Inductive Position Sensor Harmonic Distortion Reduction
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Solution Overview
Problem
Inductive position sensors face challenges in accurately determining the angular position of objects due to harmonic and other distortions in the received signal, which decrease the sensor's accuracy.
Innovation Solution
The implementation of an inductive position sensor design that includes a stator with an excitation coil and receiver coils, where the receiver coils are configured with loops offset by a portion of a harmonic period to nullify harmonic distortions, and a control unit to generate an angular position signal based on the receiver coil voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional receiver coil with uniformly spaced loops is used, then the sensor structure is simple, but harmonic distortions degrade the measurement precision
Solution Approach 1:
The patent applies asymmetry by offsetting the second loop relative to the first loop by a specific portion of a harmonic period (e.g., one-half of the harmonic period). This asymmetric configuration causes the loops to generate harmonic voltages that are out of phase, enabling destructive interference that nullifies harmonic distortions in the combined receiver coil voltage, thereby improving angular position determination accuracy without requiring complex external filtering circuits
Solution Approach 2:
The receiver coil is segmented into multiple loops (first loop and second loop) with different spatial configurations. Each loop independently generates receiver coil voltages with specific harmonic characteristics, and their series connection allows the harmonics to cancel each other out, achieving harmonic nullification through structural segmentation rather than post-processing
2Measurement precision
If loops are offset to nullify harmonics, then measurement precision improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies the loop offset parameter as a fraction of the harmonic period (e.g., one-half of the harmonic period), which corresponds to a specific angular displacement. This parameter-based definition allows manufacturers to achieve harmonic nullification by controlling the angular position of loops during assembly, providing a clear manufacturing target that balances performance requirements with fabrication capabilities
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 configuration effectively nullifies harmonic distortions, improving the accuracy of the angular position determination and enhancing the overall performance of the inductive position sensor.
Implementation Method 1
an excitation coil being inductively coupled to the target, and a receiver coil... such that a receiver coil voltage is generated at the receiver coil
Implementation Method 2
The second loop can be offset, on the stator and relative to the first loop, by a portion of a harmonic period corresponding with a harmonic for nullification in the receiver coil voltage
Data Source
AI summary
An inductive position sensor can include a first target coil, included in a target, and including a first outer lobe that has a size based on a first shift ratio of a harmonic period of a receiver coil, and a first inner lobe having a size based on a second shift ratio of the harmonic period where the harmonic period corresponds with a harmonic and the first shift ratio is different from the second shift ratio. The inductive position sensor also include a second target coil including a second outer lobe having a size based on the second shift ratio, and a second inner lobe having a size based on the first shift ratio.