Encoder IIR Filter Noise Reduction
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Solution Overview
Problem
Conventional encoders face challenges in effectively reducing noise-induced errors in positional information detection due to limitations in filtering capabilities, particularly for frequencies equal to or less than the maximum frequency of the incremental signal, leading to erroneous detection of a driven body's position.
Innovation Solution
An encoder system incorporating an IIR filter unit that generates second positional information by filtering first positional information using a predetermined filter coefficient, with a counter unit storing high-order digits and an overflow processing unit adjusting delay information to mitigate noise and discontinuities, thereby enhancing filtering characteristics and reducing erroneous detections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a low pass filter is used to filter the incremental signal, then noise reduction is achieved, but filtering characteristics are restricted and cannot reduce noise with frequency equal to or less than the maximum frequency of the incremental signal
Solution Approach 1:
The patent changes the filtering approach from frequency-based filtering of the incremental signal to time-based filtering of positional information. By applying a low pass filter to positional information (which has different frequency characteristics) rather than the incremental signal, the system achieves noise reduction across a broader frequency range including frequencies equal to or less than the maximum frequency of the incremental signal.
2Measurement precision
If filtering is applied to reduce noise, then positional information accuracy improves, but erroneous detection may still occur when noise frequency is within the signal frequency range
Solution Approach 1:
The patent introduces positional information as an intermediary between the incremental signal and the final position detection. The low pass filter is applied to this intermediary signal (positional information) rather than directly to the incremental signal, allowing noise reduction while maintaining detection reliability across a wider frequency spectrum.
3Manufacturing precision
If the delay information falls outside the predetermined range, then filtering accuracy is maintained, but the count value and delay information require adjustment to prevent overflow
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the delay information and count value. When the delay information falls outside the predetermined range, the system automatically adjusts the count value to bring the delay information back within the valid range, preventing overflow and maintaining filtering accuracy through continuous self-correction.
Data Source
AI summary
An encoder includes a positional information generation unit configured to generate first positional information based on a detected signal which is output by a sensor unit, and an IIR filter unit configured to output second positional information obtained by performing filtering on the first positional information. In the IIR filter unit, a counter unit stores a predetermined high-order digit of the first positional information as a count value, and an input unit subtracts the count value from the first positional information to thereby generate input information. A computation unit generates an internal computation result based on delay information which is an internal computation result stored in a delay information storage unit, input information, and a predetermined filter coefficient, and generates output information on which filtering is performed. An output unit adds the count value and the output information to thereby generate second positional information. A changing unit changes a value of the delay information based on a unit of change of the input information when the value of the delay information falls outside of a predetermined range, and changes the count value.