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 intended object and other factors, leading to frequent machine stoppages due to false detections, which impairs productivity while compromising safety.
Innovation Solution
The sensor employs malfunction notification and variable update mechanisms to differentiate between light obstruction caused by the detection target and other factors by setting reference values for light entrance and obstruction durations, enabling accurate analysis and notification of malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If response speed is enhanced to reliably stop machine when human body enters dangerous region, then safety is improved, but light obstruction may be detected even for short period causing frequent machine stoppages
Solution Approach 1:
The sensor performs preliminary validation of optical axes and pre-processes light reception signals before making obstruction determinations. By validating optical axes in advance and performing multiple light emission/detection cycles, the system prepares detection data beforehand, enabling rapid response to actual obstructions while filtering out transient false signals through pre-established baseline information.
Solution Approach 2:
The system continuously monitors light reception signals and compares them against reference values and historical data. When light obstruction is detected, the control signal switches to off-state, and the system continues to monitor subsequent signals to confirm whether the obstruction persists. This feedback mechanism allows the sensor to distinguish between temporary disturbances (like insects) and genuine safety threats, reducing false stoppages while maintaining rapid response capability.
2Measurement precision
If light obstruction detection sensitivity is increased to detect all obstructions, then detection precision is improved, but false detection from insects or optical axis deviation increases
Solution Approach 1:
The system dynamically adjusts detection parameters including light emission timing, reception threshold levels, and determination criteria based on validated optical axis characteristics. By changing these parameters adaptively, the sensor achieves high sensitivity for genuine obstructions while setting thresholds that filter out minor variations caused by insects or slight optical misalignments.
Solution Approach 2:
The sensor performs multiple light emissions and detections beyond the minimum single measurement. By conducting excessive detection cycles (multiple times the theoretical minimum), the system accumulates sufficient data to distinguish true obstructions from noise, using the redundancy of multiple measurements to improve reliability without sacrificing detection sensitivity.
3Reliability
If multiple light emissions and detections are performed to reduce false determination, then reliability is improved, but response time increases
Solution Approach 1:
The system performs light emissions and detections in continuous sequence without idle intervals between cycles. Optical axes are validated continuously, and light reception signals are monitored without interruption. This continuous operation allows multiple measurements to be taken in rapid succession, accumulating reliable detection data while minimizing total response time compared to batch processing approaches.
Solution Approach 2:
Optical axis validation and initial light reception measurements are performed in advance before actual obstruction detection is needed. By establishing baseline information about valid optical paths and expected signal characteristics beforehand, the system reduces the processing time required during actual detection events, enabling rapid response while maintaining the benefit of multiple pre-collected measurements.
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
This approach allows for precise differentiation between valid and invalid light obstruction states, reducing false stoppages and enhancing sensor performance by accurately identifying and addressing the cause of malfunctions.
Implementation Method 1
a light emitting element 10 and a light receiving element 20 are disposed opposite to each other... the optical axes are sequentially validated, optical scan processing is repeatedly performed to detect the existence or non-existence of light at the entrance of the validated optical axis
Data Source
AI summary
A multiple optical axis photoelectric sensor is provided that stops a control output according to light being obstructed in a detection area. First and second variable signals indicate the duration of an optical axis scan processing for which light entrance detection and light obstruction detection are obtained, respectively. The first and second variable signals are updated according to results of each scan in the optical axis scan processing. When the value of the first variable reaches a predetermined first reference value, and when a final value of the second variable 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 signal of the sensor is erroneously switched due to a cause other than an object of a detection target can correctly be made.