Footplate Sensor Segmentation for Center of Gravity Estimation
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Solution Overview
Problem
Conventional sensors for estimating the center of pressure (CoP) in walking rehabilitation robots are expensive, bulky, and prone to inaccurate detection, especially when trying to estimate the left and right portions of the foot, due to their design and arrangement requirements.
Innovation Solution
A system and method using a modularized position-dependent variable resistance sensor mounted on a footplate, which divides the sole area into sections and applies pressure to a circular-shaped sensor unit with protruding parts to estimate the center of gravity by calculating an angle value from the output voltage, allowing for precise detection of the CoP.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional sensors (multi-axis load cells, strain gauges, pneumatic tubes) are used to estimate center of pressure, then measurement capability is provided, but the sensors are expensive, bulky, and prone to inaccurate detection
Solution Approach 1:
The sensor module is segmented into multiple independent FSR sensors arranged in a specific geometric pattern. Each FSR sensor independently measures pressure at its location, and the controller segments the calculation process to determine CoP coordinates by processing signals from individual sensors. This segmentation enables accurate CoP detection while using simple, inexpensive components.
Solution Approach 2:
The patent uses multiple identical FSR sensors (simple pressure-sensitive elements) arranged in a specific configuration to replicate the measurement capability of complex sensors. By copying the sensing function across multiple simple units rather than using one complex sensor, the system achieves accurate CoP detection with lower cost and complexity.
2Ease of manufacture
If FSR sensors are used to estimate center of pressure, then cost is reduced, but accurate detection of left and right portions of the foot is difficult
Solution Approach 1:
The FSR sensors are positioned at specific locations corresponding to different regions of the foot (heel, toe, medial side, lateral side). Each sensor location is optimized to detect pressure from specific foot regions, enabling the system to accurately determine left-right positioning and other spatial characteristics using simple FSR sensors.
Solution Approach 2:
The patent transitions from point-based pressure detection to area-based pressure distribution detection by arranging multiple FSR sensors in a two-dimensional configuration. This dimensional arrangement allows the system to detect not only pressure magnitude but also the spatial distribution of pressure across the foot, enabling accurate determination of left-right and anterior-posterior positions.
3Measurement precision
If multiple FSR sensors are arranged to detect center of pressure, then detection accuracy improves, but sensor arrangement and calibration becomes complex
Solution Approach 1:
The FSR sensors are arranged in an asymmetric configuration that naturally corresponds to the anatomical structure of the foot and the expected pressure distribution patterns. This asymmetric arrangement simplifies the calibration process by aligning sensor positions with functional foot regions, reducing the need for complex calibration procedures while maintaining high measurement accuracy.
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 precise and stable detection of the center of pressure with a relatively inexpensive sensor module, achieving a 95% matching ratio with conventional FSR array structures, and can be operated at a lower cost while maintaining accuracy.
Implementation Method 1
a sensor unit which is a modularized position-dependent variable resistance sensor
Data Source
AI summary
Provided are a system and method for estimating the center of gravity of a walking rehabilitation robot, the system being provided with: a sensor module for estimating the point of the center of gravity, and provided with: a sensor unit mounted on a footplate to sense the pressure when a person walks; output means for outputting a voltage value corresponding to preset conditions according to a pressure signal sensed by the sensor module; and estimating means for calculating an angle value corresponding to the voltage value outputted by the output means, and estimating the center of gravity, wherein a body center can be estimated by obtaining an accurate detection using a small-sized system that has a relatively low-cost sensor module installed therein.