Encoder Position Calculation Using Speed-Adaptive Amplitude Correction
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Solution Overview
Problem
Conventional encoder correction methods fail to accurately calculate the position or angle of an inspection target due to amplitude changes in sine and cosine wave signals caused by movement speed, leading to deformation of Lissajous waveforms and difficulties in determining offset errors.
Innovation Solution
A method that acquires temporary movement speed of the inspection target, calculates amplitude correction values based on pre-acquired relationships between movement speed and signal amplitudes, corrects signal amplitudes, and calculates offset errors using corrected amplitudes to determine the position or angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional correction methods are used to calculate position or angle from sine and cosine wave signals, then the calculation can be performed using standard arctangent operations, but measurement accuracy deteriorates when the inspection target moves at varying speeds due to amplitude changes deforming the Lissajous waveform
Solution Approach 1:
The invention applies dynamics by making the correction values adaptive to movement speed. Instead of using fixed correction values, the system dynamically adjusts the correction values based on the detected movement speed of the inspection target. This allows the correction mechanism to adapt to varying speeds, maintaining measurement accuracy across different operating conditions by selecting appropriate correction values from a lookup table or through interpolation.
Solution Approach 2:
The invention changes the parameter of correction values based on movement speed. By establishing a relationship between movement speed and correction values (through calibration processes), the system modifies the correction parameters dynamically. This parameter change approach allows the correction values to reflect the actual amplitude variations caused by different movement speeds, thereby maintaining Lissajous waveform integrity and measurement accuracy.
2Reliability
If correction values are updated during movement of the inspection target, then continuous correction can be applied, but the amplitude changes due to movement speed cause Lissajous waveform deformation making offset error calculation difficult
Solution Approach 1:
The invention applies preliminary action by performing calibration processes to establish the relationship between movement speed and correction values before actual measurement operations. The system pre-calculates and stores correction values for different movement speeds in a lookup table. During operation, the system simply retrieves the appropriate pre-calculated correction values based on detected movement speed, avoiding the need to perform complex real-time calculations and offset error analyses during movement.
3Measurement precision
If the amplitude of sine or cosine wave signals changes due to movement speed, then the signals reflect actual dynamic conditions, but the Lissajous waveform becomes deformed preventing accurate offset error calculation
Solution Approach 1:
The invention changes the correction values based on movement speed parameters. By establishing a calibration relationship between movement speed and correction values, the system dynamically adjusts correction parameters to compensate for amplitude changes. This parameter change approach maintains the ideal circular Lissajous waveform shape even when amplitude variations occur due to different movement speeds, enabling accurate offset error calculation and position measurement.
Data Source
AI summary
A method for calculating a position or an angle of an inspection target based on a sine wave signal and a cosine wave signal output from an encoder or a laser interferometer, includes acquiring a temporary movement speed of the inspection target, calculating an amplitude correction value corresponding to the temporary movement speed using information representing a relationship between a movement speed of the inspection target and amplitudes of the sine wave signal and the cosine wave signal acquired in advance, correcting the amplitudes of the sine wave signal and the cosine wave signal using the amplitude correction value, and calculating an offset error in a Lissajous waveform using the sine wave signal and the cosine wave signal the amplitudes of which are corrected with the amplitude correction value and calculating the position or the angle of the inspection target using the offset error.