Stacked Variable Reluctance Resolver to Eliminate Toothing Harmonics
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Solution Overview
Problem
The modulation by toothing harmonics in variable reluctance resolvers complicates signal processing and reduces precision in measuring the angle of rotation.
Innovation Solution
A variable reluctance resolver design with a rotor comprising a stack of elementary strata, where each stratum is angularly offset by an offset angle equal to (N−1)/N times the tooth angle, eliminating the toothing harmonic signals by ensuring poles pass in a temporally offset manner relative to stator teeth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rotor with periodic air gap variation is used to enable angle measurement, then the resolver can detect rotation angle, but toothing harmonic signals are generated that complicate signal processing and reduce precision
Solution Approach 1:
The rotor is segmented into multiple elementary strata stacked along the axial direction. Each stratum contains pole pairs that are angularly offset from one another, specifically by an offset angle equal to (N-1)/N times the tooth angle, where N is the number of strata. This segmentation allows the toothing harmonic signals generated by each stratum to be temporally distributed rather than coincident, thereby reducing the overall harmonic distortion in the detected signal.
Solution Approach 2:
The invention transitions from a conventional single-plane rotor design to a multi-layered three-dimensional structure. By stacking elementary strata along the axial dimension and applying angular offsets between layers, the solution exploits the third dimension to eliminate toothing harmonics without compromising the fundamental angle detection function.
2Measurement precision
If multiple elementary strata are stacked with angular offset to eliminate toothing harmonics, then signal precision is improved, but device complexity increases
Solution Approach 1:
The rotor is divided into N identical elementary strata, each with the same geometric pattern but angularly offset from adjacent strata. This segmentation approach allows for standardized manufacturing of individual strata that can be stacked and assembled, reducing overall manufacturing complexity despite the multi-layered structure.
Solution Approach 2:
The key parameter controlling the angular position of each stratum is the offset angle, defined as (N-1)/N times the tooth angle. By precisely controlling this single parameter during assembly, the complex multi-layered structure can be manufactured with consistent performance, thereby managing device complexity through parameter standardization.
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 significantly reduces or eliminates the toothing harmonic error, enhancing the precision of angle and speed measurements.
Implementation Method 1
A variable reluctance resolver comprises a rotating portion, called a rotor, and a fixed portion called a stator... the width of the air gap delimited between the rotor surface and the facing stator surface varies periodically between a maximum value and a minimum value
Implementation Method 2
The set of windings comprises an excitation winding on which an alternating electric voltage with a frequency of several kHz is applied, and at least two angle detection windings at the ends of which an electric voltage is measured
Data Source
AI summary
The invention relates to a variable reluctance resolver (10), comprising a rotor (20) and a stator (30) coaxial with the rotor (20), the stator (30) comprising a plurality of teeth (31), two consecutive teeth (31) forming a tooth angle (ΘD), the rotor (20) comprising a stack of elementary strata coaxially stacked along a central axis (X), characterised in that each elementary stratum defines at least one pair of poles (21M, 21m), the stack comprising a first elementary stratum (25) defining the bottom of the stack and at least one upper elementary stratum (26) superimposed on the first elementary stratum (25), each upper elementary stratum (26) being angularly offset by an offset angle (ΘP) about the central axis (X) with respect to the underlying elementary stratum, the offset angle (ΘP) being equal to the tooth angle (ΘD) multiplied by (N−1)/N, N being the number of stacked elementary strata (25, 26).