The Benefits of Code Abstraction in Industrial Control Operations

Question:

Hello everyone, we would appreciate it if you could provide your insights on code abstraction and Object-Oriented Programming (OOP) for discrete industrial control operations. In my opinion, for a discrete process such as turning a pump on or off, it is more advantageous to make the process as transparent as possible using a visual language like ladder logic or Function Block Diagram (FBD) to clearly depict the process without any abstraction. This differs from using Structured Text (ST) to abstract the input and output, create objects or functions, and call them. While many rungs or function blocks can be condensed into a few lines of ST, what are the benefits and drawbacks of each approach? Nowadays, PLCs are incredibly powerful, so is it preferable to observe the process activation on a single ladder or sheet rather than having to navigate through multiple function calls?

Top Replies

Using a Function Block (FB) for a motor start with buttons may have some processing overhead due to passing parameters. However, for systems with multiple motors and various parameters like Start, Rotation, alarms, and HMI information such as color, utilizing FBs can be beneficial. Instead of individually coding each motor, a well-designed FB can provide a common solution for all motors. Think of it as a block on a ladder, where you can easily monitor the status of control bits through inputs and outputs to quickly identify any issues. This simplifies troubleshooting and streamlines operations for complex motor systems.

If the maintenance technicians assigned to debug the system are proficient in ladder logic, it would be wise to continue utilizing their expertise. However, if they lack knowledge beyond ladder logic, be prepared for frequent late-night or early-morning troubleshooting calls. James.

BeepBob inquired about the preference between code abstraction and object-oriented programming (OOP) for discrete industrial control operations. In my opinion, for straightforward processes like turning a pump on or off, it is beneficial to use a visual language like ladder logic or function block diagrams (FBD) to clearly depict the process without abstracting it. On the other hand, using Structured Text (ST) allows for abstraction by creating objects and functions, condensing many rungs or function blocks into a few lines of code. What are the advantages and disadvantages of each approach? With the advanced capabilities of PLCs nowadays, is it more efficient to have the process visualized on one ladder diagram or sheet rather than navigating through multiple function calls? It's important to note that the choice between languages and program design is separate. Many programmers use abstraction in ladder logic. For example, Output := (Start OR Output) AND Stop;

In the world of programming, each language serves as a unique tool for specific tasks. Just like using a hammer for driving nails and a wrench for other purposes, choosing the right language is crucial for efficiency and effectiveness. When programming manual operations for a machine, ladder logic is the go-to choice. On the other hand, when automating sequences, ST programming is likely the better option. A well-developed FB should be like a black box to the end-user. The exterior of the block should provide clear indications of any issues, making troubleshooting easier for programmers. It's all about using the right tool for the right job.

If you are dealing with a basic motor control system involving start, stop, and output, it is best to keep it simple and use a ladder logic approach. However, for more complex systems with functions such as reversing, Variable Frequency Drive (VFD), alarms, and HMI display animations, it is recommended to create a function (AOI) for each motor instead of writing multiple rungs of code. This approach makes it easier to troubleshoot as you can easily identify the information being passed to and from the function. Additionally, many Integrated Development Environments (IDEs) allow you to right-click on the function related to a specific motor to view the code within the function and its status for that particular instance.

I agree with your statement about ladder logic or FBDs simplifying the understanding of discrete control operations, especially for troubleshooting and maintenance purposes. However, I'd view this lack of abstraction not necessarily as an advantage in all situations, but rather as a trade-off. When your control system starts to get complex, OOP and abstraction bring clear benefits of modularity, structure and reusability of code. Even if modern PLCs are powerful, efficient code design can benefit the system by reduced scan times and increased reliability. The key is to find a balance, taking into consideration the nature and scope of your project, as well as the technical knowledge of the people who will be interacting with the system.

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Frequently Asked Questions (FAQ)

FAQ: 1. What is the benefit of using code abstraction and Object-Oriented Programming (OOP) in discrete industrial control operations?

Answer: - Answer: Code abstraction and OOP can enhance the transparency and efficiency of processes by simplifying complex operations into reusable objects or functions.

FAQ: 2. How does using visual languages like ladder logic or Function Block Diagram (FBD) differ from Structured Text (ST) in industrial control operations?

Answer: - Answer: Visual languages like ladder logic or FBD provide a straightforward representation of processes, while ST allows for abstraction of input and output through objects and functions.

FAQ: 3. What are the benefits of condensing many rungs or function blocks into a few lines of Structured Text (ST) in industrial control operations?

Answer: - Answer: Condensing code into a few lines of ST can improve code readability, maintenance, and efficiency.

FAQ: 4. Is it preferable to observe process activation on a single ladder or sheet rather than navigating through multiple function calls in PLCs?

Answer: - Answer: Observing process activation on a single ladder or sheet can offer a more straightforward and intuitive view of the control system, enhancing monitoring and troubleshooting capabilities.

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