Resolver Signal Converter Band-Pass Filter Noise Reduction
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Solution Overview
Problem
General resolver-digital converters suffer from frequency dependence and detection angle errors due to disturbance noise from magnetic fields and PWM-driven motors, which affect the accuracy of digital angle outputs.
Innovation Solution
A resolver signal converter and method that employ band-pass filters and sampling synchronous rectifiers to filter and process resolver signals, eliminating the need for tracking loops and reducing noise influence, with features like phase correction and reduced sampling rate for enhanced accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a tracking loop is used to convert resolver signals to digital angle data, then the converter can operate with simple structure, but frequency dependence occurs causing detection angle errors
Solution Approach 1:
The patent extracts and removes the tracking loop component from the converter structure. By eliminating the tracking loop, the frequency dependence that causes detection angle errors is removed, while the converter still achieves accurate angle conversion through direct synchronous detection and arctangent calculation methods.
2Object-affected harmful factors
If conventional filtering is used to remove noise, then noise attenuation is achieved, but harmonic noise and offset errors are amplified
Solution Approach 1:
The patent changes the parameter of filter type from conventional low-pass or band-stop filters to a specifically designed band-pass filter with center frequency matching the excitation signal frequency. This parameter change allows the filter to attenuate disturbance noise including PWM switching noise while preserving the fundamental resolver signal components, preventing amplification of harmonic noise and offset errors.
3Loss of information
If the converter processes all frequency components, then complete signal information is maintained, but noise including PWM switching noise affects the output
Solution Approach 1:
The patent applies local quality by designing the band-pass filter to selectively process only the frequency components around the excitation signal frequency, while rejecting other frequency components including PWM switching noise. This localized frequency processing maintains the essential signal information needed for accurate angle detection while eliminating harmful noise frequencies.
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 solution effectively reduces detection angle errors by eliminating frequency dependence and attenuating disturbance noise, improving the accuracy of resolver signal conversion without amplifying harmonic noise or offset errors.
Implementation Method 1
a first band-pass filter which passes, among frequency components of a first resolver signal which is a sine wave output from a resolver, a predetermined bandwidth whose center frequency is a frequency of an excitation signal
Implementation Method 2
a first sampling synchronous rectifier configured to sample the first resolver signal which has passed through the first band-pass filter, while synchronizing the first resolver signal with a reference signal which is based on the excitation signal
Implementation Method 3
When an alternate current is supplied to the excitation coil, an AC voltage is generated at each detection coil in accordance with a relative angle between a stator and a rotor
Data Source
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AI summary
A resolver signal converter and a resolver signal conversion method amplify and perform analogue-digital conversion on a sine wave output from a resolver; thereafter, among frequency components of the sine wave output, pass and thereby extract a predetermined bandwidth of which the center frequency is the frequency of an excitation signal, by means of a band-pass filter; sample the sine wave output while synchronizing the sine wave output with a reference signal which is based on the excitation signal; and generate a detection angle signal sine value from the sampled signal. Similarly, a detection angle signal cosine value is generated from a cosine wave output from the resolver. A detection angle is calculated based on the detection angle signal sine value and the detection angle signal cosine value. Accordingly, an influence, on an input resolver signal, of disturbance noise such as noise caused due to a magnetic field generated by a motor and switching noise caused due to PWM driving, is eliminated, and frequency dependence of arithmetic processing is eliminated. As a result, detection angle errors are reduced.