Complex Baseband Resolver Demodulation for Precise Rotor Position
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Solution Overview
Problem
Existing resolver systems face challenges in accurately measuring rotor position due to noise in signals, differing delays and gains in sampling electronics, and slight misalignments of secondary windings, leading to imprecision and errors in computing angular position.
Innovation Solution
The method involves high-speed sampling of output signals from the resolver's secondaries, demodulating these signals to recover gain, and applying digital signal processing techniques to correct noise, delay differences, gain imbalances, and phase errors, thereby improving the accuracy of rotor position measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sampling is performed exactly at AC peaks to simplify processing, then processing complexity is reduced, but measurement precision deteriorates due to noise sensitivity and electronic delays
Solution Approach 1:
The patent applies preliminary action by performing demodulation and correction operations before final position computation. The system recovers gain information from the primary winding output and applies corrections for delay differences and gain imbalances before computing the arctangent, thereby preparing the signals in advance to eliminate the need for peak sampling while maintaining high precision
Solution Approach 2:
The patent replaces the mechanical/electronic timing approach (sampling at AC peaks) with a signal processing approach (demodulation and digital correction). By substituting the peak-sampling method with complex baseband processing, the system achieves both simplified processing architecture and improved measurement precision through digital signal correction techniques
2Measurement precision
If secondary windings are mounted exactly 90° apart to achieve ideal sine-cosine output, then measurement accuracy is improved, but manufacturing precision deteriorates due to alignment difficulties
Solution Approach 1:
The patent applies feedback by using the primary winding output signal to recover gain information that is then used to correct imbalances in the secondary winding outputs. The system measures the actual gain differences caused by manufacturing tolerances and applies compensating corrections, thereby achieving high measurement accuracy without requiring perfect 90° alignment of the secondaries
Solution Approach 2:
The patent changes the parameter being controlled from physical alignment angle to electrical gain balance. Instead of requiring the secondaries to be physically aligned at exactly 90°, the system allows manufacturing tolerances in alignment but compensates by adjusting and correcting the electrical gain parameters through demodulation and digital processing, thereby decoupling measurement accuracy from manufacturing precision requirements
3Measurement precision
If noise filtering is applied to improve signal quality, then measurement precision is improved, but loss of information increases due to potential signal distortion
Solution Approach 1:
The patent extracts the useful signal information from the noisy carrier signal through demodulation. By recovering the gain information from the primary winding output and separating it from the high-frequency AC excitation signal, the system removes the noise-carrying carrier while preserving the position-encoded gain information, thereby improving signal quality without losing measurement information
Solution Approach 2:
The patent uses the demodulated gain information as an intermediary to correct noise effects. The recovered gain from the primary winding serves as a reference that allows the system to correct noise-induced errors in the secondary outputs through ratio calculations and arctangent computation, thereby filtering noise while preserving the essential position information
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 approach enhances the precision and accuracy of rotor position measurement, reducing errors caused by noise and system imperfections, and allows for more reliable computation of angular position and velocity.
Implementation Method 1
a resolver having an input primary and one or more output secondaries magnetically coupled to the input primary
Data Source
AI summary
Monitoring rotating machine position using a resolver having an input primary and one or more output secondaries magnetically coupled to the input primary. The method includes exciting the input primary with an exciter input signal, causing a first scaled version of the exciter input signal to appear in a first output secondary. Output from the first output secondary is collected. The collected output from the first output secondary is demodulated to recover gain from the input primary.