PLC Video Timestamp Correction for Log Time Synchronization
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Solution Overview
Problem
Existing techniques for synchronizing the time affixed to moving images with log record times in factory automation systems are limited, as they do not accommodate widespread imaging devices like network cameras or webcams, which lack dedicated low-delay imaging trigger lines.
Innovation Solution
A programmable logic controller (PLC) with a clock element, log record means, image data acquisition means, frame rate measurement means, and image storage means that corrects the time affixed to moving image data based on the frame rate, allowing synchronization with log record times using general-purpose communication cables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated low-delay imaging trigger line is used to connect the imaging device and the PLC, then the time affixed to the moving image can be accurately synchronized with the log record time, but the system cannot use widespread imaging devices such as network cameras or webcams and requires a dedicated imaging device
Solution Approach 1:
The patent introduces a general-purpose communication cable as an intermediary medium between the imaging device and PLC, replacing the dedicated trigger line. This mediator enables time synchronization functionality while allowing compatibility with standard imaging devices that have common communication interfaces, thus resolving the contradiction between synchronization accuracy and device versatility
Solution Approach 2:
The patent changes the communication interface parameter from a dedicated trigger line to a general-purpose communication cable. This parameter change allows the system to accommodate widespread imaging devices while maintaining time synchronization capability through software-based timing mechanisms and frame rate measurement
2Adaptability or versatility
If a general-purpose communication cable is used to connect the imaging device and the PLC, then widespread imaging devices can be used, but time inconsistency occurs between the moving image time and log record time due to clock differences, jitter, and latency
Solution Approach 1:
The patent implements a feedback mechanism where the PLC measures the frame rate of the moving image based on the clock signal and uses this information to correct the time affixed to each frame. This feedback loop compensates for time inconsistencies caused by clock differences, jitter, and latency, maintaining synchronization accuracy while using general-purpose communication cables
Solution Approach 2:
The patent performs preliminary time correction by measuring the frame rate in advance and calculating the appropriate time adjustment before affixing the time to the moving image frames. This preliminary action ensures that time synchronization is maintained throughout the recording process, preventing cumulative timing errors
Data Source
AI summary
A programmable logic controller or PLC (10) includes a clock element (120), a log recorder (101) that records a log together with a record time into a storage device (110) based on a clock signal output from the clock element, an image data acquirer (102) that acquires moving image data indicating a moving image captured by an imaging device from the imaging device, a frame rate measurer (103) that measures a frame rate of the moving image indicated by the moving image data based on the clock signal output from the clock element (120), a corrector (104) that corrects a time to be affixed to the moving image indicated by the moving image data based on the frame rate, and an image storage (105) that stores, into the storage device (110), new moving image (DM) data indicating a moving image affixed with the time corrected by the corrector (104).