Worn Sensor Force Control for Motion Artifact Reduction
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Solution Overview
Problem
Existing body-worn devices for measuring physiological parameters are unreliable, particularly during exercise and movement, due to motion artifacts and inaccurate measurements.
Innovation Solution
A wrist-worn device with a securing band, light sources, and light receivers that control the amplitude of the received light signal within an envelope control band by adjusting the force perpendicular to the wrist, combined with additional sensors for improved accuracy and comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If body worn devices are used to measure physiological parameters during exercise and movement, then the ability to monitor health status during activity is improved, but measurement reliability deteriorates due to motion artifacts and inaccurate readings
Solution Approach 1:
The device dynamically adjusts the pressing force applied by the actuator based on real-time measurement quality feedback. The control unit modifies the force magnitude to optimize contact between sensors and skin, maintaining reliable measurements during varying levels of physical activity and motion conditions
Solution Approach 2:
The measurement system implements feedback control where the control unit continuously monitors the quality of physiological parameter measurements and adjusts the pressing force accordingly. This closed-loop control ensures that measurement reliability is maintained by adapting the contact pressure to current motion conditions and signal quality
2Measurement precision
If pressing force is increased to improve contact between sensors and skin, then measurement accuracy is improved, but user comfort deteriorates
Solution Approach 1:
The pressing force is dynamically adjusted rather than maintained at a constant high level. The actuator applies only the necessary force to achieve adequate sensor-skin contact for accurate measurements, reducing excessive pressure that would cause discomfort during prolonged wearing
Solution Approach 2:
The device automatically optimizes the pressing force through feedback control, adjusting the contact pressure to the minimum necessary level for accurate measurements. This self-adjusting mechanism eliminates the need for manual adjustment and prevents both insufficient and excessive pressing forces that would affect comfort
3Ease of operation
If pressing force is decreased to improve user comfort, then wearing comfort is improved, but measurement precision deteriorates
Solution Approach 1:
The control unit continuously monitors measurement quality and adjusts the pressing force in real-time. When measurement accuracy drops below acceptable thresholds, the system automatically increases the pressing force to restore adequate sensor-skin contact, ensuring measurement precision is maintained without requiring permanently high force levels
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 provides more reliable and accurate measurements of physiological parameters like heart rate, oxygen saturation, and respiration rate, even during exercise and movement, by minimizing the impact of motion artifacts and ambient light.
Implementation Method 1
at least one light source having a light emitting surface and at least one light receiver having a light receiving surface... emitting light in a wavelength range by the at least one light source... producing a received light signal by the at least one light receiver corresponding to a received intensity of light received
Data Source
Figure 1~2
Figure 3a~3b
Figure 4
AI summary
Method and device for measuring a signal representative of a physiological parameter of a user. A body worn device (1) includes a securing band (2) and at least one sensor for measuring the signal. The sensor is arranged on the securing band of the device such that when worn, the at least one sensor abuts against the body of the user. A value of the signal is measured using the sensor. An amplitude envelope control band is defined having an envelope upper amplitude value and an envelope lower amplitude value. The amplitude of the measured value is controlled to be within the amplitude envelope control band by controlling a force pressing the at least one sensor in a direction substantially perpendicular to the body of the user.