Self-Adaptive Pedometer Threshold Control for Step Detection
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Solution Overview
Problem
Conventional pedometers using fixed acceleration thresholds for step detection suffer from significant errors due to variability in gait patterns caused by factors like terrain, shoe type, and speed, leading to incorrect step counting and distance measurement.
Innovation Solution
A self-adaptive pedometer device with a processing unit that modifies acceleration thresholds based on the acceleration signal's amplitude and temporal extension, using a comparator and threshold-adaptation circuit to dynamically adjust reference thresholds, ensuring accurate step detection and distance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed reference threshold is used for acceleration peak detection, then the device structure remains simple, but step detection accuracy deteriorates due to gait variability
Solution Approach 1:
The patent implements dynamic threshold adaptation by continuously adjusting the reference threshold based on the envelope of the acceleration signal. The threshold evolves over time to match the varying amplitude characteristics of different gaits, transforming the static comparison mechanism into a dynamic one that adapts to walking, running, and other movement patterns.
Solution Approach 2:
The patent changes the parameter of the reference threshold from a fixed value to a variable that depends on the signal envelope. By computing the envelope through rectification and smoothing operations, the system dynamically adjusts the threshold parameter to match the instantaneous amplitude characteristics of the acceleration signal, thereby maintaining detection accuracy across varying conditions.
2Measurement precision
If the threshold is set low to detect all possible steps, then sensitivity improves, but false detection increases due to noise and spurious signals
Solution Approach 1:
The patent introduces feedback by using the detected acceleration signal itself to adjust the reference threshold. The envelope of the signal provides continuous feedback about the current amplitude level, and this feedback is used to dynamically set the threshold, creating a self-regulating system that adapts to the actual signal characteristics rather than relying on predetermined fixed values.
Solution Approach 2:
The system performs self-service by automatically adjusting its own threshold parameter based on the characteristics of the input signal. The envelope computation and threshold adaptation are performed autonomously by the device without external intervention, allowing the system to self-regulate its detection sensitivity according to the actual gait patterns being measured.
3Object-generated harmful factors
If the threshold is set high to avoid false detection, then noise rejection improves, but step detection completeness deteriorates
Solution Approach 1:
The dynamic threshold adaptation allows the system to maintain high noise rejection when the signal amplitude is low while ensuring complete step detection when amplitude increases. The threshold rises and falls with the signal envelope, providing high rejection during quiet periods and high sensitivity during active movement, thus resolving the contradiction between noise rejection and detection completeness.
4Device complexity
If fixed thresholds are used for different detection points, then device complexity remains low, but adaptability to different gaits deteriorates
Solution Approach 1:
The patent implements a universal threshold adaptation mechanism that handles multiple gait types (walking, running, jogging) and different detection points (heel, midfoot, forefoot) through a single envelope-based threshold computation system. This multi-functional approach eliminates the need for separate fixed thresholds for each gait type or detection point, thereby improving adaptability without proportionally increasing complexity.
Data Source
AI summary
In a pedometer device for detecting and counting steps of a user on foot, an accelerometer sensor detects a vertical acceleration generated during the step. A processing unit, connected to the accelerometer sensor, processes an acceleration signal relating to the acceleration in order to detect the occurrence of a step, and in particular compares the acceleration signal with a first reference threshold. The processing unit automatically adapts the first reference threshold as a function of the acceleration signal. In particular, the processing unit modifies the first reference threshold as a function of an envelope of the amplitude of the acceleration signal.