Position Detector Abnormality Detection via Signal Switching
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Solution Overview
Problem
Existing position detectors fail to accurately detect errors caused by scratches or dust, especially when the abnormality is of the same size as the cycle width, leading to undetectable errors in position measurement.
Innovation Solution
A position detector system that uses a light emitter and receiver configuration to generate both periodic and abnormality detection signals, allowing for the detection of scratches or dust by switching between these signals based on external control, with the abnormality detection signals being constant regardless of phase, enabling effective abnormality determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single periodic signal is used for position detection, then the device structure is simple, but abnormalities such as scratches or dust cannot be detected
Solution Approach 1:
The patent divides the signal generation into two separate signal generation units: one for generating periodic signals (first signal) and another for generating abnormality detection signals (second signal). This segmentation allows the system to detect abnormalities by comparing the second signal against a reference, while maintaining a relatively simple overall structure.
Solution Approach 2:
The position detector is designed to perform multiple functions: it can detect both normal position information (via periodic signals) and abnormalities (via abnormality detection signals). The light emitter and light receiver are used for both periodic position detection and abnormality detection, making the system multi-functional without requiring completely separate hardware.
2Measurement precision
If comparison of periodic signals is used for abnormality detection, then some abnormalities can be detected, but errors cannot be detected when the abnormality size matches the cycle width
Solution Approach 1:
The patent introduces an abnormality detection signal (second signal) as an intermediary that is specifically designed to detect abnormalities. This second signal is generated separately from the periodic position signal and can be compared against a reference signal to detect abnormalities such as scratches or dust, even when their size matches the cycle width, thereby improving detection coverage.
3Reliability
If the sensor covers an area larger than the pattern reading area, then correct position can be obtained by shifting reading area, but the device becomes more complex and time-consuming
Solution Approach 1:
The patent generates abnormality detection signals continuously in advance using a separate signal generation unit, so that when an abnormality occurs, the system can immediately compare the second signal with the reference signal to detect the abnormality. This eliminates the need for time-consuming reading area shifting operations, as the abnormality detection is performed in real-time through signal comparison.
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
The system can accurately detect abnormalities such as scratches or dust, ensuring reliable position measurement by generating specific signals that highlight the presence of errors, even when they match the cycle width, thereby improving the accuracy of position detection.
Implementation Method 1
a light emitter 101 and a light receiver 103 which receives the light reflected by the scale 102
Implementation Method 2
a light emitter 101 and a light receiver 103 which receives the light reflected by the scale 102
Data Source
Figure 1~2
Figure 3~5
Figure 6A~6B
AI summary
A position detector, including: a scale including a pattern array formed cyclically in a movement direction, the scale being provided to a fixed member or a movable member; a detector including detection elements arranged in the movement direction, the detector being provided to the other; a generating unit that selectively generates, from signals received from the detection elements, a first signal obtained by a first combination of the signals or a second signal obtained by a second combination of the signals; an output unit that outputs the first or second signal received from the generating unit; and a switcher that switches over between the first and second signals as a signal to be generated, in which: the first signal changes within a first range, corresponding to a relative position; and the second signal does not change beyond a second range smaller than the first range, corresponding to the relative position.