Factory Controller Publish-Subscribe Gating for Reliable Data Reception
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Solution Overview
Problem
Existing factory automation communication systems, such as those using programmable controllers, lack reliability in data transmission as they broadcast data without verifying reception capability of other controllers, leading to potential data loss.
Innovation Solution
A communication system employing a publish/subscribe-type protocol where control devices transmit data only when the receiving controllers satisfy a predetermined reception allowing condition, ensuring reliable data receipt even in the absence of a connection establishment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is broadcast without checking reception capability, then transmission speed is fast and simple, but data reception reliability deteriorates
Solution Approach 1:
The system performs preliminary actions by having subscriber devices send reception status information before data transmission occurs. The publisher device checks this status information to determine whether the subscriber can receive data, ensuring reliable transmission before the actual data exchange happens.
Solution Approach 2:
The system implements feedback mechanisms where subscriber devices continuously send reception status information (such as buffer status, processing state) back to publisher devices. This feedback loop enables the publisher to make informed decisions about whether to transmit data, improving reception reliability while maintaining protocol simplicity.
2Reliability
If connection establishment is required before data transmission, then data reception reliability improves, but communication time increases
Solution Approach 1:
The system performs preliminary actions by having subscriber devices send reception status information before data transmission occurs. The publisher device checks this status information to determine whether the subscriber can receive data, ensuring reliable transmission before the actual data exchange happens.
Solution Approach 2:
The system maintains continuous transmission by having subscriber devices continuously send reception status information and publisher devices continuously check and transmit data when conditions are met. This eliminates idle connection establishment and teardown phases, keeping the communication channel continuously useful.
3Reliability
If reception status checking is implemented, then data transmission reliability improves, but communication protocol complexity increases
Solution Approach 1:
The system extracts the reception status checking function from the core data transmission protocol and implements it as a separate, simple status information exchange mechanism. This separation allows the protocol to remain simple while still providing reliable transmission through the extracted status checking capability.
Data Source
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AI summary
Reliability with which a control device at a transmission destination can receive data is improved. In a communication system in which a plurality of control devices for factory automation are connected to a network, a communication protocol among the control devices includes a publish/subscribe type. Each of the control devices includes: a data storage unit in which control data is stored; a publisher unit that transmits data including a state of the control device of the publisher unit itself to other control devices than the control device; and a subscriber unit that receives data from each of the other control devices. When a state of each of the other control devices that is received by the subscriber unit satisfies a reception allowing condition, the publisher unit transmits the control data of the control device of the publisher unit itself.