Field Bus Control Cycle Setting Using Stored Propagation Delays
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Solution Overview
Problem
In factory automation systems using field bus systems, propagation delays can prevent all slave devices from completing processes within a control cycle, making synchronous control unreliable and challenging to achieve.
Innovation Solution
A control device with a user application processing part and a communication management part that detects and manages slave devices, measures and stores propagation delay times for each slave device, allowing for the determination of a control cycle that enables cyclic synchronous control without requiring real-time measurement at startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the control cycle is set based on the number and topology of slave devices, then the control cycle setting is simplified, but propagation delay causes synchronous control to fail
Solution Approach 1:
The system performs preliminary measurement of propagation delay times for each slave device before determining the control cycle. The control device measures the propagation delay time from itself to each slave device and stores these values. Based on these pre-measured delay times, the control cycle is determined to ensure all slave devices can complete their processes within the cycle, thereby achieving reliable synchronous control while maintaining ease of operation.
2Reliability
If propagation delay time is measured at startup, then accurate control cycle setting is achieved, but startup time increases
Solution Approach 1:
The control device performs propagation delay time measurements and stores these values in advance during system initialization or setup phase. When the control cycle needs to be determined, the pre-stored propagation delay times are directly used without requiring real-time measurement, thus achieving accurate control cycle setting while minimizing startup time loss.
Solution Approach 2:
Instead of measuring propagation delay times in real-time for each control cycle determination, the system creates a copy of the measured delay time values and stores them for reuse. This copied data allows rapid determination of the control cycle without repeating the measurement process, significantly reducing the time required while maintaining accuracy.
3Reliability
If propagation delay times of all slave devices are stored, then accurate control cycle determination is possible, but storage requirements and system complexity increase
Solution Approach 1:
The control device stores propagation delay times locally in its own memory or storage unit, organized by slave device identification. Each propagation delay time is associated with the specific slave device it corresponds to, allowing the control device to efficiently retrieve the appropriate delay time when determining the control cycle without requiring complex external storage systems.
Data Source
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, which are communication targets of control data having been set using a setting tool, and the slave devices are connected to a filed bus. 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 that are the communication targets of the control data.