Time-Synchronized Network Control With Selective Frame Resend
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Solution Overview
Problem
Existing control systems in factory automation (FA) require inefficient repeated frame transmissions, leading to excessive communication bandwidth usage, despite the need for reliable communication among units.
Innovation Solution
A control system where apparatuses are time-synchronized and configured to periodically exchange frames, with resend requests sent only when frames fail to arrive at defined times and specific cycle conditions are met, optimizing communication by limiting bandwidth consumption and ensuring reliable data transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the master unit transmits multiple transmission frames addressed to different slave units successively multiple times without waiting for response, then reliable communication among units is achieved, but the amount of frame transfer becomes large and communication bandwidth is excessively consumed
Solution Approach 1:
The system pre-configures transfer paths and timing information for each apparatus before communication occurs. Each apparatus stores information about which frames should arrive at what time through which path, allowing it to proactively detect non-arrival and request resends only when necessary, rather than using blanket multiple transmissions
Solution Approach 2:
The system implements a feedback mechanism where receiving apparatus monitor frame arrivals against expected timing. When a frame does not arrive at the expected time, the receiving apparatus sends a resend request back to the transmitting apparatus, which then retransmits only that specific frame. This selective feedback-based resend approach maintains reliability while minimizing unnecessary traffic
2Reliability
If resend requests are transmitted whenever frames do not arrive, then communication reliability is improved, but communication bandwidth consumption increases
Solution Approach 1:
The system applies partial action by sending resend requests only for specific frames that fail to arrive at their expected time, rather than retransmitting all frames or using excessive multiple transmissions. This selective approach ensures reliability for critical frames while avoiding unnecessary bandwidth consumption
Solution Approach 2:
The system uses periodic frame transmission with predetermined timing intervals. Each frame is expected to arrive at specific periodic intervals, and resend requests are triggered only when this periodic pattern is disrupted by non-arrival, creating a rhythm of normal operation interrupted only by necessary corrections
Data Source
AI summary
A control system, apparatus, and method are provided. In the control system, plural apparatuses in time synchronization with one another are connected to a network, and the network transfers a frame periodically exchanged by the apparatuses. The apparatuses include a control device and an apparatus controlled by the control device. Each apparatus in the control system is connected over the network, to a first apparatus that transmits a frame that arrives at each of the apparatuses and a second apparatus that receives a frame transmitted from each of the apparatuses. Each apparatus includes information on a frame transfer path and transfer timing based on a synchronous time. When a frame does not arrive at defined time through the transfer path and when a condition associated with a cycle is satisfied, one or more of the apparatuses is configured to transmit a resend request through the transfer path.