Programmable Controller Duplexed Network Communication Reliability
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Solution Overview
Problem
Existing programmable controller network systems face communication disruptions due to abnormalities in the communication unit or network breakages, and are limited to specific network formations, such as optical annular systems, which are costly and unreliable when multiple breaks occur.
Innovation Solution
A programmable controller with a primary and secondary communication unit connected to different networks, allowing the CPU to prioritize the primary unit for communication and switch to the secondary unit if necessary, enabling communication through two networks and supporting various network formations like ring or bus types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single communication unit is used in the programmable controller, then the device complexity is reduced, but communication reliability deteriorates when the communication unit or network experiences abnormalities
Solution Approach 1:
The system dynamically changes the operational state of communication units based on detected abnormalities. When the primary communication unit or its network experiences a failure, the system transitions from single-unit operation to dual-unit operation, altering the operational parameters to maintain communication reliability
Solution Approach 2:
The programmable controller is equipped with a secondary communication unit as a standby component before any failure occurs. This redundant unit remains dormant or in a lower priority state during normal operation but is immediately activated when the primary communication unit fails, providing pre-prepared protection against communication failures
2Reliability
If an optical cable in annular form is used for network duplexing, then communication reliability is improved against single breakage, but the cost increases and reliability deteriorates when multiple breaks occur
Solution Approach 1:
The system uses standard wire cables instead of expensive optical cables for network connections. While wire cables are less expensive, the system compensates for their lower inherent reliability through the intelligent dual communication unit architecture that can switch between different networks, achieving reliable communication without the high cost of optical infrastructure
Solution Approach 2:
The communication units are designed to operate across multiple network types and configurations. The programmable controller can function with various network formations (star, bus, ring, daisy-chain) and cable types (wire, optical) by utilizing both communication units, making the system universally adaptable without being locked into expensive specialized infrastructure
3Reliability
If the network is configured in annular form with optical cables, then single breakage is tolerated, but the system becomes disconnected when two or more breaks occur
Solution Approach 1:
The system adds a dimensional aspect to network redundancy by utilizing two separate communication units that can access different networks independently. Instead of relying on a single annular network's topological redundancy, the system creates parallel communication pathways through multiple network interfaces, allowing communication to continue even when one entire network becomes disconnected
4Quantity of substance
If wire cables or bus-type wiring are used instead of optical cables, then the cost is reduced, but the network cannot be duplexed in traditional configurations
Solution Approach 1:
The system implements dynamic communication unit selection based on real-time network status. The programmable controller continuously monitors the health of its communication units and networks, dynamically switching between primary and secondary communication units depending on which network is currently operational, thereby maintaining reliable communication with cost-effective wire cable infrastructure
Data Source
AI summary
A duplexed network system is formed with a plurality of programmable controllers and two different networks. Each of the programmable controllers includes a CPU unit, a primary communication unit connected to one of these networks (the first network) and a secondary communication unit connected to the other of the networks (the second network). The primary communication unit serves to compile participation status of nodes connected to the first network. The CPU unit gives priority to the primary communication unit when a request to transmit a communication command is issued to both the primary and secondary communication units. The primary communication unit serves to judge, when a request to transmit a communication command to an addressee node is received from the CPU unit, whether transmission to the addressee node is possible based on the participation status of the first network, to transmit the communication command if the transmission is judged to be possible and to request the secondary communication unit to transmit the communication command if the transmission is judged to be not possible.