PLC Duplex System Data Synchronization via Slave Station Inversion
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Solution Overview
Problem
In programmable logic controller duplex systems, when switching from a standby to a control system, there is a risk of using outdated data to control a slave station, and existing methods increase the processing load of the control system, leading to potential control issues and inefficiencies.
Innovation Solution
A programmable logic controller with a state monitoring unit and system switching control unit that transmits status information to a slave device, ensuring that only up-to-date control data is used by switching the standby system to the control system upon detection of hindrance, without increasing the processing load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is transmitted from the slave station to both the control system and standby system, then the standby system can hold the same data as the control system, but the programmable logic controller that has been switched to the control system may use old data to control the slave station
Solution Approach 1:
The slave station is configured to transmit data to the standby programmable logic controller in advance, before the standby unit needs to take over control. This preliminary data preparation ensures that when switching occurs, the standby unit already possesses current data, eliminating the problem of using outdated data after system switching.
2Reliability
If data is periodically transferred from the control system to the standby system, then the standby system holds updated data, but the processing load of the control system increases and scan time increases
Solution Approach 1:
Instead of having the control system transmit data to the standby system (traditional approach), the invention inverts the data flow direction by having the slave station transmit data directly to both the control system and the standby system. This eliminates the additional processing burden on the control system while ensuring data synchronization.
3Loss of information
If the standby system receives control data from the slave station, then data freshness is maintained, but the slave station must manage multiple data transmission paths
Solution Approach 1:
The slave station is designed with multi-functionality to transmit control data to multiple destinations (both control and standby programmable logic controllers) simultaneously. This universal data transmission capability maintains data freshness in the standby system without requiring complex separate transmission mechanisms, as the slave station handles multiple transmission paths through its enhanced functionality.
Data Source
AI summary
A programmable logic controller includes a state monitoring unit to monitor a state of another programmable logic controller that is a counterpart in the duplication, and a system switching control unit to transmit, to a slave device, status information including information indicating whether the programmable logic controller is a control system or a standby system, to receive the control data that is addressed to the programmable logic controller that is the control system and is transmitted from the slave device in a case where the programmable logic controller is the control system, and to switch the programmable logic controller to the control system when hindrance in the another programmable logic controller is detected in a case where the programmable logic controller is the standby system.