Programmable Controller CPU Redundancy for Special-Function Module Synchronization
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Solution Overview
Problem
Existing programmable logic controllers (PLCs) in factory automation lack redundancy in their special-function modules, which can lead to system failures if these modules are not maintained in a synchronized state, compromising safety and reliability.
Innovation Solution
A programmable controller with two CPU units, each equipped with a detachably attached special-function module, where one CPU unit is active and the other is in standby mode, with data exchange through a common memory to ensure synchronized calculations and seamless switching in case of failures, maintaining identical data states across modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two CPU units are doubled up with identical functions and programs, then system reliability is improved through redundancy, but the special-function modules remain unsynchronized and can cause system failures
Solution Approach 1:
The patent applies the copying principle by having the standby CPU unit replicate the user program and data from the active CPU unit. The standby unit maintains an identical copy of the program in its memory, ensuring that when switching occurs, the system continues operation without data loss or desynchronization. This is achieved through the standby unit receiving and storing the same user program that the active unit executes.
2Reliability
If the standby CPU unit executes the same user program as the active unit, then seamless switching is enabled, but computational resources are wasted due to redundant calculations
Solution Approach 1:
The patent applies partial action by having the standby CPU unit execute only a simplified version of the user program - specifically, it performs basic program execution and data maintenance without carrying out the full computational workload. The standby unit maintains program state and readiness but does not perform complete calculation cycles, thus reducing energy consumption while preserving the ability to switch seamlessly.
3Speed
If the special-function module is made intelligent and high-performance, then control speed and level are improved, but the complexity of maintaining synchronization between doubled-up modules increases
Solution Approach 1:
The patent introduces the CPU unit as an intermediary between the special-function module and the external system. The CPU unit manages the complexity of synchronization by handling data exchange, program loading, and state maintenance for the intelligent special-function module. This intermediary role simplifies the overall system architecture by centralizing the synchronization management function in the CPU unit rather than requiring direct coordination between multiple special-function modules.
Data Source
AI summary
A programmable controller includes two CPU units each having a detachably attached special-function module for carrying out a calculation process, each of the two CPU units recognizing conditions of the other CPU unit, one of them becoming an active unit and the other becoming a standby unit such that when the active unit fails and goes down the standby unit is switched to become active and resumes operations. The special-function module attached to the active CPU unit becomes an active module and carries out control processes with the active CPU unit and the other special-function module attached to the standby CPU unit becomes a standby module.