Drift-Free Plantar Pressure Calculation Using LiTCEM Correction
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Solution Overview
Problem
Conventional in-sole based solutions for calculating plantar pressure parameters using piezoelectric sensors suffer from drift issues due to non-linear force-voltage responses and hysteresis, leading to inaccurate results, especially when data is acquired over long durations.
Innovation Solution
A wearable apparatus and method utilizing off-the-shelf piezoelectric sensors and a 6-Degree Of Freedom (DOF) Inertial Measurement Unit (IMU) to acquire raw data samples, which are then processed using a Linear Temporal Cumulated Error Model (LiTCEM) correction method to calculate drift-free static pressure values and plantar pressure parameters, such as Vertical Ground Reaction Force (VGRF) and Centre of Pressure (CoP) location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If piezoelectric sensors are used for calculating plantar pressure parameters, then cost is reduced, but measurement precision deteriorates due to drift and hysteresis
Solution Approach 1:
The patent introduces an intermediary correction algorithm (LiTCEM) that processes the raw sensor data from piezoelectric sensors. This algorithm acts as a mediator between the imperfect sensor output and the required accurate pressure parameters, compensating for drift and hysteresis effects through mathematical correction rather than hardware modification.
Solution Approach 2:
The patent changes the parameters of the piezoelectric sensors by applying dynamic correction factors and calibration parameters through the LiTCEM algorithm. This transforms the raw voltage output into corrected pressure values that compensate for the sensors' inherent non-linearities and drift characteristics.
2Reliability
If dynamic sensor data is integrated to obtain static pressure data, then plantar pressure parameters are calculated, but drift is intensified due to hysteresis loss
Solution Approach 1:
The patent applies preliminary correction actions before the integration process. The LiTCEM algorithm pre-processes the dynamic sensor data by removing drift components and hysteresis effects before the data is integrated to obtain static pressure values, preventing error accumulation rather than correcting it afterward.
Solution Approach 2:
The patent implements a feedback mechanism where the correction algorithm continuously monitors the sensor output and applies real-time compensation. The system uses the relationship between applied force and voltage output to dynamically adjust correction factors, creating a closed-loop system that counteracts drift and hysteresis effects.
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 accurate, drift-free plantar pressure parameters for gait monitoring, enhancing the reliability of walking pattern analysis and reducing costs by using affordable, off-the-shelf sensors, while effectively addressing the limitations of existing systems.
Implementation Method 1
a plurality of piezoelectric sensors placed within a sole of a footwear at different positions representing pressure points of a foot
Implementation Method 2
raw 3-axis accelerometer values and raw 3-axis gyroscope values acquired from the 6-Degree Of Freedom (6DOF) Inertial Measurement Unit (IMU)
Implementation Method 3
raw 3-axis accelerometer values and raw 3-axis gyroscope values acquired from the 6-Degree Of Freedom (6DOF) Inertial Measurement Unit (IMU)
Data Source
AI summary
The present disclosure provides wearable apparatus and method for calculating drift-free plantar pressure parameters for gait monitoring of an individual. Most conventional techniques use different kind of sensors placed in in-sole based wearable apparatus but are costly and not effective in calculating accurate plantar pressure parameters. The disclosed wearable apparatus uses off-the shelf piezoelectric sensors that are widely available in market with less cost. The drift-free plantar pressure parameters are calculated using drift-free static pressure data obtained by numerically integrating acquired dynamic sensor data from the piezoelectric sensors, using a LiTCEM correction mechanism. A 6-DOF Inertial Measurement Unit (IMU sensor) helps in isolating zero-pressure duration indicating when a foot of the individual is in air during a stride, while obtaining the drift-free static pressure data. The disclosed wearable apparatus calculate the drift-free plantar pressure parameters for long duration and facilitates monitoring walking patterns of the individual.