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Introduction
As a PLC (Programmable Logic Controller) engineer, we face numerous complex control systems and engineering problems every day. Some of these issues may arise from equipment failures, while others may be due to process inefficiencies or improper program design. Regardless of the situation, we need to address and resolve them using structured thinking. In this article, I will share my practical programming experience and explore how to deconstruct complex problems using structured thinking to tackle challenges in PLC programming.
1
What is Structured Thinking?
Structured thinking refers to a way of thinking about problems in a hierarchical and systematic manner. When faced with complex issues, structured thinking helps us grasp the overall framework of the problem and break it down into smaller, more manageable parts. It enables us to analyze various aspects of the problem, identify root causes, and design appropriate solutions.
The close integration of PLC programming and structured thinking allows us to troubleshoot, debug systems, and optimize designs more efficiently. Through structured thinking, we can clarify the relationships between different modules, enhance the readability and maintainability of programs, and reduce the likelihood of errors.
2
Deconstructing Complex Problems: How to Break Down Challenges in PLC Programming?
In the process of PLC programming, complex problems often arise from the interplay of multiple factors. For example, a simple production line control system may need to handle a large number of sensor inputs, actuator controls, and alarm functions. If we do not break it down from a holistic perspective and jump straight into coding, we can easily fall into the trap of “local optimization” or “detail dilemmas,” leading to a complex and hard-to-maintain system design.
2.1
Modular Thinking
When facing complex PLC programming issues, we should divide the problem into several modules for consideration. For instance, when designing a control program for an automated production line, we can categorize the system into several main modules based on different functional requirements, such as: input signal processing module, logic judgment module, actuator control module, and alarm handling module.
By adopting a modular thinking approach, we can address the specific issues of each module one by one. Once each module is designed, we can then integrate them into a complete system. This layered and modular structured approach can effectively simplify the overall system design process.
2.2
Using Flowcharts and State Diagrams
To clearly understand the relationships between various modules, we can use tools like flowcharts and state diagrams to visualize the system. These graphical tools help us clarify control processes and logical judgments, intuitively displaying the inputs, outputs, and transformation relationships between modules.
For example, when writing a simple start-stop control program, we can draw a state diagram to clearly show the state transitions of the system from “start” to “run” and then to “stop.” This way, we can more intuitively capture potential system anomalies or vulnerabilities and take preventive measures in advance.
2.3
Simulation and Debugging
After completing the initial module design, we need to verify the correctness of the program through simulation and debugging. In this process, structured thinking also plays a crucial role. We can simulate and debug each module one by one, gradually eliminating errors and ensuring that each module works as expected. Only after all modules have been debugged can we integrate them into the final complete system.
3
Case Analysis of Structured Thinking in PLC Programming
Start Control of Automated Production Line
Suppose we need to design a start control program for an automated production line. In traditional programming thinking, engineers might directly write control code, such as “when the start button is pressed, start the motor; when the stop button is pressed, stop the motor.” However, this approach often overlooks the complex situations during the startup of the production line, such as:
Preconditions for motor startup (e.g., confirmation of temperature, pressure, sensor signals)
Exception handling during the startup process (e.g., motor startup failure, excessive temperature)
Safety monitoring after startup (e.g., automatic fault detection, alarm triggering)
Through structured thinking, we can decompose the start control function into multiple modules: precondition checking, start control, fault handling, and safety monitoring. The implementation of each module can refer to the following steps:
Precondition Checking Module: Ensure that temperature, pressure, sensors, and other conditions meet the startup requirements.
Start Control Module: When all conditions are met, start the motor; if conditions are not met, the system triggers an alarm and stops operation.
Fault Handling Module: If startup fails, the system should immediately enter fault handling mode, log the error, and provide maintenance prompts.
Safety Monitoring Module: During startup, the system continuously monitors the motor status, temperature, etc., and automatically shuts down in case of anomalies to prevent equipment damage.
This structured modular design not only helps us clarify the specific implementation of each function but also makes the program easier to debug and maintain.
4
The Practical Application of Structured Thinking: How to Improve Efficiency in PLC Programming?
4.1
Improving Readability and Maintainability
In PLC programming, structured thinking helps us write clearer and more understandable code. A good code structure not only helps us quickly locate issues during development but also reduces the likelihood of errors during later maintenance.
For example, we can use appropriate naming, clear comments, and suitable module divisions to make the logic of the code more apparent. If someone needs to maintain our program later, they can quickly understand the role of each module, reducing the learning curve.
4.2
Reducing Error Probability
In complex control systems, various errors and anomalies are inevitable. Through structured thinking, we can consider various potential issues during the early stages of system design and take preventive measures. For instance, when designing an automated production line, we can account for sensor failures, motor anomalies, etc., and incorporate corresponding fault tolerance mechanisms into the program. This way, when issues arise during system operation, they can be detected and addressed promptly, reducing the frequency of failures.
4.3
Improving Debugging Efficiency
Structured thinking allows us to clearly identify the source of problems and conduct debugging more effectively. When a system fails, we can use a modular debugging approach to systematically check for issues. For example, when debugging a temperature control system, if the heater fails to start, we can first check whether the temperature sensor is functioning correctly, and then check if there are issues with the heater control module. By eliminating fault points one by one, we can significantly improve debugging efficiency.
Conclusion
As PLC engineers, structured thinking is not only an effective programming skill but also a method for solving complex problems. By breaking down complex control systems into multiple modules, we can better understand the role of each module and provide more efficient pathways for problem-solving. In practical PLC programming, we should cultivate the habit of using structured thinking and integrate it into our daily development, debugging, and maintenance work. By continuously optimizing our thinking methods and programming skills, we can better tackle complex engineering challenges and design more stable and reliable automation systems.
I hope every PLC engineer can consistently apply structured thinking in their work, continuously deconstruct complex problems, and achieve more efficient work and learning.
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