PLC User Program Switching With Variable Address Retention
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Solution Overview
Problem
Existing programmable logic controllers (PLCs) require a production line stop to switch user programs, leading to decreased operation rates due to the difficulty in rewriting large-scale user programs efficiently.
Innovation Solution
A programmable logic controller with a processor and data memory that maintains variable addresses and values during a program switch, allowing seamless transition from a first user program to a second updated version without stopping the PLC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PLC is stopped to switch user programs, then the program switching can be completed safely, but the production line operation rate decreases
Solution Approach 1:
The patent applies preliminary action by pre-allocating multiple storage areas (first storage area and second storage area) for user programs before switching is needed. The new user program is prepared and loaded into the second storage area in advance, so that when switching is required, the PLC can simply switch the execution target between storage areas without stopping for program construction or loading, thereby maintaining continuous operation while ensuring safe program switching.
2Productivity
If the user program is switched while operating the PLC, then the production line operation rate is maintained, but the stop time increases due to the time required to construct relationships between variables and storage areas
Solution Approach 1:
The patent applies preliminary action by pre-establishing variable-information pairs for each variable before program switching. Each variable is associated with information indicating its storage area location in advance. When switching occurs, the system simply updates the variable-information pairs to point to the new storage area locations, rather than constructing variable relationships during the switch, dramatically reducing switching time while maintaining high productivity.
Solution Approach 2:
The patent applies segmentation by dividing the user program into multiple segments that can be stored in different storage areas independently. Each segment can be managed and switched separately, allowing the system to switch only the necessary program portions without reconstructing relationships for the entire program, thereby reducing the time required for program switching while maintaining operational productivity.
3Ease of manufacture
If the PLC stops sequence control to switch user programs, then the program switching can be performed, but the stop time of the production line increases
Solution Approach 1:
The patent applies preliminary action by pre-preparing the new user program in a second storage area before it is needed for execution. The program is fully constructed and stored in advance, so that when switching is required, the PLC only needs to switch the execution target between storage areas without stopping sequence control or pausing production, thereby enabling easy program switching while minimizing production line stop time.
Data Source
AI summary
A user program is efficiently switched while operating a PLC. The PLC may include a processor repeatedly executing a logic operation based on the user program, and a memory storing values of variables accessed according to the user program executed by the processor. An instruction is issued to switch to a second user program, which is an updated version of a first user program, while the processor is executing the first user program. Variable information for identifying a variable to be maintained and a variable to be changed by an update from the first user program to the second user program is created. An address in which a value of the variable to be maintained is stored is maintained, and an address in which a value of the variable to be changed is stored is assigned at a break of the logic operation with the logic operation being stopped.