PLC Controller Dual-Mode Database Access for Debugging
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Solution Overview
Problem
In configurations where a Programmable Logic Controller (PLC) is connected to another system, such as a database system, debugging of user programs becomes complicated due to the need for the PLC to be started up before the other system operates, requiring dummy system startups and complex verification processes.
Innovation Solution
A controller with a communication interface connected to a database system, an instruction executing unit, and an access processing unit that operates in two modes: one for transmitting statements and another for sending execution results without transmitting statements, facilitating debugging by allowing the PLC to simulate database interactions without actual system operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the PLC is connected to a database system and the PLC is started up before the database system operates, then the control operation of the PLC can be verified early, but the debugging process becomes complicated due to the need for dummy system startups and complex verification processes
Solution Approach 1:
The patent introduces a dummy database system as an intermediary component that mediates between the PLC and the actual database system. This dummy system receives SQL statements from the PLC during the startup phase and returns predetermined response data, allowing the PLC to be verified without requiring the actual database system to be operational. The dummy database system is then replaced or connected to the real database system when it becomes available, simplifying the overall verification process.
2Productivity
If dummy systems are used to verify PLC operations before the database system is operational, then early verification is possible, but the debugging process becomes more complex
Solution Approach 1:
The patent creates a dummy database system that copies the essential interface and communication protocol of the actual database system. This copy includes the ability to receive and parse SQL statements and return response data in the same format as the real system. By using this simplified copy during the startup phase, the PLC can be verified without the complexity of setting up and managing the full database system infrastructure.
Data Source
AI summary
A technique for facilitating debugging in a user program which operates by cooperation of a PLC and another system in a control system including a controller and another system. A CPU unit has a communication interface, executes a user program, calls DB connection service in accordance with an instruction included in the user program, and generates a statement to access a database device. In the DB connection service, operation is performed while switching a first mode and a second mode. In the first mode, a statement according to an access instruction is generated, the generated statement is transmitted to a database system, and a result of a response is sent to the user program. In the second mode, without transmitting the statement to the database device, a result of execution corresponding to the statement is sent to the user program.