Encoder Offset Correction via Gain-Offset Lookup Table
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Solution Overview
Problem
Existing position detection systems using 2-phase sinusoidal signals in encoders face a time lag and precision errors due to amplitude center offset, which are not adequately addressed by existing automatic gain control methods that require measurement points within a certain range for correction.
Innovation Solution
An offset correction device that includes an amplitude adjuster, an offset corrector, and a storage unit to store the relationship between gain and offset amounts, allowing for simultaneous gain adjustment and offset correction, reducing time lag and calculation load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If automatic gain control is performed to adjust the gain of the detection signal, then the intensity of the detection signal is within the predetermined range, but the amplitude center of the detection signal is offset
Solution Approach 1:
The patent applies preliminary action by pre-storing the relationship between gain values and offset amounts in a table during the setup phase. When gain adjustment is needed, the system simply looks up the corresponding offset amount from the pre-stored table rather than performing complex real-time calculations, enabling immediate offset correction that compensates for the gain-induced amplitude center shift.
Solution Approach 2:
The patent utilizes parameter changes by establishing a correspondence between gain parameters and offset amount parameters. The storage table stores pairs of (gain value, offset amount), allowing the system to adjust both parameters simultaneously - when gain is changed to control signal intensity, the corresponding offset amount is applied to correct the amplitude center position.
2Measurement precision
If measurement points within a certain range in the period of the sine wave are used for correction, then offset correction can be performed, but there is a time lag from the timing of gain switching until the offset is corrected
Solution Approach 1:
The patent eliminates time lag by performing the offset correction action in advance. The relationship between gain and offset amount is pre-calculated and stored in a table during system initialization. When gain switching occurs, the offset correction is immediately applied by looking up the pre-stored value, eliminating the need for real-time measurement point collection and calculation.
Solution Approach 2:
The patent uses copying by creating a lookup table that copies the relationship between gain values and offset amounts. Instead of calculating offset correction in real-time, the system copies the pre-determined offset amount from the storage table corresponding to the current gain value, enabling immediate correction without computational delay.
3Measurement precision
If existing offset correction techniques are used, then offset can be corrected, but the correction process requires complex calculations and measurement points
Solution Approach 1:
The patent simplifies the correction process by performing complex calculations in advance. The relationship between gain and offset amount is pre-calculated and stored in a table during system setup. During operation, the system only needs to perform a simple table lookup based on the current gain value, dramatically reducing computational complexity while maintaining correction accuracy.
Data Source
AI summary
An offset correction device includes: an amplitude adjuster that adjusts an amplitude of a detection signal output from an encoder by adjusting a gain of the detection signal so that the amplitude is within a predetermined range; an offset corrector that corrects an offset of an amplitude center of the detection signal; and a storage that stores a relationship between the gain and an offset amount in advance, wherein the offset corrector refers to the relationship stored in the storage when the amplitude adjuster changes the gain, obtains the offset amount corresponding to the changed gain, and corrects the offset based on the obtained offset amount.