PLC Control Program Arbitration for Conflict-Free Instruction Updates
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Solution Overview
Problem
In factory automation systems using multiple programmable logic controllers (PLCs), the fixed operation of control programs leads to challenges in freely disposing control programs across PLCs without conflicts, particularly in managing operation times and avoiding interference between control instructions.
Innovation Solution
A control system with a network of PLCs, each equipped with program storage, an operation module, and an arbitration module that disperses and arbitrates control programs to prevent conflicts by statically determining operation times and generating identification information for control instructions, allowing flexible program disposition without interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If control programs are fixed to specific PLCs, then system stability is maintained, but flexibility in program disposition is reduced
Solution Approach 1:
The system segments control programs into independent units that can be individually assigned to different PLCs. Each control program is treated as a separate entity that can be disposed freely among multiple PLCs without affecting the stability of the entire system, thus achieving both flexibility and reliability.
Solution Approach 2:
An arbitration module is introduced as an intermediary between control programs and PLCs. This module automatically manages the assignment and execution timing of control programs across multiple PLCs, preventing conflicts while allowing flexible program disposition. The arbitration module ensures that programs are executed in the correct sequence and that only one PLC executes a given program at a time, maintaining system stability.
2Productivity
If multiple control programs update the same control instruction simultaneously, then processing speed is improved, but conflicts occur between updates
Solution Approach 1:
The arbitration module performs preliminary actions by determining the execution timing of each control program before actual execution. It assigns specific time slots to programs that update the same control instruction, ensuring that updates occur in a predetermined sequence without conflicts, thus maintaining both speed and reliability.
Solution Approach 2:
The system implements periodic action by cycling through control programs in a predetermined sequence. Each program that updates a shared control instruction is executed in its designated time slot within a control cycle, allowing multiple programs to efficiently update instructions without simultaneous conflicts, thereby maintaining processing speed while preventing errors.
3Adaptability or versatility
If control programs are freely disposed among PLCs, then system adaptability is improved, but complexity of managing operation times increases
Solution Approach 1:
The arbitration module implements self-service by automatically managing the complex task of assigning and coordinating operation times for control programs across multiple PLCs. The system eliminates the need for manual timing configuration and conflict resolution, allowing users to freely dispose programs while the arbitration module handles the complexity of timing management autonomously.
Data Source
AI summary
A control system includes plural control devices connected to a network, each of the control devices including a program storage, an operation module, and an arbitration module. The program storage stores a control program including a command to calculate and update a control instruction that is a value related to control of a control target. The operation module operates the control program of the program storage of the control device. The arbitration module disposes plural control programs including a command to calculate and update an identical control instruction in another one of the plural control devices, and arbitrates an operation time between the plural control programs such that updatings of the identical control instruction do not conflict with each other in the plural control programs.