Foot-Mounted Sensor Systems for Gait Analysis
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Solution Overview
Problem
Existing instrumented shoe systems for gait analysis are bulky, expensive, and not practical for consumer use outside of laboratory settings, due to issues such as obtrusiveness, edge effects, motion artifacts, mechanical damage, and sensitivity to humidity and heat.
Innovation Solution
A wearable footwear sensor system comprising two separate foot sensor subsystems, each equipped with force sensors, accelerometers, and gyroscopes, generating time-stamped data that is processed to determine characteristics like balance, weight distribution, and foot movement, and integrated with a data processor system for real-time analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If discrete in-shoe sensors are used at anatomical points, then gait analysis data can be collected, but the sensors become obtrusive and irritating to users
Solution Approach 1:
The insole is divided into multiple discrete sensor regions, each with sensors positioned at specific anatomical locations. This segmentation allows precise measurement at key points while distributing the obtrusiveness across multiple small components rather than one large sensor array.
Solution Approach 2:
Sensors are strategically positioned only at specific anatomical points where pressure data is most valuable (heel, metatarsal heads, toe regions). This local placement provides targeted measurement precision while minimizing the overall sensor presence and user discomfort compared to full-coverage sensing.
2Measurement precision
If discrete in-shoe sensors are used, then gait analysis is possible, but edge effects occur between sensor material and surrounding insole
Solution Approach 1:
Adhesive layers and mounting structures are pre-applied to sensor components before insertion into the insole. This preliminary preparation ensures proper positioning and secure attachment, eliminating gaps and edge effects that would otherwise create measurement artifacts at the boundaries between sensor and insole material.
Solution Approach 2:
Adhesive layers and intermediate mounting materials are introduced between the sensor elements and the insole substrate. These intermediaries create smooth transitions and eliminate direct contact edges, preventing edge effects while maintaining measurement fidelity at the sensor locations.
3Measurement precision
If discrete sensors are placed in the shoe, then gait data can be collected, but motion artifacts occur due to shear stress
Solution Approach 1:
Multiple sensor elements are combined into integrated sensor assemblies that move together as unified units within the insole. This merging reduces relative motion between adjacent sensors and minimizes shear stress-induced artifacts, while the entire assembly is anchored to prevent unwanted movement during gait.
Solution Approach 2:
Sensors are pre-secured to the insole structure using adhesives and mounting mechanisms before the shoe is worn. This preliminary fixation ensures sensors maintain their designated positions relative to anatomical landmarks during movement, eliminating motion artifacts that would occur with loose or poorly attached sensors.
4Measurement precision
If instrumented insoles are used, then pressure measurement is possible, but mechanical damage occurs at electrical connections
Solution Approach 1:
Traditional wired electrical connections are replaced with wireless communication technologies. Sensors transmit pressure data wirelessly to external devices, eliminating physical electrical connections that would be subject to mechanical stress, fatigue, and damage from repeated bending and movement during shoe wear.
Solution Approach 2:
If wired connections are used, they are embedded within flexible printed circuit boards or thin flexible cables that can bend and flex with the insole and shoe deformation. These flexible interconnects resist mechanical damage by distributing stress along their length rather than concentrating it at connection points.
5Measurement precision
If sensors are placed in the shoe, then gait analysis can be performed, but sensor performance is affected by humidity and heat
Solution Approach 1:
Sensors are encapsulated within flexible protective films and encapsulants that provide environmental barriers while maintaining sensor flexibility. These thin film enclosures protect sensitive electronic components from humidity and heat exposure during shoe wear, preventing performance degradation without adding significant rigidity or bulk.
Solution Approach 2:
Sensors are sealed within protective enclosures that create a controlled, protected environment isolated from external humidity and heat. This encapsulation creates an inert atmospheric barrier around sensitive components, preventing moisture ingress and thermal damage while allowing the sensors to function accurately in the harsh shoe environment.
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 provides accurate, real-time data on foot characteristics and movements, enabling effective gait analysis without the limitations of existing technologies, and can be interfaced with gaming systems or biomechanical analysis tools.
Implementation Method 1
each including two or more sensor devices selected from the group consisting of: a force sensor
Implementation Method 2
each including two or more sensor devices selected from the group consisting of: an accelerometer
Implementation Method 3
each including two or more sensor devices selected from the group consisting of: a gyroscope
Data Source
AI summary
A method is disclosed for foot sensors to be used to determine at least two characteristics of a subject's activity by using a combination of sensors for force and foot orientation/motion/position. A wearable footwear ecosystem is comprised of the subject's footwear, sensor-enabled insoles or insertable devices, in- or on-footwear electronics that is hard wired to the sensors and may contain additional sensors such as accelerometers, a master device and means to communicate (typically wirelessly) among the various sensor platforms, and the master device including clock synchronization. Correlating the time stamps for data among various sensors, and the master device communicating wirelessly is critical to accurate determination of the desired characteristics. Multiple force-sensitive resistors on a common substrate are individually optimized for dynamic range. Pulse sensors using arrays of such force-sensitive resistors are implemented. The resultant system can profitably be used for gaming, biometric monitoring, and activity tracking.