Fiber Bragg Grating Sensors for Stator Force Measurement
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Solution Overview
Problem
Current measurement techniques for electric motors are inadequate for accurately predicting noise radiated by electric motors and addressing electromagnetic forces acting on a stator, due to electromagnetic interference and inaccuracy in strain gauge and piezoelectric sensor measurements, which affects the precision of simulation results.
Innovation Solution
The use of embedded Fiber Bragg Grating (FBG) optical sensors to directly measure strain within the stator of electric machines, which are minimally intrusive and immune to electromagnetic interference, allowing for accurate evaluation of non-static forces and enabling the derivation of motor torque and rotor position information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauge sensors are placed in the stator to measure forces, then measurement capability is improved, but electromagnetic interference increases and measurement accuracy deteriorates
Solution Approach 1:
The patent replaces electrical strain gauge sensors with optical fiber Bragg grating sensors. The optical fiber sensor uses optical principles instead of electrical principles to measure strain, making it immune to electromagnetic interference while maintaining measurement capability in the stator of electric motors.
Solution Approach 2:
The patent introduces optical fiber as an intermediary medium between the measurement target (stator) and the measurement system. The optical fiber transmits optical signals that are unaffected by electromagnetic fields, serving as a mediator that isolates the measurement system from electromagnetic interference while still capturing mechanical strain information.
2Speed
If piezoelectric sensors are used to measure low frequency forces, then measurement frequency range is improved, but measurement accuracy deteriorates due to creep and non-linearities
Solution Approach 1:
The patent replaces piezoelectric sensors with optical fiber Bragg grating sensors. The optical sensing mechanism does not suffer from creep or hysteresis effects that plague piezoelectric materials, providing accurate measurements across a wide frequency range including low frequencies and DC conditions.
3Ease of manufacture
If holes are drilled to install strain gauges, then sensor installation is facilitated, but magnetic flow is disturbed and measurement accuracy deteriorates
Solution Approach 1:
The patent uses optical fiber sensors that can be installed without drilling holes into the stator. The optical fiber can be placed in the air gap or on the surface, eliminating the need for invasive drilling that would disrupt magnetic flux paths while still enabling force measurement.
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
This solution provides precise and real-time monitoring of mechanical forces and operational conditions, enabling overload protection, virtual sensing, and field-oriented control, while reducing the need for additional sensors and improving the accuracy of simulation results.
Implementation Method 1
a first Fiber Bragg Grating (FBG) element is placed between the stacked metal lamina... comparing spectral properties of applied and received or applied and reflected light of the FBG element
Data Source
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AI summary
Systems and a method for measuring of at least one mechanical force in a stator of an electrical machine are provided, wherein the stator of said electrical machine comprises a multiple stacked metal lamina, wherein at least one Fiber Bragg Grating (FBG) element is placed between two of the lamina, in particular in a rotor-facing tooth of the lamina. Also disclosed are methods directed to field oriented control of electrical machines.