Force Sensor Self-Diagnosis via Dual Displacement Sensors
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Solution Overview
Problem
Conventional force sensors, particularly capacitance type sensors, are prone to failures due to condensation, impact, overload, and foreign matter, leading to metal fatigue and increased costs for diagnosis, which complicates the determination of sensor functionality and requires multiple sensors for normal operation assessment.
Innovation Solution
A force sensor design featuring a deformable body with a tilting portion and interconnected deformable elements, coupled with displacement sensors, allows for self-diagnosis through electric signal analysis, enabling normal operation determination using a single sensor and reducing the risk of metal fatigue-related failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple force sensors are arranged in parallel for failure diagnosis, then the reliability of force detection is improved, but the cost and device complexity increase
Solution Approach 1:
The force sensor is divided into multiple independent detection units (first and second displacement sensors) that measure different aspects of the deformable body's behavior. Each unit can independently detect displacement, and by comparing their outputs, the system can diagnose failures without requiring multiple complete sensor assemblies, thus improving reliability while controlling complexity
Solution Approach 2:
The force sensor performs self-diagnosis by internally comparing the outputs of its own displacement sensors. The detection circuit monitors whether the sensors are functioning normally by analyzing the relationship between their detection values, eliminating the need for external diagnostic equipment or multiple redundant sensor systems
2Reliability
If multiple force sensors are used for failure diagnosis, then the diagnostic capability is improved, but the installation space increases
Solution Approach 1:
Multiple displacement sensors (first and second sensors) are integrated within a single force sensor assembly, sharing common structural elements like the deformable body and housing. This merging approach enables comprehensive diagnostic capability while minimizing the installation space required, as all diagnostic functions are contained within one compact unit rather than requiring separate sensor installations
3Ease of manufacture
If conventional capacitance type force sensor is used, then the cost is reduced, but the reliability deteriorates due to metal fatigue from overload and repeated load
Solution Approach 1:
The patent changes the measurement parameter from direct capacitance measurement (which requires fragile parallel plate structures susceptible to metal fatigue) to displacement measurement using displacement sensors. This parameter change allows the use of more durable deformable body structures that can withstand overload and repeated loading while maintaining cost-effectiveness and manufacturing simplicity
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 proposed force sensor facilitates cost-effective and sensitive self-diagnosis, reducing the need for multiple sensors and minimizing the impact of environmental factors like temperature changes and common mode noise, while effectively detecting applied forces and moments.
Implementation Method 1
a deformable body having a force receiving portion and a fixed portion and configured to generate elastic deformation by a force applied to the force receiving portion
Data Source
AI summary
A force sensor includes: a deformable body having a force receiving portion and a fixed portion; a displacement body configured to generate a displacement by elastic deformation generated in the deformable body; and a detection circuit configured to detect an applied force on the basis of the displacement generated in the displacement body, in which the deformable body includes: a tilting portion arranged between the force receiving portion and the fixed portion; a first deformable portion that connects the force receiving portion and the tilting portion; and a second deformable portion that connects the fixed portion and the tilting portion, the displacement body includes a displacement portion connected to the tilting portion and separated from the fixed portion, the detection circuit includes a first displacement sensor and a second displacement sensor arranged in the displacement portion, and the detection circuit outputs a first electric signal indicating an applied force on the basis of a detection value of the first displacement sensor, and outputs a second electric signal indicating an applied force on the basis of a detection value of the second displacement sensor, and then determines whether force detection is performed normally on the basis of the first electric signal and the second electric signal.