Camera Input Expansion Unit for Precise PLC Image Synchronization
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Solution Overview
Problem
In systems combining programmable logic controllers (PLCs) and cameras for monitoring production facilities, achieving precise time synchronization between device value acquisition and camera image acquisition is challenging due to communication delays, making troubleshooting time-consuming and manpower-intensive.
Innovation Solution
A programmable logic controller with a camera input expansion unit that includes a CPU-mounted unit, a camera input expansion unit processor, an image-recorder, and an image capture interface, where the camera input expansion unit generates an ON/OFF signal for image capture based on stored setting information, allowing precise time synchronization through a dedicated image-capture trigger line without command interpretation, thus avoiding time delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If communication network is used to connect PLC and camera, then system integration is achieved, but time synchronization precision deteriorates due to communication delay
Solution Approach 1:
The system is segmented into two parts: communication-based integration (PLC to expansion unit) and direct trigger signaling (expansion unit to camera via image-capture-trigger line). This segmentation allows communication functions to be maintained while time-critical trigger signals use a dedicated low-latency path.
Solution Approach 2:
The camera input expansion unit acts as an intermediary between the PLC and the camera. It receives communication from the PLC and generates direct ON/OFF trigger signals to the camera, mediating between the two devices to achieve both integration and precise synchronization.
2Ease of operation
If camera is connected through communication network to PLC, then remote monitoring is enabled, but time synchronization becomes difficult due to communication delay
Solution Approach 1:
The camera input expansion unit serves as an intermediary that receives monitoring commands from the PLC via communication network and translates them into precise direct trigger signals for the camera, enabling remote monitoring with high time synchronization accuracy.
Solution Approach 2:
The system replaces pure communication-based control with a hybrid approach: communication for command transmission and direct electrical signaling (ON/OFF signals on image-capture-trigger line) for time-critical trigger transmission, substituting communication delay with direct electrical signal transmission.
3Measurement precision
If dedicated image-capture-trigger line is used, then time synchronization precision is improved, but device complexity increases
Solution Approach 1:
The camera input expansion unit performs multiple functions: it acts as a communication interface between PLC and camera, a trigger signal generator, and a device for storing and managing image data. This multi-functionality justifies the added wiring complexity by consolidating multiple roles in a single device.
Solution Approach 2:
The expansion unit as an intermediary consolidates the complexity of managing both communication protocols and direct trigger signaling in one device, rather than requiring separate systems for each function. The dedicated trigger line complexity is offset by the simplification achieved through centralized control.
Data Source
AI summary
A camera input expansion unit includes a camera-setting-information storage, a camera expansion processor, an image-recorder, and an image capture interface. The camera-setting-information storage stores setting information on the camera including the conditions of the image capture trigger. The camera expansion processor generates an ON/OFF signal for defining the image capture trigger based on the setting information of the camera. Based on the ON/OFF signal as the image capture trigger, the camera expansion processor acquires the image data which is generated by the camera. The image-recorder records the image data acquired by the camera expansion processor. The image capture interface is provided between the camera expansion processor and the camera. The image capture interface has an image-capture-trigger line propagating the ON/OFF signal to the camera and an image communication line propagating the image data generated by the camera to the camera expansion processor.