Inductive Force Sensor Circuit for Drift-Compensated Measurement
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Solution Overview
Problem
Conventional force sensors face challenges with temperature drift, lifetime drift, and overloading due to the unreliable fastening of strain gages to spring elements, leading to inaccurate force measurements.
Innovation Solution
A force sensor system utilizing a deformation body with multiple coils arranged at different lateral positions, where the deformation of the body changes the distances between the coils differently, allowing an evaluation circuit to determine force based on the measured values of these distances, compensating for drifts through a linear combination of coefficients dependent on the stiffness of the deformation body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If strain gages are adhesively bonded to spring elements for force measurement, then force measurement capability is achieved, but reliability deteriorates due to unreliable fastening under temperature drift and overloading
Solution Approach 1:
The patent replaces the mechanical adhesive bonding of strain gages with an inductive sensing system. Coils are positioned near the deformation body to detect changes in inductance caused by deformation, eliminating the need for mechanical fastening of strain gages and thereby improving reliability while maintaining measurement precision.
Solution Approach 2:
The patent uses changes in inductance parameter of coils as the measurement basis instead of resistance changes of strain gages. The inductance of the coils varies with the distance between the coils and deformation body, providing a reliable electrical parameter that reflects force-induced deformation without mechanical bonding issues.
2Measurement precision
If conventional strain gage-based force sensors are used, then force measurement is possible, but measurement precision deteriorates due to temperature drift and lifetime drift
Solution Approach 1:
The patent replaces strain gage-based measurement with inductive sensing. The coils detect deformation through changes in magnetic field coupling, which is less sensitive to temperature variations compared to adhesive-bonded strain gages, thereby reducing temperature drift and improving measurement precision.
Solution Approach 2:
The patent introduces an intermediary evaluation circuit that processes the inductive signals from multiple coils. This circuit compensates for temperature and lifetime drifts by analyzing the combined signal characteristics, ensuring stable and accurate force measurements despite environmental changes.
3Reliability
If multiple coils are arranged at different lateral positions to improve measurement robustness, then reliability improves through drift compensation, but device complexity increases
Solution Approach 1:
The patent divides the sensing function into multiple separate coils arranged at different lateral positions along the deformation body. Each coil provides an independent measurement, and the evaluation circuit combines these segmented measurements to compensate for drifts, improving reliability while keeping each individual coil simple in structure.
Solution Approach 2:
The patent adds the lateral position dimension to the coil arrangement, positioning coils at different locations along the deformation body rather than only at different heights. This spatial distribution in multiple dimensions enables better drift compensation while maintaining manageable complexity through systematic arrangement.
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 provides robust force measurement by compensating for thermal expansion and other drifts, ensuring accurate force determination despite environmental changes, with improved reliability and precision.
Implementation Method 1
The first coil is arranged at a first lateral position along the deformation body at a first distance from the deformation body and is configured to form a first signal characteristic (such as a resonant frequency, an impedance, an inductance or a variable derived therefrom), which is described by a first measured value, based on a size of the first distance at the first lateral position
Implementation Method 2
The first coil is arranged at a first lateral position along the deformation body at a first distance from the deformation body and is configured to form a first signal characteristic (such as a resonant frequency, an impedance, an inductance or a variable derived therefrom)
Implementation Method 3
The deformation body is configured to be subjected to a force and to undergo a deformation dependent on a (bending) stiffness of the deformation body under the influence of the force
Data Source
AI summary
A force sensor includes a deformation body configured to be subjected to a force and to undergo a deformation dependent on a stiffness of the deformation body under the influence of the force; at least a first coil arranged at a first lateral position along the deformation body at a first distance from the deformation body and configured to form a first signal characteristic, which is described by a first measured value, based on a size of the first distance at the first lateral position; and a second coil arranged at a second lateral position along the deformation body at a second distance from the deformation body and configured to form a second signal characteristic, which is described by a second measured value, based on a size of the second distance at the second lateral position The deformation of the deformation body changes the first and the second distance differently.