Patient Monitoring Device Calibration via Accelerometer Orientation
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Solution Overview
Problem
Existing patient monitoring devices require active user cooperation for calibration, which is not feasible for patients who are unwell, unconscious, or unable to remain still, leading to inaccuracies in posture tracking.
Innovation Solution
A method and device that calibrate by aligning the measurement reference frame with the user's reference frame before and after attachment, using acceleration measurements to determine a transformation matrix, allowing for accurate posture estimation without user involvement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a calibration procedure requires active user involvement to adopt multiple postures, then measurement precision can be improved through accurate orientation determination, but ease of operation deteriorates because unwell or unconscious patients cannot cooperate
Solution Approach 1:
The device performs calibration automatically without requiring user participation. The processor executes calibration routines that autonomously determine orientation by analyzing accelerometer data during device attachment and removal events, enabling the system to self-calibrate even when the patient is unconscious or unable to cooperate
Solution Approach 2:
The calibration procedure is performed in advance during device attachment or removal events, before actual monitoring begins. The processor captures orientation data at these predetermined moments when the device transitions between worn and unworn states, establishing the transformation matrix prior to any posture monitoring
2Measurement precision
If the device reference frame is aligned with the user's body reference frame during attachment, then measurement precision improves, but device complexity increases due to the need for calibration procedures
Solution Approach 1:
The patent replaces complex mechanical alignment procedures with electronic signal processing. Instead of physically aligning the device with the user's body through manual calibration, the processor uses accelerometer data and mathematical transformations to computationally determine and correct orientation misalignment
Solution Approach 2:
The system changes the approach from physical alignment to parameter-based correction. By measuring acceleration vectors and calculating transformation matrices that adjust for orientation differences, the system compensates for misalignment through mathematical parameter transformation rather than mechanical adjustment
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
Enables accurate monitoring of patient posture and vital signs without requiring active user cooperation, ensuring reliable data collection even for patients who cannot follow calibration protocols.
Implementation Method 1
measure the inclination of the device based on an observation of gravity
Data Source
AI summary
A method of calibrating a monitoring device to be attached to a user is provided. Prior to attachment of the device, the device is aligned with respect to the user such that the measurement reference frame of the device is substantially aligned with a reference frame of the user. A first measurement of the orientation of the device with respect to a world reference frame is obtained. After attachment of the device, a second measurement of the orientation of the device with respect to a world reference frame is obtained. A transformation matrix is determined for use in transforming subsequent measurements obtained by the device into the reference frame of the user. The matrix is calculated using the first and second measurements and information on the amount of rotation of the device relative to the user about a vertical axis in the world reference frame between the first and second measurements being taken.