Optical Axis Photoelectric Sensor for False Obstruction Detection
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Solution Overview
Problem
Conventional multiple optical axis photoelectric sensors fail to distinguish between light obstruction caused by the detection target and other causes, leading to incorrect output switching and reduced productivity due to frequent machine stoppages.
Innovation Solution
Incorporation of malfunction notification means, variable update means, and notification control means to differentiate between light obstruction caused by the detection target and other causes by setting reference values for light entrance and obstruction durations, allowing for accurate analysis and notification of malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the response speed is enhanced to reliably stop the machine when a human body enters the detection area, then the light obstruction may be detected even when caused by short-period obstructions such as insects or optical axis deviation, leading to frequent false machine stoppages
Solution Approach 1:
The sensor performs preliminary detection by counting the number of times light obstruction occurs and the duration of each obstruction before triggering a machine stop. This preliminary action allows the system to distinguish between temporary obstructions (insects, optical deviations) and genuine safety threats (human body entry), thereby maintaining productivity while ensuring safety.
2Reliability
If the light obstruction detection sensitivity is increased to ensure safety, then the sensor cannot distinguish between light obstruction caused by the detection target and other causes, making it difficult to specify the cause of obstruction
Solution Approach 1:
The sensor incorporates feedback mechanisms that continuously monitor and count the number of light obstruction events and their durations. This feedback information is processed to determine whether the obstruction pattern matches that of a genuine detection target or represents a false cause (insect, optical deviation), enabling accurate cause identification while maintaining high detection sensitivity.
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 correct differentiation between valid and erroneous output switching, reducing unnecessary machine stoppages and improving productivity by identifying and addressing the cause of light obstruction.
Implementation Method 1
a plurality of light emitting elements 10 and an optical receiver 2 in which as many light receiving elements 20 as the light emitting elements 10 are provided
Implementation Method 2
processing of detecting whether light emitted from the light emitting element of the activated optical axis enters the corresponding light receiving element
Data Source
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AI summary
In a multiple optical axis photoelectric sensor that stops a control output according to light being obstructed in a detection area, a first variable Con indicating a duration of optical axis scan processing for which a determination result that the detection area is in a light entrance state (light entrance detection) is obtained, and a second variable Coff indicating a duration of the optical axis scan processing for which a determination result that the detection area is in a light obstruction state (light obstruction detection) is obtained, are updated according to results of each scan in optical axis scan processing. If the value of the first variable Con, which is updated while the determination continues that the detection area is in the light entrance state, reaches a predetermined first reference value, and if a final value of the second variable Coff, which is updated according to the previous determination that the detection area is in the light obstruction state, is equal to or lower than a predetermined second reference value, a notification is made that the light obstruction is detected due to a malfunction. As a result of this notification, whether output is erroneously switched due to a cause other than an object of a detection target can correctly be made.