Magnetoelastic Torque Sensing with Three-Sensor Field Compensation
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Solution Overview
Problem
Existing magnetoelastic torque sensors struggle with accurate torque measurement due to interference from homogeneous and linear magnetic fields, requiring multiple magnetized areas and complex compensation methods.
Innovation Solution
A magnetoelastic torque sensor with at least three magnetic field sensors, arranged to detect components of the magnetic flux density, uses distance ratios and weighted measurement signals to compensate for interference fields, allowing for accurate torque calculation without approximations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple magnetized areas are used to compensate for interference fields, then measurement precision is improved, but device complexity and size increase
Solution Approach 1:
The patent segments the measurement function across three magnetic field sensors positioned at different locations, allowing each sensor to contribute to both torque measurement and interference field compensation without requiring multiple magnetized areas on the shaft
Solution Approach 2:
The patent extracts the interference field compensation function from the shaft structure itself and relocates it to the sensor arrangement and evaluation unit, which calculate and subtract interference components based on the known geometric relationships between sensors
2Measurement precision
If multiple magnetized areas are used to compensate for interference fields, then measurement precision is improved, but the sensor size increases
Solution Approach 1:
The patent utilizes the spatial dimension by positioning three sensors at different locations around the shaft, creating a three-dimensional measurement geometry that enables interference field compensation without adding axial length through multiple magnetized areas
3Measurement precision
If complex compensation methods are used to eliminate interference fields, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The evaluation unit uses feedback from multiple sensors to continuously calculate and compensate for interference fields, adjusting the torque measurement based on the measured magnetic field components from each sensor position
Solution Approach 2:
The patent changes the measurement parameters by utilizing the known distances and geometric relationships between sensors as fixed parameters in the evaluation algorithm, simplifying the compensation calculation to linear combinations of sensor readings
4Device complexity
If approximations are used in torque calculation to eliminate interference fields, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent performs preliminary action by pre-determining the geometric relationships and distance ratios between sensors during manufacturing, allowing these fixed parameters to be hard-coded into the evaluation algorithm for efficient, approximation-free calculations
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 sensor achieves interference-free torque measurement by eliminating homogeneous and linear interference fields, reducing sensor size, and maintaining accuracy despite initial positioning and magnetization tolerances.
Implementation Method 1
at least three magnetic field sensors, each having at least one measuring axis and configured to detect a component of the magnetic flux density of a magnetic field in the direction of the at least one measuring axis
Implementation Method 2
When the shaft is subjected to torque, a magnetic field is generated in the area outside the shaft. This field is proportional to the torque applied to the shaft at every point
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention relates to a magnetoelastic torque sensor (10) having an evaluation unit (6) and at least three magnetic field sensors. The evaluation unit (6) is designed to capture at least one measurement signal from a first magnetic field sensor (1), at least one measurement signal from a second magnetic field sensor (2) and at least one third measurement signal from a third magnetic field sensor (3) of the magnetoelastic torque sensor (10) and to determine, by means of the at least one measurement signal from the first magnetic field sensor, the at least one measurement signal from the second magnetic field sensor, the at least one measurement signal from the fourth magnetic field sensor and the ratio of the distance (23) between the second magnetic field sensor (2) and the third magnetic field sensor (3) in an axial direction (111) to a distance (12) between the first magnetic field sensor (1) and the second magnetic field sensor (2) in the axial direction (111), a torque exerted on the shaft (5). The invention further relates to a method for determining a torque using a magnetoelastic torque sensor (10) of this kind.