Distance Measuring Sensor False Positive Detection
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Solution Overview
Problem
Distance-measuring monitoring sensors often generate false positive object detection signals due to small occluding objects like dust, raindrops, or snowflakes, leading to unnecessary shutdowns of machines or vehicles, which reduces their availability and may compromise safety response times.
Innovation Solution
A method that evaluates reception light pulses by checking three test conditions: the number of pulses, edge impact scenarios, and reflector presence to determine if the first reception light pulse originates from a safety-critical object, allowing the distance to be determined based on the time of flight of either the first or second pulse depending on these conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple evaluation of consecutive scanning cycles is used to filter false positives, then reliability improves, but response time deteriorates
Solution Approach 1:
The system performs preliminary actions by evaluating multiple test conditions (number of pulses, edge impact scenarios, reflector presence) before final object detection is confirmed. This preliminary filtering of reception light pulses based on predetermined criteria allows the system to quickly eliminate false positives from occluding objects like raindrops or dust, while maintaining fast response time by not waiting for multiple scanning cycles.
2Loss of time
If the monitoring sensor uses simple object detection, then response time is fast, but false positive detection increases
Solution Approach 1:
The system applies local quality by using different evaluation criteria for different types of detected objects. Instead of a uniform detection approach, it locally adapts the evaluation by checking specific test conditions (pulse number, edge impact, reflector presence) that are appropriate for distinguishing safety-critical objects from non-critical occluding objects, thereby improving detection accuracy without compromising response time.
3Reliability
If the system shuts down on any detected object, then safety is maximized, but availability deteriorates due to false positives
Solution Approach 1:
The system uses feedback by continuously monitoring reception light pulses and comparing them against predetermined test conditions. This feedback mechanism allows the system to distinguish between safety-critical objects that require shutdown and non-critical occluding objects like raindrops or dust that should be ignored, thereby maintaining high safety standards while preventing unnecessary shutdowns that would reduce availability.
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 reduces false positive object detection signals from non-critical occluding objects, ensuring safety-critical objects are correctly identified without impairing the monitoring of potentially dangerous machines or vehicles.
Implementation Method 1
The distance of the object from the monitoring sensor can be determined on the basis of the time of flight of a light pulse, i.e. on the duration of time between the transmission of the light pulse and the reception of the associated reception light pulse by the light receiver
Implementation Method 2
at least one light receiver that is configured to receive light pulses as reception light pulses that are reflected or remitted by at least one object possibly present in the protected field
Data Source
AI summary
A method of operating a monitoring sensor comprising a light transmitter; a light receiver; and a deflection unit is described, with the method comprising the steps:a) detecting a respective detected signal that comprises a time curve of a reception signal received for an angle of rotation;b) determining the number of reception light pulses in the detected signal;c) generating a detection signal that comprises information on the determined position of an object, wherein checks are made in accordance with first, second and third test conditions, and with the first test condition being checked in a first test step, and one of the second and third test conditions being checked in possibly performed second and/or third test steps respectively.