Elastomeric Shell Sensor with Embedded FBG for Force Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current robotic systems lack effective force sensing capabilities, particularly for detecting anticipated and unanticipated loads in real-time, due to limited mechanical sensors and poor sensitivity in harsh environments, which is critical for tasks like space robotics and medical surgery.
Innovation Solution
A flexible shell sensor made of elastomer with embedded optical fiber Bragg gratings, routed through apertures, measures force-induced strain by detecting wavelength shifts, allowing for precise force and displacement measurement, and features a hexagonal pattern for stress concentration and thermal shielding with copper mesh for reduced creep and thermal compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical sensors are used for force sensing, then the robot can detect loads, but the sensors are limited in number and sensitivity, and poorly identify arbitrarily-located impacts
Solution Approach 1:
The patent replaces mechanical force sensors with optical fiber Bragg grating (FBG) sensors that measure strain through optical wavelength shifts. This substitution enables high-sensitivity force detection without the limitations of mechanical sensor complexity and distribution requirements
Solution Approach 2:
The patent embeds FBG sensors within a flexible elastomeric shell structure. The shell deforms under applied loads, transferring strain to the embedded optical fibers. This flexible embedding approach enables arbitrary-located impact detection throughout the robot appendage without requiring discrete mechanical sensors at each location
2Reliability
If FBG sensors are embedded in metal parts and composites, then stress monitoring is achieved, but the sensors are susceptible to electromagnetic noise and harsh environments
Solution Approach 1:
The patent uses optical fiber FBG sensors instead of electrical sensors, replacing susceptibility to electromagnetic noise with immunity to such interference. The optical measurement principle (wavelength shift) is inherently immune to electromagnetic fields, enabling reliable operation in harsh environments including space robotics applications
Solution Approach 2:
The patent embeds FBG sensors in an elastomeric composite material that provides both mechanical support and environmental protection. The elastomer matrix protects the delicate optical fibers while allowing strain transfer, creating a composite structure that enhances sensor reliability in harsh conditions
3Productivity
If multiple sensors are placed along a single fiber for multiplexing, then measurement capability increases, but sensor placement and calibration complexity increases
Solution Approach 1:
The patent employs a single optical fiber containing multiple FBG sensors at different wavelengths, enabling one fiber to perform multiple sensing functions simultaneously. This multi-functional approach allows monitoring of strain at multiple locations along the robot appendage using a single interrogator system, increasing productivity while managing complexity through wavelength-division multiplexing
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 high sensitivity and accuracy in force measurement, with submicrostrain resolution, resistance to electromagnetic noise, and thermal stability, enabling precise localization and orientation of applied forces, enhancing robotic precision and safety in challenging environments.
Implementation Method 1
an optical fiber having one or more Bragg gratings positioned in the passageways for the measurement of force and deflection
Implementation Method 2
FBGs reflect light with a peak wavelength that shifts in proportion to the strain to which they are subjected
Implementation Method 3
Deflection of the sensor, such as by a force applied to the contact region, causes an incremental strain in one or more passageways where the optical fiber is located
Data Source
AI summary
A sensor for force is formed from an elastomeric cylinder having a region with apertures. The apertures have passageways formed between them, and an optical fiber is introduced into these passageways, where the optical fiber has a grating for measurement of tension positioned in the passageways between apertures. Optionally, a temperature measurement sensor is placed in or around the elastomer for temperature correction, and if required, a copper film may be deposited in the elastomer for reduced sensitivity to spot temperature variations in the elastomer near the sensors.