Inductive Angle Sensor Offset Coil Error Compensation
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Solution Overview
Problem
Inductive angle sensors face systematic errors in measuring rotation angles due to low harmonic content in the low-frequency signal component, leading to inaccuracies, especially with complex coil geometries and varying air gaps, which are costly and difficult to correct without precise manufacturing and calibration.
Innovation Solution
The inductive angle sensor design incorporates two pickup coil arrangements with k-fold symmetry, where the coils are rotationally offset by a geometric angle α, allowing for signal combination to compensate for systematic errors, enabling precise angle measurements without complex geometries or precise air gap knowledge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If very specific coil geometries and high-precision manufactured targets are provided to correct systematic error, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The pickup coil arrangement is divided into multiple individual pickup coils (at least two) that are offset from one another by a defined rotation angle. Each coil generates a separate signal that is subsequently combined mathematically to compensate for systematic errors, eliminating the need for complex single-coil geometries
Solution Approach 2:
Signals from multiple offset pickup coils are merged through mathematical combination (signal processing) to generate a compensated angle signal. This combining approach achieves error correction that would otherwise require complex individual coil designs
2Measurement precision
If mathematical correction formulas or lookup tables are provided to correct systematic error, then measurement precision is improved, but the system requires precise air gap knowledge which is difficult to obtain in mass production
Solution Approach 1:
The system performs self-calibration by automatically determining the air gap from the measured signals and using this information to select appropriate correction factors from a lookup table. This eliminates the need for manual air gap measurement and precise manufacturing control
Solution Approach 2:
The system uses the measured angle signals to infer the actual air gap condition, then applies feedback-based correction by selecting correction factors from a pre-stored lookup table that compensates for the determined air gap, enabling adaptive error correction without precise manufacturing
3Device complexity
If a single pickup coil arrangement is used, then device complexity is reduced, but systematic angle errors cannot be compensated
Solution Approach 1:
The pickup coils are deliberately positioned asymmetrically at specific offset angles (e.g., 45°, 135°, 225°, 315°) rather than symmetrically. This asymmetric arrangement, combined with mathematical signal combination, enables systematic error compensation while maintaining relatively simple device structure
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 design effectively compensates for systematic angle errors, providing precise angle signals for targets with arbitrary designs, regardless of air gap variations, and reduces measurement inaccuracies, making it suitable for mass-produced sensors.
Implementation Method 1
The field coil is fed an input signal, for example an AC signal. In response thereto the field coil generates a magnetic field that decouples from the field coil.
Implementation Method 2
The rotor opposite has an inductive target that the magnetic field couples into. In response thereto the inductive target produces eddy currents that in turn generate a secondary magnetic field
Implementation Method 3
The secondary magnetic field then couples into a pickup coil arrangement arranged on the stator. In response thereto the pickup coil arrangement generates an output signal that represents the angle between the stator and the rotor.
Data Source
AI summary
An inductive angle sensor includes an inductive target arrangement with k-fold symmetry and a first pickup coil arrangement with k-fold symmetry and a second pickup coil arrangement with k-fold symmetry. A combination apparatus is designed to combine signals of the first pickup coil arrangement with signals of the second pickup coil arrangement and, on the basis thereof, to ascertain an angle-error-compensated rotation angle. The single pickup coils of the first and second pickup coil arrangements are each rotationally offset about the axis of rotation R by a geometric offset angle α relative to one another. Additionally, the entire first pickup coil arrangement is rotationally offset relative to the entire second pickup coil arrangement about the axis of rotation R by a geometric offset angle ρ.