Magnetoelastic Torque Sensor Compensation for Interference Fields
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Solution Overview
Problem
Existing magnetoelastic torque sensors struggle with accurate torque measurement due to interference fields, requiring multiple magnetized regions for compensation, which increases sensor size and complexity.
Innovation Solution
A magnetoelastic torque sensor with at least three magnetic field sensors, strategically positioned to measure and compensate for homogeneous and linear interference fields using signal ratios and an evaluation unit, allowing for interference field elimination without approximations, thus reducing sensor size and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple magnetized regions are used for interference field compensation, then measurement precision is improved, but device complexity and size increase
Solution Approach 1:
The patent replaces the mechanical approach of using multiple magnetized regions with a mathematical signal processing approach. Instead of physically adding more magnetized regions to compensate for interference fields, the invention uses a calculation formula that processes signals from sensors positioned at different locations to eliminate homogeneous and linear interference field components mathematically, thereby reducing structural complexity while maintaining measurement precision.
Solution Approach 2:
The patent changes the approach from modifying the physical structure (adding magnetized regions) to modifying the measurement parameters (sensor positions and signal weighting). By carefully selecting sensor positions along the shaft and applying appropriate weighting factors in the calculation, the system achieves interference compensation through parameter optimization rather than structural complexity.
2Measurement precision
If multiple magnetized regions are used for interference field compensation, then measurement precision is improved, but the sensor size increases
Solution Approach 1:
The patent substitutes the need for extended axial length (which would be required for multiple magnetized regions) with a mathematical calculation approach. The signal processing formula combines measurements from sensors at different axial positions with appropriate weighting to eliminate interference components, achieving the same compensation effect without requiring additional axial space for extra magnetized regions.
Solution Approach 2:
The patent shifts the problem from a spatial dimension (adding magnetized regions along the axial direction) to a computational dimension (signal processing and mathematical combination). By moving the compensation function from the physical domain to the computational domain, the system achieves interference rejection without increasing the physical dimensions of the sensor.
3Device complexity
If approximations are used in torque calculation, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent replaces approximate compensation methods with an exact mathematical solution. The calculation formula is designed to precisely eliminate homogeneous and linear interference field components through weighted combination of sensor signals, providing accurate torque determination without requiring complex iterative algorithms or approximations.
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 accurate torque determination by compensating for interference fields, reducing the need for additional magnetized regions and maintaining compact size, while ensuring precise torque measurement.
Implementation Method 1
at least three magnetic field sensors (1, 2, 3), each having at least one measurement axis and being set up to acquire a component of a magnetic flux density of a magnetic field in the direction of the at least one measurement axis
Implementation Method 2
A magnetoelastic torque sensor having a partially magnetized shaft has been available for years. When a torque load is applied to the shaft, a magnetic field arises in the area outside the shaft that is at each point proportional to the torque exerted on the shaft
Data Source
AI summary
A magnetoelastic torque sensor having an evaluation unit and at least three magnetic field sensors. The evaluation unit acquires at least one measurement signal of a first magnetic field sensor, at least one measurement signal of a second magnetic field sensor and at least one third measurement signal of a third magnetic field sensor of the magnetoelastic torque sensor, and to determine a torque exerted on the shaft using the at least one measurement signal of the first magnetic field sensor, the at least one measurement signal of the second magnetic field sensor, the at least one measurement signal of the fourth magnetic field sensor, and a ratio of a distance between the second magnetic field sensor and the third magnetic field sensor in an axial direction to a distance between the first magnetic field sensor and the second magnetic field sensor in the axial direction.