Field Bus Control Cycle Setting Using Propagation Delay Times
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Solution Overview
Problem
In factory automation systems, the propagation delay times of slave devices connected to a field bus can prevent completion of processes within a control cycle, making synchronous control unreliable and difficult to achieve at high speeds.
Innovation Solution
A control device with a communication management part that includes a control cycle determination part and a propagation delay time measurement part, which measures and stores propagation delay times for slave devices, allowing for the determination of a control cycle that enables cyclic synchronous control without requiring real-time measurement at each startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the control cycle is set based on the number and topology of slave devices, then the communication speed is improved, but the synchronous control reliability deteriorates due to propagation delay variations
Solution Approach 1:
The patent measures and stores propagation delay times for all slave devices during an initialization phase before actual control operations begin. This preliminary measurement allows the control cycle to be accurately determined based on actual device characteristics rather than conservative estimates, enabling faster control cycles while maintaining synchronous control reliability.
Solution Approach 2:
The patent changes the control cycle parameter from a fixed or conservatively estimated value to a dynamically determined value based on measured propagation delay times. By adjusting the control cycle parameter to match actual system characteristics, the system achieves both high communication speed and reliable synchronous control.
2Measurement precision
If real-time measurement of propagation delay time is performed at each startup, then the synchronous control accuracy is improved, but the startup time increases
Solution Approach 1:
The patent performs propagation delay time measurements during an initialization phase at startup and stores these values for reuse. This preliminary measurement approach ensures accurate delay time data is captured once, eliminating the need for repeated real-time measurements during subsequent operations, thus reducing startup time while maintaining measurement precision.
Solution Approach 2:
The patent creates a stored copy of measured propagation delay times that can be reused across multiple control operations. Instead of remeasuring each time, the system uses the stored copy of delay time data, significantly reducing the time required for startup and reinitialization while maintaining the accuracy of the original measurements.
3Ease of operation
If a fixed control cycle is used for all slave devices, then the control simplicity is improved, but the process completion reliability deteriorates for devices with higher propagation delays
Solution Approach 1:
The patent determines the control cycle parameter based on the maximum propagation delay time measured across all slave devices. This approach adjusts the control cycle to accommodate the slowest device in the network, ensuring all devices can complete their processes reliably within each cycle while maintaining a unified control mechanism that preserves operational simplicity.
Data Source
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AI summary
Provided is a control device comprising a communication management part and a user application processing part. The user application processing part is for detecting slave devices that are connected to a field bus and that control data having been set using a setting tool is communicated to. The communication management part is for managing the communication of the control data in accordance with a control cycle. The communication management part determines the control cycle using a pre-stored propagation delay time for each of the slave devices subject to communication.