Force Sensor Resonant Frequency Shift for Pico-Newton Detection
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Solution Overview
Problem
Existing force measurement technologies, such as strain gauges, face challenges in accurately measuring small forces in the pico-Newton range and are prone to errors due to assembly imperfections and difficulties in detecting compressive forces.
Innovation Solution
A force sensor with an oscillating structure that changes resonant frequency in response to applied forces, utilizing a magnetic field and alternating current to excite vibrations, allowing for precise measurement of forces down to the pico-Newton range through the detection of resonant frequency shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are used to measure forces, then force measurement is possible, but very small forces in the pico-Newton range cannot be measured and measurement accuracy deteriorates due to mounting imperfections
Solution Approach 1:
The patent applies mechanical vibration by exciting a proof mass to oscillate at its resonant frequency. The resonant frequency of the proof mass changes when forces act on it, causing distortion. By measuring the shift in resonant frequency, forces as small as the pico-Newton range can be detected with high precision, eliminating the limitations of strain gauge-based methods.
2Ease of manufacture
If strain gauges are mounted by gluing, then force measurement is enabled, but measurement accuracy deteriorates due to mounting imperfections
Solution Approach 1:
The patent replaces the mechanical strain gauge mounting system with an electromagnetic excitation and detection system. Instead of using strain gauges that require gluing to the proof mass, the invention uses a magnetic field to excite the proof mass and measures its resonant frequency shifts. This substitution eliminates mounting imperfections entirely, as no physical attachment is required between the sensing element and the proof mass.
3Adaptability or versatility
If conventional force sensors are used, then general force measurement is possible, but very small forces down to the pN range cannot be measured
Solution Approach 1:
The patent changes the measurement parameter from static strain measurement to dynamic resonant frequency measurement. By monitoring the resonant frequency of a proof mass, which changes in response to applied forces, the system achieves the capability to measure extremely small forces in the pico-Newton range while maintaining versatility for general force measurement applications.
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
Enables accurate measurement of very small forces by detecting changes in resonant frequency, providing a reliable and precise method for force detection, including two-dimensional and three-dimensional force resolution and torque measurement.
Implementation Method 1
the at least one conductor can be supplied with an alternating voltage in order to excite, particularly in an unloaded state of the force sensor, the at least one oscillation mode of the oscillating structure at the resonance frequency by utilizing the Lorentz force when the oscillating structure is in a magnetic field
Implementation Method 2
the spatial displacement of the suspension areas causes a detuning of a resonance frequency of at least one vibration mode of the vibration structure, and the magnitude of the detuning depends on the magnitude of the spatial displacement of the suspension areas
Data Source
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AI summary
Force sensor (1) comprising a frame (2) and also an oscillation structure (4) which has a plurality of arms (3a-d) and can oscillate freely in the frame (2), wherein the arms (3a-d) are fixed to suspension regions (6a-d) of the frame (2) and run transverse to one another at least in sections, wherein at least one guiding means (5a-d) is provided, which guiding means extends along at least two arms (3a-b; 3b-c; 3c-d; 3d-a), wherein an AC voltage can be applied to the at least one guiding means (5a-d) in order to excite at least one oscillation mode of the oscillation structure (4) with a resonant frequency using Lorentz force (FL), wherein the force sensor (1) is designed such that the suspension regions (6a-d) are at least partially spatially displaced relative to one another when a force (7) is applied to the frame (2), that the magnitude of the spatial displacement (8) of the suspension regions (6a-d) depends on the magnitude of the force (7), that the spatial displacement (8) of the suspension regions (6a-d) causes detuning of the resonant frequency, the magnitude of which depends on the magnitude of the spatial displacement (8).