Single Axis Accelerometer Step Detection via Rectified Signal Analysis
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Solution Overview
Problem
Existing medical devices, both implantable and wearable, face challenges in accurately detecting and tracking patient steps due to limitations such as power consumption, size constraints, and the need for frequent battery charging, while external devices have disadvantages like falling off and being unsuitable for wet environments.
Innovation Solution
A medical device system utilizing a single axis accelerometer to detect steps by processing a rectified signal generated from a moving window analysis, with an auto-adjusting threshold to identify qualifying steps, allowing for efficient step counting without the need for frequent battery charging and improved durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a single axis accelerometer is used for step detection, then power consumption is reduced and device size is minimized, but measurement precision and detection accuracy may be compromised
Solution Approach 1:
The patent implements dynamic threshold adjustment where the threshold for step detection is not fixed but adapts based on the patient's activity level and historical data. The processing circuitry continuously learns and adjusts the threshold to distinguish genuine steps from normal movements, maintaining high detection accuracy despite using a single axis accelerometer with limited data dimensions.
Solution Approach 2:
The patent transforms the accelerometer signal through multiple processing stages including rectification, filtering, and feature extraction. By changing the parameter representation of the raw acceleration data into derived features like signal amplitude, frequency characteristics, and temporal patterns, the system achieves accurate step detection with minimal hardware complexity.
2Reliability
If implantable medical devices are used for step tracking, then durability and continuous monitoring are improved, but power consumption increases and battery charging frequency increases
Solution Approach 1:
The patent replaces complex mechanical step counting mechanisms with signal processing-based detection using a single axis accelerometer. This substitution reduces the computational burden and power consumption while maintaining reliable continuous monitoring capability through sophisticated algorithms that process minimal sensor data efficiently.
Solution Approach 2:
The processing circuitry performs step detection at optimized intervals rather than continuously analyzing every data point. By implementing periodic processing with duty cycling and event-triggered analysis, the system maintains reliable monitoring while significantly reducing average power consumption and extending battery life.
3Ease of manufacture
If external wearable devices are used for step detection, then ease of manufacture and low cost are achieved, but reliability decreases due to falling off and environmental susceptibility
Solution Approach 1:
The patent merges the step detection functionality with the implantable medical device itself, combining cardiac monitoring and activity tracking into a single integrated system. This integration eliminates the need for separate wearable devices, ensuring continuous reliable monitoring while leveraging the existing implantable device's durability and secure positioning within the patient's body.
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 system effectively detects and tracks patient steps with low power consumption, reducing the need for frequent battery charging and enhancing durability, providing motivation for improved activity levels and therapy progress monitoring.
Implementation Method 1
an accelerometer circuitry configured to output a signal indicative of variations in accelerations along a single axis of movement of patient
Implementation Method 2
rectification of the output signal comprises generating a rectified value for each of a plurality of moving windows imposed over the output signal, wherein generating the rectification value for each of the plurality of moving windows comprises determining a current value of the output signal for the window, determining a maximum value for a portion of the output signal enclosed by the window, and subtracting the current value from the maximum value
Implementation Method 3
analyze the rectified signal to detect the occurrence of a step taken by a patient based on the rectified signal
Data Source
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AI summary
Examples described herein include a medical device system comprising an accelerometer circuitry configured to output a signal indicative of variations in accelerations along a single axis of movement of patient; and processing circuitry configured to receive the output signal from the accelerometer, and to rectify the output signal to generate a rectified signal, wherein rectification of the output signal comprises generating a rectified value for each of a plurality of moving windows imposed over the output signal, wherein generating the rectification value for each of the plurality of moving windows comprises determining a current value of the output signal for the window, determining a maximum value for a portion of the output signal enclosed by the window, and subtracting the current value from the maximum value; and analyze the rectified signal to detect the occurrence of a step taken by a patient based on the rectified signal.