Magnetoelastic Torque Sensor With Differential Magnetic Sensing
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Solution Overview
Problem
Existing magnetoelastic torque sensors face challenges in achieving high accuracy and reduced sensitivity to external disturbance fields while maintaining a compact and customizable design, particularly in applications like E-bikes and automotive industries, where the magnetic field generated by the shaft is weak and sensitive to mounting position offsets.
Innovation Solution
A magnetoelastic torque sensor system comprising a shaft with magnetized axial sections and a magnetic sensor device with three semiconductor substrates, including a processing circuit and two magnetic sensors spaced apart to measure magnetic field components, which calculates a pairwise difference to determine torque exerted on the shaft, reducing sensitivity to external fields and allowing for flexible mounting and customization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single magnetic sensor is used to measure the magnetic field generated by the shaft, then the device complexity is reduced, but the measurement precision deteriorates due to sensitivity to external disturbance fields
Solution Approach 1:
The measurement function is segmented into two separate magnetic sensors that measure different magnetic field components. One sensor measures the radial component while the other measures the axial component, allowing differential processing to extract torque information while rejecting external disturbances
Solution Approach 2:
Each magnetic sensor is positioned at a specific location relative to the magnetized shaft sections, with sensors oriented to detect specific magnetic field components. This localized measurement approach enables selective detection of torque-related magnetic field variations while ignoring external interference
2Measurement precision
If the magnetic sensors are positioned close to the shaft to improve measurement sensitivity, then the signal-to-noise ratio improves, but the sensitivity to mounting position offsets increases
Solution Approach 1:
The system incorporates a processing circuit that calculates the difference between measurements from two magnetic sensors. This differential measurement approach provides feedback that compensates for mounting position offsets, as errors affecting both sensors equally are rejected in the difference calculation
Solution Approach 2:
The two magnetic sensors are positioned asymmetrically relative to the shaft, measuring different magnetic field components (radial and axial). This asymmetric arrangement ensures that mounting position errors do not equally affect both measurements, enabling torque extraction through differential processing
3Measurement precision
If multiple axial zones are magnetized in different circumferential directions to improve torque measurement accuracy, then the measurement precision improves, but the manufacturing complexity increases
Solution Approach 1:
The shaft is segmented into multiple axial zones, each magnetized in a specific circumferential direction. This segmentation creates distinct magnetic field patterns that enhance torque measurement accuracy while allowing standardized manufacturing processes for each zone
Solution Approach 2:
The magnetic properties of different axial zones are changed by magnetizing them in different circumferential directions. This parameter variation (magnetization direction) creates the necessary magnetic field diversity for accurate torque measurement without changing the physical structure of the shaft
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 improved accuracy and reduced sensitivity to external disturbances, enabling precise torque measurement with enhanced signal-to-noise ratio and flexibility in mounting, suitable for various applications including E-bikes and automotive use.
Implementation Method 1
Magnetoelastic torque sensors are known in the art. They are based on a reversal of the physical effect of magnetostriction (deformation of magnetic materials by means of an applied magnetic field), wherein a torque, which impacts on the magnetized shaft, causes a torsion of the shaft and as a consequence a modification of the magnetic field outside of the shaft.
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A magnetoelastic torque sensor system comprising a shaft having at least one axial section magnetized in a circumferential direction; and a magnetic sensor device arranged in the vicinity of the shaft; the sensor device comprising a first semiconductor substrate (109) having a processing circuit, a second semiconductor substrate (106a) having a first magnetic sensor (S1), and a third semiconductor substrate (106b) having a second magnetic sensor (S2), each magnetic sensor configured for measuring a magnetic field component; wherein the first, second and third semiconductor substrates are incorporated in a single packaged device; and wherein the processing circuit is configured for determining a pairwise difference between the magnetic field components, and for outputting a signal or a value indicative of a torque exerted upon the shaft, based on said pairwise difference. A method of measuring a torque exerted upon a shaft.