Encoder Position Estimation Using Digital Filtered Data
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Solution Overview
Problem
Conventional encoders output position data at intervals where the last few data points are used, leading to noise issues and inaccurate position control due to the controller's slower processing speed compared to the encoder's detection speed.
Innovation Solution
An encoder with a position data storage and a position estimator that calculates position data at a calculation-target time point using a broader range of data points, processed through digital filters, to provide accurate position data without time delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the encoder outputs position data at high detection speed (several tens of MHz), then the detection speed is improved, but the controller cannot process the data fast enough leading to time delay and inaccurate position control
Solution Approach 1:
The encoder performs preliminary actions by calculating and storing position data at multiple future time points (first future time point and second future time point) before the current output time. This allows the controller to receive position data that has already been processed and is ready for immediate use, eliminating the time delay caused by the controller's slower processing speed.
2Device complexity
If the encoder uses only the last few position data points for output, then the processing is simple, but noise affects the accuracy of position control
Solution Approach 1:
The encoder preliminarily calculates position data at multiple future time points using the detected pattern information. By having these pre-calculated values ready, the system can select from multiple data points rather than relying on just the last few, thereby improving accuracy without significantly increasing processing complexity during operation.
3Measurement precision
If the encoder calculates and stores position data at multiple future time points, then the accuracy of position control is improved, but the device complexity increases
Solution Approach 1:
The encoder creates copies of position data at multiple future time points based on the detected pattern information. Instead of implementing a complex real-time prediction system, the encoder generates multiple copies of position data that the controller can select from, improving accuracy while keeping the encoder's structure relatively simple.
4Stability of the object's composition
If the controller processes position data at its slower speed (several KHz to dozen KHz), then the control is stable, but the position control accuracy deteriorates due to time delay
Solution Approach 1:
The encoder performs preliminary calculations of position data at multiple future time points before the controller needs them. This allows the controller to operate at its stable but slower processing speed while still receiving position data that is already prepared for future time points, thereby maintaining control stability while improving position control accuracy.
Data Source
AI summary
An encoder includes a scale having a pattern to be detected, a detecting sensor outputting a signal corresponding to the pattern, a position calculator calculating a relative position between the scale and the detecting sensor based on the signal, a position data storage storing the calculated position data, and a position estimator estimating a relative position between the scale and the detecting sensor at a calculation-target time point based on the stored position data. The position estimator estimates the position at the calculation-target time point based on positions at first and second time points each preceding the calculation-target time point by a predetermined time. The position estimator processes position data in a first time width centered on the first time point and position data in a second time width centered on the second time point to calculate the positions at the first and second time points.