dual Accelerometer Heart Rate Monitor Pulse Detection
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Solution Overview
Problem
Current heart rate monitors employing multi-axis accelerometers struggle to distinguish physiological pulses from motion artifacts caused by extraneous movements, limiting their effectiveness in emergency care scenarios.
Innovation Solution
The use of two multi-axis accelerometers placed at an angular orientation on the body surface, with vertical axes normal to the body surface to sense physiological motion and longitudinal/lateral axes parallel to the surface to sense extraneous motion, allowing for the cancellation of motion artifacts through differential and common mode signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single multi-axis accelerometer is used to detect pulse, then the device simplicity is maintained, but motion artifacts from extraneous motion conceal physiological motion
Solution Approach 1:
The system divides the detection function into multiple accelerometers positioned at different locations and orientations. Each accelerometer captures a portion of the motion signal, and through signal processing (combining differential mode signals and cancelling common mode signals), the system reconstructs the physiological pulse signal while eliminating motion artifacts.
2Measurement precision
If accelerometers are placed to sense physiological motion with vertical axes normal to body surface, then pulse detection capability is improved, but sensitivity to extraneous motion increases
Solution Approach 1:
The system extracts the harmful common mode signals (motion artifacts) from the accelerometer outputs and removes them through signal processing. By identifying and cancelling the common mode component that represents extraneous motion, the system isolates the differential mode signal that contains the physiological pulse information.
3Reliability
If two accelerometers are placed at angular orientation, then motion artifact cancellation is enabled, but device complexity increases
Solution Approach 1:
The system merges the outputs from multiple accelerometers through signal processing operations. By combining differential mode signals (which contain physiological information) and cancelling common mode signals (which contain motion artifacts), the system achieves reliable pulse detection while managing the increased complexity through systematic signal processing.
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
This approach enables reliable and accurate pulse detection by isolating physiological motion from extraneous motion artifacts, enhancing the applicability of heart rate monitoring in emergency care settings.
Implementation Method 1
a plurality of multi-axis accelerometers generate differential mode signals indicative of a sensing by the accelerometer of physiological motion of the person relative to acceleration sensing axes, and generate common mode signals indicative of a sensing by the accelerometers of extraneous motion
Data Source
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AI summary
A heart rate monitor (40) for detecting a pulse of a person (10) employs a platform (43), a plurality of multi-axis accelerometers (41R, 41L) and a pulse detector (44). The multi-axis accelerometers (41R, 41L) are adjoined to the platform (43) to generate differential mode signals (AZR, AZL) indicative of a sensing by the accelerometers (41) of physiological motion (12) of the person (10) relative to acceleration sensing axes (42R, 42L) and to generate common mode signals (AXR, AXL, AYR, AYL) indicative of a sensing by the accelerometers (41R, 41L) of extraneous motion by the person (10) relative to the acceleration sensing axes (42R, 42L). The pulse detector (44) is operably connected to the multi-axis accelerometers (41R, 41L) to generate a pulse signal (PS)as a function of a vertical alignment of the acceleration sensing axes (42R, 42L) combining the differential mode signals (AZR, AZL) and cancelling the common mode signals (AXR, AXL, AYR, AYL).