Outsole Optoelectronic Shear Sensor for Biaxial GRF Measurement
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Solution Overview
Problem
Conventional methods for measuring 3D ground reaction forces (GRFs) in unconstrained environments are expensive and bulky, and accurately measuring anteroposterior and mediolateral GRFs in real-life conditions remains challenging, especially with existing wearable sensors.
Innovation Solution
An outsole-embedded optoelectronic sensor using LED and PD pairs with movable curtains to measure biaxial GRFs, which are less affected by electromagnetic interference and can be retrofitted into existing footwear, providing real-time feedback for injury prevention and closed-loop control of robotic prostheses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional force plates or instrumented treadmills with strain gauges are used to measure 3D GRFs, then measurement precision is improved, but device complexity and portability are worsened
Solution Approach 1:
The patent replaces traditional mechanical strain gauge systems with an optoelectronic sensing system. Light-emitting diodes (LEDs) and photodiodes are used to detect shear forces through optical means, eliminating the need for bulky mechanical force plates and instrumented treadmills while maintaining measurement capability in unconstrained environments
Solution Approach 2:
The patent changes the measurement parameter from electrical resistance (strain gauges) to optical properties (light emission and detection). By using LEDs that emit light and photodiodes that detect light intensity changes caused by shear-induced misalignment, the system achieves force measurement without mechanical contact, enabling portable application
2Device complexity
If pressure-sensitive instrumented footwear is used to estimate vertical GRF, then portability is improved, but measurement precision for anteroposterior and mediolateral forces is worsened
Solution Approach 1:
The patent divides the measurement function into multiple independent sensor units distributed across the footwear. Each sensor unit contains LEDs and photodiodes oriented in different directions, allowing separate measurement of anteroposterior and mediolateral shear forces while maintaining the portable footwear structure
Solution Approach 2:
The patent transitions from measuring only vertical forces (single dimension) to measuring shear forces in multiple directions (multiple dimensions). By orienting sensor units to detect light misalignment caused by shear forces, the system captures anteroposterior and mediolateral components that were previously inaccessible in wearable applications
3Device complexity
If optoelectronic sensors are embedded in the outsole, then device complexity is reduced, but measurement precision may be affected by environmental factors
Solution Approach 1:
The patent uses the optical interaction between LEDs and photodiodes as an intermediary mechanism to measure shear forces. The light path acts as a mediator that translates mechanical shear displacement into optical intensity changes, providing a robust measurement method that is less susceptible to electromagnetic interference and environmental factors in operational environments
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 sensor accurately measures GRFs without altering the wearer's gait, enabling real-time injury prevention and improved control of robotic exoskeletons, with minimal weight and no external mounting issues.
Implementation Method 1
a first light source (e.g., a light emitting diode) and a first light receiver (e.g., a photodiode) for receiving light emitted from the first light source
Implementation Method 2
a first light receiver (e.g., a photodiode) for receiving light emitted from the first light source
Data Source
AI summary
A sensor apparatus for footwear includes at least one pair of light sources and at least one pair of light receivers, each light receiver being positioned and configured to receive light emitted from a respective one of the light sources. A pair of movable curtains functions to adjust the amount of light received by the pair of light receivers. The curtains are movable conjointly such that the amount of light received by one of the light receivers is inversely proportional to the amount of light received by the other light receiver. (FIG. 1B).