Absolute Encoder Positioning with Dual-Period Scale Signals
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Solution Overview
Problem
Absolute type encoders experience positional detection delays due to the time required for periodic signals to stabilize after switching detecting periods, which can lead to relative position shifts if the calculating time period exceeds a predetermined time.
Innovation Solution
An encoder with a scale featuring two periodic patterns of different periods, allowing the detector to switch between reading states to output signals based on these patterns, and a processor that calculates relative displacement and position using both signals simultaneously, ensuring accurate position calculation regardless of calculating time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the detector switches between different detecting periods to read multiple periodic patterns, then the absolute position detection capability is improved, but the periodic signal takes time to become stable after switching, causing positional detection delay
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correspondence relationships between phases of different periodic patterns and absolute positions. When the detector switches between detecting periods, the processor can immediately retrieve pre-computed position information based on phase correspondence, avoiding the delay that would otherwise occur while waiting for signals to stabilize. This allows the system to maintain absolute position detection capability while eliminating switching delays.
2Measurement precision
If the calculating time period is extended to ensure accurate position calculation, then the measurement precision is improved, but the relative position may shift when the calculating time period exceeds a predetermined time period
Solution Approach 1:
The patent implements feedback by continuously monitoring the calculating time period and comparing it against the predetermined threshold. When the calculating time period approaches or exceeds the threshold, the system uses the stored phase correspondence relationships to correct and adjust position calculations, ensuring that relative position accuracy is maintained even when longer calculation periods are used for improved measurement precision.
Solution Approach 2:
By pre-calculating and storing the correspondence between phase differences and absolute positions, the system has correction data ready in advance. This allows immediate adjustment of position calculations when time period issues arise, maintaining reliability without sacrificing measurement precision.
3Device complexity
If a single detector is used to read multiple periodic patterns by time-sequential switching, then the device complexity is reduced, but the detector must switch between detecting periods which causes signal instability
Solution Approach 1:
The patent prepares phase correspondence data in advance through pre-calculation and storage. When the single detector switches between detecting periods, the processor can immediately use the pre-prepared correspondence relationships to determine accurate absolute positions, eliminating the signal instability problem that would otherwise result from switching operations.
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
Enables precise calculation of relative positions even when the calculating time period exceeds the predetermined time, reducing positional detection delays and maintaining accuracy.
Implementation Method 1
a light receiving element and a magnetic detecting element
Implementation Method 2
a light receiving element and a magnetic detecting element
Data Source
AI summary
An encoder includes a scale, a detector, and a processor. The processor executes a second process while executing a first process, calculates a first relative position of one of the scale and the detector to the other of the scale and the detector when a calculation of a relative position between them starts, and then calculates a second relative position of the one to the other based on a relative displacement amount between them and the first relative position.