Magnetostrictive Torque Sensor Circuit Using Skin-Depth AC Excitation
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Solution Overview
Problem
Existing magnetostrictive torque sensors face reduced measurement accuracy due to the limited effectiveness of shot peening, which does not reach the deep parts of the magnetostrictive material, leading to decreased sensitivity and increased hysteresis.
Innovation Solution
A magnetostrictive torque sensor design that incorporates a detection circuit with AC excitation at a specific frequency to suppress the entry of magnetic flux beyond the effective depth of shot peening, utilizing a bridge circuit with inclined detection coils and a magnetic ring to enhance measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shot peening is performed on the surface of the magnetostrictive material, then hysteresis characteristics are improved, but the effect does not reach deep parts causing measurement accuracy to decrease
Solution Approach 1:
The patent applies AC excitation at a specific frequency to control the skin depth of magnetic flux penetration. By adjusting the frequency parameter, the magnetic flux is confined to the surface region where shot peening is effective, preventing deep parts from influencing measurements and thereby resolving the contradiction between improved hysteresis characteristics and measurement accuracy
Solution Approach 2:
The patent uses dynamic AC excitation instead of static DC excitation. The frequency of the AC excitation can be adjusted to control the depth of magnetic flux penetration, allowing the system to adaptively optimize measurement conditions and eliminate the negative impact of deep part variations on measurement accuracy
2Measurement precision
If AC excitation is applied at high frequency to confine magnetic flux to surface region, then measurement accuracy improves, but energy consumption increases
Solution Approach 1:
The patent optimizes the AC excitation frequency to achieve the desired skin depth for confining magnetic flux to the surface region. By carefully selecting the frequency parameter, the patent achieves measurement accuracy improvement while minimizing unnecessary energy consumption that would result from excessively high frequencies
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 solution improves measurement accuracy by ensuring the magnetic flux primarily affects the surface region where shot peening is effective, reducing hysteresis and plastic deformation, thereby enhancing the sensor's sensitivity and precision.
Implementation Method 1
a detection coil and a drive unit configured to provide AC excitation at a frequency at which a skin effect thickness is not more than the effective depth of the shot peening
Implementation Method 2
uses a magnetostrictive material having magnetostrictive characteristics in which magnetic permeability changes when a torque (rotational torque) is applied
Implementation Method 3
a drive unit configured to provide AC excitation at a frequency at which a skin effect thickness is not more than the effective depth of the shot peening
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
A detecting circuit 10 of a magnetostrictive torque sensor for detecting torque imparted to a magnetostrictive material 2 which has been subjected to shot peening is provided with a detecting coil 11 provided around the magnetostrictive material 2, and a drive unit 12 for performing AC excitation of the detecting coil 11, and is configured to detect the torque imparted to the magnetostrictive material 2 on the basis of a change in the inductance of the detecting coil 11, wherein the drive unit 12 performs AC excitation using a frequency at which the skin effect thickness is at most equal to the effective depth of the shot peening.