Single-Channel 3D Safety Sensor Self-Diagnostics
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Solution Overview
Problem
Industrial safety systems require reliable distance measurement sensors to ensure safety integrity levels (SILs), but existing sensors often rely on complex and costly hardware redundancy, which can introduce size, cost, and reliability issues.
Innovation Solution
An active illumination 3D sensor system with integrated diagnostic features, including an auxiliary illumination source and analysis component, performs diagnostic tests to detect failures and ensure accurate distance measurements without the need for multiple channels, using a single-channel architecture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hardware redundancy is used to ensure safety integrity levels, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The sensor system performs self-diagnostics by using an auxiliary illumination source to emit test light pulses and an image sensor to detect reflected light from the housing inner surface. This self-testing mechanism allows the system to monitor its own functionality and detect failures without requiring external redundancy hardware, thereby maintaining reliability while reducing complexity.
Solution Approach 2:
The system performs diagnostic tests before failures occur by continuously monitoring the optical path and component functionality. The auxiliary illumination source and image sensor setup enables preliminary detection of degradation or failures in the main illumination source, optical components, or image sensor, allowing preventive maintenance and avoiding safety failures.
2Reliability
If hardware redundancy is used to ensure safety integrity levels, then reliability is improved, but cost increases
Solution Approach 1:
The auxiliary illumination source serves multiple functions: it provides diagnostic test light and can also serve as a backup illumination source. The image sensor serves dual purposes by detecting both normal measurement light and diagnostic test light. This multi-functionality eliminates the need for separate redundant hardware components, reducing manufacturing costs while maintaining safety integrity.
Solution Approach 2:
The system performs self-diagnostics using its own components (auxiliary illumination source and image sensor) to monitor the functionality of the main measurement components. This self-testing capability eliminates the need for expensive external redundancy hardware, thereby reducing cost while maintaining the required safety integrity levels.
3Device complexity
If a single-channel architecture is used, then device complexity is reduced, but reliability may worsen
Solution Approach 1:
The system implements feedback through continuous diagnostic monitoring. The image sensor detects reflected light from the housing inner surface, and the system analyzes this feedback signal to determine the functionality of the optical path and components. This feedback mechanism allows the single-channel system to detect and respond to failures, maintaining reliability without requiring multiple channels.
Solution Approach 2:
The single-channel sensor system performs self-diagnostics by using the auxiliary illumination source to emit test pulses and the image sensor to detect reflected light. This self-monitoring capability compensates for the lack of redundant channels, allowing the system to detect failures and maintain reliability while keeping the architecture simple and single-channel.
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 enhances reliability and accuracy of distance measurements, reducing the probability of dangerous failures and meeting SIL requirements without the need for hardware redundancy, thus simplifying and cost-effectively maintaining safety standards.
Implementation Method 1
an active illumination three-dimensional (3D) sensor system includes an illumination source configured to emit light pulses to a monitored area; an image sensor configured to measure a quantity of light received at a pixel of the array of pixels and generate electrical charge in proportion to the quantity of light; a distance determination component configured to determine a distance of a surface within the monitored scene based on analysis of the one or more digital data values
Implementation Method 2
an auxiliary illumination source mounted inside a housing of the 3D sensor system and oriented to emit auxiliary light pulses toward an inner surface of the housing; wherein the image sensor is further configured to perform, during a diagnostic test sequence, a measurement of a subset of the auxiliary light pulses reflected from the inner surface of the housing and received at the pixel as reflected auxiliary light pulses
Data Source
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AI summary
An active illumination three-dimensional sensor device is configured with a number of diagnostic functions that can satisfy the requirements of industrial safety within the context of a single-channel safety sensor architecture. The sensor diagnostic functions provide sufficient diagnostic coverage for an optical safety sensor (e.g., a time-of-flight safety sensor) to achieve a desired safety integrity level without the need for multiple channels. The diagnostic features can be applied to one or more components along the single-channel path (e.g., the sequencer, the illumination source, input and/or output optics, image sensor pixel, etc.) to provide a level of diagnostic coverage that renders the optical safety sensor suitable for use within industrial safety applications requiring high safety integrity levels.