Accelerometer Step Counting by Zero-Crossing Time Width
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Solution Overview
Problem
Existing pedometer technologies inaccurately count steps due to combined signals being counted as a single step when they should be counted as two, leading to erroneous step counting.
Innovation Solution
A measurement device that uses an accelerometer to identify time widths between zero crossings in acceleration waveforms during walking or running, counting waveforms over a predetermined threshold as two steps and those below as one step, with threshold adjustments based on walking or running conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If step counting is performed based on peak height of acceleration waveform, then the measurement process is simple, but combined signals equivalent to two steps are erroneously counted as one step
Solution Approach 1:
The patent changes the parameter used for step detection from peak height to time width between zero crossings. This parameter transformation allows the system to distinguish between single steps and combined signals, as combined signals exhibit different time width characteristics compared to single steps, thereby improving measurement accuracy without significantly increasing system complexity
Solution Approach 2:
The patent introduces a new dimension for analysis by using time width measurement between zero crossings instead of amplitude-based peak detection. This dimensional shift in the measurement approach enables differentiation of signal patterns that were previously indistinguishable using only peak height criteria
2Device complexity
If threshold-based peak detection is used, then the measurement method is simple, but small swing amplitude peaks are missed leading to inaccurate step counting
Solution Approach 1:
The patent transforms the detection parameter from amplitude-based (peak height) to time-based (duration between zero crossings). This parameter change makes the detection method insensitive to swing amplitude variations, allowing reliable detection of steps regardless of whether the swing is large or small, thereby improving detection reliability
Solution Approach 2:
The patent replaces the mechanical threshold-based amplitude detection system with a time-interval-based detection system. This substitution eliminates the problem of missing small amplitude peaks, as the time width measurement does not depend on signal strength but rather on the temporal characteristics of the acceleration waveform
3Productivity
If combined signals are counted as single peaks, then the counting process is straightforward, but the step count becomes inaccurate
Solution Approach 1:
The patent changes the counting criterion from peak amplitude to time width between zero crossings. Combined signals naturally exhibit different time width characteristics compared to single steps, allowing the system to automatically distinguish and count them separately without complex processing, thus maintaining efficiency while improving accuracy
Solution Approach 2:
The patent uses the time width measurement as feedback to determine whether a detected signal represents one step or two steps. By comparing the measured time width against expected ranges, the system provides automatic feedback-based classification that improves counting accuracy while maintaining a straightforward counting process
Data Source
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AI summary
A measurement device includes: an accelerometer; a storage; and at least one processor. In accordance with instructions stored in the storage, the processor acquires data of an acceleration waveform during walking or running of a user from the accelerometer, identifies a time width between a first timing and a second timing based on the acceleration waveform, and counts steps based on the acceleration waveform. The acceleration waveform changes from a negative value to a positive value at the first timing. The acceleration waveform changes from a positive value to a negative value at the second timing. When a predetermined condition is satisfied in counting the steps, the processor counts the acceleration waveform whose time width is greater than a predetermined threshold as two steps and count the acceleration waveform whose time width is smaller than the predetermined threshold as one step.