Semiconductor Strain Gauge Array Multiplexing
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Solution Overview
Problem
Conventional strain gauges require extensive placement and wiring for accurate strain measurement in aircraft components, making it difficult to efficiently monitor structural stress across large surfaces, especially in lightweight aircraft where hundreds of gauges are needed.
Innovation Solution
A semiconductor strain monitoring system featuring an array of 4-resistor bridges with thin film transistors for addressability, fabricated using lithographic processes on a silicon on insulator wafer, bonded to a polyimide film substrate, allowing for row-column select multiplexing and easy attachment to surfaces, providing voltage signals corresponding to strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional strain gauges are used to monitor structural stress across large surfaces, then measurement precision is improved, but device complexity and wiring requirements increase significantly
Solution Approach 1:
The patent divides the measurement function into multiple discrete sensor elements arranged in arrays or networks. Each sensor element can be independently addressed and measured, allowing distributed strain monitoring across large surfaces while reducing individual wiring complexity through multiplexed readout circuits.
Solution Approach 2:
The patent employs strain sensors with integrated electronics that can perform multiple functions including strain measurement, temperature compensation, and self-diagnosis. This multi-functionality reduces the need for separate measurement systems and simplifies overall device complexity while maintaining measurement precision.
2Measurement precision
If hundreds of separate strain gauges are deployed on aircraft wings, then comprehensive strain coverage is improved, but ease of operation deteriorates due to extensive wiring
Solution Approach 1:
The patent combines multiple strain gauge elements into integrated sensor arrays with shared readout circuits and power supply. This merging approach maintains comprehensive strain coverage across aircraft surfaces while dramatically reducing wiring requirements through common signal paths and multiplexed data acquisition.
Solution Approach 2:
The patent transitions from one-dimensional linear strain gauge arrangements to two-dimensional arrays and networks distributed across aircraft surfaces. This dimensional expansion enables comprehensive area coverage while using systematic addressing schemes that simplify data acquisition compared to managing hundreds of individual gauges.
3Measurement precision
If semiconductor strain gauges with high gauge factors are used, then measurement precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes the high gauge factor of semiconductor materials to achieve superior measurement precision. By carefully controlling semiconductor doping levels and crystal orientation during fabrication, the system achieves high sensitivity while managing manufacturing precision through standardized fabrication processes and statistical process control.
Solution Approach 2:
The patent employs standardized semiconductor fabrication processes that replicate identical sensor elements across multiple devices. This copying approach ensures consistent gauge factors and reduces variability, allowing high measurement precision to be achieved through repeatable manufacturing rather than requiring extreme precision in each individual device.
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 offers significantly higher gauge factors compared to metal strain gauges, enables rapid data acquisition, and reduces human interpretation through automated sensor selection and data processing, providing comprehensive strain profiles with minimal surface impact and easy application on large areas.
Implementation Method 1
The piezoresistive effect describes the changing electrical resistance of a material due to applied mechanical stress. The piezoresistive effect of semiconductor materials can be several orders of magnitudes larger than the geometrical piezoresistive effect in metals
Implementation Method 2
A Wheatstone bridge is a device for measuring electrical resistance. Each strain gauge in the array of strain gauges includes a 4-resistor bridge for providing a voltage potential corresponding to the strain in the bridge
Data Source
AI summary
A strain monitoring system including an array of semiconductor strain gauges. Each strain gauge in the array of strain gauges includes a lithographically fabricated 4-resistor bridge for providing a voltage potential corresponding to the strain in the bridge and thin film transistors to provide addressability to each 4-resistor bridge in the array. After completion of the array of strain gauges, in preferred embodiments the array of strain gauges are transferred to polyimide film which is in turn bonded to a surface region of the component to be tested for strains. Each bridge provides voltage signals corresponding to the strain to which the material under the bridge is being subjected. In preferred embodiments control and data acquisition function are separated from the semiconductor strain gage array. Preferred embodiments the system are utilized to monitor strains on components of aircraft, especially light weight robotic aircraft.